This research was supported by the Chinese University of Hong Kong through the Direct Grants 4053077 and 4441179, RGC Competitive Earmarked Research Grants, 402812 and 14304314, and Area of Excellence AoE/P-02/12.

1. Setup of Interference Lithography
NOTE: Interference lithography is used to fabricate the periodic arrays12. The schematic setup, as is shown in Figure 1, is built up as follows:
<ol>
	<li>Focus the 325 nm laser from a HeCd multimode laser to a 13X UV objective lens and pass it through a 50 &#956;m pinhole based spatial filter for mode cleaning.</li>
	<li>Place two 2.5 cm diameter irises 30 cm apart to further filter the central region of the diverging light. After the second iris, the beam diameter equals 2.5 cm and increases very slowly with distance, which is &#60; 3 cm at 1 m distance from the second iris. The light is assumed to be nearly collimated. 
	NOTE: The output from second iris should be uniform when checked by naked eyes.</li>
	<li>Steer the collimated beam to a Lloyd&#39;s mirror interferometer. The Lloyd&#39;s setup contains a prism-based sample holder and a 5.04 cm mirror positioned perpendicular to it. The direct and reflected illuminations together create a stable standing wave along the sample surface for patterning. The prism acts as an antireflection device. 
	NOTE: The period P of the standing wave can be written as: <img alt="Equation 9" src="/files/ftp_upload/56735/56735eq9.jpg" />, where &#955; = 325 nm and &#945; is the incident angle with respect to sample normal, as is shown in Figure 1. The incident angle can be tuned by rotating the Lloyd&#39;s setup.</li>
</ol>
2. Periodic Array Preparation
NOTE: The sample is prepared under the standard procedure suggested by the manufacturer. All the procedures are performed at room temperature.
<ol>
	<li>Use a 1 cm2 glass substrate. Clean the glass with methanol and acetone for 10 min each in an ultrasonic bath and then pre-bake it on a hot plate at 200 &#176;C for 1 h to remove dirt.</li>
	<li>Spin-coat the glass substrate with a 5 nm thick adhesion layer and a 100 nm thick negative SU-8 photoresist with a two-speed spin-coater.
	<ol>
		<li>Dilute the SU-8 photoresist with Gamma-Butyrolactone in a ratio of 1:5 (v/v) so that the thickness can be controlled close to 100 nm after spin-coating.</li>
		<li>Dispense 3-5 drops (0.2 mL) of adhesion solution on the glass substrate and spin at 600 rpm for 10 s and 3600 rpm for 1 min, consecutively.</li>
		<li>Repeat step 2.2.2 with 5-7 (0.3 mL) drops of diluted SU-8 from step 2.2.1 at the same speed. 
		NOTE: The adhesion layer improves the adhesion between the glass substrate and the photoresist so that the photoresist would not peel off during developing. The thickness of the SU-8 layer is controlled by the concentration and the speed of spin-coater.</li>
	</ol>
	</li>
	<li>Prebake the sample on 65 &#176;C and 95 &#176;C hotplates for 1 min each. Ovens are not recommended here.</li>
	<li>Transfer the sample to the prism in the interferometer. Add a drop of refractive index matching oil (n=1.45) to attach the sample on the prism. Place it as close to the mirror as possible. 
	NOTE: The sample is attached on prism surface due to the surface tension of the oil. The refractive index of oil is chosen to be the same as prism and glass substrate to eliminate back reflection from the interference.</li>
	<li>For a two-dimensional square lattice, expose the sample twice with the same exposure time but orthogonal directions; that is, expose the sample and then rotate it by 90&#176; for the second exposure. When the photoresist is exposed to a 325 nm light, it crosslinks and cannot be dissolved by the SU-8 developer. 
	NOTE: The diameter D of the array can be controlled by adjusting the exposure time.</li>
	<li>Hard bake the sample at 65 &#176;C and 95 &#176;C for 2 min to prevent film cracking.</li>
	<li>Immerse the whole sample in developer for 2 min with continuous agitation to dissolve the unexposed area.</li>
	<li>Immerse the sample in isopropyl alcohol for 1 min to rinse the residuals and then dry it with compressed air. A nanohole array is then produced.</li>
</ol>
3. Gold Film Deposition and Light Emitter Coating
<ol>
	<li>Attach the sample to the sample holder of the radio-frequency magnetron sputtering deposition system with double-sided tape for Au film deposition.</li>
	<li>Pump down the chamber to a 2x10-6 Torr base pressure using a turbomolecular pump and then back fill it with 6x10-3 Torr ultra-high purity Ar gas.</li>
	<li>Use a 5 cm diameter 99.9% Au target and place a shutter between the sample and the target. Use low power (50 W) to reduce the deposition rate as well as the surface roughness. With the shutter closed, pre-sputter the target for 10 min to remove dirt.</li>
	<li>Open the shutter to process deposition at room temperature for 20 min. A film thickness of 100 nm is routinely deposited to ensure that the plasmonic system is optically thick with no transmission.</li>
	<li>Once the sample is ready, spin-coat the light emitting materials such as organic dyes or quantum dots on the metal surface to form a thin layer of dielectrics.
	<ol>
