Codirectional grating-coupled filter for wavelength selective photodetection

Wavelength selective photodetection employing a vertical coupler filter is described based on a GaAs/AlGaAs pin structure. The filter centre wavelength was varied depending on the grating period by 12.8nm/μm for the transverse electric mode. Frequency response indicated that a cutoff frequency was at least 1 GHz. The proposed device has the potential for use in wavelength selective photodetection having a 3dB bandwidth down to 1 nm or less; the device is only 1 mm long.