Small laser Doppler velocimeter based on the self-mixing effect in a diode laser

Area of Science:

• Optics and Photonics
• Laser Technology
• Measurement Science

Background:

• Traditional velocimeters can be complex and bulky.
• Accurate velocity measurement is crucial in various scientific and industrial applications.
• Diode lasers offer a compact and cost-effective light source.

Purpose of the Study:

• To present a simple and small-scale velocimeter based on diode laser technology.
• To demonstrate velocity measurements using light scattering and Doppler frequency.
• To investigate the performance differences between single-mode and multimode lasers for velocimetry.

Main Methods:

• Utilized a diode laser with a gradient-index lens for light emission and collection.
• Employed the interference of back-scattered light with intra-cavity laser light to induce Doppler frequency shifts.
• Detected Doppler frequency fluctuations via photodiode or by measuring diode laser voltage.
• Performed experimental validation using a rotating disk covered with white paper.

Main Results:

• The developed velocimeter successfully measured the velocity of a rotating disk.
• Significant differences in performance were observed between single-mode and multimode lasers.
• Multimode lasers demonstrated the capability for differential distance measurements.

Conclusions:

• A compact and effective diode laser velocimeter has been developed.
• The choice of laser mode (single vs. multimode) impacts velocimeter performance and functionality.
• Multimode diode lasers offer additional capabilities for distance measurement in addition to velocity.