New catadioptric objectives have been developed with large bandwidths in the DUV, high numerical apertures (NAs), and small size. This can be achieved using a single glass material. Designs are specifically optimized for loose alignment tolerances and ease of manufacturability. Applications include broad band DUV imaging and high resolution immersion imaging for industrial microscopy and life sciences.
Efficient phase conversion of laser light can be achieved using continuous distributed phase plates (DPPs) for applications in laser-beam shaping and laser-beam smoothing. These DPPs are deep, surface-relief, continuous phase plates that exhibit near-unity energy efficiency, envelope and power spectrum flexibility, and reduced near-field intensity modulation as compared to stepped diffractive optics. Specific DPP designs for inertial-confinement-fusion laser systems, used to irradiate fuel capsules, is presented.
An inherently fringe stable interferometer, with uniform recording-plane exposure, produces transmission gratings with uniformly high efficiency. The surface-relief structures recorded in positive photoresist are ideal for their transfer into specialized candidate materials. These structures have many applications in high-power lasers including beam smoothing, pulse compression, and low-reflection surfaces. Also, accurate modeling of surface-relief grating efficiencies, using the actual groove profile, allows optimization of grating parameters.
In the OMEGA Upgrade laser system 60 beams are used to symmetrically irradiate the target. To achieve optimum fuel compression, the beams must irradiate the target uniformly, requiring excellent beam quality in each beam and nearly identical temporal waveforms so that target irradiation remains balanced throughout the course of the implosion process. Propagation of high intensity, pulse-shaped IR and UV laser beams through long air paths leads to losses and decreased beam quality due to stimulated rotational Raman scattering (SRRS). With short pulses, it is necessary to use transient Raman theory to include build up and relaxation of the medium. Imperfect beam quality leads to intensity not spots that can lower the effective threshold for Raman scattering. A detailed analysis of the system to determine energy efficiency and beam quality necessitates a four-dimensional (4-D) treatment of both the optical beam and the air path. In this paper we outline the 4-D modeling of the OMEGA Upgrade laser and describe full-scale experimental investigations of SRRS in air.
Surface-relief, holographic transmission gratings are generated in positive photoresist with excellent performance characteristics. High intrinsic grating efficiencies of 99% are obtained using an inherently fringe-stable holographic interferometer, which is maximally insensitive to incident pointing errors, to create high aspect ratio nonsinusoidal grooves. Uniform exposures are achieved over apertures of 100 mm in diameter using scanning techniques. Repeatable results are achieved by maintaining pre-exposure and post-exposure processing along with the various exposure parameters.