Q：What is responsivity of an opto-electric sensor?

      A:   Responsivity (R) depicts the level of sensitivity of an opto-photoelectric sensor to optical radiation energy, which is defined as photocurrent generated by per unit of incident optical power, with a unit of A/W. Physically R represents the capability of an opto-electric sensor to convert optical radiation energy into output current (or voltage). Usually R varies with incident light wavelength, bias voltage and temperature. The reason that R varies with incident light wavelength is because that each semiconductor material has different reflection and absorption indexes at different wavelength. In addition, temperature change would affect the optical constants of semiconductor materials, as well as photo-carrier collection efficiency of an opto-electric sensor. Moreover, the magnitude of bias voltage would influence the collection efficiency of photo-generated carriers and the depletion layer width of the opto-electric sensor.