We demonstrate a new type of four-pass dye laser amplifier that can reduce the possibility of parasitic oscillation between optical components used in the amplifier. Pumping the amplifier with a 5.6-mJ Q-switched doubled Nd:YAG laser output, we obtain high-peak-power pulsed output of an incident cw narrow-bandwidth dye laser beam with a power gain greater than 2 × 106. Subsequent amplification of the pulse with a conventional dye amplifier yields 42% energy efficiency. When a temporally stretched pumping pulse is used, the eventual bandwidth of the final output is measured to be 130 MHz.

Four-pass amplifier for the pulsed amplification of a narrow-bandwidth continuous-wave dye laser.

In this paper, a four-passed ytterbium-doped fiber amplifier (YDFA) is discussed. The gain and the pump and the signal light propagation characteristics of the four-passed YDFA are described. It is found that, while using a shorter length of the fiber, a four-passed fiber amplifier can realize the same output power as a single-pass fiber amplifier, and, for the same fiber lengths, a four-passed fiber amplifier offers a significantly higher power than its single-pass counterpart.

A four-passed ytterbium-doped fiber amplifier

A simple qualitative model of beams focused stimulated Brillouin scattering (SBS), capable of providing a sufficiently accurate description of the Stokes pulse profile, was developed. The characteristics of deformation of a laser pulse during amplification in two-pass and four-pass amplifiers with an SBS mirror were investigated theoretically and experimentally for fully overlapping pulses. The influence of pumping and spontaneous emission was ignored. Approximate formulas were derived for determination of the duration of an output pulse and of its leading edge. The parameters required for the most effective control of the output pulse profile were determined. (nonlinear optical phenomena and devices)

Investigation of distortions of the laser pulse profile in multipass amplifiers with a stimulated-Brillouin-scattering mirror

We demonstrate a new design for a four-pass dye laser amplifier that can be used to reduce amplified spontaneous emission (ASE) in the amplifier output beam. Compared with the results obtained from normal operation of the four-pass dye laser amplifier without a frequency-selective device, by using a diffraction grating in the amplifier we can reduce the ASE ratio by a factor in excess of 10 and increase output energy by ∼4%. The obtained ASE ratio of the four-pass amplifier system is <1.5%.

Suppression of amplified spontaneous emission from a four-pass dye laser amplifier.

Different ways of varying the output pulse duration in laser schemes comprising a powerful master oscillator, a multipass amplifier, and a stimulated Brillouin scattering (SBS) mirror are suggested and realized experimentally. Conditions are determined at which introduction of losses between a SBS mirror and an amplifier allow variation of the output pulse duration without any significant decrease in energy. The use of two different SBS media (SnCl4 and freon) allows construction of a laser where the output pulse duration is varied between 6 and 40 ns and the energy loss is no more than 30%.

Nd:YAG laser with a stimulated-Brillouin-scattering mirror and variable pulse duration

The possibility of increasing the radiation energy extraction from active elements of YAG:Nd lasers using an oscillator combined with a double-pass amplifier, as well as a four-pass scheme, is shown. >

Phase conjugation to upgrade efficiency of solid-state-laser energy conversion to narrow-band TEM/sub 00/ mode pulses

Difference frequency mixing (DFM) of high power single-spatial-mode near-IR laser diodes is an attractive method ofproducing tunable mid-infrared radiation. Such mid-IR sources operate at room temperature and can be reduced to compact size for use in a broad range of spectroscopic and commercial gas sensing applications. There have been several recent demonstrations of mid-IR generation by quasi-phasematched DFM in periodically poled LiNbO, (PPLN),i'2with up to 31 FW of power generated at 4.3 p m wavelength using laser diodes as both pump and signal s o ~ r c e s . ~ In this work, we demonstrate a singlefrequency, continuously tunable mid-IR source based on laser diode DFM and its application to high resolution CO, spectroscopy. Output power levels up to 23 pW are generated at 4.3 p m wavelength with 70 GHz of electronic continuous tunability and a linewidth less than 20 MHz. The absorption spectra of different isotopes of CO, are clearly resolved by use of this mid-IR source. A diagram of the continuously tunable mid-IR source is shown in Fig. 1. Two high power single-frequency tunable laser diodes are combinedwith a dichroic beamsplitter and focused into a 14-mm-long bulk PPLN crystal having 21.0-pm poling period. These laser diodes are based on SDL model TC40 systems and generate continuously tunable narrowbandwidth near-IR radiation near 960 nm and 785 nm wavelengths at single-spatial-inode 25 ~ hp=785.50 nm

A.Z. Matveyev

Papers

Phase conjugation to upgrade efficiency of solid-state-laser energy conversion to narrow-band TEM/sub 00/ mode pulses

Raman converter of tunable radiation into mid/far IR with large shift of Stokes wavelength