		<li>For the styryl 8 dye used in the reference9, dissolve 20 &#181;g of styryl 8 and 500 &#181;g of polyvinyl alcohol polymer&#160;(PVA) in 5 mL of methanol.</li>
		<li>Dispense 3-5 drops (0.2 mL) of dye solution on the sample and spin at 600 rpm for 10 s and 3600 rpm for 1 min consecutively. The thickness is estimated to be 80 nm. 
		NOTE: Water soluble or insoluble polymer can be used as anchoring material depending on the type of emitting material. However, the polymer should be non-emissive so that it would not interfere with the photoluminescence measurements. Polyvinyl alcohol polymer (PVA)&#160;is recommended for dissolving water-soluble dyes such as rhodamine 6G and styryl 8.</li>
	</ol>
	</li>
</ol>
4. Reflectivity Measurements for Determining the SPP Decay Rates
NOTE: The polarization- and angle-resolved reflectivity spectroscopy setup is shown in Figure 2. It consists of a goniometer with three rotation stages for independently changing the sample orientation (stage 1) and detection angle (stage 2) as well as the sample azimuthal angle (stage 3).
<ol>
	<li>Use a broadband white light from a quartz lamp as the light source. First couple it to a multimode fiber bundle and then collimate it by a pair of collinear face-to-face objective lenses (5X and 60X). Illuminate the light beam on the sample at different incident angles by changing sample orientation. Place a pair of incident polarizer and detection analyzer before and after the sample for polarization-dependent measurements. 
	NOTE: The face to face objectives act as a lens system that collimates and expands the white light source from the multimode fiber.</li>
	<li>Use a multimode fiber to collect the specular reflection from the sample, which is connected to a spectrometer and a CCD detector for spectroscopy.</li>
	<li>Align the setup carefully to ensure both the sample orientation stage and detection rotation stages are concentric, i.e., their rotation axes are collinear.</li>
	<li>Calibrate the setup with a flat Au film. Measure the reflection spectra at different incident angles and compare them with the theoretical reflection spectra calculated by Fresnel equations using a known Au dielectric function. The two sets of data should be consistent with less than 5% of error.</li>
	<li>Once the setup is ready, measure the linearly polarized, p or s, reflection spectra of the sample at different incident angles. The step size of the incident angle is 0.5&#176; and the wavelength resolution is 0.66 nm. To collect the spectra under multiple incident angles, a control program is written for automation including the mechanical motion, shutter control, data acquisition, background subtraction, etc. 
	NOTE: This step is done computationally. The program is available upon request. Please send an email to the corresponding author for the source code if needed.</li>
	<li>Contour plot the reflectivity vs. wavelength and incident angle to obtain the dispersion relation of the plasmonic system for mode identification and decay rate determination. 
	NOTE: The sample azimuthal angle is to locate the position in the Brillouin zone. For example, for square lattice sample, rotate the sample azimuthally so that one of its periods is parallel with the incident plane and this defines the &#915;-X direction. Rotate the sample by 45&#176; to define the &#915;-M direction.</li>
	<li>If the incident polarized is set at 45&#176; with respect to the incident plane and the analyzer is at -45&#176;, measure the orthogonal, or cross-polarized, reflectivity mapping.</li>
	<li>Extract the p-polarized and orthogonal reflection spectra and fit them by using CMT9,12,13, as described in the Discussion to determine the decay rates of SPPs.</li>
</ol>
5. Photoluminescence Measurements for Determining the Emission Power Ratio
Note: The angle- and polarization-resolved photoluminescence setup is shown in Figure 3.
<ol>
	<li>Replace the broadband light source with 514&#160;nm argon ion or 633 nm HeNe laser. Use a laser line filter with a full width half maximum (FWHM) less than 5 nm to clean the laser spectrally and place a half-wave plate to control the polarization state of the laser beam. The goniometer and the detection unit remain unchanged. Place a notch filter before the detection unit to remove the laser line, which buries the luminescence. 
	NOTE: The wavelength of the laser depends on the type of emitting materials. Higher photon energy is required to excite the material with shorter emission wavelength.</li>
	<li>To measure the emission power ratio for Eq. (2) &#38; (3), conduct two types of measurements: the detection and incident scans. The interplay between the incident and detection scans assist in determining <img alt="Equation 10" src="/files/ftp_upload/56735/56735eq10.jpg" />, <img alt="Equation 11" src="/files/ftp_upload/56735/56735eq11.jpg" />, <img alt="Equation 12" src="/files/ftp_upload/56735/56735eq12.jpg" />, and <img alt="Equation 13" src="/files/ftp_upload/56735/56735eq13.jpg" />.</li>
	<li>For the incident scan, vary the incident angle continuously but fix the detection angle with respect to the sample normal. 
