Boosted Second Harmonic Generation and Cascaded Sum Frequency Generation from a Surface Crystallized Glass Ceramic...

Area of Science:

• Materials Science
• Nonlinear Optics
• Photonics

Background:

• Developing efficient micro/nano devices for second-order nonlinear optics is challenging.
• Whispering gallery mode (WGM) resonators offer potential for enhanced optical nonlinearities.

Purpose of the Study:

• To demonstrate enhanced second-harmonic generation (SHG) and cascaded sum frequency generation (SFC) in surface-crystallized glass microspheres.
• To explore the use of Ba₂TiSi₂O₈ crystal layers on glass microspheres for cavity-enhanced nonlinear optics.

Main Methods:

• Fabrication of core-shell microspheres with a 6-µm Ba₂TiSi₂O₈ crystal layer on a glass core.
• Utilizing whispering gallery modes for efficient coupling with the nonlinear crystal layer.
• Characterization of second-harmonic generation (SHG) and cascaded sum frequency generation (SFC) performance.

Main Results:

• Achieved up to 80 times stronger SHG compared to non-resonant samples due to cavity enhancement.
• Demonstrated ultra-wideband SHG (860–1600 nm) with high-contrast polarization characteristics.
• Observed a two-magnitude enhancement in cascaded sum frequency generation (SFC).

Conclusions:

• The core-shell microsphere design efficiently couples Ba₂TiSi₂O₈ with WGMs, leading to enhanced nonlinear optical responses.
• This strategy effectively boosts nonlinear optical effects in glass ceramics.
• Opens new avenues for applications in photonics and optical communications.