Broadband Laser Ranging (BLR) is a recently developed instrument for measuring the position of rapidly moving surfaces. Two gas gun experiments were performed to characterize a 16-channel Broadband Laser Ranging system. The precision of the measured position data exceeded expectations and has revealed systematic errors of up to 12 microns. These errors appear to be caused by the interaction of the data analysis routines with the recording hardware's frequency-dependent signal response.

Broadband laser ranging uses spectral interferometry and a dispersive Fourier transform to perform high repetition rate position measurements of explosively-driven surfaces typically moving at several km/s. A broadband fiber laser and fiber interferometer record distance as a relative delay between short pulses, and the beat spectrum of the pulses is mapped into the time domain via long propagation in dispersive fiber. Optical amplification and a fast oscilloscope allow the dispersed spectrum to be recorded in real-time, often at measurement rates of 20-40 MHz. The third-order phase of the dispersive fiber causes distortions in mapping the spectrum into time that must be compensated for when analyzing the measured data. We characterize the accuracy and precision of BLR systems by performing a scan of static positions and comparing our single-shot measurements against position measurements from a commercial Michelson interferometer. We demonstrate a combination of hardware and data analysis that measures position to within 30 microns over a 27 cm range with very high precision.

Broadband laser ranging (BLR) is essentially a spectral interferometer used to infer distance to a moving target. The light source is a mode-locked fiber laser, and chromatic dispersion maps the spectral interference pattern into the time domain, yielding chirped beat signals at the detector. A BLR record is a sequence of these chirped signals, representing consecutive target positions. To infer distance to a target, each underlying pulse envelope must be consistently registered and subtracted despite environmentally-induced variability. Then, nonlinear transformation of the phase is applied to remove the chirp, an FFT is performed to determine the peak frequency of the de-chirped signal, and a calibration factor relating de-chirped frequency to distance results in target position. Here, these analysis steps are discussed in detail.

Broadband Laser Ranging (BLR) is a new diagnostic being developed in collaboration across multiple USA Dept. of Energy (DOE) facilities. Its purpose is to measure the precise position of surfaces and particle clouds moving at speeds of a few kilometers per second. The diagnostic uses spectral interferometry to encode distance into a modulation in the spectrum of pulses from a mode-locked fiber laser and uses a dispersive Fourier transformation to map the spectral modulation into time. This combination enables recording of range information in the time domain on a fast oscilloscope every 25-80 ns. Discussed here are some of the hardware design issues, system tradeoffs, calibration issues, and experimental results. BLR is being developed as an add-on to conventional Photonic Doppler Velocimetry (PDV) systems because PDV often yields incomplete information when lateral velocity components are present, or when there are drop-outs in the signal amplitude. In these cases, integration of the velocity from PDV can give incorrect displacement results. Experiments are now regularly fielded with over 100 channels of PDV, and BLR is being developed in a modular way to enable high channel counts of BLR and PDV recorded from the same probes pointed at the same target location. In this way instruments, will independently record surface velocity and distance information along the exact same path.

Highly phase-mismatched nonlinear interactions can generate spatially localized optical fields that can affect the performance of nonlinear optical devices. We present a theoretical description of the generation of such spatially localized optical fields by ultrafast pulses. The effects of temporal walk-off and pump depletion are discussed, along with methods for suppression of the localized field while maintaining the performance of the nonlinear device. The model is validated by the measurement of the spatial profile of the localized field in a quasi-phase-matched (QPM) aperiodically poled lithium niobate (A-PPLN) waveguide. Finally, we fabricate and characterize A-PPLN devices with a 33% duty cycle to reduce the locally generated field by 90%.

We measure the complex transfer function (CTF) of aperiodically poled lithium niobate waveguide devices and investigate the sources of CTF distortions, which are related to variations in the spatial distribution of the nonlinear coefficient and phase-mismatch profile.

