Ultraviolet amplified spontaneous emission from zinc oxide ridge waveguides on silicon substrate

Zinc oxide (ZnO) thin-film waveguides with ridge structures have been fabricated on $n$ -type (100) silicon substrates. The deposition of high-crystal-quality ZnO thin films on the lattice-mismatched silicon substrate was achieved by using the filtered cathodic vacuum arc technique. A ridge structure is defined on the ZnO thin film by plasma etching. Room temperature amplified spontaneous emission with peak wavelength at 385 nm is observed under 355 nm optical excitation. The pump threshold is found to be around $\text{0.45\hspace{0.17em}}{\mathrm{MW/cm}}^2.$ The maximum net optical gain of the ZnO waveguide is larger than $\text{120\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ at a pump intensity of $\text{1.9\hspace{0.17em}}{\mathrm{MW/cm}}^2.$