In this paper experimental results on infra-red laser oscillations in the He-Cu sputtered systems excited by an rf discharge (13.5 MHz) are reported. The results of the small- signal gain measurement of the infra-red He-Cu4 laser lines are presented.
KEYWORDS: Carbon dioxide lasers, Carbon dioxide, Network security, Oscilloscopes, Signal processing, Calibration, Plasma, Digital signal processing, Direct methods, Resistance
Two independent methods are applied to measure the impedances of an rf excited carbon-dioxide slab laser and of a discharge test chamber. The rf feedthroughs are chosen as reference ports for the measurements. One method using an adjusted matching network and a network analyzer is compared with another method measuring two signals representing current and voltage with a digital oscilloscope and processing them using a computer.
Spectroscopic measurements of N2 molecular bands emitted by the discharge of a sealed off test chamber and a 2 kW carbon-dioxide slab laser deliver detailed rotational temperature and intensity profiles in the gap between the electrodes as a function of different discharge parameters. The results give basic information on the behavior of the discharge and the main plasma parameters for further investigations.
This is a review of the recent investigations on He- Cd+, He-Kr+, He-Ar+, He-Se+ and He-Cu+ lasers excited with the transverse capacitively coupled radio-frequency discharge. The recent investigations show that the designs and operation of the radio-frequency excited lasers are much simpler than those of the hollow-cathode discharge lasers at the similar laser output parameters. Under single-line operation the radio- frequency excited He-CdP+ laser delivers output powers of 60 mW at 441.6 nm, 36 mW at 469.4 nm, and 11 mW at 431.8 nm. Both lasers exhibit the rms noise-to-signal ratio much lower than that of conventional positive column He- Cd+ lasers. These make the radio-frequency excited ion gas laser attractive for practical applications.
A continuous-wave He-Kr+ 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+ 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%.
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