Transient thermal lens in a ZnGeP(2) crystal

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Physics

Background:

• Zinc Germanium Phosphide (ZnGeP2) is a nonlinear optical crystal.
• High-power laser systems require materials with excellent thermal stability.
• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.

Purpose of the Study:

• To investigate transient thermal lensing in ZnGeP2 crystals.
• To assess the impact of thermal lensing on ZnGeP2 crystal performance under specific laser conditions.
• To determine the suitability of ZnGeP2 for high-power, modulated laser applications.

Main Methods:

• Excitation of ZnGeP2 crystals using 2.09-µm laser pulses (800-µs duration, 70-mJ energy, 30 Hz repetition rate).
• Utilizing burst-mode Q-switched pumping.
• Employing an adiabatic model to approximate laser power transmission and focal length changes.

Main Results:

• First reported observations of transient thermal lensing in ZnGeP2.
• Observed focal length changes from infinity to 10 cm within each 800-µs pulse.
• Similar thermal lensing effects were noted when the crystal was used in an optical parametric oscillator configuration.

Conclusions:

• Transient thermal lensing in ZnGeP2 is a significant phenomenon under the tested high-power conditions.
• The observed thermal lensing effect severely limits the use of ZnGeP2 in optical parametric oscillators operating under these modulated, high-power conditions.
• Further research may be needed to mitigate thermal lensing effects for high-power applications of ZnGeP2.