StarDriver was recently proposed as a highly flexible laser driver for inertial confinement fusion and high energy density physics. It envisions a laser drive consisting of very many beams at an aperture and energy where the optical technology is well-developed, used in concert to create a large scale laser driver system. In this paper we describe a StarDriver–class laser with 5120 physical beamlets disposed about the target chamber in 80 evenly spaced ports, each port containing 64 beamlets, each beamlet having about ~1.5 THz of 2D SSD bandwidth and suitable phase plates, an aperture of ~65 mm, an energy of 80 J, and frequency-converted to ~351 nm. StarDriver has many beamlets at an aperture where optical technology is well-developed, and each beamlet has energy ~100 J in a several times diffraction limited beam. The ensemble of beamlets has frequency bandwidth 2%-10%, thereby providing significant control of both hydrodynamic and laser-plasma instabilities The drive at the target is ~400 kJ, has a well-behaved low L-mode spectrum, and smooth’s very rapidly, reaching an asymptotic smoothness of <1% in less than 1 ns. We also review recent results showing that the 2ωpe instability can be significantly reduced by 20 THz bandwidth.

StarDriver was recently proposed as a highly flexible laser driver for inertial confinement fusion and high energy density physics. It envisions a laser drive consisting of many beamlets at an aperture where optical technology is well-developed, and each beamlet has energy ~100 J in a several times diffraction limited beam. Each beamlet has ~1.5THz of 2D SSD smoothing, but the ensemble of lasers has frequency bandwidth 2–10 %, thereby providing significant control of both hydrodynamic and laser-plasma instabilities. In this paper we illustrate the attractive features of the StarDriver concept with detailed calculations of beam smoothing for control of hydrodynamic instabilities in a direct drive ICF target, using a full 3D simulation of the laser drive. We describe here a StarDriver-class laser with 5120 physical beamlets disposed about the target chamber in 80 evenly spaced ports, each port containing 64 beamlets, each beamlet having about ~1.5THz of 2D SSD bandwidth and suitable phase plates, an aperture of ~65 mm, an energy of 80 J, and frequency-converted to ~351 nm. The drive at the target is ~400 kJ, has a well-behaved low L-mode spectrum, and smoothes very rapidly, reaching an asymptotic smoothness of <1 % in less than 1 ns. 2 MJ of drive at the same smoothing performance may be obtained by increasing the number of beamlets. An attractive feature of StarDriver is that the tolerances on the individual beamlet parameters are quite relaxed.

We report the first calculations of the 2 omega(pe) instability in an IFE-scale corona of a direct drive target being driven by a StarDriver-class laser. Using realistic plasma profiles (density, temperature, flow velocity and Z) taken from full hydrodynamic simulations of the capsule implosion, we propagate the StarDriver beamlets to the 1/4 critical surface using ray-tracing. We then use that 'k-space' of laser modes in a model of the absolute 2 omega(pe) instability in the inhomogeneous plasma at 1/4 critical density. Our calculations indicate that 15-20 THz of bandwidth at 351 nm wavelength (about 2% bandwidth) significantly reduces or suppresses the absolute instability at most times in the drive pulse. A bandwidth of 35 THz suppresses it at all times in the drive pulse. We note that 2% bandwidth similar to 20 THz is achievable using laser gain media available today.

