Microwave Discharge in Hollow Optical Fibers as a Pump for Gas Fiber Lasers

Abstract

To excite plasma in the core of a hollow fiber, a scheme similar to a slot antenna in the wall of a metal microwave waveguide was proposed and implemented. An analytical estimate of the magnitude of the electric field in the slot region where the fiber with a hollow core is placed has been obtained. Using the proposed scheme, the possibility of maintaining argon plasma in the core of a hollow fiber with a diameter as small as 110 μm was demonstrated. The total length of plasma column in the hollow-core fiber was up to 25 cm at Ar pressure ~10 Torr. The frequency of microwave radiation used was 2.4 GHz, the average generated power was below 20 W. The obtained luminescence spectra of argon plasma in the fiber core showed that the argon luminescence in our experiments was observed only in the form of radiation from neutral atoms. The results obtained show that the microwave slot antenna is a promising pumping scheme for gas-discharge fiber lasers based on hollow-core fibers.