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A photothermal detector consisting of a relief grating on the surface of an elastomer was fabricated and characterized. The detector has a sensitivity of the order of microwatts per square millimeter and has rise and fall times of the order of tens of seconds. Numerical and analytical modeling account for the behavior of the detector.

A modification of the Cary Model 14 for radiometry is described which allows recording in microwatts per square mlllimeter per nanometer on the ordinate and linear wavelength on the abscissa through the range 250-2500 nm. A 5.08-cm diam rotating integrating sphere is used to compare standard to unknown sources at a 30 c/s rate. The undispersed radiation from the sphere is directed through the entrance slit of the monochromator. After dispersion by the monochromator the energy is received by a single phototube or PbS detector as alternate pulses of standard and unknown energy. This design results in common optical elements throughout the instrument except for the standard and unknown sources themselves. An electrical calibration system permits an ordinate scale reading irradiance directly in microwatts per square centimeter per nanometer with simple provisions for range change. The instrument provides a dynamic range of 2 x 10(6) to 1. A large open area is provided for mounting unknown sources. The entrance optical system is designed so that remote sources can be viewed conveniently.