HeNe laser for a high-precision phase-shifting interferometer based on peak power locking and weak thermal coupling.

Area of Science:

• Optics and Photonics
• Laser Physics
• Precision Metrology

Background:

• Precise interferometry requires stable, several-milliwatt Helium-Neon (HeNe) lasers, which are currently lacking.
• Commercial frequency stabilization techniques for HeNe lasers often result in significant power loss.
• Laser coherence fluctuations can lead to unstable interferogram contrast in spatiotemporal domains.

Purpose of the Study:

• To propose a new light source schema for stable, several-milliwatt HeNe laser output.
• To overcome power loss issues associated with commercial HeNe laser stabilization.
• To improve interferogram contrast and measurement accuracy in interferometric applications.

Main Methods:

• A weak thermal coupling structure driven by thermoelectric coolers (TECs) was developed based on a thermal conduction model.
• Operating temperature of the HeNe laser tube was regulated via feedback from a reference light's intensity signal.
• Peak power locking was employed to maintain the operating mode at the peak gain position, avoiding power loss.

Main Results:

• Achieved a stable two-milliwatt HeNe laser output.
• Demonstrated a wavelength drift of only 0.04 pm within 24 hours.
• Obtained stable single-longitudinal-mode output, enhancing laser coherence.

Conclusions:

• The proposed method successfully provides a stable, several-milliwatt HeNe laser source, overcoming limitations of existing techniques.
• The laser's stable output and coherence improve surface shape measurement accuracy for irregular components.
• Enhanced repeatability accuracy was observed in vibrating environments, demonstrating the laser's robustness.