Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator

Area of Science:

• Photonics and optical engineering
• Materials science
• Nonlinear optics

Background:

• Whispering gallery mode (WGM) microresonators are crucial for studying low-threshold nonlinear optical phenomena.
• Crystalline materials offer superior optical properties compared to amorphous materials, including high refractive indices, nonlinearities, and transparency.
• Non-centrosymmetric crystalline structures enable second-order nonlinear optical processes like frequency doubling.

Purpose of the Study:

• To report a novel fabrication method for crystalline zinc selenide (ZnSe) microcylindrical resonators.
• To demonstrate the application of these resonators for tunable, low-power continuous-wave second harmonic generation (SHG).

Main Methods:

• Fabrication of crystalline ZnSe microcylindrical resonators using a semiconductor fiber platform.
• Demonstration of SHG by pumping the resonator with a telecommunications band source.
• Phase-matching achieved between different higher-order radial modes for efficient frequency conversion.

Main Results:

• Successful fabrication of crystalline ZnSe microresonators.
• Observation of visible red light emission via SHG.
• Tunable, low-power continuous-wave operation demonstrated.
• Efficient spatial overlap between pump and signal modes within the resonator.

Conclusions:

• The developed ZnSe microresonators are effective for low-power nonlinear optical applications.
• The fiber platform offers geometrical flexibility for device design.
• The ultra-wide transmission window of ZnSe (500-22000 nm) makes these resonators suitable for diverse applications, including spectroscopy and quantum information systems.