With the rapid development of micro optoelectronic device and integration techniques in PMMA fiber, micro-structure
integration in PMMA fiber such as diffraction gratings graved by focusing fslaser inside the PMMA fiber is becoming
popular. However, the white light induced by interaction of femtosecond pulse with PMMA has a property that is similar
to laser beam has been founded, and generated a continuous spectrum from ultraviolet to infrared. Ti:sapphire
femtosecond laser systems with 1kHz, 45fs, 1mJ were used to get the white continuum spectrum in PMMA . The white
continuum spectrum from 440nm to1100nm has been recorded. Also White light filament induced by fslaser at lower
thredhold power inside the PMMA than others , and this white light filaments will damage the PMMA fiber and induce
refractive-index change so as to affect micro optoelectronic device and integration techniques application in PMMA
fiber.
Nonlinear optical properties of optical materials are important factors. Degenerate four-wave
mixing (DFWM), as a detective tool for yielding effectivex (3) values, is imposed the condition of phase
matching on the incident and generated signal beams. Nowadays DFWM with forward geometry
(FDFWM) has found increasing usage. However, phase-match is automatically achieved in the back
phase-conjugated geometry but in the forward folded boxcars geometry. Also, the efficiency of DFWM
reaches its maximum value when all three input beams are of the same intensity with regardless of the
absorption coefficient and the detuning conditions. Further, weak signal beams under the strong
background of stray light are hardly positioned and distinguished. To solve the problems, a new
optoelectronic technique for detecting forward DFWM spectroscopy on iodine vapor has been performed.
With the help of the detecting system, phase matching can be easily achieved in the optical arrangement.
Finally Real-time detecting the rate of signal to noise so as to timely decrease the stray light with correct
methods. This system makes it feasible that the potential application of FG-DFWM is used as a diagnostic
tool in combustion research and environment monitoring.
Degenerate four-wave mixing (DFWM) is a nonlinear optical process that has been developed as a
detective tool for making quantitative measurements of gas dynamic properties in the various environments.
This technique can be used to measure temperature and species concentration in both flames and plasma
environments. The resulting coherent signal beam makes DFWM particularly attractive for luminous and
harsh environments, compared to incoherent techniques, such as laser-induced fluorescence (LIF). Forward
DFWM with self-stability of spilt-beam system has been demonstrated in iodine vapor. It's found that there
exists no LIF because of collision quenching at atmospheric pressure and room temperature. But observed
vivid DFWM spectroscopy (554-556nm) of iodine vapor at 0oC and room temperature. Furthermore,
DFWM can probe non-fluorescing species. We describe a novel advanced sensor method for measuring
temperature of gas flows using DFWM. This technique without suffering of severe quenching problems at
atmospheric pressure is of importance to trace atom, molecular and radical in combustion diagnosis.
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