Measurement of the dispersion properties of large aperture mirrors at arbitrary incidence angle and polarization state

In this paper, we introduce a simple technique to measure mirror dispersion at angles of incidence from 0 to 55 degrees, on up to 12” large aperture optics. A 160 mm diameter round mirror and a 142x100 mm rectangular-shaped mirror have been scanned over with micrometer spatial accuracy in order to investigate the dispersion properties across their surfaces. The measurement is based on spectrally resolved interferometry, consisting of a Michelson-interferometer and a combined visible and infrared spectrometer. A tungsten halogen lamp with 10 mW average power makes it possible to measure the dispersion properties over the 500-1300 nm spectral range. The mirror to be measured is part of sample arm of the Michelson-interferometer in a fixed position, while the interferometer can be translated along two axes. At the input of the interferometer we inserted a wire-grid polarizer, and sensitivity of the chirp mirrors to the polarization state have been measured at different incidence angles. We used the Fourier Transform method to process the recorded interference fringes. The group delay dispersion and the third order dispersion are obtained up to ±0.5 fs 2 and ±2 fs 3 accuracy, respectively. To present the flexibility of the device we also scanned several different chirped mirrors including +135 fs 2 and -500 fs 2 at the 800 nm central wavelength.