Experimental method based on wavelength-modulation spectroscopy for the characterization of semiconductor lasers...

Area of Science:

• Optics and Photonics
• Spectroscopy
• Laser Physics

Background:

• Laser diodes exhibit combined intensity and frequency modulation when their injection current is modulated.
• Characterizing these modulations is crucial for applications relying on precise laser control.
• Wavelength-modulation spectroscopy (WMS) is a sensitive technique for gas analysis.

Purpose of the Study:

• To present an experimental method for characterizing combined intensity and frequency modulation in laser diodes.
• To develop methods for determining laser frequency deviation and the phase shift between intensity and frequency modulation.
• To validate the proposed methods experimentally.

Main Methods:

• Utilizing wavelength-modulation spectroscopy (WMS) with a modulated laser diode probing a gas absorption line.
• Analyzing harmonic signals generated during the WMS process.
• Developing a theoretical model to extract modulation parameters from harmonic signals.
• Experimental validation using a 2-microm distributed-feedback laser and a CO2 absorption line.

Main Results:

• Successful characterization of combined intensity and frequency modulation in a laser diode.
• Determination of laser frequency deviation and the phase shift between intensity and frequency modulation.
• Experimental results show full agreement with a traditional method in the 400 Hz-30 kHz range.

Conclusions:

• The presented experimental method provides an effective means to characterize laser diode modulation parameters.
• The developed techniques accurately determine frequency deviation and phase shifts.
• This method offers a reliable approach for laser characterization in spectroscopic applications.