Theoretical and Experimental Study of Heterodyne Phase-Sensitive Dispersion Spectroscopy with an Injection-Current-Modulated Quantum Cascade Laser

We report the theoretical and experimental study of calibration-free heterodyne phase-sensitive dispersion spectroscopy (HPSDS) in the mid-infrared using a direct current modulated mid-infrared quantum cascade laser (QCL). The modulation of QCL current at several hundred MHz or higher generates the synchronous frequency and intensity modulation of the QCL emission. An analytical model of the phase of the beat note signal in HPSDS is derived by considering the absorption and dispersion processes and incorporating the QCL modulation parameters. In the experiment, a 4.5 μm QCL modulated at 350 MHz was used to measure N2O at 200 Torr in a 10 cm gas cell. The N2O concentrations inferred from the analytical model were compared with the nominal values to show good agreement over the concentration range of 189−805 ppm with a standard deviation <3%. When the QCL wavelength was locked at the line-center of the molecular transition, it was of interest to find that the theoretical model was simplified to that used for near-infrared HPSDS with an electro-optical modulator for laser modulation.

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Frequency Control of a Mid-Infrared Quantum Cascade Laser Frequency Comb by Near-Infrared Light Injection and Intensity Modulation

10.1109/cleo/europe-eqec52157.2021.9542065 ◽

2021 ◽

Author(s):

K. Komagata ◽

A. Shehzad ◽

M. Hamrouni ◽

R. Matthey ◽

F. Kapsalidis ◽

...

Keyword(s):

Quantum Cascade Laser ◽

Near Infrared ◽

Frequency Comb ◽

Frequency Control ◽

Laser Frequency ◽

Intensity Modulation ◽

Infrared Light ◽

Near Infrared Light ◽

Mid Infrared ◽

Quantum Cascade

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Applications of Quantum Cascade Laser Spectroscopy in the Analysis of Pharmaceutical Formulations

Applied Spectroscopy ◽

10.1177/0003702816662609 ◽

2016 ◽

Vol 70 (9) ◽

pp. 1511-1519 ◽

Cited By ~ 8

Author(s):

Nataly J. Galán-Freyle ◽

Leonardo C. Pacheco-Londoño ◽

Andrés D. Román-Ospino ◽

Samuel P. Hernandez-Rivera

Keyword(s):

Infrared Spectroscopy ◽

Laser Spectroscopy ◽

Quantum Cascade Laser ◽

Near Infrared ◽

Limit Of Detection ◽

Active Pharmaceutical Ingredient ◽

Attenuated Total Reflection ◽

Analytical Sensitivity ◽

Mid Infrared ◽

Quantum Cascade

Quantum cascade laser spectroscopy was used to quantify active pharmaceutical ingredient content in a model formulation. The analyses were conducted in non-contact mode by mid-infrared diffuse reflectance. Measurements were carried out at a distance of 15 cm, covering the spectral range 1000–1600 cm−1. Calibrations were generated by applying multivariate analysis using partial least squares models. Among the figures of merit of the proposed methodology are the high analytical sensitivity equivalent to 0.05% active pharmaceutical ingredient in the formulation, high repeatability (2.7%), high reproducibility (5.4%), and low limit of detection (1%). The relatively high power of the quantum-cascade-laser-based spectroscopic system resulted in the design of detection and quantification methodologies for pharmaceutical applications with high accuracy and precision that are comparable to those of methodologies based on near-infrared spectroscopy, attenuated total reflection mid-infrared Fourier transform infrared spectroscopy, and Raman spectroscopy.

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