This work was supported in part by the Washington Space Grant Consortium under Award NNX10AK64H.

1.规划实验<ol><li>进行文献的调查，以评估之前完成的工作使用感兴趣的激光介质，这对于这个实验是CH 2 F 2。确定所有已知的激光辐射以及有关该行的所有信息，如波长和频率。可用13,31称为激光辐射的几个调查- 37。 </li><li>编译作为重点放在事先傅立叶激光介质的分子的所有光谱研究改造34和光声研究38,39。 </li></ol> 2.生成远红外激光辐射<ol><li>安全概述。 <ol><li>制定与CO 2和远红外激光系统工作时，包括适当护眼实验室标准作业程序。 </li></ol></li><li>校准和标定。 <ol><li>校准每个CO2 升使用ASER基于光栅的频谱分析仪，根据生产商的方案设计的二氧化碳激光器。 </li><li>对准末端反射镜和使用He-Ne激光，使得它们的辐射被聚焦在MIM二极管检测器耦合镜中的远红外线激光腔。 </li><li>直接从CO 2激光器泵入远红外激光腔通过一个氯化钠窗口辐射以约72○具有相对于所述腔轴线的角度。 </li><li>直接来自两个CO 2的参考激光器要么它们各自的低压力荧光基准单元或共线到使用波束分离器和附加反射镜的MIM二极管检测器的辐射。 </li></ol></li><li>检测远红外激光辐射。 <ol><li>使用标准的金属波兰语镍基每隔数天。 </li><li>压接一个25微米的钨丝成铜柱和弯曲线到configur通货膨胀如图 3所示。 </li><li>调整导线的长度，因此，它是被测量的辐射的10至20个波长之间。 </li><li>电化学通过施加电压（大约3.5至5伏）到该溶液中蚀刻该金属丝在饱和氢氧化钠（NaOH）溶液的尖端。 </li><li>再蚀刻具有低电压（小于1伏）的前端。这个变粗糙的电线的前端，并提高二极管的性能。 </li><li>冲洗导线用蒸馏水。 </li><li>将铜后进入MIM二极管的住房，一旦线是干的。 </li><li>放置电线与使用一个精细螺旋输送机和级系统的镍基极接触。触点产生跨越100至500Ω的二极管的电阻检测和测量的远红外激光辐射时通常使用。 </li></ol></li><li>代远红外激光辐射。 <ol><li>将CO 2泵浦激光器在一个特定的激光EM传输停滞， 例如 ，9 第36页 。 </li><li>旋转上的 CO 2泵激光器的千分表来回来实现对波束停止最大强度。 </li><li>调节CO 2的泵浦激光器的光栅的倾斜来实现对波束停止最大强度。 </li><li>重复步骤2.4.2和2.4.3，直到输出功率为CO 2泵浦激光器优化出现在梁停止。 </li><li>从CO 2泵浦激光的路径中删除束停止。 </li><li>打开并对准光断续进入的 CO 2泵激光器的光束路径。 </li><li>打开的CH 2 F 2气缸阀引入的远红外线激光介质进入远红外激光腔。 </li><li>调整的入口管线的计量阀，直到大约10帕达到的压力。 注意:只有近似压力是必要的，因为它被用作系统扫描所述远红外激光c进行方式avity。 </li><li>设置输出耦合器的位置，使得其最外端部是从激光腔的作为对激光谐振腔的外部指示的校准尺度的中间大约1厘米。 注意:只有近似位置是必要的，因为它被用作系统扫描的远红外线激光腔中的方法。 </li><li>通过旋转校准千分表来回调整可移动的远红外激光反射镜的约0.25毫米增量的位置。同时调通过其增益曲线的CO 2的泵浦激光器通过改变跨越CO 2的泵激光器的压电换能器（PZT）施加的电压的频率。 </li><li>如果没有信号在示波器显示器上观察到，重复步骤准则草案2.4.10与输出耦合器移动到其下一个位置，其中所述尖端是约1.5厘米，从激光谐振腔，作为对激光的外侧由在刻度盘的中间腔。 </li><li>如果没有信号在示波器显示器上观察到，重复步骤准则草案2.4.10与输出耦合器移动到其下一个位置，其中所述尖端是约2厘米的激光腔的作为对激光的外侧由在刻度盘的中间腔。 </li><li>如果没有信号在示波器显示器上观察到，重复步骤2.4.9至2.4.12具有大约19 Pa的远红外激光器压力与在入口线的计量阀调节。 </li><li>如果没有信号在示波器显示器上观察到，重复步骤2.4.9至2.4.12具有大约27 Pa的远红外激光器压力与在入口线的计量阀调节。 </li><li>如果没有信号在示波器显示器上观察到的，将波束停止入的 CO 2的泵浦激光器的路径和关闭阀门的CH 2 F 2气缸直到远红外激光器压力是约0帕。 </li><li>设置的 CO 2泵使用步骤2.4.2至2.4.4激光到下一个激光发射，例如，9个P 34，优化输出功率。 </li><li>重复步骤2.4.5至2.4.16直到通过CO 2泵激光器产生的所有排放被使用。当搜索远红外激光线，把重点放在CO 2泵浦激光器发射的频率与在步骤1.2确定任何吸收区域重叠。 </li></ol></li><li>表征远红外激光辐射。 <ol><li>同时调节远红外线激光介质的压力，施加到CO 2泵激光器的PZT的电压，而输出耦合器的位置，直到远红外线激光发射器的输出功率被最大化（由最大峰到确定从MIM二极管检测器的峰值信号作为观察示波器显示，类似上图4）。 </li><li>转动千分表顺时针直到远红外线激光发射上观察到示波器显示。记录千分表的位置。 </li><li>转动千分表顺时针为对应于相同的远红外线激光发射一个额外的20个模态。记录千分表的位置。 </li><li>减去步骤2.5.2和2.5.3的千分表的位置。除以10这种差异，得到远红外激光器发射的波长。 </li><li>重复步骤2.5.2至2.5.4一个总共五次并平均远红外线激光发射的波长。通过遍历至少20相邻的纵向模式测定平均激光波长为±0.5μm的1-Σ不确定性。 </li><li>测量的远红外激光辐射的极化，相对于CO 2的泵浦辐射，使用一个金线栅偏振器（394线/ cm）或一个布鲁斯特偏振器。 </li></ol></li></ol> 3.确定远红外激光频率<ol><li>认荷兰国际集团的CO 2激光参考排放。 <ol><li>计算是根据它测得的波长的远红外线激光发射的频率。 </li><li>识别组的 CO 2激光参考线，其频率差在几GHz计算出的频率为远红外线激光发射40。用于这种测量的一种典型的列表显示在表1中。 </li></ol></li><li>搜索外差拍信号。 <ol><li>识别所述第一组的 CO 2激光参考线，并设置在它们各自的激光发射每条CO 2基准激光。 </li><li>使用步骤2.4.2至2.4.4和显示器电源电表优化输出功率每个CO 2激光参考。 <ol><li>调整光圈，无论是内部或外部的各个基准激光，使得如通过在所示的监视器功率计测量从每个CO 2的参照用激光的功率大约为100毫瓦图2。 </li></ol></li><li>阻止使用波束停止，同时疏通从CO 2激光器参考辐射的CO 2泵浦激光器的辐射。 </li><li>打开并对准光断续进入的 CO 2激光器参考的共线光束路径。 </li><li>优化最大峰-峰电压上使用多个反射镜，分束器的MIM二极管检测器的每个的 CO 2参考激光发射，和2.54厘米焦距的ZnSe平凸透镜，同时观察示波器上的输出， 与图5类似。 </li><li>阻止使用波束停止，同时疏通从CO 2泵浦激光辐射的CO 2激光器参考辐射。 </li><li>重新优化的 CO 2泵激光器和远红外线激光，根据需要，从而使远红外线激光发射具有与观察到在示波器上的最大峰-峰电压。 </li><li>断开吨他MIM二极管检测器输出的示波器，并将其连接到放大器的输出频谱分析仪观察。 </li><li>不阻止从CO 2激光器参考辐射。 </li><li>卸下光盘菜刀调节二氧化碳泵和参考激光器。 </li><li>设置频谱分析仪上的40 MHz的范围内，并通过使用频谱分析仪的调节旋钮手动扫描这个频率范围内搜索的拍音信号在1.5GHz的增量。 </li><li>如果没有拍频信号被观测到，来自放大器断开MIM二极管的输出，并把它连接到示波器。 </li><li>方框从CO 2激光器参考辐射并重新插入光断续进入的 CO 2激光器泵的路径。 </li><li>重复步骤3.2.2至必要3.2.13直到频谱分析仪已被用于搜索0和12千兆赫之间的差拍信号。 </li><li>如果没有拍频信号被观测到，REPE在步骤3.2.2至3.2.14与另一组的CO 2的参考激光线直到该差拍信号被观察到或CO 2的参照用激光线的所有可能的组是耗尽。 </li></ol></li><li>稳定的CO 2的参考频率。 <ol><li>介于0和900V，施加电压到第一CO 2的参照用激光的PZT，使得从各自的荧光基准单元的信号是在中心处的羔羊浸， 在图6中示出并在观察示波器，如图7。 </li><li>激活使用定制的锁定/伺服放大器，以便它保持锁定到兰姆凹陷的中心施加到第一CO 2的参照用激光的PZT反馈电压。 </li><li>重复步骤3.3.1和3.3.2的第二CO 2激光参考。 </li><li>直观地监视前置放大器的示波器上的输出，如在图7中，连接到确定基准激光器保持锁定状态。 </li></ol></li><li>测量拍频。 <ol><li>居中的频谱分析仪显示器上的拍频信号，并调整其振幅最大化显示其大小。 </li><li>将频谱分析仪，以查看节拍信号的两个同时的痕迹， 如在图8中，通过选择清除写入特征为迹线1和线2的一个跟踪将显示瞬时信号，而另一个将记录的最大信号（使用在频谱分析仪第二一丝最大保持功能）。 </li><li>上旋转的远红外激光腔中的千分表来回增益曲线对于给定的腔模式。 </li><li>使用频谱分析仪上的视图功能得到对称的图案，一旦冻结第二（最大保持）跟踪。 </li><li>略微转动千分表顺时针降低远红外激光腔的长度。同时观察潜艇equent小移在频谱分析仪上拍频由于在远红外激光的频率这种轻微增加。 </li><li>发生在全宽标志的对称模式（最大保持迹​​线）的使用与频谱分析仪三角洲特征标记功能，半高点。 </li><li>测量使用的频谱分析仪的跨度对特征拍频信号的中心频率。 </li><li>重复步骤3.4.1至3.4.7。 </li><li>在脱离/伺服驱动器锁每个CO 2激光引用从它的中心频率解锁每个激光器，重新优化每个CO 2激光参考。 </li><li>使用步骤3.3.1至3.3.4重新锁定参考激光器。 </li><li>为总共6次测量重复步骤3.4.1至10年3月4日。一旦完成，解开其中心频率每个CO 2激光参考。 </li><li>使用这些节拍FRE计算的远红外线激光发射的订正频率quencies获得精确的预测的第二组的 CO 2参考激光线。 </li><li>识别一组不同的CO 2的参考激光线，其频率差在计算出的频率为远红外激光器发射的几GHz。 </li><li>优化的下一组上的MIM二极管检测器的 CO 2激光器的参考线，并使用步骤3.2.2通过在必要3.2.15获得拍频信号。 </li><li>使用步骤3.3.1至3.3.4锁定一套新的二氧化碳参考激光线。 </li><li>为总共6次测量重复步骤3.4.1至10年3月4日。一旦完成，解开其中心频率每个CO 2激光参考。 </li><li>插入光束停止进入的 CO 2泵和参考激光器的路径。 </li></ol></li><li>计算的远红外线激光的频率。 <ol><li>计算未知远红外激光频率，ν 区，使用所测量的是在通过关系频 FIR = |νCO 2（Ⅰ）-νCO 2（II）的 | ±|ν 拍 |式。 1 其中|νCO 2（Ⅰ）-νCO 2（II）的 |是差频由两个CO 2激光器的参考和综合的幅度|ν 拍 |是拍频的幅度。该±符号公式。 1，从步骤3.4.5实验确定。 </li><li>获得的平均频率，并计算不确定。 </li></ol></li></ol>

