An efficient two-cell stimulated Brillouin scattering (SBS) pulse-compressor design that can be scaled to large laser-pulse energies is described and a numerical model has been developed that accurately predicts the performance of this pulse-compressor system over a wide range of operating parameters. The compression of a 2.5 J input pulse from a width of 15.8 to 1.7 ns is experimentally demonstrated with 80 percent energy efficiency. A design of an SBS pulse compressor to compress a 25 J pulse to a pulse width less than 1 ns with 80 percent energy efficiency is presented. >

High-energy SBS pulse compression

A new approach to the transient pulse compression by stimulated Brillouin scattering (SBS) is presented. The theoretical analysis involving the time-dependent SBS gain in explicit form leads to a nonlinear system of partial differential equations, solved numerically by a generalization of the split-step method. It is shown theoretically and confirmed experimentally that the phonon lifetime is not always an appropriate parameter that determines the lower limit to the pulse duration in SBS compressors. A half-cycle gain regime is found for pulses shorter than the phonon lifetime. Hence, under proper conditions, pulses as short as half the acoustic period can be produced.

Pulse compression to the subphonon lifetime region by half-cycle gain in transient stimulated Brillouin scattering

A He-Ne laser at λ = 612 nm, stabilized to saturated absorption features of 127I2 in an external cell [and with no cell inside the laser cavity] is presented. The successive-2-sample deviation for an averaging time of 10 s is not larger than 0.15 kHz or 3 × 10-13 of the laser frequency. The uncertainty of the laser frequency due to variations of the laser power or of the beam geometry is less than 5 kHz. But dramatic frequency shifts occur when the returning beam touches an obstacle. Single and multiple linear-regression analyses of the pressure and modulation dependence seem to offer a measure of the reproducibility and of technical or physical perturbations. Linewidth and asymmetry of the peaks have been studied, and the frequency differences of 9 hyperfine components have been determined.

An improved He-Ne laser at λ = 612 nm, stabilized by means of an external absorption cell

A laser pulse temporal compression technique combining stimulated Brillouin scattering (SBS) and laser-induced breakdown (LIB) is proposed in which the leading edge of the laser pulse is compressed using SBS, and the low intensity trailing edge of the laser pulse is truncated by LIB. The feasibility of the proposed scheme is demonstrated by experiments in which a pulse duration of 8 ns is compressed to 170 ps. Higher compression ratios and higher efficiency are expected under optimal experimental conditions.

Pulse temporal compression by two-stage stimulated Brillouin scattering and laser-induced breakdown

We have observed for the first time simultaneous occurrence of phase conjugation and pulse shortening in stimulated back scattering of nanosecond laser pulses from thin film of smectic and nematic liquid crystals, and from thick samples of isotropic cholesterics. Aberration correction capability and high compression ratio are obtained.

Simultaneous occurrence of phase conjugation and pulse shortening in stimulated scattering in liquid crystal mesophases

In a 127I2 stabilized 633‐nm He‐Ne laser, the effects of saturation dispersion in iodine on the inverted Lamb dips of the iodine hyperfine components are discussed. Analytical expressions for the second and third harmonic of the frequency modulated dips are derived. Dispersion is found to influence strongly the modulation dependent frequency shifts of the absorption line centers and also introduce asymmetry in the second harmonic.

Effects of iodine saturation dispersion on the 127I2 stabilized He‐Ne laser

An experiment demonstrating optical pulse narrowing of a 6943‐A, 20‐ns ruby laser pulse to a few ns in the isophase of the liquid‐crystal cholesteryl oleate is reported. An analytical expression is derived for the backscattered intensity at the entrance to the scattering cell. Also, rough estimates of the pulse widths, time to reach intensity maximum, and asymmetry of the pulse shape are presented.

D. N. Ghosh Roy

Papers

Effects of iodine saturation dispersion on the 127I2 stabilized He‐Ne laser

Optical pulse narrowing by backward, transient stimulated Brillouin scattering