Passive Q-Switching and Mode-Locking of a Carbon - Laser Using the Halogenated Benzene Derivatives as Saturable Absorbers.

Benzene and 11 of its halogenated derivatives were studied as possible Q-switching agents for the low pressure CO2 laser. They represent a class of compounds which have one or more strong absorption bands in the 9 to 11 microns spectral region which tend to persist from one member of the class to another because of the structural similarity of the molecules. The molecules studied were: benzene, chlorobenzene, bromobenzene, o-dichlorobenzene, m-dichlorobenzene, m-difluorobenzene, m-fluorophenol, pentafluorobenzene, hexafluorobenzene, o-chlorotoluene, bromopentafluorobenzene and pentafluorotoluene. The first 9 of these mode-locked and Q-switched the laser for 123 laser line-saturable absorber combinations. The last three compounds did not Q-switch the laser on any line. The CO2 laser used was a flowing-gas, large bore, low pressure laser with an active cavity 1.8 m long.