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A review of the methods for generation of iodine for oxygen-iodine lasers (OIL) is presented. The chemical and physical
methods for production of both atomic (AI) and molecular (MI) iodine have been searched in order to improve the
efficiency and/or technology of OILs. These trials were motivated by the estimations that a substantial part of singlet
oxygen (SO) could be saved with these methods and the onset of the laser active medium will be accelerated. Vapour of
MI can be generated by the evaporation of solid or pressurized liquid I2, or synthesized in situ by the reaction of Cl2 with
either HI or CuI2. The chemical methods of generation of AI are based on the substitution of I atom in a molecule of HI
or ICl by another halogen atom produced usually chemically. The discharge methods include the dissociation of various
iodine compounds (organic iodides, I2, HI) in the RF, MW, DC-pulsed or DC-vortex stabilized discharge. Combined
methods use discharge dissociation of molecules (H2, F2) to gain atoms which subsequently react to replace AI from the
iodine compound. The chemical methods were quite successful in producing AI (up to the 100% yield), but the
enhancement of the laser performance was not reported. The discharge methods had been subsequently improving and
are today able to produce up to 0.4 mmol/s of AI at the RF power of 500 W. A substantial enhancement of the discharge-
OIL performance (up to 40%) was reported. In the case of Chemical-OIL, the enhancement was reported only under the
conditions of a low I2/O2 ratio, where the “standard” I2 dissociation by SO is slow. The small-signal gain up to 0.3 %/cm
was achieved on the supersonic COIL using the HI dissociated in the RF discharge. Due to the complicated kinetics of
the RI-I-I2-SO system and a strong coupling with the gas flow and mixing, the theoretical description of the problem is
difficult. It, however, seems that we can expect the major improvement of the OIL performance for those systems, where
the SO yield is rather low (DOIL) or for the high-pressure COIL, where the quenching processes are important and the
shortage of the distance needed for the preparation of active media is essential.
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