| 摘要 |
PURPOSE:To detect even light having energy smaller than the forbidden band width of a semiconductor constituting a semiconductor diode, by allowing a homogeneous or heterogeneous junction type semiconductor diode to receive light tin such a state that forward bias is applied to said diode. CONSTITUTION:Coming light 23 is condensed by a condensing system 13 to be modulated by a chopper 14 and only light having a wavelength band to be detected is selected by an optical filter 15 to be incident on a homogeneous or heterogeneous junction type diode 16. The junction type diode 16 is mounted in a cooling Dewar 21 in order to reduce heat noise to be cooled. A light detection circuit detects the conductivity variable of the diode 16 as a terminal voltage change in such a state that forward bias is applied to the junction type diode 16. The light detection circuit and a preamplifier 19 are connected by a coupling condenser 22 and only a voltage change component is transmitted. The voltage change component is amplified by the preamplifier 19 and a narrow band-pass amplifier 20 to be outputted to the outside. By this method, even light having energy smaller than the forbidden band width of a semiconductor constituting a semiconductor diode can be detected. |
