Continuous wave terahertz generation up to 2THz by photomixing on ion-irradiated In0.53Ga0.47As at 1.55μm wavelengths

We report the generation of continuous terahertz waves from microwave frequencies of up to $2\mathrm{THz}$ obtained by photomixing two optical waves at $1.55\mu \mathrm{m}$ wavelengths in ion-irradiated ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$ interdigitated photomixers. A $200\mathrm{nm}$ thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than $40\mathrm{nW}$ at $0.5\mathrm{THz}$ and $10\mathrm{nW}$ at $1\mathrm{THz}$ have been achieved. Considering the observed saturation of the output power with the increase of bias voltage, the optimum excitation conditions regarding optical power and bias voltage are discussed.