	NOTE: This step is done computationally. This configuration selectively excites the incoming SPPs, which are incident angle dependent, while monitoring the variation of the emission under the chosen detection angle. In other words, the emission increases when the incident angle fulfills the phase matching equation in Eq. (1).
	<ol>
		<li>Contour plot the photoluminescence spectra against wavelength and the incident angle for the incident scan mapping. Measure the mappings for different detection angles but the relative intensities are found the same. Therefore, the incident scan probes the effect of the incoming SPPs on the emission or simply the excitation enhancement, which allows us to measure <img alt="Equation 10" src="/files/ftp_upload/56735/56735eq10.jpg" /> and <img alt="Equation 11" src="/files/ftp_upload/56735/56735eq11.jpg" />.</li>
	</ol>
	</li>
	<li>For the detection scan, fix the incident angle with respect to the sample normal but vary the detection angle. 
	NOTE: This step is done computationally.
	<ol>
		<li>Similarly, contour plot the photoluminescence spectra with wavelength and detection angle yields the detection scan mapping. As the SPP emission arises from the radiation damping of SPPs, the emission is strongly detection angle dependent. Therefore, under constant excitation, the emission increases when the detection angle fulfills Eq. (1). This configuration probes the emission enhancement and allows us to determine <img alt="Equation 12" src="/files/ftp_upload/56735/56735eq12.jpg" /> for different &#945;th order as long as it has well-defined detection angle dependence.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Okamoto, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-plasmon-enhanced+light+emitters+based+on+InGaN+quantum+wells.">Surface-plasmon-enhanced light emitters based on InGaN quantum wells.</a> Nature Materials. 3 (9), 601-605 (2004).</li><li>Akselrod, G. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leveraging+Nanocavity+Harmonics+for+Control+of+Optical+Processes+in+2D+Semiconductors.">Leveraging Nanocavity Harmonics for Control of Optical Processes in 2D Semiconductors.</a> Nano Letters. 15 (5), 3578-3584 (2015).</li><li>Gontijo, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coupling+of+InGaN+quantum-well+photoluminescence+to+silver+surface+plasmons.">Coupling of InGaN quantum-well photoluminescence to silver surface plasmons.</a> Physical Review B. 60 (16), 11564 (1999).</li><li>Huang, K. C. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antenna+electrodes+for+controlling+electroluminescence.">Antenna electrodes for controlling electroluminescence.</a> Nature Communications. 3, 1005 (2012).</li><li>Atwater, H. A., Polman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonics+for+improved+photovoltaic+devices.">Plasmonics for improved photovoltaic devices.</a> Nature Materials. 9 (3), 205-213 (2010).</li><li>Anker, J. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biosensing+with+plasmonic+nanosensors.">Biosensing with plasmonic nanosensors.</a> Nature Materials. 7 (6), 442-453 (2008).</li><li>Chen, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitation+enhancement+of+CdSe+quantum+dots+by+single+metal+nanoparticles.">Excitation enhancement of CdSe quantum dots by single metal nanoparticles.</a> Applied Physics Letters. 93 (5), 053106 (2008).</li><li>Birowosuto, M. D., Skipetrov, S. E., Vos, W. L., Mosk, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observation+of+Spatial+Fluctuations+of+the+Local+Density+of+States+in+Random+Photonic+Media.">Observation of Spatial Fluctuations of the Local Density of States in Random Photonic Media.</a> Physical Review Letters. 105 (1), 013904 (2010).</li><li>Cao, Z. L., Ong, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+coupling+rate+of+light+emitter+to+surface+plasmon+polaritons+supported+on+nanohole+array.">Determination of coupling rate of light emitter to surface plasmon polaritons supported on nanohole array.</a> Applied Physics Letters. 102 (24), 241109 (2013).</li><li>Lin, M., Cao, Z. L., Ong, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+the+excitation+rate+of+quantum+dots+mediated+by+momentum-resolved+Bloch-like+surface+plasmon+polaritons.">Determination of the excitation rate of quantum dots mediated by momentum-resolved Bloch-like surface plasmon polaritons.</a> Optics Express. 25 (6), 6029-6103 (2017).</li><li>Nikolaev, I. S., Lodahl, P., Driel, A. F. V., Koenderink, A. F., Vos, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strongly+nonexponential+time-resolved+fluorescence+of+quantum-dot+ensembles+in+three-dimensional+photonic+crystals.">Strongly nonexponential time-resolved fluorescence of quantum-dot ensembles in three-dimensional photonic crystals.</a> Physical Review B. 75 (11), 115302 (2007).</li><li>Cao, Z. L., Lo, H. Y., Ong, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+absorption+and+radiative+decay+rates+of+surface+plasmon+polaritons+from+nanohole+array.">Determination of absorption and radiative decay rates of surface plasmon polaritons from nanohole array.</a> Optics Letters. 37 (24), 5166-5168 (2012).</li><li>Haus, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Waves and Fields in Optoelectronics. , (1984).</li></ol>

