Photochemistry and Spectroscopy Department

Institute of Physical Chemistry, Polish Academy of Sciences


The optical system of the laser plays a double role: it acts as a generator and an amplifier of the laser beam. The beam crosses the cuvette (K) with dye solution along two paths: B1,– generation, B2, amplification (output). The main dispersive element,– diffraction grating – is situated in the laser cavity at the constant sliding angle of about 2 degrees. Radiation reflected from the grating reaches the swinging mirror M1. The cavity mirror M2 closes the laser resonator. The angle α between the planes of the M1 mirror and the grating defines a resonance wavelength and is controlled by means of drive S1 based on a stepping motor. To monochromatize laser emission further, a Fabry-Perot etalon (LambdaPhysik) can be inserted into the laser cavity. The drive S2 tunes the etalon within the basic laser line by changing the angle β between the etalon and the mirror M1. Mechanical transmissions of the drives are chosen so that both stepping motors make the same number of steps during a scan.The laser is equipped with 3 gratings (Jobin-Yvon) of different spectral ranges (3600/mm for 320-450 nm, 2400/mm for 420-640 nm, 1200/mm for 610-860 nm) fixed in one holder. One can change the range by a simple shift of the holder. In the analogous fashion one can change the operating range of the etalon, provided with 3 pairs of dielectric coatings working in corresponding wavelength intervals. According to our knowledge, a grating incidence dye laser with intracavity etalon has not been described previously.The beam is divided into B1 and B2 by means of beam dividing cube C with a sharp cube edge CE. It has been demonstrated that profiles of the beams divided this way keep their gaussian intensity distribution. The cube has a vertical drive to optimize the B1/B2 intensity ratio. Pumping light (parallel beam ~3 cm in diameter) is focused onto the dye cuvette along the B1 and B2 by means of a cylindrical lens L and two wedges W1, W2. A laser generation threshold with Rhodamine 101 / methanol dye solution was achieved at ~2.5 mJ/pulse pumping energy with etalon inserted.The full width at half maximum of the laser output is ≤0.1 cm-1 with and 0.5-0.8 cm-1 without the etalon.