Abstract

Efficient frequency mixing in new non-linear materials, like periodically-poled (PP) crystals, is actually opening new spectral windows to high resolution spectroscopy. This provides additional degrees of freedom for an appropriate selection of the transitions to investigate. Difference frequency generation of radiation in PP-LiNbO₃, at a wavelength tunable around 4.3 μm, has proven to be an extremely sensitive tool for CO₂ detection and has recently taken to the first demonstration, in our laboratory, of saturated-absorption spectroscopy of molecular transitions at powers as low as 10 μW [1], A special care has been devoted to reduction of excess noise of the source to approach the quantum limit. A systematic study has also been performed in order to have a fill control on far-field beam shapes. For this purpose, a numerical routine has been implemented, that calculates the three-dimensional evolution of the complex field, generated in the periodically-poled material. We are presently taking advantage of the peculiar features of this source to make a more stringent experimental test of the symmetrization postulate for bosons [2] and we will report about our new experimental results.

© 2000 IEEE