The authors declare that they have no competing financial interests.

In this protocol, there are several critical steps. First, mechanical stability is crucial in sample preparation. The standing wave generated by Lloyd&#39;s setup is sensitive to the phase difference between two illumination beams. Therefore, any vibration during the exposure time will degrade the uniformity and edge sharpness of the nanohole. It is highly recommended to operate in a vibration-free environment, e.g., an optical table with vibration isolation supports. In addition, high power laser is also desired to minimize vibration as it reduces exposure time accordingly. Second, the pinhole in step 1.1 must be chosen properly. The hole size should be small enough to perform mode cleaning on one side and still large enough to transmit sufficient power for exposure on the other side. We recommend a 50 &#956;m pinhole and 13X objective for the HeCd multimode laser. Third, it is noted that the Lorentzian line shape of orthogonal reflectivity is valid only when rp&#8776; rs, where rp and rs are non-resonant reflectivity for p- and s-polarized illumination12. However, for a nanohole array with glancing incident angle or some anisotropic metamaterials, the difference between rp and rs cannot be neglected and the resulting reflectivity yields <img alt="Equation 23" src="/files/ftp_upload/56735/56735eq23.jpg" />, giving rise to Fano lineshape.
In summary, this protocol describes a method to determine the excitation and coupling rates between the light emitters and SPPs from 2D metallic periodic arrays. The rate is measured by angle- and polarization-resolved reflectivity and photoluminescence spectroscopy, both of which are frequency domain techniques. Compared with conventional time-resolved techniques, this method not only differentiates the excitation and decay processes of SPMF, which are not considered in most fluorescence enhancement studies, but also determines the coupling rates of light emitters to different SPP modes. As time-resolved techniques only measure the total lifetime of a light emitter and are unable to identify the contributions from different resonant modes, our method would certainly add value to this field especially when light emitters are being placed in a complex resonance system. For a periodic plasmonic system, <img alt="Equation 24" src="/files/ftp_upload/56735/56735eq24.jpg" /> mode has a well-defined decay direction whereas direct emission is assumed to be isotropic. Their differences in emission direction give rise to the mode identification. As directional emission is a universal behavior in nanomaterials, such differentiation can be easily extended to other resonant systems like metamaterials and photonic crystals. We anticipate this technique to be an enabling technology for studying fluorescence enhancement between light emitters and resonant cavities.

Surface plasmon mediated fluorescence (SPMF) has received considerable attention recently1,2,3,4,5,6. When light emitters are placed in close proximity to a plasmonic system, energy can be transferred between the emitters and surface plasmon polaritons (SPPs). In general, the strong plasmonic fields can strongly enhance the excitation of the emitters2. At the same time, the emission rate is also increased because of the large density-of-states created by SPPs, yielding the well-known Purcell effect3. These two processes work hand in hand in producing the SPMF. As SPMF has stimulated numerous applications in solid-state lighting1,4, energy harvesting5, and bio-detection6, it is currently under intensive investigation. In particular, the knowledge of the energy transfer rates from the SPPs to the emitters and vice versa, i.e., the excitation and coupling rates, is of great importance. However, the excitation and emission processes are usually entangled together, study on this aspect is still lacking. For example, most of the studies only determine the excitation efficiency ratio, which simply compares the emission with and without SPPs7. The exact measurement of the excitation rate is still missing. On the other hand, conventional time-resolved techniques such as fluorescence lifetime spectroscopy are routinely used for studying the dynamics of the emission process, but they are unable to separate the coupling rate from the total decay rate8. Here, we describe how one can determine them by combining the rate equation model and the temporal coupled mode theory9,10. Remarkably, we find that the excitation and coupling rates can be expressed in terms of measurable quantities, which can be accessed by performing angle- and polarization-resolved reflectivity and photoluminescence spectroscopy. We will first outline the formulation and then describe the instrumentation in detail. This approach is entirely frequency domain based and it does not require any time-resolved accessories such as ultra-fast lasers and time-correlated single-photon counters, which are expensive and sometimes difficult to implement8,11. We anticipate this technique to be an enabling technology for determining the excitation and coupling rates between light emitters and resonant cavities.
The SPMF in periodic systems is briefed here. For a periodic plasmonic system where Bloch-like SPPs can be generated, other than direct excitation and emission, which are characterized by the excitation efficiency&#160;&#951; and spontaneous emission rate &#915;r, the emitters can be excited by incoming SPPs and decay via outgoing SPPs. In other words, under resonance excitation, incoming SPPs are generated to create strong plasmonic fields that energize the emitters. Once the emitters are excited, energy from them can be transferred to outgoing SPPs, which subsequently radiatively dissipate to far-field, giving rise to enhanced emission. They define SPMF. For simple two-level emitters, the excitation refers to the increased transition of electrons from the ground to the excited states whereas the emission defines the decay of electrons back to the ground states, accompanied by photon emission at wavelengths defined by the energy difference between the excited and ground states. The excitation and emission conditions for the SPMF are required to fulfill the well-known phase matching equation to excite the incoming and outgoing SPPs9
<img alt="Equation 1" src="/files/ftp_upload/56735/56735eq1.jpg" /> (1)
where &#949;a and &#949;m are the dielectric constants of the dielectrics and the metal,&#160;&#952; and&#160;&#966; are the incident and azimuthal angles, P is the period of the array,&#160;&#955; is the excitation or emission wavelength, and m and n are the integers specifying the order of SPPs. For excitation, the in-plane wavevector of the laser beam will be Bragg scattered to momentum match with the incoming SPPs and the &#952; and&#160;&#966; together define the specified incident configuration for exciting the SPPs to enhance the electronic absorption at the excitation wavelength &#955;ex. Likewise, for the emission, the outgoing SPPs will be reversely Bragg scattered to match with the light line and the angles now represent the possible emission channels at the emission wavelength &#955;em. However, it is noted that as the emitters can couple their energy to vectorial propagating SPPs with <img alt="Equation 2" src="/files/ftp_upload/56735/56735eq2.jpg" /> that has the same magnitude <img alt="Equation 3" src="/files/ftp_upload/56735/56735eq3.jpg" /> but different directions, the SPPs can decay via various combination of (m,n) to far-field following Eq. (1).
By using the rate equation model and temporal coupled mode theory (CMT), we find that the excitation rate &#915;ex, i.e., the energy transfer rate from SPPs to emitters, can be expressed as9,12,13
<img alt="Equation 4" src="/files/ftp_upload/56735/56735eq4.jpg" /> (2)
where &#951; is the aforementioned direct excitation rate in the absence of the incoming SPPs, &#915;tot is the total decay rate of the incoming SPPs&#160;<img alt="Equation 5" src="/files/ftp_upload/56735/56735eq5.jpg" /> in which &#915;abs and &#915;rad are the Ohmic absorption and radiative decay rates of SPPs, and&#160;<img alt="Equation 6" src="/files/ftp_upload/56735/56735eq6.jpg" /> is the photoluminescence power ratio with and without the incoming SPPs. On the other hand, the coupling rate &#915;c, i.e., the energy transfer rate from emitters to SPPs, can be written as:
<img alt="Equation 7" src="/files/ftp_upload/56735/56735eq7.jpg" /> (3)
where &#915;r is the direct emission rate, <img alt="Equation 8" src="/files/ftp_upload/56735/56735eq8.jpg" /> is the photoluminescence power ratio between the &#945;th SPP mediated decay and direct ports, and &#915;rad&#945; and &#915;tot are the radiative decay rates for the &#945;th port and the total decay rates. We will see that while all the SPP decay rates can be measured by reflectivity spectroscopy, the emission power ratio can be determined by photoluminescence spectroscopy. Details of the formulations can be found in reference9,10.

