Absolute wavelength scan of a laser with microprocessor control

Abstract

A new technique for scanning a narrow-bandwidth pulse dye laser is described. The laser output frequency is locked to the setting of a high-resolution spectrometer via a closed-loop microcomputer control. With this a correlated movement of grating and the etalon of the dye laser is possible without the need to calibrate their relative setting. By periodic resetting of the etalon constant performance of the laser is guaranteed over the complete range of the dye in use. A scan over many free spectral ranges is performed by scanning the spectrometer and locking the dye laser to it. Due to the closed-loop technique severe imperfections in the mechanical components for the wavelength setting in the laser are fully compensated and a smooth scan with the inherent resolution of the laser is achieved. A high-resolution test scan of a known two-photon transition is provided for comparison.