Certain commercial equipment is identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the authors, nor does it imply that the equipment identified is necessarily the best available for the purpose.

有迹象表明，需要一些额外的讨论中的协议中的几个关键步骤。当测量的远红外激光波长，如在步骤2.5.3概述的，它保证了远红外激光器发射的正在使用相同的模式是重要的。 （即TEM 00，TEM 01，等）可在激光腔中产生一个远红外激光波长的多种模式，从而以识别所使用的适当的相邻的腔模以测量波长13,29是很重要的， 41。以协助消除高阶模式，虹膜包括在每个激光腔内。当准确测量远红外线激光频率，当务之急是激光器，尤其是CO 2的参考激光器，工作在他们的基本（TEM 00）模式。虹膜也用来确保跟踪通过在频谱分析仪的远红外线激光是对称的图案。对于情况多远的地方由特定的 CO 2泵线生成-红外激光的波长，例如在9 P 04，一组吸收滤光片，校准波长的情况下，用于帮助区分远红外激光的波长。它们也可以被用来衰减任何散射的 CO 2激光辐射离开的远红外线激光腔。 第2.4节描述的远红外激光辐射的产生。过大量调查，我们已经发现，多个不同的波长可以由相同的 CO 2激光泵套在稍微不同而产生偏移频率。例如，9个P 04 的 CO 2泵激光器能够产生的289.5和724.9微米波长CH 2 F 2在一个泵的频率而被使用稍微不同的频率从9个P 04生成此调查期间所测量的其余波长CO 2泵浦激光器。这是accompl通过改变施加到该调谐的 CO 2泵激光器的频率通过其加宽增益曲线（约±45从它的中心频率MHz的在该实验）的PZT的电压ished。虽然没有在2.4节具体阐述，我们认为这是寻找远红外激光辐射一个值得注意的特点。 对于其中在相同的偏移频率相同的 CO 2泵激光线产生多个远红外激光辐射的情况下，激光谐振器干涉（或空腔扫描）可以被执行以辅助识别不同远红外激光辐射而产生。 图9示出的部分的典型的激光谐振器的干涉，与输出功率绘制为降低远红外激光腔长度42的功能- 45。 正如在3.4节，两套不同的 CO 2的概述参考激光器用于测量的远红外激光频率。这有助于消除对拍频是高于还是低于CO 2的参考激光之间产生的差频的不确定性。除了提供一种方法来独立地确认的远红外线激光频率，它与弱拍信号，其中观察拍频的轻微移作为远红外线激光频率的增加是很有挑战性的工作时特别有用。 所述MIM二极管检测器是必需成分，以本实验系统，由于其高的速度，灵敏度和宽光谱覆盖范围23,24。但是，也有一些限制的MIM型二极管检测器，包括机械不稳定，容易产生电磁干扰，重现性差，并且限制到最大功率它能够同时保持其灵敏度检测。同时测量远红外激光FRequencies，所述MIM二极管检测器的灵敏度，发现随着时间的推移迅速降低，如果从每个CO 2的参照用激光的功率超过150毫瓦。 超出MIM二极管检测器，主要限制本技术是远红外激光器4,31,46的稳定性。在实验系统的当前配置的一个限制是不能测量的 CO 2泵激光器的偏移频率。如所提到的，所述偏移频率被定义为所使用的CO 2的泵浦激光器以产生远红外激光发射和CO 2泵激光器的中心频率的频率之间的差。因而它代表的远红外线激光介质的吸收频率和CO 2泵激光器的中心频率之间的差。通常情况下，偏移频率是容易使用被无意中散射出O型的任何的 CO 2激光辐射测量f显示远红外激光腔。在我们的当前配置然而，极少的 CO 2激光辐射可用于这种测量。测量偏移频率的其他方法可以结合到该项目的未来迭代。这包括使用附加的分束器和反射镜以将泵辐射到MIM二极管检测器的一个部分上。分配分光转变到远红外激光发射25,34时的偏移频率的测量是有益的。 远红外激光频率也已通过外差两层光学泵浦远红外激光器和微波源上的MIM二极管检测器从而两个远红外激光器中的一个的频率是已知的，并用作参考频率47测量。使用其他技术，如用类似的discu太赫兹频率梳合成，能更加准确的使用远红外线的频率是可能的ssed的参考文献。 48-54。测量激光频率扩展的光泵浦分子激光器从太赫兹成像55赫兹应用中的作用，其作为太赫兹辐射的高分辨光谱13,20的源极，以及协助所述复谱与其激射相关的分析角色媒体19,34,37。

