Digital micromirror devices (DMDs) have found many scientific research applications. We present adaptive optics techniques exploiting the point spread function (PSF) of a DMD pixel to enhance the fidelity of image-projection-based laser machining. Femtosecond laser pulses with intensity profiles spatially shaped by a DMD were demagnified to a sample via a microscope objective, with ~10 DMD mirrors, each of width ~10µm, approximately projecting to the optical setup diffraction limit of ~1µm. A single DMD mirror then scales geometrically to dimensions well below the diffraction limit, permitting various techniques to enhance machining. By digitally shifting an intensity mask on the DMD between pulses while the sample remains static, machined features with resolutions below the single-exposure diffraction limit are produced (similar to pitch splitting multiple exposure techniques), with a reduction of <2.5x achieved in nickel. By combining digital image shifts with real-time sample image recognition algorithms, point-to-point positional accuracy is camera-resolution-limited (~500nm) rather than translation stage-limited. Furthermore, the PSF allows near-continuous intensity distributions rather than binary on/off intensity patterns, and have been used to produce variable-depth surface texturing (up to 40nm depth changes with 2µm period demonstrated in metals) features via single shots. Algorithms have been used to automate optical proximity corrections for arbitrary intensity masks in order to reduce machining errors due to optical filtering. These techniques are being combined to produce <1cm2 size, highly complex substrates for the production of biologically-friendly cell growth assays, with the viability of human bone stem cells on flexible substrates demonstrated.
PbSe quantum dots (QDs) were grown in high-refractive-index low-melting-temperature leadphosphate glass. QDs with various sizes ranging from 2 nm to 5.3 nm were grown by controlling the growth parameters, heat-treatment temperature and time. The corresponding room-temperature exciton absorption was tuned within the infrared region from 0.93 μm to 2.75 μm. Photoluminescence was measured for samples with absorption peaks above 0.95eV. Real time quantum dot growth was demonstrated by monitoring the evolution of exciton absorption with temperature and time duration. As a demonstration of the use of QDs in laser applications, the saturation fluence (F<sub>sat</sub>) of one of the QDs was evaluated and found to be ~2.1 μJ/cm2 at 1.2 μm.
High Harmonic Generation is a well established technique for generating Extreme Ultraviolet radiation. It is a promising
technique for both structure and spectroscopic imaging due to both the high flux and coherence of the source, and the
existence of multiple absorption edges at the generated wavelengths. To increase the flux, a focussing device can be
used. Here we present focussing results for a Mo/Si spherical mirror that has been used in an off-axis arrangement, and
give extensive analysis of the resulting astigmatic focus and its consequence on diffractive imaging. The astigmatic beam
exists as a vertical and horizontal focus, separated by a circle of least confusion. With the help of a theoretical model we
show that the most intense part of the beam is always the second line foci and that the phase at the focus is strongly
saddle-shaped. However, this phase distortion cannot explain the significant interference peak splitting that is
experimentally observed in our diffraction patterns. Instead we propose that the beam quality is degraded upon reflection
from the multilayer mirror and it is this asymmetric phase distortion that causes the diffraction peak splitting.