Self-mixing interference in a diode laser: experimental observations and theoretical analysis

Area of Science:

• Optics
• Laser Physics
• Optical Sensing

Background:

• Self-mixing interference, also known as backscatter modulation, occurs when light from a laser is reflected back into its cavity.
• This phenomenon is crucial for various optical sensing applications.

Purpose of the Study:

• To experimentally investigate self-mixing effects in diode lasers.
• To theoretically analyze the self-mixing phenomenon.
• To compare self-mixing interferometry with conventional interferometry.

Main Methods:

• Utilizing a diode laser to transmit light through free space or optical fiber to a movable target.
• Detecting optical backscatter from the target and feeding it back into the laser.
• Conducting theoretical analysis alongside experimental validation.

Main Results:

• Self-mixing interference is independent of laser coherence length, laser mode (single-mode or multimode), and fiber type (single-mode or multimode).
• The phase sensitivity and modulation depth of self-mixing interference are comparable to conventional interferometers.
• The direction of phase movement can be determined from the interference signal.

Conclusions:

• Self-mixing interferometry is a robust technique for optical sensing of physical parameters.
• Fiber-based self-mixing interferometry offers advantages such as simplicity, compactness, self-alignment, and self-detection compared to conventional methods.