首先由HÖCKER执行的远红外激光频率的测量和同事在1967年他们测量的频率用于从直接放电氰化氢激光的311和337微米的排放量与微波信号的高次谐波将它们混合在硅二极管1。为了测量更高的频率，链激光器和谐波混频装置用于产生激光谐波2。最终2稳定化的二氧化碳（CO 2）激光器被选择，以合成所需的差频率3,4。今天，远红外线激光频率可达4太赫兹可以使用由两个产生的差频的只有第一谐波这种技术来测量稳定化的 CO 2参考激光器。更高频率的激光辐射也可以使用二次谐波测定，如由甲醇同位素异冠心病2 9 ​​赫兹激光排放OH和CH 3 </sUB&gt; 18 OH 5,6多年来，激光频率的精确测量已经影响了一些科学实验7,8和允许通过的电表由度量衡在巴黎大会一个新的定义， 1983年9 - 11 外差技术，如所描述的那些，已经在由光泵分子激光器产生的远红外激光频率测量也是很有好处的。由于光泵分子激光器由Chang和桥12的发现，千光泵远红外激光排放已产生与多种激光媒体。例如，二氟甲烷（CH 2 F 2）和其同位素产生超过250激光辐射时光学地由CO 2激光器泵浦。它们的波长范围是从大约95.6至1714.1微米13 - </s达&gt; 15近75％，这些激光排放有其频率测量，而一些已光谱分配16 - 18。 这些激光器，和它们的精确测量的频率，已经于高分辨率光谱的进步起到了至关重要的作用。它们提供的激光气体的红外光谱研究的重要信息。通常，这些激光频率被用来验证红外和远红外光谱的分析，因为它们提供的激发振动状态的水平，往往从吸 ​​收光谱19直接难以接近之间的连接。它们也可以作为初级辐射来源的研究调查过性，短命的自由基与激光磁共振技术20。有了这个极其敏感的技术，在顺磁性原子，分子转动和振转塞曼光谱和分子离子可以是Recorded而且随着调查用来创建这些自由基的反应率的能力进行分析。 在这项工作中，一个光泵浦分子激光， 如图 1所示，已被用来产生从二氟甲烷远红外激光辐射。这个系统包括一个连续波（CW） 的 CO 2激光器的泵和一个远红外激光腔。的反射镜内部的远红外激光腔重定向的 CO 2激光辐射向下抛光铜管，在经过26反射终止于所述腔的端部，散射任何剩余泵辐射之前。因此，远红外激光介质是使用横向泵送几何激发。产生激光的动作，若干变量被调节，同时一些，和所有随后的优化一次激光辐射是观察。 在该实验中，远红外激光辐射由金属INSU监视荡器 - 金属（MIM）点接触型二极管检测器。自1969年以来21所述的MIM二极管检测器已用于激光频率测量- 23在激光频率的测量，所述MIM二极管检测器之间的两个或更多个辐射源入射到二极管谐波混频器。所述MIM二极管探测器由一个削尖的钨丝接触经过光学研磨的镍基24。镍基体具有天然存在的薄氧化物层，其在绝缘层。 27以下最初在文献中记载的方法-一次激光发射检测，它的波长，偏振，强度和优化的操作压力，而其频率使用三激光外差技术25测定的记录。 4. 图2显示了光泵浦激光分子与具有独立的频率站两个附加连续波CO 2激光器参考bilization系统，利用在4.3微米的荧光信号的兰姆凹陷来自外部，低压参考单元28。这个手稿概述用于搜索远红外激光排放以及推定方法其波长和准确地确定它们的频率的过程。关于三激光外差技术细节以及各种部件和系统的运行参数可以在补充表A中一起引用4，25-27，29和30。