<table border="0" cellpadding="0" cellspacing="0" style="width:817px;" width="818">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">SU-8</td>
			<td style="width:213px;">MicroChem</td>
			<td style="width:119px;">SU-8 2000.5</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Adhesion solution</td>
			<td style="width:213px;">MicroChem</td>
			<td style="width:119px;">Omnicoat</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;width:319px;">SU-8 Thinner (Gamma-Butyrolactone)</td>
			<td style="width:213px;">MicroChem</td>
			<td style="width:119px;">SU-8 2000 Thinner</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">SU-8 Developer</td>
			<td style="width:213px;">MicroChem</td>
			<td style="width:119px;">SU-8 Developer</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Spin Coater</td>
			<td style="width:213px;">Chemat Technology</td>
			<td style="width:119px;">KW-4A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">HeCd laser</td>
			<td style="width:213px;">KIMMON KOHA CO., LTd</td>
			<td style="width:119px;">IK3552R-G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Shutter</td>
			<td style="width:213px;">Thorlabs</td>
			<td style="width:119px;">SH05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Objective for sample preparation</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">U-13X</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Pinhole</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">PNH-50</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Iris</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">M-DI47.50</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Prism</td>
			<td style="width:213px;">Thorlabs</td>
			<td style="width:119px;">PS611</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Rotation stage for sample preparation</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">481-A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Supttering Deposition System</td>
			<td style="width:213px;">Homemade</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Rotation Stage 1</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">URM80ACC</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Rotation Stage 2</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">RV120PP</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Rotation Stage 3</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">SR50PP</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Detection arm</td>
			<td style="width:213px;">Homemade</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Quartz lamp</td>
			<td style="width:213px;">Newport</td>
			<td align="right" style="width:119px;">66884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Fiber Bundle</td>
			<td style="width:213px;">Newport</td>
			<td align="right" style="width:119px;">77578</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Objective for measurement</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">M-5X &#38; M-60X</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Polarizer &#38; Analyzer</td>
			<td style="width:213px;">Thorlabs</td>
			<td style="width:119px;">GT15</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Multimode Fiber</td>
			<td style="width:213px;">Thorlabs</td>
			<td style="width:119px;">BFL105LS02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Spectrometer</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">MS260i</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">CCD</td>
			<td style="width:213px;">Andor</td>
			<td style="width:119px;">DV420-OE</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">514nm Argon Ion Laser</td>
			<td style="width:213px;">Spectra-Physics</td>
			<td style="width:119px;">177-G01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">633nm HeNe Laser</td>
			<td style="width:213px;">Newport</td>
			<td style="width:119px;">R-32413</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">CdSeTe quantum dot</td>
			<td style="width:213px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">q21061mp</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Polyvinyl alcohol polymer (PVA)</td>
			<td style="width:213px;">SIGMA-ALDRICH</td>
			<td align="right" style="width:119px;">363073</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:319px;">Control program</td>
			<td style="width:213px;">National Instruments</td>
			<td style="width:119px;">LabVIEW</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of the excitation and coupling rates between light emitters and surface plasmon polaritons

