Frequency shifts in injection-seeded optical parametric oscillators with phase mismatch

Area of Science:

• Nonlinear optics
• Laser physics

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• Controlling spectral properties like frequency shifts is essential for OPO applications.

Purpose of the Study:

• To investigate and quantify frequency shifts in an injection-seeded, pulsed optical parametric oscillator (OPO) with intentional phase mismatch.
• To compare experimental observations with analytical and numerical models.

Main Methods:

• Utilized a potassium titanyl phosphate (KTP) ring OPO pumped by a 532-nm laser.
• Intentionally introduced phase mismatch to observe its effect on signal pulse frequency.
• Employed analytical and 2D transient numerical models including diffraction, walk-off, and pump depletion.

Main Results:

• Observed frequency shifts up to +/-400 MHz, approximately linear with phase mismatch and increasing with pump fluence.
• Achieved nearly transform-limited linewidths (<130 MHz) at zero phase mismatch.
• Numerical model showed good agreement with experimental data, outperforming the simple analytical model.

Conclusions:

• Intentional phase mismatch is an effective method for controlling OPO signal frequency.
• Numerical modeling provides accurate predictions of spectral characteristics in pulsed OPOs.
• The study advances understanding and control of spectral properties in pulsed OPOs.