<table><tbody><tr><td>Vacuum pump</td><td>Leybold</td><td>Trivac D4A</td><td>HE-175 oil; Quantity = 3</td></tr><tr><td>Vacuum pump</td><td>Leybold</td><td>Trivac D8B or D16B</td><td>Fomblin Fluid; Quantity = 1 of each</td></tr><tr><td>Vacuum pump</td><td>Leybold</td><td>Trivac D25B</td><td>HE-175 oil; Quantity = 1</td></tr><tr><td>Optical chopper with controller</td><td>Stanford Research Systems</td><td>SR540</td><td></td></tr><tr><td>Lock-in amplifier</td><td>Stanford Research Systems</td><td>SR830</td><td></td></tr><tr><td>Spectrum analyzer</td><td>Agilent</td><td>E4407B</td><td>ESA-E Series, 9 kHz to 26.5 GHz Spectrum Analyzer</td></tr><tr><td>Amplifier&amp;nbsp;</td><td>Miteq</td><td>AFS-44</td><td>Provides amplification of signals between 2 and 18 GHz. The amplifier is powered by a Hewlett Packard triple output DC power supply, model E3630A.</td></tr><tr><td>Amplifier&amp;nbsp;</td><td>Avantek</td><td>AWL-1200B</td><td>Provides amplification of signals less than 1.2 GHz.</td></tr><tr><td>Power supply</td><td>Hewlett Packard</td><td>E3630A</td><td>Low voltage DC power supply for amplifier.</td></tr><tr><td>Power supply</td><td>Glassman</td><td>KL Series</td><td>High voltage power supply for the CO&lt;sub&gt;2&lt;/sub&gt; lasers; Quantity = 2; negative polarity</td></tr><tr><td>Power supply</td><td>Fluke</td><td>412B</td><td>High voltage power supply used with the NIST Asymmetric HV Amp</td></tr><tr><td>Detector</td><td>Judson Infrared Inc</td><td>J10D</td><td>For fluorescence cell; Quantity = 2</td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; laser spectrum analyzer</td><td>Optical Engineering&amp;nbsp;</td><td>16-A</td><td>Currently sold by Macken Instruments Inc.</td></tr><tr><td>Thermal imaging plates with UV light</td><td>Optical Engineering&amp;nbsp;</td><td></td><td>Primarily used for aligning the CO&lt;sub&gt;2&lt;/sub&gt; reference lasers. Currently sold by Macken Instruments Inc.</td></tr><tr><td>Resistors</td><td>Ohmite&amp;nbsp;</td><td>L225J100K</td><td>100 kW, 225 W. Between 4 to 6 resistors are used in each ballast system. Each CO&lt;sub&gt;2&lt;/sub&gt; laser has its own ballast system. Fans are used to cool the resistors.</td></tr><tr><td>HV relay, SPDT</td><td>CII Technologies</td><td>H-17</td><td>Quantity = 3; one for each CO&lt;sub&gt;2&lt;/sub&gt; laser</td></tr><tr><td>Amplifier&amp;nbsp;</td><td>Princeton Applied Research</td><td>PAR 113</td><td>Used with fluorescence cell; Quantity = 2</td></tr><tr><td>Oscilloscope</td><td>Tektronix</td><td>2235A</td><td>Similar models are also used; Quantity = 2</td></tr><tr><td>Oscilloscope/Differential amplifier</td><td>Tektronix</td><td>7903 oscilloscope with 7A22 differential amplifier</td><td></td></tr><tr><td>Power meter with sensor</td><td>Coherent</td><td>200</td><td>For use below 10 W.&amp;nbsp; This is the power meter shown in Figure 2.</td></tr><tr><td>Power meter with sensor</td><td>Scientech, Inc</td><td>Vector S310</td><td>For use below 30 W</td></tr><tr><td>Multimeter</td><td>Fluke</td><td>73III</td><td>Similar models are also used; Quantity = 3</td></tr><tr><td>Data acquisition</td><td>National Instruments</td><td>NI cDAQ 9174 chassis with NI 9223 input module</td><td>Uses LabVIEW software</td></tr><tr><td>Simichrome polish</td><td>Happich GmbH</td><td></td><td>Polish for the Nickel base used in the MIM diode detector. Although the Nickel base can be used immediately after polishing, a 12 hour lead time is typically recommended.</td></tr><tr><td>Pressure gauge</td><td>Wallace and Tiernan</td><td>61C-1D-0050</td><td>Series 300; for CO&lt;sub&gt;2&lt;/sub&gt; laser; Quantity = 3</td></tr><tr><td>Pressure gauge with controller</td><td>Granville Phillips</td><td>Series 375</td><td>For far-infrared laser</td></tr><tr><td>Zirconium Oxide felt</td><td>Zircar Zirconia</td><td>ZYF felt</td><td>Used as a beam stop</td></tr><tr><td>Zirconium Oxide board</td><td>Zircar Zirconia</td><td>ZYZ-3 board</td><td>Used as a beam stop; Quantity = 4</td></tr><tr><td>Teflon sheet</td><td>Scientific Commodities, Inc</td><td>BB96312-1248</td><td>1/32 inch thick; used for the far-infrared laser output window</td></tr><tr><td>Polypropylene</td><td>C-Line sheet protectors</td><td>61003</td><td>used for the far-infrared laser output window</td></tr><tr><td>Vacuum grease</td><td>Apiezon</td><td></td><td></td></tr><tr><td>Power supply</td><td>Kepco</td><td>NTC 2000</td><td>PZT power supply</td></tr><tr><td>PZT tube</td><td>Morgan Advanced Materials</td><td></td><td>1 inch length, 1 inch outer diameter, 0.062 inch thickness, reverse polarity (positive voltage on outside); Quantity = 3</td></tr><tr><td>ZnSe (AR coated)</td><td>II-VI Inc</td><td></td><td>CO&lt;sub&gt;2&lt;/sub&gt; laser window (Quantity = 3), lens, and beam splitter (Quantity 3)</td></tr><tr><td>NaCl window</td><td>Edmond Optics</td><td></td><td>Quantity = 1</td></tr><tr><td>CaF window</td><td>Edmond Optics</td><td></td><td>Quantity = 2</td></tr><tr><td>Laser mirrors and gratings</td><td>Hyperfine, Inc</td><td></td><td>Gold-coated; includes positioning mirrors</td></tr><tr><td>Glass laser tubes and reference cells</td><td>Allen Scientific Glass</td><td></td><td></td></tr><tr><td>MIM diode detector</td><td>Custom Microwave, Inc</td><td></td><td></td></tr><tr><td>Other</td><td></td><td></td><td>Other materials include magnetic bases, base plates, base clamps, XYZ translation stage, etc.</td></tr></tbody></table>

characterizing far-infrared laser emissions and the measurement of their frequencies

