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Optimization of Mid-Infrared Passive and Active Devices that Enhance Mid-Infrared Quantum Cascade Laser-Based Gas Spectroscopy.

机译：优化了增强中红外量子级联激光光谱的中红外无源和有源器件。

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摘要

Gas sensors have now become a part of our everyday routine. Particularly, the development of gas sensors for security, environmental and health applications has gained momentum in recent years. In most applications, gas sensors that are highly sensitive, highly selective, portable, robust, allow real-time data analysis and room temperature operation are desired. This dissertation explores the development of novel passive and active optical devices that are important in enhancing Quantum Cascade (QC) laser-based mid-infrared (mid-IR) gas spectroscopy. The thesis covers four major projects.;In the first part, a technique is developed for the fabrication and characterization of mesas with similar optical and electrical properties as QC lasers. The technique presented is quick and minimally invasive. More importantly, relevant intersubband QC laser information such as the peak emission wavelength and its full width at half maximum (FWHM), turn-on voltage and maximum operating current density, can be quickly verified. Characterization results of the mesas when compared with results from QC lasers made from the same wafer differ by less than 10%.;In the second part, the development and characterization of III-V semiconductor subwavelength resonant grating (SRG) structures are presented. Relative transmittance resonant depths up to 79% and a FWHM of 49 nm were achieved at 0°. In the reflection measurements, a relative reflectance of 76% and FWHM of 41.8 nm were reported at 20°. This is the first work on III-V semiconductor-based mid-IR SRGs. When coupled with a QC laser, single mode operation, a necessity in high resolution QC laser-based gas sensors for selectivity and specificity of wavelengths, can be achieved.;The third part is a presentation of the design, fabrication and characterization of a special kind of room temperature quantum well infrared photodetector (QWIP) which acts as both a passive optical element (beamsplitter) and a mid-IR detector. A 4.6 mum light incident on this QWIP is partially reflected, partially absorbed and the rest transmitted through it. Reflection, photocurrent and transmission signals simultaneously measured are presented. In a mid-IR gas sensor, these three signals are useful for different purposes: a main signal that interacts with the target gas; a reference signal; and a signal for laser source stabilization.;In the final project, the development and results of two successful deployments of a QC laser open path gas sensor (QCLOPS) to Ghana are presented. The main target gases are benzyl alcohol and 2-methylphenol (gases present in wood smoke used in fish smoking) and water vapor. Water vapor concentrations from QCLOPS when compared to results from a commercial humidity sensor show very close agreement. The wood smoke measurements reported are very spectrally complex. Possible techniques for resolving the combined spectrum into its individual component spectra and lessons learnt in using QCLOPS in resource constrained and harsh climatic conditions are discussed.
机译：气体传感器现已成为我们日常工作的一部分。特别是，近年来，用于安全，环境和健康应用的气体传感器的发展势头强劲。在大多数应用中，需要高度灵敏，高度选择性，便携式，坚固，能够进行实时数据分析和室温操作的气体传感器。本文探讨了新型无源和有源光学器件的开发，这些器件对增强基于量子级联（QC）激光的中红外（mid-IR）气相光谱学至关重要。论文涵盖了四个主要项目：第一部分，开发了一种制造和表征具有与QC激光器类似的光学和电学性质的台面的技术。提出的技术是快速且微创的。更重要的是，可以快速验证相关的子带间QC激光信息，例如峰值发射波长及其半峰全宽（FWHM），开启电压和最大工作电流密度。与同一晶片制成的QC激光器相比，台面的表征结果相差不到10％。第二部分介绍了III-V半导体亚波长谐振光栅（SRG）结构的发展和表征。相对透射率共振深度在0°时达到79％，FWHM为49 nm。在反射测量中，在20°下的相对反射率为76％，FWHM为41.8 nm。这是基于III-V半导体的中红外SRG的第一项工作。当与QC激光器结合使用时，可以实现单模操作，这是基于高分辨率QC激光器的气体传感器对波长的选择性和特异性的必要性。第三部分介绍了特殊器件的设计，制造和特性一种室温量子阱红外光电探测器（QWIP），既用作无源光学元件（分束器），又用作中红外探测器。入射在此QWIP上的4.6毫米光被部分反射，部分吸收，其余的则通过它透射。介绍了同时测量的反射，光电流和透射信号。在中红外气体传感器中，这三个信号可用于不同目的：与目标气体相互作用的主信号；参考信号；在最后一个项目中，将介绍两次向加纳成功部署QC激光开放路径气体传感器（QCLOPS）的开发和结果。主要目标气体是苯甲醇和2-甲基苯酚（用于鱼熏的木烟中存在的气体）和水蒸气。与商用湿度传感器的结果相比，QCLOPS的水蒸气浓度显示出非常接近的一致性。报告的木烟测量在光谱上非常复杂。讨论了将组合光谱分解为单个光谱的可能技术，并讨论了在资源受限和恶劣气候条件下使用QCLOPS的经验教训。

著录项

  • 作者

    Bentil, Ekua Nuama.;

  • 作者单位

    Princeton University.;

  • 授予单位 Princeton University.;
  • 学科 Engineering Electronics and Electrical.;Physics Optics.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 211 p.
  • 总页数 211
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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