The performance of photon-drag detectors at high laser intensities

The response of germanium photon-drag detectors at high CO2-laser intensities is found to be nonlinear. Depending on the conditions, both superlinearity and saturation can be observed. It is known that the absorption of germanium at 10.6 μm decreases at high intensities, while the resistivity increases. It is shown that the nonlinear behavior of drag detectors can be satisfactorily accounted for by taking account of these two effects. In consequence, it is shown that it is possible to design germanium photon-drag detectors, without sacrifice of sensitivity, which are linear within a few percent up to power densities of about 40 MW.cm^-2.