的产生和远红外线辐射的随后的测量发现在高分辨率光谱，射电天文学，和太赫兹成像众多应用。约45年，连贯，远红外辐射的产生使用光泵分子激光器已经完成。一旦远红外激光辐射被检测到，这些激光辐射的频率被用三激光外差技术测量。利用这种技术，该未知频率从光泵浦分子激光器是具有两个稳定的，红外线参考频率之间的差频混合。由独立的二氧化碳激光器生成这些基准频率，每个稳定来自外部，低压参考细胞使用荧光信号。的已知和未知的激光频率之间所产生的跳动是由一个金属 - 绝缘体 - 金属点接触二极管检测器，其输出上的规格观察监视特鲁姆分析仪。这些激光排放之间的拍频随后测量并结合已知的参考频率来推断未知远红外激光频率。与此技术测量的产生的一种-Σ分数不确定性对激光频率是在10 7±5份。准确确定远红外激光器发射的频率是非常关键的，因为它们经常被用来作为对其他测量值的参考，如在高采用激光磁共振自由基 - 分辨率光谱调查。作为该调查，二氟甲烷，CH 2 F 2的一部分，用作远红外线的激光介质。在所有八远红外激光的频率进行测定，第一次用频率范围从0.359至1.273的THz。这三个激光排放此调查期间被发现和报告与他们的最佳操作压力，偏振相对于CO 2的</suB&gt;泵浦激光器和力量。

如所提到的，报告了远红外激光器发射的频率是一个平均的至少12次测量与至少两个不同组的CO 2的参考激光线进行的。 表2概述当使用所记录的为235.5微米激光发射的数据9 P 04 CO 2泵浦激光器。对于这种远红外线激光发射，拍频的14个人测量记录。在使用9 R 10和 9个P 38 的 CO 2基准激光的排放量记录在第一组测量。对于步骤3.4.5，作为远红外线激光频率略有增加，也观察到拍频增加。这表示远红外线激光频率大于所述差频率的之间的大小的9 R 10和 9个P 38 的 CO 2激光器的参考，|νCO 2（Ⅰ）-νCO 2（Ⅱ）|。因此，符号Øf由于方程1的拍频为阳性这组的 CO 2参考激光器。相反，第二组测量中使用的9 R 16和 9个P 34 的 CO 2基准激光的排放。当步骤3.4.5进行，在拍频的降低，观察而远红外激光频率略有增加。这表示远红外线激光频率为小于9 R 16和 9个P 34 的 CO 2激光器的参考之间的差频的幅度。因此，对于这组的 CO 2激光器参考等式1中的拍频的符号是负的。如表 2所示，计算出的远红外激光频率，ν 的FIR，对于这两种情况保持不变，以内的±0.12兆赫1-Σ标准偏差。 与此实验技术测定的平均远红外激光频率中列出<s仲&gt;表3和顺序排列的CO 2的泵线。平均激光频率被报告了与它们相应的波长和波数，用1 -1 = 29 979.2458兆赫计算。所有的远红外激光的频率分别在最佳操作条件下测得的。贯穿本研究，几种以前报道的频率进行测定，被认为是在与已发表的值一致。所述一个-Σ分数不确定性，Δν，用这种技术测定的远红外激光频率是±5×10 - 7。这种不确定性是从已知的频率与该系统中，远红外激光器的加宽增益曲线的对称性和宽度，并测量4,25,31的精度再现而得。 此调查中发现的远红外激光辐射后出现的&#39;W＆强度＃8217;对应于范围在功率为0.001〜0.01毫瓦。为了比较，甲醇的118.8微米线，观察到本系统中使用9个P 36 的 CO 2泵具有18 W.另外一个功率时成为VVS具有功率略高于10毫瓦， 表3包括每个新的偏振远红外激光发射测量相对于其各自的 CO 2的泵浦激光器。在大多数情况下，只有一个极化观察主宰，要么一个偏振平行或垂直于所述的 CO 2泵激光器。对于没有观察到占主导地位的两极分化，其中的情况下，两个偏振已经上市。 总之，通过二氟甲烷使用具有横向泵送几何结构的光学泵浦分子激光系统生成8个远红外激光辐射。这包括具有235.5，335.9，和416.8微米波长的三个远红外激光器发射的发现。一旦检测到，三激光外差技术是用来测量频率为每一个观察到远红外激光发射。频率为这些激光辐射范围从0.359至1.273 THz和报告为±5份在10 7分数不确定性。 <img alt="图1" src="/files/ftp_upload/53399/53399fig1.jpg" /> 使用横向泵送几何图1 选自由二氧化碳泵激光器和远红外线激光腔的光泵分子激光系统的示意图。该远红外激光介质是兴奋。转载自编号小的修改。 15与施普林格科学与商业媒体许可。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53399/53399fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 三激光差频率测量系统的 图2 示意图。该外差系统包括光泵分子激光器利用横向泵送几何和两个附加二氧化碳参考激光器。未示出的是用于监测和稳定由每个激光器产生的辐射的电子系统。 ©[2015年] IEEE。转载，稍作修改和批准，从参考文献。 27. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53399/53399fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/53399/53399fig3.jpg" /> 图3. 在通过放大透镜观察的MIM点接触二极管检测器中使用的钨丝的导线的长度约为2毫米。对于最好的弹簧作用，在弯曲角度应该接近90°并且所有处于同一平面上。 <img alt="图4" src="/files/ftp_upload/53399/53399fig4.jpg" /> 图4. 由光泵CH 2的274.8微米激光发射F 2使用作为观察的示波器显示器上的9个P 04 的 CO 2泵激光器产生的波形的 CO 2的泵辐射由光学斩波器在约45操作调制赫兹。所述MIM二极管检测器的电阻约为100和信号约为6μV（峰 - 峰值）。示波器显示屏设置在10μV/分度。 <img alt="图5" src="/files/ftp_upload/53399/53399fig5.jpg" /> 图 5. 左和中间的照片显示从每个CO 2基准激光输出，9 R 16和 9个P 34，分别的各个调制的示波器信号约为4毫伏的功率（峰-峰值）为约100毫瓦，如通过测定显示器功率计。右侧照片显示了来自两个参考激光器组合信号为大约7毫伏（峰 - 峰），指示两个参考信号适当混合上的MIM二极管检测器。所述MIM二极管检测器的电阻约为100Ω。在每张照片的示波器显示屏设置在1 mV /分。 CO 2的辐射是由光斩波器在约70赫兹操作调制。 <img alt="图6" src="/files/ftp_upload/53399/53399fig6.jpg" /> 图6. 在低压饱和荧光信号（6帕） 的 CO 2，同时用9 R 24 CO 2的激光发射。该图是由通过外部斩波在52赫兹调制的 CO 2参考激光发射而施加到CO 2基准激光的PZT的电压从0升至大约570 V在约13分钟获得的。锁相放大器设置为300毫秒的时间常数和200mV的灵敏度。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53399/53399fig6large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图7" src="/files/ftp_upload/53399/53399fig7.jpg" /> 图 7. 低压饱和荧光信号（6帕） 的二氧化碳，同时使用作为观察示波器上的9 R 24 CO 2激光发射，左边的照片显示，示波器显示，当PZT电压距离的中心兰姆凹陷，在日大约80 V.是照片。中间和右边的照片显示在示波器显示屏时，PZT电压要么是立即向兰姆凹陷中心的左边或右边，大约278并在这些照片分别为295诉<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53399/53399fig7large.jpg" target="_blank">请点击此处查看该图的放大版本。 。</a> <img alt="图8" src="/files/ftp_upload/53399/53399fig8.jpg" /> 图8. 光泵CH 2的235.5微米的激光发射F 2使用9 P 04 CO 2泵浦激光器和9 R 16和 9个P 34 CO 2激光器参考之间的拍频信号。大约25 MHz的跨度是典型的使用。多数差拍信号都在±5千兆赫观察。但是，也有在这些查找参数具有低信号 - 一定频率区域噪声。因此，使用一个稍大搜索区域有时是有益的。 <img alt="图9" src="/files/ftp_upload/53399/53399fig9.jpg" /> 图9. 部分的典型激光谐振器干涉（或空腔扫描）由一组相对应的谐振器的方式离散峰的，由在没有激光发生区域隔开。该扫描显示了通过光学泵浦CH产生的511.445微米激光发射使用2 F 2的9 R 28 CO 2的泵。在千分尺的位置的减小对应于远红外激光腔中的长度（镜至反射镜分离）的降低。所述MIM二极管检测由该远红外线激光发射所产生的20μV峰 - 峰最大信号。来自检测器的输出使用锁定放大器被记录，在一个300毫秒的时间常数设置和20μVsensitivitY，接口到计算机。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53399/53399fig9large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="表格1" src="/files/ftp_upload/53399/53399table1.jpg" /> 表1:CO 2激光器参考其差值频率接近的计算频率为235.5微米的激光发射的光泵CH 2 F 2集时使用9 P 04 CO 2激光器的发射激发。 <img alt="表2" src="/files/ftp_upload/53399/53399table2.jpg" /> 表2:测量拍频为235.5微米的激光发射的光泵CH 2 F 2时，使用9个P 04 CO 2激光器的发射激发。两组CO 2的参考激光器使用d，来产生所述已知频率差（|νCO 2（Ⅰ）-νCO 2（II）|）。 <img alt="表3" src="/files/ftp_upload/53399/53399table3.jpg" /> 表3:从光学泵浦CH 2 F 2新远红外激光频率。 <img alt="表4" src="/files/ftp_upload/53399/53399table4.jpg" /> 补充表答:实验系统的技术细节，包括一些相关的商业组件。