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising from metallic periodic arrays without involving time-resolved techniques. We have formulated the rates by quantities that can be measured by simple optical measurements. The instrumentation based on angle- and polarization-resolved reflectivity and photoluminescence spectroscopy will be described in detail here. Our approach is intriguing due to its simplicity, which requires routine optics and several mechanical stages, and thus is highly affordable to most of the research laboratories.

An example of an Au periodic array is given in the inset of Figure 4a8. The plane view SEM image shows that the sample is a 2D square lattice circular hole array with a period of 510 nm, a hole depth of 280 nm, and a hole diameter of 140 nm. The p-polarized reflectivity mapping taken along the &#915;-X direction is shown in Figure 4a. The dash line is calculated by the phase matching equation Eq. (1) indicating that (m = -1, n = 0) SPPs are excited.
When the polarizer and analyzer are set at orthogonal positions, the corresponding reflectivity mapping is shown in Figure 4b. We see that the mapping is almost identical to the linear polarized mapping except the background now becomes zero as the non-resonant reflection is removed by the analyzer. In addition, the reflectivity profiles are changed from dips to peaks as only the SPP radiation damping remains after the removal of the background.
In fact, the dispersion relation is a good tool for studying SPMF. Assuming the laser excitation wavelength is 700 nm, incoming SPPs will be generated at a 19&#176; incident angle and they will interact with the emitters if their absorption band matches. On the other hand, SPP emission will be detected at a 23&#176; incident angle if the emission occurs at 730 nm. Therefore, the SPP resonances allow us to excite the incoming SPPs for excitation enhancement and to locate the outgoing SPPs for emission enhancement.
We spin coat CdSeTe quantum dots doped PVA polymer on the array10. Figure 5a &#38; 5b display the p-polarized and orthogonal reflectivity mapping taken along the along the &#915;-X direction, showing the (-1,0). Figure 5c &#38; 5d shows the corresponding photoluminescence incident and detection scan mappings taken at the detection and incident angles of 0&#176; and 0&#176;, respectively. The laser wavelength &#955;ex is 633 nm. In fact, consistent with the reflectivity mapping, we see that strong emission occurs at an incident angle of 18.5&#176; where the incoming (-1,0) SPPs are excited. On the other hand, from the detection scan, the strong resemblance between the reflectivity and the photoluminescence verifies that the emissions are enhanced when the outgoing SPPs are excited.
The determination of the excitation and coupling rates requires the SPP decay rates and photoluminescence power ratios10. To determine the decay rates at 633 nm along the &#915;-X direction, the p-polarized and orthogonal reflectivity spectra extracted from Figure 5a &#38; 5b are shown in Figure 6a. The p-polarized spectrum shows a Fano-like profile that can be described as <img alt="Equation 14" src="/files/ftp_upload/56735/56735eq14.jpg" />, where rp is the nonresonant reflectivity and &#969;SPP is the resonant photon energy, whereas the orthogonal counterpart follows <img alt="Equation 15" src="/files/ftp_upload/56735/56735eq15.jpg" />, exhibiting a Lorentzian lineshape12. They are then best fitted and the total and radiative decay rates, &#915;tot and &#915;rad, are 95.08 and 27.15 meV (with h).
On the other hand, the photoluminescence power ratio is obtained as follows. From the incident scan in Figure 5c, the emission profile at the emission wavelength &#955;em = 690 nm, where the direct emission locates, is extracted in Figure 6b. The power ratio <img alt="Equation 16" src="/files/ftp_upload/56735/56735eq16.jpg" />, which is defined as the direct emission with and without the incoming SPPs, simply is the intensity at 18.5&#176; divided by the flat background (6.896). <img alt="Equation 17" src="/files/ftp_upload/56735/56735eq17.jpg" /> is then determined to be 574.04 meV.
On the other hand, the coupling rate is emission wavelength dependent. The emission wavelength at 690 nm is chosen as an example. The total and radiative decay rates, &#915;tot and &#915;rad, are 60.06 and 17.12 meV (with h), respectively. The detection scan profile is extracted from Figure 5d and displayed in Figure 6c. The power ratio <img alt="Equation 18" src="/files/ftp_upload/56735/56735eq18.jpg" /> is defined as the (-1,0) SPP emission divided by the half-space direct emission assuming that the sample has no transmission. Since the detector covers a solid angle &#916;&#937;~ &#960;3/7202 sr, for a Lambertian surface, <img alt="Equation 19" src="/files/ftp_upload/56735/56735eq19.jpg" />, where b follows the background in Figure 6c as <img alt="Equation 20" src="/files/ftp_upload/56735/56735eq20.jpg" />. On the other hand, the <img alt="Equation 21" src="/files/ftp_upload/56735/56735eq21.jpg" /> is given as the peak profile divided by &#916;&#937;. As a result, <img alt="Equation 22" src="/files/ftp_upload/56735/56735eq22.jpg" /> is found to be 0.805.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56735/56735fig1.jpg" /> 
Figure 1. Schematic of interference lithography. A 325 nm laser light focused through a spatial filter and then is illuminated on a Lloyd&#39;s mirror interferometer where the sample is located. The standing wave forms along the sample surface for exposure. Inset: schematics of the top and side view of the sample completed in section 2. <a href="/files/ftp_upload/56735/56735fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56735/56735fig2.jpg" /> 
Figure 2. Polarization- and angle-resolved reflectivity spectroscopy. (a) Schematics of polarization- and angle-resolved reflectivity spectroscopy. Three rotation stages are used for constructing the goniometer. A multimode fiber coupled spectrometer and CCD detector is used for detection. A broadband white light source is used for reflectivity measurements. (b) Real-life image of the major part (black dash box in (a)) of the polarization- and angle-resolved reflectivity spectroscopy. <a href="/files/ftp_upload/56735/56735fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56735/56735fig3.jpg" /> 
Figure 3. Schematics of polarization- and angle-resolved photoluminescence spectroscopy. A 514 or 633 nm laser is used for photoluminescence. <a href="/files/ftp_upload/56735/56735fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56735/56735fig4.jpg" /> 
Figure 4. Reflectivity mappings and deduced decay rates. (a) The p-polarized reflectivity mapping of an Au array taken along the &#915;-X direction. The dash line is calculated by using the phase matching equation, showing (-1,0) SPPs are excited at different wavelengths. Inset: the plane-view SEM image of the array. (b) The corresponding orthogonal reflectivity mapping showing that the background is nulled and the reflectivity dips now become peaks. (c) The plot of &#915;tot and &#915;rad as a function of wavelength. The results are reproduced from reference9. <a href="/files/ftp_upload/56735/56735fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56735/56735fig5.jpg" /> 
Figure 5. The reflectivity, incident and detection scan mappings of an array coated with CdSeTe quantum dots taken along the &#915;-X direction. The (a) p-polarized and (b) orthogonal reflectivity mappings and the corresponding photoluminescence (c) incident and (d) detection scan mappings taken at detection and incident angle = 0&#176; and 0&#176;, respectively. The laser wavelength &#955;ex is 633 nm. The results are reproduced from reference10. <a href="/files/ftp_upload/56735/56735fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56735/56735fig6.jpg" /> 
Figure 6. Representative reflectivity, incident and detection scan profile. (a) The p-polarized and orthogonal reflectivity spectra together with the best fits for determining &#915;tot and &#915;rad at 633 nm. (b) The extracted (b) incident and (c) detection scan profiles. The results are reproduced from reference10. <a href="/files/ftp_upload/56735/56735fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons at JoVE.com

Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

This protocol describes the instrumentation for determining the excitation and coupling rates between light emitters and Bloch-like surface plasmon polaritons arising from periodic arrays.

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising ...

determination-excitation-coupling-rates-between-light-emitters

Nanyang Technological University

Research

JoVE Journal

Engineering

6.7K Views.  Sun Yat-sen University. This protocol describes the instrumentation for determining the excitation and coupling rates between light emitters and Bloch-like surface plasmon polaritons arising from periodic arrays. 

Video: Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on photoconduction, which has been one of the most commonly used techniques for terahertz generation 1-8. Terahertz generation in a photoconductive emitter is achieved by pumping an ultrafast photoconductor with a pulsed or heterodyned laser illumination. The induced photocurrent, which follows the envelope of the pump laser, is routed to a terahertz radiating antenna connected to the photoconductor contact electrodes to generate terahertz radiation. Although the quantum efficiency of a photoconductive emitter can theoretically reach 100%, the relatively long transport path lengths of photo-generated carriers to the contact electrodes of conventional photoconductors have severely limited their quantum efficiency. Additionally, the carrier screening effect and thermal breakdown strictly limit the maximum output power of conventional photoconductive terahertz sources. To address the quantum efficiency limitations of conventional photoconductive terahertz emitters, we have developed a new photoconductive emitter concept which incorporates a plasmonic contact electrode configuration to offer high quantum-efficiency and ultrafast operation simultaneously. By using nano-scale plasmonic contact electrodes, we significantly reduce the average photo-generated carrier transport path to photoconductor contact electrodes compared to conventional photoconductors 9. Our method also allows increasing photoconductor active area without a considerable increase in the capacitive loading to the antenna, boosting the maximum terahertz radiation power by preventing the carrier screening effect and thermal breakdown at high optical pump powers. By incorporating plasmonic contact electrodes, we demonstrate enhancing the optical-to-terahertz power conversion efficiency of a conventional photoconductive terahertz emitter by a factor of 50 10.

