A reduced capacitance concept for high-speed optical position-sensitive devices (PSDs)

Position-sensitive devices (PSDs) in which the junction capacitance is reduced by using a mesh-type resistive layer with 125- mu m pitch and 30- mu m stripwidth are discussed. The temporal responses to pulsed excitation illuminated at the center are characterized by a rise time of less than 550 ns, which is shorter than that of the conventional type. The 14-mm*14-mm PSD has a junction capacitance of less than 180 pF, which is estimated to be lower than that of a conventional-type PSD by a factor of 2.4. By suitably selecting the mesh pitch and width, it is possible to reduce the temporal response by one or two orders of magnitude.<
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