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Dorrer, C.

Publications and source records attributed to Dorrer, C..

28 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Direct optical measurement of the on-shot incoherent focal spot and intensity contrast on the OMEGA EP laser

Characterizing the prepulse temporal contrast of optical pulses is required to understand their interaction with matter. Light with relatively low intensity can interact with the target before the main high-intensity pulse. Estimating the intensity contrast, instead of the spatially averaged power contrast, is important to understand intensity-dependent laser–matter interactions. A direct optical approach to determining the on-shot intensity of the incoherent pedestal on an aberrated high-intensity laser system is presented. The spatially resolved focal spot of the incoherent pedestal preceding the main coherent pulse and the intensity contrast are calculated using experimental data. Furthermore, this technique is experimentally validated on one of the chirped pulse amplification beamlines of the OMEGA EP Laser System. The intensity contrast of a 1-kJ, 10-ps laser pulse is shown to be ~10× higher than the power contrast because of the larger spatial extent of the incoherent focal spot relative to the coherent focal spot.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Single-shot high-resolution characterization of optical pulses by spectral phase diversity

The concept of spectral phase diversity is proposed and applied to the temporal characterization of optical pulses. The experimental trace is composed of the measured power of a plurality of ancillary optical pulses derived from the pulse under test by adding known amounts of chromatic dispersion. The spectral phase of the pulse under test is retrieved by minimizing the error between the experimental trace and a trace calculated from the optical spectrum using the known diagnostic parameters. An assembly composed of splitters and dispersive delay fibers has been used to generate 64 ancillary pulses whose instantaneous power can be detected in a single shot with a high-bandwidth photodiode and oscilloscope. Pulse-shape reconstruction for pulses shorter than the photodetection impulse response has been demonstrated.The diagnostic is experimentally shown to accurately characterize pulses from a chirped-pulse–amplification system when its stretcher is detuned from the position for optimal recompression. As a result, various investigations of the performance with respect to the number of ancillary pulses and the range of chromatic dispersion generated in the diagnostic are presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

OPCPA front end and contrast optimization for the OMEGA EP kilojoule, picosecond laser

OMEGA EP is a large-scale laser system that combines optical parametric amplification and solid-state laser amplification on two beamlines to deliver high-intensity, high-energy optical pulses. The temporal contrast of the output pulse is limited by the front-end parametric fluorescence and other features that are specific to parametric amplification. The impact of the two-crystal parametric preamplifier, pump-intensity noise, and pump-signal timing is experimentally studied. The implementation of a parametric amplifier pumped by a short pump pulse before stretching, further amplification, and recompression to enhance the temporal contrast of the high-energy short pulse is described.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Self-phase modulation compensation in a regenerative amplifier using cascaded second-order nonlinearities

Self-phase modulation limits the amplification of short optical pulses because of spatial self-focusing and spectral broadening. Cascaded nonlinearities are theoretically and experimentally investigated for intracavity nonlinearity compensation in a neodymium-doped yttrium-lithium-fluoride (Nd:YLF) regenerative amplifier. Experimental results are in good agreement with simulations. Spectral broadening is significantly reduced, allowing for efficient amplification in a Nd:YLF power amplifier.

Dorrer, C.↗
DOE OSTI2014

Spectral and temporal properties of optical signals with multiple sinusoidal phase modulations

Optical signals generated by multiple sinusoidal temporal phase modulations (multi-FMs) applied to a monochromatic field are studied from the viewpoint of their optical spectrum and temporal modulations arising from spectral impairments. Statistical analysis based on the central limit theorem shows that the signals' optical spectrum converges to a normal distribution as the number of modulations increases, allowing one to predict the frequency range containing a given fraction of the total energy with the associated cumulative density function. The conversion of frequency modulation to amplitude modulation is analyzed and simulated for arbitrary multi-FM signals. These developments are of theoretical and practical importance for high-energy laser systems, where optical pulses are phase modulated in the front end to smooth out the on-target beam profile and prevent potentially catastrophic damage to optical components.

Dorrer, C.↗
DOE OSTI2013

Analysis of Pulse Replicators for High-Bandwidth, High-Dynamic-Range, Single-Shot Optical Characterization

Optical pulse replicators generate multiple replicas of an optical waveform that are averaged to increase the signal-to-noise ratio of single-shot, high-bandwidth temporal measurements. Processing a replicated waveform requires that the delayed realizations of the waveform under test be retimed properly before averaging. Delay miscalibration significantly reduces the measurement bandwidth. Processing algorithms based on edge alignment, centroid matching, and minimization of the distance between replicas decrease the impact of the detrimental bandwidth reduction, and a global distance minimization, simultaneously taking into account the distance between all pairs of retimed replicas, has the best performance, even in the presence of significant measurement noise. The general impact of chromatic dispersion on the averaged waveform is derived in the framework of the temporal transport-of-intensity equation, and the measurement error is quantified for various optical signals.

Dispersion, fiber optics, frequency response, opti↗
DOE OSTI2013

Simulations of the propagation of multiple-FM smoothing by spectral dispersion on OMEGA EP

A one-dimensional (1-D) smoothing by spectral dispersion (SSD) system for smoothing focal-spot nonuniformities using multiple modulation frequencies has been commissioned on one long-pulse beamline of OMEGA EP, the first use of such a system in a high-energy laser. Frequency modulation (FM) to amplitude modulation (AM) conversion in the infrared (IR) output, frequency conversion, and final optics affected the accumulation of B-integral in that beamline. Modeling of this FM-to-AM conversion using the code Miró. was used as input to set the beamline performance limits for picket (short) pulses with multi-FM SSD applied. This article first describes that modeling. The 1-D SSD analytical model of Chuang is first extended to the case of multiple modulators and then used to benchmark Miró simulations. Comparison is also made to an alternative analytic model developed by Hocquet et al. With the confidence engendered by this benchmarking, Miró results for multi-FM SSD applied on OMEGA EP are then presented. The relevant output section(s) of the OMEGA EP Laser System are described. The additional B-integral in OMEGA EP IR components upstream of the frequency converters due to AM is modeled. The importance of locating the image of the SSD dispersion grating at the frequency converters is demonstrated. In conclusion, since frequency conversion is not performed in OMEGA EP’s target chamber, the additional AM due to propagation to the target chamber’s vacuum window is modeled.

36 MATERIALS SCIENCE↗