Research on the one mirror inclined three mirror cavity (OMITMiC) photodetectors in the laboratory is reported. In the structure of photodetectors, it is the inclined mirror that makes the filtering cavity and the absorption cavity decoupled, thus narrow spectral response linewidth, wavelength tunable and high quantum efficiency can be achieved simultaneously. On the basis of the theoretical analysis and experimental verification on the principle with separated optical components, the vertical taper structure, the key part in the whole integrated device was realized, by dynamic etch mask technique. Moreover, the first integrated device of this type was fabricated. A spectral linewidth less than 6 nm and a quantum efficiency of 52.6% have been achieved experimentally. Research on the one mirror inclined three mirror cavity (OMITMiC) photodetectors in the laboratory is reported. In the structure of photodetectors, it is the inclined mirror that makes the filtering cavity and the absorption cavity decoupled, thus narrow spectral response line width, wavelength tunable and On the basis of the theoretical analysis and experimental verification on the principle with separated optical components, the vertical taper structure, the key part in the whole integrated device was realized by dynamic etch mask technique. Moreover, the first integrated device of this type was fabricated. A spectral linewidth less than 6 nm and a quantum efficiency of 52.6% have been achieved experimentally.