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

We demonstrate the first achievement of continuous-wave (CW) pumped second harmonic generation (SHG) in few- and mono-layer gallium selenide (GaSe) flakes, which are coated on silicon photonic crystal (PC) cavities. Because of ultrahigh second order nonlinearity of the two-dimensional (2D) GaSe and localized resonant mode in the PC cavity, SHG's pump power is greatly reduced to microwatts. In a nine-layer GaSe coated PC cavity, while the optical power inside the GaSe flake is only 1.

Study on the Low Temperature Photoluminescence Spectra of II-VI Group Telluride Bulk Crystals.

The dominant point defects in II-VI group telluride bulk crystals grown from melt usually varied due to different growth conditions and cooling history, in turn affect the electrical and optical behaviors of corresponding single crystals and devices. Low temperature photoluminescence (PL) spectra acts as a contact-less and non-destructive technique, can be used to evaluate the behaviors of point defects and impurities in the as-grown telluride bulk crystals. With the purpose of comparing the defect structures in un-doped ZnTe and CdTe crystals grown under Te-rich condition, 8.