OECD reviews of higher education in regional and city development, State of Victoria, Australia

With more than 5.3 million inhabitants Victoria is the second most populous state in Australia. Once a manufacturing economy, Victoria is now transforming itself into a service and innovation-based economy. Currently, the largest sectors are education services and tourism. In terms of social structure, Victoria is characterised by a large migrant population, 24% of population were born overseas and 44% were either born overseas or have a parent who was born overseas. About 70% of the population resides in Melbourne. Victoria faces a number of challenges, ranging from an ageing population and skills shortages to drought and climate change and increased risk of natural disasters. Rapid population growth, 2% annually, has implications for service delivery and uneven development as well as regional disparities. There are barriers to connectivity in terms of transport and infrastructure, and a high degree of inter-institutional competition in tertiary education sector. The business structure in Victoria includes some highly innovative activities such as in biotechnology, but other sectors, especially those with high number of small and medium-sized enterprises, are lagging behind. Most of the larger manufacturing enterprises are externally controlled and there is uncertainty over the long term investments they will make in the state, as well as the place of Victoria in the global production networks

Observation of Biexcitonic Optical Bistability and Optical Limiting in CuCl

Experimental evidence for the occurrence of optical bistability using the biexciton two-photon resonance in CuCl is presented. These observations agree with recent theoretical predictions that require an intensity of 10 MW/cm2 and 10-μm-thick etalons with 90% reflective coatings. Earlier much less demanding predictions neglected two important physical effects: unsaturable background absorption at the biexciton from the tail of the exciton resonance and broadening of the biexciton resonance with intensity

Preparation of random phase plates for laser beam smoothing

Phase plates are required for removing aberrations from laser beams caused by inhomogeneities in the optical components of the laser. The first type of plate that we prepared consisted of a bi-level optical component that caused spatial smoothing of the beam by breaking it up into a fine scale spatial structure. This was made by etching a pattern directly into the substrate using HF/NH{sub 4}F. Components up to 80 cm in diameter were prepared but these are only 85% efficient because of beam losses in secondary maxima. Multilevel designs are more efficient and we have prepared 5 inch diameter samples with 16 levels. These require four separate etch steps but have efficiencies greater than 90%

Scaling to Ultra-High Intensities by High-Energy Petawatt Beam Combining

The output pulse energy from a single-aperture high-energy laser amplifier (e.g. fusion lasers such as NIF and LMJ) are critically limited by a number of factors including optical damage, which places an upper bound on the operating fluence; parasitic gain, which limits together with manufacturing costs the maximum aperture size to {approx} 40-cm; and non-linear phase effects which limits the peak intensity. For 20-ns narrow band pulses down to transform-limited sub-picosecond pulses, these limiters combine to yield 10-kJ to 1-kJ maximum pulse energies with up to petawatt peak power. For example, the Advanced Radiographic Capability (ARC) project at NIF is designed to provide kilo-Joule pulses from 0.75-ps to 50-ps, with peak focused intensity above 10{sup 19} W/cm{sup 2}. Using such a high-energy petawatt (HEPW) beamline as a modular unit, they discuss large-scale architectures for coherently combining multiple HEPW pulses from independent apertures, called CAPE (Coherent Addition of Pulses for Energy), to significantly increase the peak achievable focused intensity. Importantly, the maximum intensity achievable with CAPE increases non-linearly. Clearly, the total integrated energy grows linearly with the number of apertures N used. However, as CAPE combines beams in the focal plane by increasing the angular convergence to focus (i.e. the f-number decreases), the foal spot diameter scales inversely with N. Hence the peak intensity scales as N{sup 2}. Using design estimates for the focal spot size and output pulse energy (limited by damage fluence on the final compressor gratings) versus compressed pulse duration in the ARC system, Figure 2 shows the scaled focal spot intensity and total energy for various CAPE configurations from 1,2,4, ..., up to 192 total beams. They see from the fixture that the peak intensity for event modest 8 to 16 beam combinations reaches the 10{sup 21} to 10{sup 22} W/cm{sup 2} regime. With greater number of apertures, or with improvements to the focusability of the individual beams, the maximum peak intensity can be increased further to {approx} 10{sup 24} W/cm{sup 2}. Lastly, an important feature of the CAPE architecture is the ability to coherently combine beams to produce complex spatio-temporal intensity distributions for laser-based accelerators (e.g. all-optical electron injection and acceleration) and high energy density science applications such as fast ignition

Color separation gratings for diverting the unconverted light away from the NIF target

