Microwatts continuous-wave pumped second harmonic generation in few- and mono-layer GaSe

Area of Science:

• Materials Science
• Photonics
• Nanotechnology

Background:

• Two-dimensional (2D) materials offer unique optical properties.
• Silicon photonics is a key technology for integrated optical devices.
• Nonlinear optical processes are crucial for advanced photonic applications.

Purpose of the Study:

• To demonstrate continuous-wave (CW) pumped second harmonic generation (SHG) in few- and mono-layer gallium selenide (GaSe) flakes.
• To investigate the integration of 2D GaSe with silicon photonic crystal (PC) cavities for enhanced nonlinear optics.
• To explore the potential of 2D GaSe for chip-integrated nonlinear optical devices.

Main Methods:

• Coating few- and mono-layer GaSe flakes on silicon PC cavities.
• Utilizing continuous-wave (CW) laser pumping for SHG experiments.
• Measuring and comparing SHG efficiency in GaSe with third harmonic generation in silicon.

Main Results:

• Achieved the first demonstration of CW pumped SHG in few- and mono-layer GaSe on silicon PC cavities.
• Significantly reduced SHG pump power to microwatts due to GaSe's high nonlinearity and PC cavity resonance.
• Observed SHG in GaSe to be over 650 times stronger than third harmonic generation in silicon, despite lower optical power in GaSe.

Conclusions:

• 2D GaSe exhibits significant potential for enhancing nonlinear optical processes in silicon photonics.
• The integration of 2D materials with photonic crystals opens new avenues for chip-integrated active photonic devices.
• This work expands the application scope of 2D materials into the nonlinear optical regime for optoelectronics.