1.8 W, high efficiency, pump-enhanced, narrow linewidth optical parametric oscillator at 3.8 µm

Area of Science:

• Nonlinear Optics
• Laser Physics
• Quantum Optics

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• Achieving high efficiency and narrow linewidth in continuous-wave (CW) OPOs remains a key research objective.
• Pump-enhancement strategies can significantly improve OPO performance.

Purpose of the Study:

• To demonstrate a high-efficiency, continuous-wave, narrow-linewidth, pump-enhanced optical parametric oscillator (OPO) operating at 3.8 µm.
• To investigate the impact of oblique crystal placement on OPO performance and stability.
• To characterize the output power, linewidth, and beam quality of the developed OPO.

Main Methods:

• Utilized a 1064 nm fiber laser with an 18 kHz linewidth as the pump source.
• Employed a pump-enhanced OPO configuration for improved quantum efficiency.
• Implemented a low-frequency modulation locking technique for output power stabilization.
• Obliquely aligned the nonlinear crystal to the pump beam to mitigate feedback effects.

Main Results:

• Achieved a maximum quantum efficiency exceeding 60% with 3 W of pump power.
• Generated idler light at 3819.9 nm with a maximum output power of 1.8 W and a linewidth of 363 kHz.
• Demonstrated excellent tuning performance of the OPO.
• Oblique crystal placement increased maximum output power by 19% and improved beam quality (M² factors of 1.30 and 1.33).

Conclusions:

• The developed pump-enhanced OPO demonstrates high efficiency and narrow linewidth operation at 3.8 µm.
• The low-frequency modulation locking technique effectively stabilizes output power.
• Oblique crystal alignment is a viable method to enhance output power and beam quality by preventing feedback.
• This OPO system shows significant potential for various spectroscopic and sensing applications.