A 110-TW multiple-beam laser system with a 5-TW wavelength-tunable auxiliary beam for versatile control of laser-plasma interaction

Abstract

A Ti:sapphire laser system has been constructed with two synchronized main beams of 110 TW and 13 TW, and a 5-TW wavelength-tunable synchronized auxiliary beam for versatile control of laser-plasma interaction. The first main beam provides 3.3-J, 30-fs, 810-nm pulses, and the second 450-mJ, 34-fs, 805-nm pulses. The auxiliary beam comes from amplified spectral windows selected from a supercontinuum of high spatial coherence and provides 38-fs pulses with tunable wavelengths (870-920 nm). The two main beams can be focused down to M 2 = 1.2 and 1.1, with 77 and 81 % energy enclosed in the focal spots, respectively. The energy fluctuations are 1.1 and 1.8 %, and the pointing fluctuations are 4.5 and 4.8 lrad, respectively. By using a preamplifier and saturable absorber before the pulse stretcher to suppress amplified spontaneous emission, the temporal contrast of the 110-TW main beam reaches 4 Â 10 À10 at the -100-ps timescale. Even though the auxiliary beam is generated from a highly nonlinear process, by confining the supercontinuum generation in a single self-trapping filament, a spatial coherence close to the main beams can be achieved. It can be focused down to M 2 = 1.3, with 72 % energy enclosed in the focal spot. The energy fluctuation is 2.6 %, and the pointing fluctuation is 4.7 lrad. The versatility of synchronized multiple-beams with tunable wavelengths, good energy and pointing stability, and the spatiotemporal quality of the laser system has been essential to our experiments in high-harmonic generation, extreme-UV lasers, and laser-wakefield accelerators in which precision control of laser-plasma interaction is facilitated by a concerted sequence of driving pulses.

Femtosecond Probing of Plasma Wakefields and Observation of the Plasma Wake Reversal Using a Relativistic Electron Bunch

“…The experiments were carried out using the 100-TW laser platform at National Central University, Taiwan [24]. The relativistic electron beam is generated by focusing a 25-TW, 40 fs (full width at half maximum, FWHM), Tisapphire laser pulse to give a peak normalized vector potential a 0 = 2.0 into a 8 × 10 18 cm −3 density plasma produced using a gas mixture of 95% helium and 5% nitrogen.…”

Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses

“…1b). When an ultra-short (36 ± 2 fs, FWHM), energetic (580 ± 9 mJ), 810 nm wavelength drive laser pulse 37 passes through, it produces both a fully ionized plasma via fieldinduced ionization 38 and a highly nonlinear wake 39 throughout the structure. Briefly, the ponderomotive force of the focused laser pulse is large enough to expel nearly all the plasma electrons leaving behind the more massive ions.…”

“…1b. The 810 nm, 36 ± 2 fs (FWHM) drive-laser pulse 37 (red) with a contrast of 10 8 containing 580 ± 9 mJ energy is focused onto the low-density side of Gas jet 1 (hydrogen) to a spot size w 0 = 13.5 ± 1.0 μm. Approximately 60% of the laser energy is within the beam waist (1/e 2 of intensity), corresponding to an estimated Strehl ratio of 0.7.…”

High-resolution phase-contrast imaging of biological specimens using a stable betatron X-ray source in the multiple-exposure mode

“…1. The experiment was carried out with the ultra-short high power Ti:sapphire laser system at National Central University 30 . The 30–40-TW driving laser pulse (energy 1.1–1.4 J, FWHM duration 36 fs) was focused using an f/8.3 off-axis parabolic mirror, with 50% energy enclosed in a Gaussian fitted spot of ∼16- µ m (FWHM) diameter.…”