Watch this Scientific Journal Video about Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies at JoVE.com

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies

We describe the generation of far-infrared radiation using an optically pumped molecular laser along with the measurement of their frequencies with heterodyne techniques. The experimental system and techniques are demonstrated using difluoromethane (CH2F2) as the laser medium whose results include three new laser emissions and eight measured laser frequencies.

表征远红外激光辐射及其频率的测量

The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and ...

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Nanyang Technological University

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Electronic Structure of Atoms

SCIENTISTS IN ACTION

12.0K 次观看.  Central Washington University. We describe the generation of far-infrared radiation using an optically pumped molecular laser along with the measurement of their frequencies with heterodyne techniques. The experimental system and techniques are demonstrated using difluoromethane (CH2F2) as the laser medium whose results include three new laser emissions and eight measured laser frequencies.

视频: Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies

Implementation of a Reference Interferometer for Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system&#8217;s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events.

A reference interferometer technique, which is designed to remove undesirable laser jitter noise for nanodetection, is utilized for probing an ultra-high quality factor microcavity. Instructions for assembly, setup, and data acquisition are provided, alongside the measurement process for specifying the cavity quality factor.

一个参考干涉仪的Nanodetection实施

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing ...

科研

工程学

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

外腔半导体激光器的原子物理的构建与鉴定

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With ~102-103 repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as ~10-4, sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 &#181;g, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent.

Key steps of protein function, in particular backbone conformational changes and proton transfer reactions, often take place in the microsecond to millisecond time scale. These dynamical processes can be studied by time-resolved step-scan Fourier-transform infrared spectroscopy, in particular for proteins whose function is triggered by light.

