Current and frequency modulation characteristics for continuous-wave quantum cascade lasers at 9.06 μm.

Area of Science:

• Optics and Photonics
• Laser Physics
• Spectroscopy

Background:

• Quantum cascade lasers (QCLs) are semiconductor lasers emitting in the mid-infrared.
• Frequency modulation (FM) is a technique used to encode information onto a carrier wave.
• Understanding current-induced FM in QCLs is crucial for developing advanced spectroscopic applications.

Purpose of the Study:

• To investigate the characteristics of current-induced frequency modulation (FM) in continuous-wave quantum cascade lasers (QCLs) at 9.06 μm.
• To measure the frequency tuning rate and phase shift between intensity modulation and FM.
• To validate the findings with a numerical model for ambient water vapor detection.

Main Methods:

• Utilized two continuous-wave quantum cascade lasers (QCLs) operating at 9.06 μm.
• Measured frequency tuning rate and phase shift across modulation frequencies from 10 Hz to 200 kHz.
• Employed wavelength modulation spectroscopy for ambient water vapor detection.

Main Results:

• The frequency tuning rate of the QCLs was found to be dependent on both modulation frequency and amplitude.
• Phase shift between intensity modulation and FM was characterized.
• Successful detection of ambient water vapor using the tested QCL was achieved.

Conclusions:

• Current-induced FM in QCLs exhibits complex behavior influenced by modulation parameters.
• The characterized FM properties are suitable for spectroscopic applications like gas sensing.
• The study validates the use of QCLs for precise environmental monitoring.