Monitoring the effects of photostability in the back-geometry degenerate four wave mixing

Abstract

The effects of photostability on the ration of signal to noise in degenerate four-wave mixing (DFWM) using backward geometry have been first investigated in iodine vapor. Frequency-doubled outputs from a multi-mode Nd:YAG laser pumped dye laser, which laser dye PM580 was dissolved in the ethanol. Though phase-match is automatically achieved in the backward folded boxcars geometry, weak signal beams under the strong background of stray light are hardly detected because of the photostability on the ratio of signal to noise in DFWM experiments. To solve the problems, a new image processing system for detecting backward DFWM spectroscopy on iodine vapor is reported. This system is composed of CCD camera, imaging processing card and the related software. With the help of the detecting system, the focal image and the beam image of the pump laser's conjugation beam in backward geometry DFWM experiment have been obtain, in which demonstrated that the backward geometry can't compensate the beam excursion. The DFWM signal is sensitive to disturb of the environment, which leads to the phase conjugation fidelity decreased. The study of photostability on the ratio of signal to noise in DFWM experiment is of importance to trace atom, molecular and radical in combustion diagnosis.