质子转移和蛋白质构象动力学的光敏蛋白的时间分辨步进扫描傅立叶变换红外光谱

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高分辨率声子辅助准共振荧光光谱仪

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

激光驱动的超快分子旋转直接成像

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

化学

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the wavelength of the strong-field ionizing pump pulse from the commonly used 800 nm into the near-infrared (1200-1600 nm), the contribution of adiabatic electron tunneling to the ionization process increases relative to multiphoton absorption. Adiabatic ionization results in predominant population of the ground electronic state of the ion upon electron removal, which effectively prepares a coherent vibrational state (&#34;wave packet&#34;) amenable to subsequent excitation. In our experiments, the coherent vibrational dynamics are probed with a weak-field 800 nm pulse and the time-dependent yields of dissociation products measured in a time-of-flight mass spectrometer. We present the measurements on the molecule dimethyl methylphosphonate (DMMP) to illustrate how using 1500 nm pulses for excitation enhances the amplitude of coherent oscillations in ion yields by a factor of 10 as compared to 800 nm pulses. This protocol may be implemented in existing pump-probe setups through the incorporation of an optical parametric amplifier (OPA) for wavelength conversion.

We present a protocol for probing ultrafast vibrational coherences in polyatomic radical cations that result in molecular dissociation.

强场绝热电离多原子自由基阳离子超快振动相干的测量

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the ...

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species in the ppm-to-single-percent range. The main purpose of the method is the spatially resolved detection of low-concentration species, which have no transitions in the visible or near-IR spectral range that could be used for detection. IR-DFWM is a nonintrusive method, which is a great advantage in combustion research, as inserting a probe into a flame can change it drastically. The IR-DFWM is combined with upconversion detection. This detection scheme uses sum-frequency generation to move the IR-DFWM signal from the mid-IR to the near-IR region, to take advantage of the superior noise characteristics of silicon-based detectors. This process also rejects most of the thermal background radiation. The focus of the protocol presented here is on the proper alignment of the IR-DFWM optics and on how to align an intracavity upconversion detection system.

Here, we present a protocol to perform sensitive, spatially resolved gas spectroscopy in the mid-infrared region, using degenerate four-wave mixing combined with upconversion detection.

用于定量气体传感的红外退化四波融合与上转换检测

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species ...

Label-free Single Molecule Detection Using Microtoroid Optical Resonators

Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental studies on the behavior of molecules. Single molecule detection techniques commonly utilize labels such as fluorescent tags or quantum dots, however, labels are not always available, increase cost and complexity, and can perturb the events being studied. Optical resonators have emerged as a promising means to detect single molecules without the use of labels. Currently the smallest particle detected by a non-plasmonically-enhanced bare optical resonator system in solution is a 25 nm polystyrene sphere1. We have developed a technique known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that can surpass this limit and achieve label-free single molecule detection in aqueous solution2. As signal strength scales with particle volume, our work represents a &#62; 100x improvement in the signal to noise ratio (SNR) over the current state of the art. Here the procedures behind FLOWER are presented in an effort to increase its usage in the field.

We have developed a label-free biosensing system based on optical resonator technology known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that is capable of detecting single molecules in solution. Here the procedures behind this work are described and presented.

无标记单分子检测使用微型环光学谐振器

Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental ...

生物工程

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional &#960;-conjugate Systems

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near infrared (near-IR) transitions, because it can overcome the low sensitivity of spontaneous Raman spectrometers in the near-IR region. Here, we describe technical details of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer that we have recently developed. A description of signal generation and optimization, measurement, data acquisition, and calibration and correction of recorded data is provided as well. We present an application of our spectrometer to analyze the excited-state dynamics of &#946;-carotene in toluene solution. A C=C stretch band of &#946;-carotene in the second lowest excited singlet (S2) state and the lowest excited singlet (S1) state is clearly observed in the recorded time-resolved stimulated Raman spectra. The femtosecond time-resolved near-IR stimulated Raman spectrometer is applicable to the structural dynamics of &#960;-conjugate systems from simple molecules to complex materials.

Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of &#946;-carotene in toluene is shown as a representative application.

超快时间解析近红外刺激拉曼测量功能 +偶联系统

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near ...

High-definition Fourier Transform Infrared (FT-IR) Spectroscopic Imaging of Human Tissue Sections towards Improving Pathology

High-definition Fourier Transform Infrared (FT-IR) spectroscopic imaging is an emerging approach to obtain detailed images that have associated biochemical information. FT-IR imaging of tissue is based on the principle that different regions of the mid-infrared are absorbed by different chemical bonds (e.g., C=O, C-H, N-H) within cells or tissue that can then be related to the presence and composition of biomolecules (e.g., lipids, DNA, glycogen, protein, collagen). In an FT-IR image, every pixel within the image comprises an entire Infrared (IR) spectrum that can give information on the biochemical status of the cells that can then be exploited for cell-type or disease-type classification. In this paper, we show: how to obtain IR images from human tissues using an FT-IR system, how to modify existing instrumentation to allow for high-definition imaging capabilities, and how to visualize FT-IR images. We then present some applications of FT-IR for pathology using the liver and kidney as examples. FT-IR imaging holds exciting applications in providing a novel route to obtain biochemical information from cells and tissue in an entirely label-free non-perturbing route towards giving new insight into biomolecular changes as part of disease processes. Additionally, this biochemical information can potentially allow for objective and automated analysis of certain aspects of disease diagnosis.

High-definition Fourier Transform Infrared FT-IR Spectroscopic Imaging of Human Tissue Sections towards Improving Pathology

Fourier Transform Infrared (FT-IR) spectroscopic imaging is a fast and label-free approach to obtain biochemical data sets of cells and tissues. Here, we demonstrate how to obtain high-definition FT-IR images of tissue sections towards improving disease diagnosis.