We describe methods for the design, fabrication, and experimental characterization of plasmonic photoconductive emitters, which offer two orders of magnitude higher terahertz power levels compared to conventional photoconductive emitters.

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Synchrotron X-ray Microdiffraction and Fluorescence Imaging of Mineral and Rock Samples

In this report, we describe a detailed procedure for acquiring and processing&#160;x-ray microfluorescence (&#956;XRF), and Laue and powder microdiffraction two-dimensional (2D) maps at beamline 12.3.2 of the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. Measurements can be performed on any sample that is less than 10 cm x 10 cm x 5 cm, with a flat exposed surface. The experimental geometry is calibrated using standard materials (elemental standards for XRF, and crystalline samples such as Si, quartz, or Al2O3 for diffraction). Samples are aligned to the focal point of the x-ray microbeam, and raster scans are performed, where each pixel of a map corresponds to one measurement, e.g., one XRF spectrum or one diffraction pattern. The data are then processed using the in-house developed software XMAS, which outputs text files, where each row corresponds to a pixel position. Representative data from moissanite and an olive snail shell are presented to demonstrate data quality, collection, and analysis strategies.

We describe a beamline setup meant to carry out rapid two-dimensional x-ray fluorescence and x-ray microdiffraction mapping of single crystal or powder samples using either Laue (polychromatic radiation) or powder (monochromatic radiation) diffraction. The resulting maps give information about strain, orientation, phase distribution, and plastic deformation.

In this report, we describe a detailed procedure for acquiring and processing&#160;x-ray microfluorescence (&#956;XRF), and Laue and powder ...

Scattering And Absorption of Light in Planetary Regoliths

Theoretical, numerical, and experimental methods are presented for multiple scattering of light in macroscopic discrete random media of densely-packed microscopic particles. The theoretical and numerical methods constitute a framework of Radiative Transfer with Reciprocal Transactions (R2T2). The R2T2 framework entails Monte Carlo order-of-scattering tracing of interactions in the frequency space, assuming that the fundamental scatterers and absorbers are wavelength-scale volume elements composed of large numbers of randomly distributed particles. The discrete random media are fully packed with the volume elements. For spherical and nonspherical particles, the interactions within the volume elements are computed exactly using the Superposition T-Matrix Method (STMM) and the Volume Integral Equation Method (VIEM), respectively. For both particle types, the interactions between different volume elements are computed exactly using the STMM. As the tracing takes place within the discrete random media, incoherent electromagnetic fields are utilized, that is, the coherent field of the volume elements is removed from the interactions. The experimental methods are based on acoustic levitation of the samples for non-contact, non-destructive scattering measurements. The levitation entails full ultrasonic control of the sample position and orientation, that is, six degrees of freedom. The light source is a laser-driven white-light source with a monochromator and polarizer. The detector is a mini-photomultiplier tube on a rotating wheel, equipped with polarizers. The R2T2 is validated using measurements for a mm-scale spherical sample of densely-packed spherical silica particles. After validation, the methods are applied to interpret astronomical observations for asteroid (4) Vesta and comet 67P/Churyumov-Gerasimenko (Figure 1) recently visited by the NASA Dawn mission and the ESA Rosetta mission, respectively.

Numerical and experimental methods are presented for multiple scattering of light in discrete random media of densely-packed particles. The methods are utilized to interpret the observations of asteroid (4) Vesta and comet 67P/Churyumov-Gerasimenko.

Theoretical, numerical, and experimental methods are presented for multiple scattering of light in macroscopic discrete random media of densely-packed ...

Accurate Determination of the Equilibrium Surface Tension Values with Area Perturbation Tests

We demonstrate two robust protocols for determining the equilibrium surface tension (EST) values with area perturbation tests. The EST values should be indirectly determined from the dynamic surface tension (DST) values when surface tension (ST) values are at steady-state and stable against perturbations. The emerging bubble method (EBM) and the spinning bubble method (SBM) were chosen, because, with these methods, it is simple to introduce area perturbations while continuing dynamic tension measurements. Abrupt expansion or compression of an air bubble was used as a source of area perturbation for the EBM. For the SBM, changes in the rotation frequency of the sample solution were used to produce area perturbations. A Triton X-100 aqueous solution of a fixed concentration above its critical micelle concentration (CMC) was used as a model surfactant solution. The determined EST value of the model air/water interface from the EBM was 31.5 &#177; 0.1 mN&#183;m-1 and that from the SBM was 30.8 &#177; 0.2 mN&#183;m-1. The two protocols described in the article provide robust criteria for establishing the EST values.

Two protocols for determining the equilibrium surface tension (EST) values using the emerging bubble method (EBM) and the spinning bubble method (SBM) are presented for a surfactant-containing aqueous phase against air.

We demonstrate two robust protocols for determining the equilibrium surface tension (EST) values with area perturbation tests. The EST values should be ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...