Polarimetric  infrared spectroscopic imaging using quantum cascade lasers

Phal, Yamuna; Yeh, Kevin; Bhargava, Rohit

doi:10.1117/12.2544392

Cited by 7 publications

(8 citation statements)

References 37 publications

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“…Spectral analyses in a variety of applications have been conducted with the simplest and most prevalent configuration of an IR source and detector, a common motif in spectral recording . Much recent effort has been focused on adding greater molecular information − and speed, , while the image quality is commonly accepted to be optimized by following optical design rules from theoretical models. The emergence of quantum cascade lasers (QCL) is also challenging the conventional performance of IR imaging by offering possibilities for recording and analyses to optimize instrument capability that go beyond Fourier transform IR imaging systems. , The speed and signal-to-noise ratio (SNR) trade-offs in emerging systems are enabling us to ask more fundamental questions on how data quality, optical configuration, and spectral processing may act in concert to maximize information from chemical imaging.…”

Section: Introductionmentioning

confidence: 99%

Resolution Limit in Infrared Chemical Imaging

et al. 2022

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Chemical imaging combines the spatial specificity of optical microscopy with the spectral selectivity of vibrational spectroscopy. Mid-infrared (IR) absorption imaging instruments are now able to capture high-quality spectra with microscopic spatial detail, but the limits of their ability to resolve spatial and spectral objects remain less understood. In particular, the sensitivity of measurements to chemical and spatial changes and rules for optical design have been presented, but the influence of spectral information on spatial sensitivity is as yet relatively unexplored. We report an information theory-based approach to quantify the spatial localization capability of spectral data in chemical imaging. We explicitly consider the joint effects of the signal-to-noise ratio and spectral separation that have significance in experimental settings to derive resolution limits in IR spectroscopic imaging.

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Section: Introductionmentioning

confidence: 99%

Resolution Limit in Infrared Chemical Imaging

et al. 2022

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“…Most of these can be met or outran with FT-IR imaging. A specimen of biological origin adds a level of difficulty to this approach, and among all FT-IR studies determining molecular orientation, only a few were focused on biological samples, especially tissues. − Although the most recent study used Stokes vector and a quantum cascade laser microscope to investigate fiber orientation in breast tissue surgical section, that approach does not offer insights into vibrational mode orientation. This is especially challenging because a biological specimen contains a multitude of different molecules and deciphering contributions from each is a daunting task.…”

Section: Introductionmentioning

confidence: 99%

Macromolecular Orientation in Biological Tissues Using a Four-Polarization Method in FT-IR Imaging

et al. 2020

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Fourier transform infrared spectroscopy has emerged as a powerful tool for tissue specimen investigation. Its nondestructive and label-free character enables direct determination of biochemical composition of samples. Furthermore, the introduction of polarization enriches this technique by the possibility of molecular orientation study apart from purely quantitative analysis. Most of the molecular orientation studies focused on polymer samples with a well-defined molecular axis. Here, a four-polarization approach for Herman’s in-plane orientation function and azimuthal angle determination was applied to a human tissue sample investigation for the first time. Attention was focused on fibrous tissues rich in collagen because of their cylindrical shape and established amide bond vibrations. Despite the fact that the tissue specimen contains a variety of molecules, the presented results of molecular ordering and orientation agree with the theoretical prediction based on sample composition and vibration directions.

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“…Unlike thermal emitters such as globars, QCL sources are intrinsically polarized and are coupled with high intensity illumination, making them an effective candidate for spectroscopic polarimetry 173,174 and vibrational circular dichroism 175 applications with high S/N and high spatial localization measurements. Hence, another performance merit for lasers, specifically for polarization imaging, is the degree of polarization of the output beam.…”

Section: Infrared Sourcementioning

confidence: 99%

Design Considerations for Discrete Frequency Infrared Microscopy Systems

2021

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Discrete frequency infrared (DFIR) chemical imaging is transforming the practice of microspectroscopy by enabling a diversity of instrumentation and new measurement capabilities. While a variety of hardware implementations have been realized, considerations in the design of all-IR microscopes have not yet been compiled. Here we describe the evolution of IR microscopes, provide rationales for design choices, and the major considerations for each optical component that together comprise an imaging system. We analyze design choices in illustrative examples that use these components to optimize performance, under their particular constraints. We then summarize a framework to assess the factors that determine an instrumentâs performance mathematically. Finally, we summarize the design and analysis approach by enumerating performance figures of merit for spectroscopic imaging data that can be used to evaluate the capabilities of imaging systems or suitability for specific intended applications. Together, the presented concepts and examples should aid in understanding available instrument configurations, while guiding innovations in design of the next generation of IR chemical imaging spectrometers.

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Polarimetric infrared spectroscopic imaging using quantum cascade lasers

Cited by 7 publications

References 37 publications

Resolution Limit in Infrared Chemical Imaging

Resolution Limit in Infrared Chemical Imaging

Macromolecular Orientation in Biological Tissues Using a Four-Polarization Method in FT-IR Imaging

Design Considerations for Discrete Frequency Infrared Microscopy Systems

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