We propose a novel method to minimize laser–plasma instabilities and improve laser–plasma coupling by the use of multi-beam laser architecture with a large system frequency bandwidth and many beamlets per unit solid angle. The StarDriver™, laser driver is constructed from 104 to 105 individual lasers, each delivering nominally 100 J in pulses of ~3–30 ns at a nominal wavelength of ~355 nm with better than 3–5 diffraction-limited performance. The beamlets are individually relatively narrowband to facilitate maximum laser performance, but the ensemble of beamlets span a wide frequency range. Currently available laser media enable Δω/ω ~ 2 % at 355 nm with the possibility of system bandwidths approaching 10 % in the future. The many beamlets of StarDriver™ provide optimal asymptotic smoothing for hydrodynamic instabilities (0–1 %), innovative focusing strategies including zooming, and the large bandwidth enables extremely rapid hydrodynamic smoothing times ~30 fs. The distribution of frequencies among the beamlets allows flexibility for fine control of the seeding of the Rayleigh–Taylor instability. The ultra-broad bandwidth combined with the large total k-spectrum of the laser drive in the plasma corona may enable complete suppression of the most problematic laser–plasma instabilities such as stimulated Brillouin backscatter, stimulated Raman scatter, cross-beam energy transfer, and the two plasmon decay instability. StarDriver™ offers potentially superior flexibility in laser drivers for inertial confinement fusion, enabling almost arbitrary sequencing of wavelength, polarization, focus, and fine control of the spatio-temporal properties of the drive in the corona. The highly modular strategy of StarDriver™ should enable an attractive development pathway as well as maximizing overall system efficiency.

Recent efforts to “engineer” new nonlinear optical materials with specific desired characteristics has engendered a need for a theoretical description of optical properties which is readily accessible to chemists, yet correctly treats the essential physics of dielectric response. This paper describes a simple empirical molecular orbital model which gives useful insights into the relationship between chemical composition, crystalline structure, and optical susceptibilities. We compare the probabilities of finding new harmonic generators in various chemical classes. Rigorous bounds on the magnitudes of linear and nonlinear optical coefficients and their anisotropies are also discussed.

I present a new treatment of the theory of nonforward stimulated Raman scattering (SRS) in the field of a phase-modulated pump, where the pump phase modulation is an arbitrary function of time. The theory is accurate enough to determine the performance limitations on laser systems where SRS is a potentially controlling parasitic. Calculations are described for the Sr-5(PO4)(3)F amplifier medium where the laser beam has a pure rf modulation typical of those attainable in the laboratory. The predictions of this theory are compared with the D'yakov approximation for SRS in the field of a laser beam whose phase is Gaussian noise. (C) 2007 Optical Society of America.

Accurate predictions of the performance of frequency conversion requires knowledge of the spatial variation of departures from the phase-matching condition in the converter crystals. This variation is caused by processes such as crystal growth and crystal surface finishing. Gravitational sag and mounting configurations also lead to deformation and stresses which cause spatially varying departures from the phase-matching condition. We have modeled the effect of gravitational forces on conversion efficiency performance of horizontal converter crystals and have shown for the NIF mounting configurations that gravity has very little effect on conversion efficiency.

Efficient frequency tripling of high-fluence, narrow-band laser pulses is routinely accomplished with a doubling crystal and a sum-frequency mixer. The addition of a second mixer can dramatically improve conversion efficiencies for the large bandwidths of interest for inertial confinement fusion. Designs that involve two doublers similarly offer a higher dynamic range of conversion efficiency versus intensity than the usual two-crystal design.

A theory is presented for the transfer of a perturbation of the electric field from the input to the output of a frequency converter. The transfer relationship for the field ripple is shown to depend on the plane-wave operating parameters of the converter. Predictions of the theory are shown to be in excellent agreement with full numerical simulations of doubling and tripling and experiments measuring ripple transfer in frequency doubling.

The effects of the phase mismatch due to cubic nonlinearity in the equations for second-harmonic generation are investigated. We show that the phase mismatch induced by the nonlinear refractive index of a doubling crystal can dramatically reduce the conversion efficiency of high-peak-power laser pulses. Simple, analytic expressions are derived for the conversion efficiency of cw radiation and for the estimation of the dispersion in the nonlinear refractive index of the doubling crystal, which is quite important in the determination of the magnitude of the nonlinear effects on maximum conversion. The consequences that these nonlinearities have on the frequency doubling of ultrashort (≤100 fs) pulses, including the additional effects of group-velocity walk-off between the pulses, are then numerically calculated.