<title>Continous-wave He-Kr+ laser oscillations in a transverse radio-frequency discharge</title>

Abstract

A continuous-wave He-Kr<SUP>+</SUP> laser with capacitively coupled transverse radio- frequency excitation is presented for the first time. The laser oscillations were obtained in a simple alumina oxide discharge tube (40 cm active length, 4.9 mm inner diameter) closed in a fused silica tube envelope. The laser discharge tube was filled with a He-Kr mixture at optimum He:Kr ratio 1000:1. The operating gas pressure ranged from 4 kPa to 16 kPa. The rf power was capacitively coupled into the discharge with 40 cm long and 4 mm wide transverse nickel electrodes mounted along the discharge tube. The discharge was maintained by an rf generator operating at 13.56 MHz with an output power up to 400 W. Transformation of the laser discharge tube impedance to the 50 ohms output resistance of the rf source and symmetrization of the rf voltage were performed by a special matching network. Continuous- wave laser oscillations were obtained at 469.4 nm, 438.7 nm, and 431.8 nm lines of Kr<SUP>+</SUP> ion. The laser output powers were 6.2 mW, 0.14 mW, and 1.27 mW, respectively. The laser action at the 438.7 nm line occurred only when the other laser lines were suppressed with a birefringent filter. The rms noise to signal ratio of the laser output power did not exceed 0.8%.