Abstract: An example photodetector includes a waveguide structure having an active waveguide comprising an absorber for converting photons conveying an optical signal into charge carriers conveying a corresponding electrical signal; a carrier collection layer for transporting the charge carriers conveying the electrical signal; and a secondary waveguide immediately adjacent to the carrier collection layer, for receiving the photons to be detected, and which is evanescently coupled to the active waveguide.

Abstract: A semiconductor photodetector is disclosed which can have a high responsivity, high saturation power, and high bandwidth. The photodetector comprises a waveguide structure comprising: an active waveguide comprising an absorber for converting photons conveying an optical signal into charge carriers conveying a corresponding electrical signal; a carrier collection layer for transporting the charge carriers conveying the electrical signal; and a secondary waveguide immediately adjacent to the carrier collection layer, for receiving the photons to be detected, and which is evanescently coupled to the active waveguide. The secondary passive waveguide layer in the photodetector epitaxial structure enables the use of fast carrier transport material to generate high intrinsic bandwidth and travelling wave techniques associated with a scheme of evanescent coupling to increase the responsivity, saturated output power and bandwidth.

Abstract: This invention describes a technique and apparatus to use any tuneable laser to generate a specified output frequency without controlling its temperature. This technique only involves a thermal sensor and a controller a determine the current(s) of voltage(s) applied to the grating or tuning section(s) to obtain the required wavelength. The control loop can be implemented using a programmed microprocessor, an amplifier and a low pass filter.