Response of microchip solid-state laser to external frequency-shifted feedback and its applications

Area of Science:

• Laser Physics
• Optical Engineering
• Metrology

Background:

• Solid-state lasers, particularly neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, are crucial in various scientific and industrial applications.
• External feedback mechanisms can significantly alter laser dynamics, offering opportunities for enhanced functionality.
• Precise, non-contact measurement techniques are in high demand across scientific disciplines.

Purpose of the Study:

• To experimentally and theoretically analyze the response of a microchip solid-state Nd:YAG laser subjected to external frequency-shifted feedback.
• To investigate the potential of this laser system for high-accuracy, contact-free measurements.
• To explore the complex dynamic responses, including chaotic oscillations, induced by feedback.

Main Methods:

• Implementation of an external frequency-shifted feedback loop on a microchip solid-state Nd:YAG laser.
• Experimental control of feedback power levels to achieve distinct laser response regimes (weak and strong).
• Theoretical analysis of the laser dynamics under feedback conditions.
• Spectral analysis of the laser output using a frequency-stabilized Nd:YAG laser.

Main Results:

• A continuous weak response was achieved by controlling feedback power, enabling nanometre-accurate, contact-free measurements of displacement, vibration, liquid evaporation, and thermal expansion in room conditions.
• A strong response regime was observed, exhibiting chaotic harmonic and parametric oscillations.
• Spectral analysis revealed laser spectral linewidth broadening associated with the strong response.

Conclusions:

• The frequency-shifted feedback Nd:YAG laser system offers a versatile platform for high-precision, non-contact metrology under standard laboratory conditions.
• The system exhibits rich nonlinear dynamics, including chaos, which are sensitive to feedback parameters.
• Observed linewidth broadening provides insights into the fundamental laser dynamics influenced by external feedback.