High-precision characterization of quantum-cascade laser frequency response using wavelength modulation spectroscopy.
Rev Sci Instrum
; 95(3)2024 Mar 01.
Article
in En
| MEDLINE
| ID: mdl-38535482
ABSTRACT
This paper investigates the impact of the quantum cascade laser's frequency modulation response on its tuning rate and tunability. We show a significant disparity in laser tuning rates and tunability between single and dual-frequency modulation schemes frequently used in typical direct absorption and wavelength modulation spectroscopy (WMS) techniques. We show that the DC-characterized tuning rate of a laser can be reduced significantly under a specific set of modulation frequencies of the laser injection current. We characterize these effects by simultaneous measurements of higher harmonic WMS of methane and nitrous oxide in the 7.8 µm spectral regions. We further show that WMS signal modulation broadening mechanisms and spectral structure, i.e., its zero-crossings and turning points, can be used to quantify such laser-modulation effects and validate laser frequency response under dual modulation schemes.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Rev Sci Instrum
Year:
2024
Document type:
Article
Affiliation country:
United States
Country of publication:
United States