Self-mixing thin-slice solid-state laser Doppler velocimetry with much less than one feedback photon per Doppler...

Area of Science:

• Laser physics
• Optical engineering
• Velocimetry

Background:

• Standard TEM00 laser operations have limitations in signal-to-noise ratio for sensitive measurements.
• Photon lifetime is a critical parameter influencing laser performance and measurement sensitivity.

Purpose of the Study:

• To investigate the effect of annular mode operations on photon lifetime in a thin-slice Nd:GdVO4 laser.
• To demonstrate the improvement in signal-to-noise ratio for self-mixing laser Doppler velocimetry (LDV) using shortened photon lifetimes.

Main Methods:

• Utilized a thin-slice Nd:GdVO4 laser with tilted laser diode end pumping to induce annular mode operations.
• Performed self-mixing laser Doppler velocimetry experiments comparing annular mode operations with standard TEM00 operations.
• Quantified the signal-to-noise ratio enhancement and minimum intensity feedback rate required for successful measurements.

Main Results:

• Observed a drastic shortening of photon lifetime associated with the formation of annular mode operations.
• Achieved a 15 dB enhancement in signal-to-noise ratio in LDV experiments due to the shortened photon lifetime.
• Determined the minimum intensity feedback rate for successful measurements to be -123 dB (0.007 photon per Doppler cycle).

Conclusions:

• Annular mode operations in thin-slice lasers can drastically shorten photon lifetime.
• Shortened photon lifetimes lead to significant signal-to-noise ratio enhancement in self-mixing LDV.
• This technique enables highly sensitive velocity measurements with minimal optical feedback.