Continuous wave near-infrared atomic Xe laser excited by a radio frequency discharge in a slab geometry

Abstract

Near-infrared atomic Xe laser lines have been generated from an Ar:He:Xe laser gas mixture excited by a radio frequency ͑rf͒ discharge in a slab geometry. A maximum continuous wave ͑cw͒ output power of 1.5 W ͑270 W/l͒ was obtained at an rf frequency of 125 MHz from a gas mixture containing Ar:He:Xe ͑50:49:1͒ at a total gas pressure of 90 Torr. © 1995 American Institute of Physics.There is a steady growing interest in sources of coherent radiation which operate in the wavelength region of 2-3 m.1 Possible applications of such systems include the design of eye-safe radars, 2-4 the monitoring of the atmosphere and in medicine. [5][6][7] Until now the research in this wavelength region was concentrated mainly on the improvement of solid state lasers made from YAG and YLF crystals doped with rare earth metals like holmium, erbium, and thulium which are capable of operating in a pulsed mode as well as cw. So far, there are no other lasers capable of delivering a cw output on a reasonably high power level in this spectral domain.Recently, we published the first results concerning a new cw rf excited Ar:He:Xe laser with an output power of about 300 mW. 8 This laser operates in a multiline mode with 90% of the output concentrated in the two strongest atomic Xe lines: the 5d͓3/2͔ 1 Ϫ6p͓1/2͔ 0 transition with a wavelength of 2.65 m and the 5d͓3/2͔1 -6p͓3/2͔ 1 transition at 2.03 m. In principle, this laser competes with the abovementioned rare earth doped solid state lasers which also emit their radiation in the same spectral range and are reported to operate at the same power level.In this letter, we report on a different approach to enhance the output power of such an rf excited atomic Xe laser. By using a laser resonator in a planar configuration which is homogeneously filled with a gas discharge plasma we were able to increase substantially the volume of the active medium. It resulted in an increase of the output power to a maximum value of 1.5 W and also improved the efficiency with a factor 4 compared to our earlier results. 8 We have tested several electrode and resonator configurations. The experimental setup is discussed in more detail elswhere.8.9 Here we will give only a brief description of the equipment used in our experiments. A signal from a low power master oscillator was amplified in a wide band rf amplifier ͑Kalmus, model 124C͒ which is capable to deliver a rf output power of 500 W in the frequency range of 10 kHz-220 MHz. The forward and reflected rf power was measured with a digital power meter ͑Thruline 4421 from Bird Electronics Corp.͒. The excitation frequency used in our experiments was varied between 100 and 125 MHz. The frequency choice in each particular case was determined by the resonance conditions for the RLC circuit formed by the discharge impedance, the capacitance of the laser structure, and the inductance of the shunting coils connected parallel to the laser electrodes. The construction of the laser head used in the experiments was basically the same as used in Ref. 8. The ground electrode...

Spectral investigation of cw rf-pumped atomic Xe laser with a slab geometry

“…1, after a short time this peak drops down again and then the output power starts to increase like in the conventional long-time operation regime. A similar behaviour occurred in the laser with metal electrodes [1]. This initial peak in the output power increases with the Ar concentration and/or the input power in both lasers.…”

“…However, at a pressure higher than about 200 mbar these values start to drop. The maximum efficiency of ~0.4% was obtained at a pressure of 160 mbar and an input power of 150 W. This result differs strongly from the the value in [1]. The efficiency is lower and it does not increase with an increase in input power.…”

“…The output characteristics of this laser are lower compared to the results presented in [1]. This is explained by the shorter active medium length and the additional losses of the electric power in the quartz walls.…”

“…The generated laser spectrum was analysed with a monochromator (SPEX 1681) equipped with a 300 lines/mm grating. More details of the setup are given in previous papers [1,4]. The input power was varied from 80 to 400 W, the laser-gas pressure from 60 to 400 mbar and the rf excitation frequency was 112.5 MHz.…”

“…A laser output power of 1.5 W and an efficiency of up to 0.8% were reported [1]. The main problem with this system was that its operation lasted for a relatively short time at the high output level.…”