Broadly tunable noncritically phase-matched ZnGeP2 optical parametric oscillator with a 2-microJ pump threshold

Area of Science:

• Nonlinear Optics
• Laser Physics
• Materials Science

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• ZnGeP2 (ZGP) is a promising nonlinear crystal for mid-infrared applications.
• High-repetition-rate sources are needed for various spectroscopic and sensing applications.

Purpose of the Study:

• To develop a high-repetition-rate OPO system using noncritically phase-matched ZGP.
• To demonstrate tunable mid-infrared output from 3.7 to 10.2 micrometers.
• To achieve a record low threshold and high quantum efficiency for ZGP-based OPOs.

Main Methods:

• Utilized a periodically poled lithium niobate OPO, pumped by a Q-switched diode-pumped Nd:YAG laser, as the pump source.
• Employed noncritically phase-matched ZnGeP2 (ZGP) in a singly resonant OPO configuration.
• Tuned the pump wavelength from 2.3 to 3.7 micrometers to achieve output tuning.

Main Results:

• Achieved continuously tunable output from 3.7 to 10.2 micrometers.
• Demonstrated a minimum ZGP OPO threshold of 2 microJ, the lowest reported for a singly resonant OPO.
• Obtained output energy greater than 20 microJ in the 6-8 micrometer range.
• Exceeded 10% quantum efficiency for converting 1-micrometer pump radiation to mid-infrared output.

Conclusions:

• The developed high-repetition-rate ZGP OPO system is highly efficient for tunable mid-infrared generation.
• The achieved low threshold and high quantum efficiency highlight the potential of ZGP for advanced optical parametric oscillation.
• This technology offers a promising source for applications requiring tunable mid-infrared radiation.