Three-photon absorption in optical parametric oscillators based on OP-GaAs.

Area of Science:

• Nonlinear Optics
• Materials Science
• Laser Physics

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• Orientation-patterned gallium arsenide (OP-GaAs) is a promising material for nonlinear optical applications due to its large nonlinear coefficients.
• Previous OPO research has explored various materials and configurations for mid-infrared generation.

Purpose of the Study:

• To report the first singly resonant (SR) and doubly resonant (DR) synchronously pumped OPOs utilizing OP-GaAs.
• To characterize the output spectra and power of these novel OP-GaAs based OPOs.
• To investigate the impact of three-photon absorption on OPO performance in the mid-infrared region.

Main Methods:

• Fabrication and characterization of SR and DR OPOs using OP-GaAs crystals.
• Synchronous pumping of the OPOs with femtosecond laser pulses.
• Spectral analysis of the generated output, covering the 3 to 6 μm range.
• Measurement of output power and investigation of nonlinear absorption effects.

Main Results:

• Successful demonstration of both SR and DR OPOs based on OP-GaAs.
• Achieved broadband output spectra from 3 to 6 μm with relatively flat power profiles (within ~3 dB).
• Observed significant three-photon absorption in OP-GaAs with a coefficient of 0.35±0.08 cm³/GW², limiting output power.
• The DR-OPO achieved the highest reported output power for a femtosecond, synchronously pumped OP-GaAs OPO.

Conclusions:

• OP-GaAs is a viable material for generating mid-infrared light using synchronously pumped OPOs.
• Three-photon absorption is a critical loss mechanism that needs to be managed for optimizing OP-GaAs OPO performance.
• Further research can focus on mitigating nonlinear absorption to enhance power scalability for mid-IR applications.