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We investigate the dependence of the intensity distribution of the impulsively stimulated rotational Raman sidebands from hydrogen gas on the polarization of the prepump and pump pulses. The results show that the energy flow direction of the pump pulse can be confined to either the Stokes side or the anti-Stokes side by changing the polarization of the 60 fs pump pulse. It is found that the use of a linearly polarized pump pulse is the most effective way to generate the largest number of Raman components as possible.

We have developed a beam stabilization system for high-power femtosecond lasers operating at a repetition rate of 1kHz. The beam pointing at a hollow fiber input was stabilized to within 1μm rms and the fluctuations of the broadened spectra and power were significantly improved. This technique enables us to increase the input power to a hollow fiber for intense few-cycle pulse generation.

We propose and demonstrate a pulse compression technique using a hollow fiber with a pressure gradient. This technique improves the spatial and spectral qualities of femtosecond laser pulses spectrally broadened by self-phase modulation, and allows an increase of the pulse energy for pulse compression. Using chirped mirrors for dispersion compensation, we have successfully compressed the pulse to less than 10 fs with an energy as high as 5 mJ.

The effect of various rare‐gas diluents on the operating performance of the e‐beam‐excited XeCl laser is theoretically analyzed. The analysis of the XeCl* pumping process and the extraction process could solve the dependence of the intrinsic efficiency, small‐signal gain, and absorption on the rare‐gas diluent. As a result, there is no appreciable difference in the intrinsic efficiency between the Ar‐based and the Ne‐based mixtures. Selecting the optimum excitation parameters, the highest intrinsic efficiency of 5% is achieved for both diluents. Although the highest small‐signal gain is achieved without a diluent gas, the extraction efficiency is reduced and the intrinsic efficiency is small due to the large amount of three‐body collisional quenching.

The output performance of the electron‐beam‐excited KrF laser operating at one atmosphere is theoretically analyzed because the KrF laser at one atmosphere can greatly reduce the design constraints on the large laser windows and the electron‐beam pressure foils in a huge laser system as the inertial confinement fusion energy driver. The KrF laser using the atmospheric pressure, argon‐free laser mixture is found to operate with an intrinsic laser efficiency as high as that of high‐pressure, aregon‐diluted mixtures. This is because three‐body collisional quenching is not a detrimental energy‐loss channel for the atmospheric pressure operation. By using higher excitation rate and shorter excitation pulse width pumping, higher intrinsic laser efficiency than conventional, argon‐diluted, high‐pressure mixtures is found to be attainable. Moreover, the specific laser energy (28 J/l, for 1‐atm Kr/F2 mixtures pumped by an electron beam of 100 ns, 600 keV, and 150 A/cm2) is comparable to that of two‐atm, argon‐rich...

High‐efficiency and high‐energy operation of HF chemical lasers was simultaneously realized using a low pressure mixture of H2/F2/O2/MoF6 initiated by an intense electron beam. The addition of small amounts of MoF6 gas to the mixture of H2/F2/O2 resulted in an increase in laser output energy and electrical and chemical efficiencies. A HF laser energy obtained from a mixture containing 17.9 Torr of MoF6 was 3.7 kJ (136 J/l) with a pulse width of 190 ns full width at half‐maximum. The corresponding electrical efficiency and chemical efficiency are 189% and 15.2%, respectively, with a low pressure (362.4 Torr) mixture of H2/F2/O2/MoF6=30/242/72.5/17.9 Torr.

Atmospheric pressure operation of a KrF laser pumped by 50‐ns electron beams was experimentally investigated. For a 1‐atm mixture of Kr and F2 without diluent, a specific output energy of 4.2 J/1 was obtained at 1.7‐MW/cm3 excitation rate. Under this condition the intrinsic efficiency was about 5% (6% was maximum at 20% Kr in argon diluent) which was comparable to that from 1‐atm normal (10% Kr) mixtures.

Using a small electron beam device, we have observed time‐dependent competition among the 1.73, 2.03, 2.63, and 2.65 μm lines of the xenon laser in a high‐pressure argon buffer. The small‐signal gain and saturation intensity for each of these lines have also been measured. The maximum specific energy output of the laser was 1.7 J/l and the efficiency was 2.3%.

Amplifier characteristics of a KrF laser were investigated as a function of Kr concentration for a wide range of input intensity. The experiments were performed with atmospheric‐pressure mixtures excited by a 65‐ns (full width at half‐maximum), 160‐A/cm2 electron beam. The extracted intensity (output intensity minus input intensity) from a single‐pass (50 cm) amplifier was maximized at an input intensity around 5 MW/cm2 and then, the power efficiencies were 12.6, 13.7, 13.3, and 11.3% for Kr concentrations of 10, 20, 40, and 99.4%, respectively. The small‐signal gain, absorption coefficient, and saturation intensity were determined for each mixture by using an analysis due to Rigrod [J. Appl. Phys. 36, 2487 (1965)]. The KrF* formation efficiency and the extraction efficiency were also obtained as a function of Kr concentration.