High-frequency modulation of the spatial field structure in a ruby laser

A laser is considered in which the nonuniformity in the deexcitation of the level populations by the standing-wave field is eliminated by a longitudinal variation of the field structure. The field is varied by two phase modulators on different sides of the active element. The phase shifts of the modulators are equal in value but opposite in sign, so that there is no detuning of the resonator and no amplitude modulation. It is shown theoretically that for a modulation amplitude _m = 1.202 the deexcitation nonuniformity is completely eliminated and only one longitudinal mode is generated. Under these conditions the linewidth of the spectrum was reduced by a factor of not less than 10.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 1, pp. 81–86, January, 1969.In conclusion we wish to thank R. D. Zaitsev for manufacturing the modulating crystals, and V. S. Mel'chenko for providing the interferometer.     

Undamped undulation superposed on the passive Q-switching pulse of a CO2 laser

An undamped undulation superposed on the pulse tail of the passive Q-switching is observed using HCOOH gas as a saturable absorber. The pulse shapes with the undulation are nicely reproduced through the rate-equation analysis in which the laser gain medium is described as a three-level system. Good agreements between the observation and the calculation are also obtained in the dependence of the period and the width of passive Q-switching pulse on laser parameters. The mechanism of the undulation is interpreted as the relaxation oscillation attributed to the relaxation from the lower laser level. The collisional rate constant of HCOOH molecule is also obtained.     

A holographic measurement of the pulse width of a Q-switched ruby laser

The pulse width of the output from a Q-switched ruby laser is measured on the basis of holography of a moving object. It is shown that, when the object is rotating, the relative brightness of the reconstructed image decreases gaussianly with increase of the velocity of the object. Furthermore, we propose how to measure the frequency sweep in the duration of the pulse and also to relax traditional restrictions on holography of a moving object.     

Three-nanosecond-equal interval sub-pulse Nd:YAG laser with multi-step active Q-switching

We demonstrate a three-nanosecond equidistant sub-pulse multi-step Q-switched Nd:Y3 Al5 O12(Nd:YAG) laser. In the time interval of 100–1000 ns, three pulses with the same nanosecond interval and the same peak power are obtained at the pulse width of 24 ns, 28 ns, and 36.6 ns, respectively. The energy is 32.5 m J, and the optical efficiency is 10.8%. The multi-step Q-switched method does not require the insertion of other optical elements into the traditional Q-switched laser, and it is very suitable to obtain pulse group output with several nanosecond pulse intervals.     

High pulse repetition frequency RF excited waveguide CO2 laser with mechanical Q-switching

In this paper, a mechanical Q-switching is used in radio frequency (RF) excited waveguide CO₂ laser to obtain high pulse repetition frequency (PRF) laser. The Q-switching system includes two confocal ZnSe lenses and a high speed mechanical chopper, which is inserted into the cavity. The peak power is up to 730 W and the pulse width 200 ns at the highest PRF 20 kHz. The laser also has the advantages of compact, small-volume, and low-cost.