Multi-pulse oscillation and instabilities in microchip self-Q-switched transverse-mode laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Laser-diode-pumped solid-state lasers, specifically Cr,Nd:YAG microchip lasers, are crucial for various applications.
• Q-switching is a technique used to achieve high-peak-power laser pulses.
• Understanding transverse mode dynamics is essential for controlling laser output.

Purpose of the Study:

• To investigate the influence of multi-transverse-mode competition and coupling on the temporal characteristics of laser-diode-pumped Cr,Nd:YAG self-Q-switched microchip lasers.
• To analyze the causes of instabilities, multi-pulse oscillations, and satellite pulse formation.
• To correlate experimental observations with theoretical models.

Main Methods:

• Experimental investigation of Cr,Nd:YAG microchip lasers under varying pump beam diameters.
• Theoretical analysis using modified coupled rate equations incorporating transverse-mode competition.
• Numerical simulations to validate experimental findings.

Main Results:

• Multi-transverse-mode operation was observed and found to significantly affect laser pulse profile, width, peak power stability, and repetition rate jitter.
• Varying the pump beam diameter led to multi-transverse-mode operation, multi-pulse oscillation, and periodical pulsation.
• Experimental and numerical results confirmed that transverse mode coupling and competition are the primary drivers of multi-pulse oscillation and pulse train instability.

Conclusions:

• Transverse mode competition and coupling are critical factors governing the stability and temporal behavior of Q-switched microchip lasers.
• The observed instabilities and multi-pulse phenomena are directly linked to the complex interactions between different transverse modes.
• The study provides a deeper understanding of mode dynamics for optimizing laser performance and stability.