Optical Amplifier for Cryogenic Detector Signals

OPTRA proposes to demonstrate a novel approach to the detection, amplification and transmission of low level detector signals from cryogenic detectors. Essential elements of the proposed work are 1) A cooled optical waveguide phase modulator that imposes a phase modulation proportional to a detector signal on an optical beam from a low power, CD type laser diode. 2) A low heat loss fiber optic link to take the modulated signal outside the detector dewar and 3) A very high resolution, homodyne phase processor, that recovers the phase information at the detector noise level and with high fidelity. This combination, the power from the laser diode and the phase modulation from the modulator provides for significant power gain in terms of electric power at the input terminals in and the power in the interferometer fringe signals out. Advantages of the approach are in principle no restrictions on the operating temperature of the modulator, very low heat loss through the fiber optic link and a high degree of immunity from electro magnetic interference.