Ultra-narrow spectral linewidth photodetector based on taper cavity

Taper-cavity based photodetectors are demonstrated. The taper-cavity shows a nonresonant effect but exhibits a remarkable absorption enhancement effect, and the wavelength selectivity of the device was decided solely by the filtering-cavity. Thus, high-speed, high quantum efficiency and ultra-narrow spectral linewidth can be achieved simultaneously. An integrated device with quantum efficiency of 75% and spectral linewidth of 0.8 nm (FWHM) was fabricated, and the absorption layer thickness is 0.119 µm.