E. Miesak

8-TW 90-fs Cr:LiSAF laser.

Ultrashort 90-fs 8-TW Fourier-transform-limited pulses are generated with chirped pulse amplification in a Cr3+:LiSrAlF6 laser system incorporating a regenerative amplifier and three additional double-pass amplifiers with increasing aperture up to 25 mm.

Multi-terawatt femtosecond Cr:LiSAF laser

We discuss the design of a Cr:LiSAF laser system capable of generating ultrashort, 90-fs Fourier-transform limited pulses with a peak power of 8 TW. Using chirped pulse amplification and flashlamp-pumped Cr:LiSAF amplifiers this system incorporates a regenerative amplifier and three additional double-pass amplifiers with increasing aperture up to 25 mm. The temporal performance as well as the spatial beam quality are discussed in detail. We discuss extension of this system to the Petawatt power level. >

110 fs Fourier-transform limited gaussian pulses from a Cr:LiSAF regenerative amplifier

Abstract We report stable operation of a flashlamp-pumped LiSrAlF 6 : Cr 3+ regenerative amplifier for femtosecond pulses using chirped pulse amplification. We achieve Fourier-transform limited pulses of 100 fs duration with a time-bandwidth product of 0.44 and a pulse energy of 1.2 mJ.

High-power 467-nm passively locked signal-resonant sum-frequency laser

We have generated more than 120 mW of TEM00 radiation at 467 nm by summing the resonantly enhanced output of an 845-nm GaAlAs tapered semiconductor amplifier with the intracavity field of a 1047-nm diode-pumped Nd:YLF laser, using a KTP crystal. Optical feedback was used to lock the frequency of the tapered amplifier to a cavity resonance.

Compact, single-frequency, high-power Nd: glass laser

A compact, single-frequency high-power Nd:glass laser was developed. Single longitudinal mode operation of the oscillator was provided by injection-seeding it with CW laser radiation. A four-pass amplifier with a spatial filter provided an output energy of 2.7 J with more than 30% extraction efficiency. The output beam divergency was twice the diffraction limit. >

Alignment Procedure for a Dual Grating Pulse Compressor

Grating pulse compressors are an integral part of chirped pulse amplification (CPA) lasers.1 Accurate alignment of the compressor is required to obtain minimum pulse-width at the output of the system. Dual grating compressors are difficult to align because they don’t function unless they are close to optimum alignment. The procedure outlined here provides a simple step-wise method of aligning a dual grating pulse compressor so that the gratings will be parallel with one another. Once this condition has been established, only the distance between the gratings needs to be adjusted to start the system operating. At this point, the compressor can be critically aligned.

Nonlinear spectrometry of chromophores for optical limiting

We describe two methods for the spectral measurement of nonlinear absorption and refraction in reverse-saturable absorber materials. In the first, we use a picosecond optical parametric oscillator to perform Z-scan at many different wavelengths to measure excited state refraction and absorption cross sections throughout the visible. The second methods uses a chirped-pulse amplification scheme to produce 100 fs pulses at 840 nm. Focusing these into sapphire generates a white light continuum that is used as a probe in an excite-probe experiment. The excitation beam is derived from the second harmonic of the remaining 840 nm light. By measurement of the transmission spectrum of the probe as a function of excite- probe delay time, we can determine the spectral dependence of the excited-state absorption cross section. Moreover, by use of Kramers-Kronig relations, the excited state refraction can also be extracted from this data. We describe our measurements using both methods in a Zn:tetrabenzporphyrine derivative (TBP). The fact that both methods give excellent agreement not only verifies the utility of continuum measurements, but also reveals some interesting properties of the excited states of TBP.

Optimum microchannel plate (MCP) configuration for use in high-speed, high-resolution x-ray imaging

Microchannel plates (MCPs) are incorporated in a wide variety of x-ray imaging and detection devices. Experimental measurements are presented in this paper which are used to determine the MCP and phosphor configuration for optimizing spatial resolution, temporal resolution, and gain in an x-ray framing camera. We investigate with the use of pulsed electron accelerating voltages to attain extraction fields higher than those possible at safe DC levels. In addition, MCPs with exit faces coated with an insulating material, in order to increase the maximum safe DC electron extraction field, were also tested.

A multi-terawatt femtosecond Cr:LiSAF laser

In the past two years Cr:LiSAF has become an attractive alternative gain medium for the high intensity amplification of femtosecond optical pulses.1-6 Cr:LiSAF uniquely combines the advantages of Ti:sapphire and Nd:glass, materials commonly used as gain media in laser systems based on chirped pulse amplification7. Cr:LiSAF has a broad spectral emission bandwidth similar to that of Ti:sapphire allowing the amplification of femtosecond optical pulses. In addition Cr:LiSAF has a relatively long upperstate lifetime of 67 μs permitting efficient flashlamp-pumping8 leading to compact laboratory sized low-cost amplifiers using a mature technology developed in many years for Nd:glass based amplifier systems.

Femtosecond continuum spectroscopy and Kramers-Kronig relations

We have developed a nonlinear spectrophotometer that can measure nondegenerate spectra from 1.7 /spl mu/m in the IR to 200 nm in the UV. Dual diode arrays for the IR and visible are used to measure the spectral changes in the transmittance against a reference beam. The pump beam is the output of a regeneratively amplified, frequency doubled, femtosecond fiber ring oscillator.