Michael Larsson

Proximity-compensated blazed transmission grating manufacture with direct-writing, electron-beam lithography

Proximity-compensated, as well as uncompensated, blazed transmission gratings with periods of 4, 8, and 16 µm were manufactured with direct-writing, electron-beam lithography in positive resist. The compensated gratings performed better than the uncompensated ones. For the 4-µm compensated grating the measured diffraction efficiency was 67%. It was 35% for the uncompensated grating. The compensation was made by repeated convolutions in the spatial domain with the electron-beam point spread function. We determined this function by retrieving the phase from the measured diffraction pattern of the uncompensated gratings.

Single photomask, multilevel kinoforms in quartz and photoresist: manufacture and evaluation

Kinoforms manufactured in photoresist by photolithographic techniques using a single, ten-level, grey scale photomask, exposed in a specially designed laser exposure system, are described. Kinoforms designed for uniform as well as for partial Gaussian beam illumination are discussed. The highest measured diffraction efficiency was 55%. Photoresist kinoforms were transferred into quartz substrates by reactive ion etching. The highest measured diffraction efficiency for the resulting all-quartz kinoforms was 53%.

Multilevel grating array illuminators manufactured by electron-beam lithography

Abstract Two-dimensional multilevel grating array generators with regular M × N fan-out patterns are designed using both nonlinear optimization and an iterative phase retrieval algorithm. Ten-level designs with fan-out of 2×2, 4×4, 1×8, and 8×8, with design efficiencies of 87%, 92%, 95% and 89% are manufactured using direct electron-beam lithography on electron resist. The measured efficiencies, 79%, 84%, 84% and 84% of transmitted light, respectively, are ∼ 10% above the theoretical efficiencies of non-separable binary-phase array illuminators.

Successive development optimization of resist kinoforms manufactured with direct-writing, electron-beam lithography

It is shown that multilevel SAL 110 resist kinoforms can be developed stepwise. Measurements of the kinoform diffraction pattern, performed between the development steps, permitted correct final developments to be made. No significant relief shape degradation was observed for development times as high as 25 min. The results imply that the electron-beam exposure doses, and hence the exposure time, can be reduced by a factor of 3 compared with doses used currently.

Nd:YAG laser machining with multilevel resist kinoforms

We demonstrate that resist kinoforms can be used for laser micromachining. A 10-level resist kinoform, manufactured by electron-beam lithography, was shown to have a diffraction efficiency of 68%. Nine diffraction-limited holes were simultaneously drilled in 0.10-mm-thick stainless steel. Marking in a silicon wafer is also demonstrated.

Optical properties of diffractive, bifocal, intraocular lenses

The resolution of diffractive, bifocal, intraocular lenses was studied with regard to pupil displacement and diameter size through computer simulations, bench measurements, and patient vision-acuity measurements. Good agreement was obtained between these three methods of investigation. In particular, we find that pupil displacements of the order of 1 mm reduce the resolution considerably for these lenses.

Laser-triggered high-voltage plasma switching with diffractive optics.

High-power lasers can be used to induce ionization of gases and thereby enable rapid triggering of electrical discharge devices, potentially faster than any devices based on mechanical or solid-state switching. With diffractive optical elements (DOEs) the laser light can conveniently be directed to positions within the gas so that an electrical discharge between two high-voltage electrodes is triggered reliably and rapidly. Here we report on two different types of DOE used for creating an electrical discharge in pure argon for potential high-voltage applications. One is the diffractive equivalent of a conventional axicon that yields an extended, and continuous, high-intensity focal region between the electrodes. The other is a multiple-focal-distance kinoform--a DOE that is designed to produce a linear array of 20 discrete foci, with high peak intensities, between the electrodes. We show that DOEs enable efficient, rapid switching and may provide increased flexibility in the design of novel electrode configurations.

Single Photomask, Multilevel Kinoforms: Manufacture And Evaluation

Kinoforms manufactured in photoresist with photolithographic techniques using a single, ten-level, grey-scale photomask, exposed in a specially designed laser exposure system, are described. Kinoforms designed for uniform as well as for partial Gaussian beam illumination are investigated. Measured diffraction efficiencies exceeded 50 percent.

Letter imaging by diffractive, bifocal intraocular lenses: a computer study

Letter imaging of ideal-model diffractive, bifocal intraocular lenses is computer simulated. How the image is influenced by letter size, pupil diameter, and pupil displacement is studied. We find that the image quality is good as long as the letter sizes are not of the same order of magnitude as the unfocused background. If the sizes are comparable, considerable image degradation occurs.

A New Kinoform Manufacturing Process

Kinoforms were manufactured by transferring computer-calculated phase-data into a photo-resist layer applied to a glass substrate. This transfer was carried out with conventional photolithographic techniques, using one single photomask exposed in discrete grey scale levels. The photomasks were generated in a specially designed PC controlled exposure system. We present kinoforms manufactured in ten levels with a pixel width of 20 μm. About SO% of the totally transmitted power was diffracted into the desired intensity distribution, and a few percent were undeflected at λ = 632.8 nm.