Optical injection locking of a singly resonant continuous-wave optical parametric oscillator

Area of Science:

• Nonlinear optics
• Laser physics
• Materials science

Background:

• Continuous-wave optical parametric oscillators (OPOs) are crucial light sources.
• Achieving stable, narrow-linewidth OPO output is essential for precision spectroscopy and quantum applications.
• Optical injection locking offers a method to control and stabilize laser frequencies.

Purpose of the Study:

• To experimentally demonstrate optical injection locking of a singly resonant OPO.
• To investigate the role of a thermally induced waveguide in achieving stable injection locking.
• To characterize the spectral linewidth reduction of the OPO signal output.

Main Methods:

• Utilized a singly resonant continuous-wave optical parametric oscillator (OPO) in a magnesium-oxide doped periodically poled lithium niobate crystal.
• Fabricated a thermally induced waveguide to improve OPO spatial modes.
• Employed an external cavity diode laser for optical injection locking at 795 nm.
• Confirmed phase coherence using interference fringes.
• Measured spectral linewidth reduction via delayed self-heterodyne spectroscopy.

Main Results:

• Successfully achieved optical injection locking of the OPO.
• Demonstrated improved OPO spatial modes due to the thermally induced waveguide, crucial for locking.
• Observed high-contrast interference fringes, confirming phase coherence.
• Reduced the OPO signal's spectral linewidth from 4.5 MHz to 0.4 MHz.
• Estimated the full locking range to be less than 1.7 MHz.

Conclusions:

• Optical injection locking is feasible for OPOs utilizing thermally induced waveguides.
• The improved spatial mode quality is key to successful injection locking.
• Significant spectral linewidth reduction was achieved, enhancing the OPO's performance for sensitive applications.