At the National Ignition Facility (NIF), home of the world's largest laser, a critical pulse screening process is used to ensure safe operating conditions for amplifiers and target optics. To achieve this, high speed recording instrumentation up to 34 GHz measures pulse shape characteristics throughout a facility the size of three football fields-which can be a time consuming procedure. As NIF transitions to higher power handling and increased wavelength flexibility, this lengthy and extensive process will need to be performed far more frequently. We have developed an accelerated high-throughput pulse screener that can identify nonconforming pulses across 48 locations using a single, real-time 34-GHz oscilloscope. Energetic pulse shapes from anywhere in the facility are imprinted onto telecom wavelengths, multiplexed, and transported over fiber without distortion. The critical pulse-screening process at high-energy laser facilities can be reduced from several hours just seconds-allowing greater operational efficiency, agility to system modifications, higher power handling, and reduced costs. Typically, the sampling noise from the oscilloscope places a limit on the achievable signal-to-noise ratio of the measurement, particularly when highly shaped and/or short duration pulses are required by target physicists. We have developed a sophisticated signal processing algorithm for this application that is based on orthogonal matching pursuit (OMP). This algorithm, developed for recovering signals in a compressive sensing system, enables high fidelity single shot screening even for low signal-to-noise ratio measurements.

Indirect drive experiments have now been carried out with laser powers and energies up to 520 TW and 1.9 MJ. These experiments show that the energy coupling to the target is nearly constant at 84% ± 3% over a wide range of laser parameters from 350 to 520 TW and 1.2 to 1.9 MJ. Experiments at 520 TW with depleted uranium hohlraums achieve radiation temperatures of ∼330 ± 4 eV, enough to drive capsules 20 μm thicker than the ignition point design to velocities near the ignition goal of 370 km/s. A series of three symcap implosion experiments with nearly identical target, laser, and diagnostics configurations show the symmetry and drive are reproducible at the level of ±8.5% absolute and ±2% relative, respectively.

We demonstrate temporal imaging for the measurement and characterization of optical arbitrary waveforms and events. The system measures single-shot 200 ps frames at a rate of 104 MHz, where each frame is time magnified by a factor of -42.4x. Impulse response tests show that the system enables 783 fs resolution when placed at the front end of a 20 GHz oscilloscope. Modulated pulse trains characterize the system's impulse response, jitter, and frame-to-frame variation.

We have achieved the NIF design goals for power and energy by delivering 1.86 MJ of ultra-violet energy in a wide dynamic range (> 300: 1), 22.5-ns shaped ignition pulse with a peak power of 520 TW.

We report recent progress in the development of RadOptic detectors, radiation to optical converters, that rely upon x-ray absorption induced modulation of the optical refractive index of a semiconductor sensor medium to amplitude modulate an optical probe beam. The sensor temporal response is determined by the dynamics of the electron-hole pair creation and subsequent relaxation in the sensor medium. Response times of a few ps have been demonstrated in a series of experiments conducted at the LLNL Jupiter Laser Facility (JLF). This technology will enable x-ray bang-time and fusion burn-history measurements with ∼ ps resolution.

Code/pulse-position-swapping (CPPS) is a communications scheme that substitutes pulse-position-modulation (PPM) symbols with optical-code-division-access (O-CDMA) codes. CPPS retains the multiple bits per symbol communication of M-ary PPM and the asynchronous multiple access of O-CDMA. Additionally, CPPS has the advantages of granular communications, common electrical bandwidth for all users independent of data rates, compatibility with free-space or guided (fiber and waveguide) communication links, and compatibility with intensity modulation/direct detection. The transmitted symbols (codes) of CPPS are translated from a deserialized bit stream that has been divided into words of length log(2)M. Thus the receivers associate the detected symbol with the original bit sequence by means of an electronically implemented look-up-table (LUT). This paper describes the architecture and design of a direct translating receiver based on map-coding, which uses optical processing to output the transmitted bit sequence without the need for a LUT. Analyses and computations characterize the receiver concept in terms of bit errors (mistranslations).

The design and performance of a time lens-based, single-shot, ultrafast waveform recording system with subpicosecond resolution and 200-ps record length is presented. The system evolved from recording rapidly changing waveforms at 104 Mframes/sec with limited dynamic range to a >20 dB dynamic range system capturing single events. Latest results demonstrate its integration with a new ultrafast optically-modulating x-ray sensor.