Influence of the buffer gas pressure on the energy characteristics of a lead vapor laser

Abstract

Energy characteristics of a lead vapor laser are investigated in wide ranges of helium buffer gas pressure variations (from 35 to 150 torr). It is demonstrated that a 4-fold increase in the buffer gas pressure results in a 25% decrease of the specific energy output. The conclusion is made about the possibility of developing a Pb laser with active element lifetime exceeding 1000 hours.Nowadays great attention is given to a study of pulse generation on self-terminated metal vapor transitions, in particular, of interest is a lead vapor laser. This is due to the following factors: lead vapor lasers oscillate in the visible range of the spectrum and possess high limiting transition efficiency, which allows high practical efficiency to be expected. A maximum amplification coefficient of ~600 dB/m was achieved on a lead atom line of 722.9 nm. The double-pulse excitation method was used to estimate a pulse repetition frequency (PRF) of ~80 kHz. It was demonstrated that the main factor determining a decrease in the lasing power during the second pulse was the residual population density of the lower working level [1]. In [2], the energy and time characteristics of the lead vapor laser were investigated for various bores. In [3] it was experimentally demonstrated that the sectioned discharge tube of the laser on Pb-Ne mixture had lower concentration threshold for lasing than the one-sectioned discharge tube under the same initial excitation conditions. More recently, the influence of the excitation pulse repetition frequency changing in the range 4-40 kHz on the lasing characteristics was investigated in [4], and a highest present-day average lasing power of 4.4 W (with lasing efficiency of 0.2%) was reached for the discharge tube of 1.6 cm bore with a volume of 120 cm3 at Ne buffer gas pressure of 20 torr. It should be noted that a TGU1-1000/25 tasitron was used in [4] as a switch thereby providing higher energy characteristics than in [1][2][3].At the same time, not all principles of Pb laser operation have been studied in ample detail and well understood. One of the problems is the possibility of Pb laser operation at high buffer gas pressures, since an increase in the active element lifetime calls for an increase in the buffer gas pressure [5].Investigations were carried out using the experimental setup shown in Fig. 1. A 722.9 nm dielectric mirror with reflection coefficient of 99% was used as a non-transmitting mirror of the resonator, and a plane-parallel glass plate was used as an output mirror. The current, voltage, and lasing Figure 1. Block diagram of the experimental setup comprising GDT 1, plane-parallel resonator 2 and 3, power supply unit 4, Rogowski loop 5, Tektronix Р6015А voltage tester 6, OPHIR (Nova II) power meter 7, Tektronix TDS-3014В oscillograph 8, plane-parallel plate 9, photodetector 10, and personal computer 11. pulses were registered with a Rogowski loop, Tektronix Р6015А voltage tester, and FÉK-24 photodetector, average lasing power was controlled by an OPHIR (Nova II) power meter. The active ...