Carrier-envelope phase stabilization of high-contrast femtosecond laser pulses with a relativistic intensity

We report on the generation of carrier-envelope phase (CEP)-stabilized pulses with a relativistic intensity and a high-contrast ratio. The CEP stabilization is achieved with a jitter of 0.95 rad0.95rad from a 0.5 kHz0.5kHz femtosecond laser pulses with a focal intensity of 2.6×1018 W/cm22.6×1018W∕cm2 and a picosecond contrast of 2.5×10−92.5×10−9. CEP noise analysis shows that the beam pointing at the pulse compressor is a dominant factor of the CEP fluctuation with our laser system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87818/2/031113_1.pd

Ultrafast Radial Transport In A Micron‐Scale Aluminum Plasma Excited At Relativistic Intensity

Using femtosecond microscopy, we observe a thermal/ionization front expand radially at ∼108cm/s from a λ2‐size spot of an aluminum target excited at >1018W/cm2. Numerical modeling shows transport is predominantly radiative and may be initially nonlocal. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87543/2/609_1.pd

Dependence of hard x-ray yield on laser pulse parameters in the wavelength-cubed regime

Conversion efficiency and electron temperature scaling laws are experimentally studied in the wavelength-cubed (λ3)(λ3) regime, where a single-wavelength focus allows low energy pulses incident on a Mo target to produce x rays with excellent efficiency and improved spatial coherence. Focused intensity is varied from 2×10162×1016 to 2×1018 W/cm2.2×1018W/cm2. Conversion efficiency and electron temperature are best described by a power law for energy scaling while an exponential law best describes the scaling of these parameters with pulse duration. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69364/2/APPLAB-84-13-2259-1.pd

Laser-ion acceleration through controlled surface contamination

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98750/1/PhysPlasmas_18_040702.pd

Generation and measurement of >10 8 intensity contrast ratio in a relativistic kHz chirped-pulse amplified laser

We report on the generation and measurement of a > 10 8 contrast ratio between main pulse and amplified spontaneous emission (ASE) from a relativistic kHz chirped-pulse amplified laser. We have enhanced the ASE contrast ratio as much as > 400 times by employing a pulse cleaner composed of a μJ preamplifier and a saturable absorber. A third-order cross-correlator with a dynamic range of > 10 9 and a scanning range of up to 4 ns has been developed for the contrast measurement. Detailed analysis of the cross-correlation trace shows that the random noise of spectral phase generates 20-ps pedestal structure starting from 10 −6 level of the main pulse.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47051/1/340_2005_Article_1881.pd

High resolution hard x-ray spectroscopy of femtosecond laser-produced plasmas with a CZT detector

We present measurement of characteristic KαKα emission from Mo, Ag, and La targets irradiated by a 60 fs, 600 mJ, 10 Hz Ti:sapphire laser pulse at 1017–1019 W/cm2.1017–1019W/cm2. These x-ray emissions can potentially be used in applications from laser-based hard x-ray sources to x-ray mammography so detailed knowledge of the spectra is required to assess imaging of the figure of merit. We show here that high resolving hard x-ray spectroscopy can be achieved, with resolving powers (E/ΔE)(E/ΔE) of 60 at 18 keV, with cadmium–zinc–telluride detection system. The KαKα conversion efficiency from the laser light to the KαKα photon was optimized thanks to this diagnostic and values as high as 2×10−52×10−5 were obtained. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70312/2/RSINAK-74-12-5035-1.pd

Study of hard x-ray emission from intense femtosecond TiTi:sapphire laser–solid target interactions

Interaction of intense TiTi:sapphire laser with solid targets has been studied experimentally by measuring hard x-ray and hot electron generation. Hard x-ray (8–100 keV)(8–100keV) emission spectrum and KαKα x-ray conversion efficiency (ηK)(ηK) from plasma have been studied as a function of laser intensity (1017–1019  W/cm2)(1017–1019W∕cm2), pulse duration (70–400)fs(70–400)fs, and laser pulse fluence. For intensity I>1×1017 W/cm2I>1×1017W∕cm2, the Ag ηKAgηK increases to reach a maximum value of 2×10−52×10−5 at an intensity I = 4×1018 W/cm2I=4×1018W∕cm2. Hot electron temperature (KTh)(KTh) and ηKηK scaling laws have been studied as a function of the laser parameters. A stronger dependence of KThKTh and ηKηK as a function of the laser fluence than on pulse duration or laser intensity has been observed. The contribution of another nonlinear mechanism, besides resonance absorption, to hard x-ray enhancement has been demonstrated via hot electron angular distribution and particle-in-cell simulations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71221/2/PHPAEN-11-9-4439-1.pd

Quasimonoenergetic electron beams with relativistic energies and ultrashort duration from laser-solid interactions at 0.5 kHz

International audienceWe investigate the production of electron beams from the interaction of relativistically-intense laser pulses with a solid-density SiO2 target in a regime where the laser pulse energy is -mJ and the repetition rate -kHz. The electron beam spatial distribution and spectrum were investigated as a function of the plasma scale length, which was varied by deliberately introducing a moderate-intensity prepulse. At the optimum scale length of λ/2, the electrons are emitted in a collimated beam having a quasimonoenergetic distribution that peaked at -0.8MeV. A highly reproducible structure in the spatial distribution exhibits an evacuation of electrons along the laser specular direction and suggests that the electron beam duration is comparable to that of the laser pulse. Particle-in-cell simulations which are in good agreement with the experimental results offer insights on the acceleration mechanism by the laser field. © 2009 The American Physical Society

Hard X-ray generation from solids driven by relativistic intensity in the lambda-cubed regime

Interaction of relativistic intensity laser pulses encompassed at focus by a volume of a few wavelengths cubed with solids is examined. Spectroscopy of hard X-rays of several metallic targets, including Cu, Ge, Mo, Ag, and Sn, irradiated in this regime at a high repetition rate (0.4 kHz), has been experimentally studied. The K α and K β peaks of all targets were obtained. Averaged electron temperatures of several tens of keV and total X-ray conversion efficiencies up to 0.02% are calculated. The X-ray source size is measured to be ∼10 micron with varying elliptical shape.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47054/1/340_2005_Article_2085.pd