Simple high-precision method for measuring the specular reflectance of optical components

We present a simple method to determine precisely the specular reflectance of optical components. The absence of transmissive elements in this method makes a wide spectral range available. High accuracy and precision are achieved with a fast, periodic change between the reference beam and the probe beam. Special efforts were made to eliminate inhomogeneities of beam intensity and detector sensitivity. With our experimental setup we obtain a precision of ±3 × 10(-4) at the wavelength of 10.6 µm and ±3 × 10(-5) at 1.06 µm for a single-bounce-measuring setup.