Spatial beam profiles from a laser-diode system with optical feedback: the importance of interference

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Laser Diode Engineering

Background:

• Laser diodes are susceptible to optical feedback, which can alter their performance.
• Understanding the impact of optical feedback is crucial for laser diode stability and application.

Purpose of the Study:

• To investigate the origin of the output beam profile in laser diodes with optical feedback.
• To demonstrate that the beam profile arises from the interference of emitted and feedback fields.
• To explore the use of interference patterns for analyzing optical feedback characteristics.

Main Methods:

• Experimental measurement of laser diode output spatial beam profiles.
• Systematic spatial manipulation (tilting, focusing, aperturing) of the optical feedback field.
• Analysis of beam profiles under varying feedback conditions and temporal coherence levels.

Main Results:

• The output beam profile is directly attributable to the interference between the laser diode's emitted field and the optical feedback field.
• Spatial manipulation of feedback significantly altered the observed beam profiles, consistent with interference phenomena.
• Sufficient temporal coherence of the laser diode output is necessary for clear observation of interference patterns.

Conclusions:

• The spatial beam profile of a laser diode with optical feedback is a direct result of field interference.
• Interference patterns provide a method to study the relative wavefronts of emitted and feedback fields.
• This phenomenon allows for the estimation of coupling coefficients in laser diode systems with optical feedback.