Most of the glass laser based inertial confinement fusion systems around the world today employ non-linear frequency conversion for converting the 1.053 micrometer light at the fundamental frequency (referred to as 1{omega} light) to either its second harmonic (called 2{omega}) at 527 nm or to its third harmonic (called 3{omega}) at 351 nm. Shorter wavelengths are preferred for laser fusion because of the improved coupling of the laser light to the fusion targets due to reduced fast electron production at shorter wavelengths. The frequency conversion process, however, is only about 60-70% efficient and the residual 30-40% of the energy remains at 1{omega} and 2{omega} frequencies. Color separation gratings (CSGs) offer a versatile approach to reducing and possibly eliminating the unconverted light at the target region. A CSG consists of a three- level lamellar grating designed so that nearly all of the 3{omega} light passes through undiffracted while the residual 1{omega} and 2{omega} energy is diverted into higher diffraction orders. The diffraction angle is determined solely by the grating period. We have demonstrated the concept of using a color separation grating. We fabricated a 345 micrometer period CSG in fused silica using lithographic processes and wet etching. The measured far field indicates that greater than 95% of the incident light is preserved in the 3{omega} zeroth order while less than 5% of unconverted 1{omega} and 2{omega} light is remaining in the zeroth order. We would like to add that diffractive optics fabricated in fused silica by wet etching in hydrofluoric acid should have high damage threshold. Our experience suggests that the damage threshold of the etched substrate is at least as high as the unetched part. 6 refs., 4 figs., 1 tab

10-kJ Status and 100-kJ Future for NIF PetaWatt Technology

We discuss the status of the NIF ARC, an 8-beam 10-kJ class high-energy petawatt laser, and the future upgrade path of this and similar systems to 100-kJ-class with coherent phasing of multiple apertures

Development of diagnostics for high-energy petawatt pulses

Applications accessed by high energy petawatt (HEPW) lasers require complete, single-shot characterization of pulse spatial, temporal, and energy characteristics. We describe techniques that enable single-shot characterization of the temporal shape and pulse contrast of HEPW pulses with >10{sup 8} dynamic range over a ns-temporal window. Approaches to measure pulse durations that span two orders of magnitude will be discussed. Finally, we describe a novel implementation of spectrally dispersed two-beam interferometry for measurement of the phase difference between two HEPW pulses. This technique can be applied to dispersion and B-integral measurements in a HEPW system, as well as to achieve precise timing of nanosecond pulses. Lastly, spectrally dispersed interferometry represents an ideal technique to enable coherent addition of HEPW pulses for production of ultrahigh intensities

Status of the "ARC", a Quad of High-Intensity Beam Lines at the National Ignition Facility

We present the status of plans to commission a short-pulse, quad of beams on the National Ignition Facility (NIF), capable of generating > 10 kJ of energy in 10 ps. These beams will initially provide an advanced radiographic capability (ARC) to generate brilliant, x-ray back-lighters for diagnosing fuel density and symmetry during ignition experiments. A fiber, mode-locked oscillator generates the seed pulse for the ARC beam line in the NIF master oscillator room (MOR). The 200 fs, 1053 nm oscillator pulse is amplified and stretched in time using a chirped-fiber-Bragg grating. The stretched pulse is split to follow two separate beam paths through the chain. Each pulse goes to separate pulse tweakers where the dispersion can be adjusted to generate a range of pulse widths and delays at the compressor output. After further fiber amplification the two pulses are transported to the NIF preamplifier area and spatially combined using shaping masks to form a split-spatial-beam profile that fits in a single NIF aperture. This split beam propagates through a typical NIF chain where the energy is amplified to several kilojoules. A series of mirrors directs the amplified, split beam to a folded grating compressor that is located near the equator of the NIF target chamber. Figure 1 shows a layout of the beam transport and folded compressor, showing the split beam spatial profile. The folder compressor contains four pairs of large, multi-layer-dielectric gratings; each grating in a pair accepts half of the split beam. The compressed output pulse can be 0.7-50 ps in duration, depending on the setting of the pulse tweaker in the MOR. The compressor output is directed to target chamber center using four additional mirrors that include a 9 meter, off-axis parabola. The final optic, immediately following the parabola, is a pair of independently adjustable mirrors that can direct the pair of ARC beams to individual x-ray backlighter targets. The first mirror after the compressor leaks a small fraction of the light that is transported to a diagnostics station where detailed measurements of the spatial and temporal characteristics of the ARC pulse will be recorded for each shot. A NIF quad of short-pulse beams will support up to eight, independently-timed, short-pulse beams, capable of producing an x-ray motion picture. Alternatively, the combined aperture of the quad can direct > 10 kJ of energy in 10 psec onto a single target, enabling research into fast ignition and high-energy-density science on the NIF. We will discuss modifications to the NIF to accommodate ARC, including features such as simultaneous NIF-ARC operation in the same NIF quad, protection against backward propagating pulses from the target and plans to coherently add split beams