DUV Laser Research Articles

Plasma Polymer Tailoring of the Topography and Chemistry of Surfaces at the Nanoscale

We demonstrate in this paper that plasma polymer can be advantageously used to provide surfaces with topography and chemical control at the nanoscale. Moreover, this technique was also proved to be of high interest to functionalize atomic force microscopy tips that were used to probe the patterned surfaces in pulsed force mode. This approach allowed demonstration by a direct observation of the possibility of generating alternating hydrophilic/hydrophobic surfaces at the nanoscale prepared by DUV laser irradiation. Such a versatile and simple route opens new possibilities in the field of smart surfaces engineering.

Direct ArF laser photopatterning of metal oxide nanostructures prepared by the sol–gelroute

We developed specific negative tone resists suitable for preparing periodic inorganicnanostructures by ArF photolithography. This approach is based on the sol–gel chemistryof modified metal alkoxides followed by DUV laser irradiation. Patterning at the nanoscalewas demonstrated by using an achromatic interferometer operating at 193 nm. In a secondstep, thermal treatment could be used to obtain metal oxide nanostructures (ZrO2,TiO2). Such thermal treatment did not affect the integrity of the nanostructures. TheDUV-induced modifications of the physico-chemical properties of the sol–gel thin filmwere followed by ellipsometry, XPS and AFM. The crystalline structure of thematerial after thermal treatment was proved by DRX analysis. Examples of periodicnanostructures are given in order to illustrate the possibilities opened by thisnew route that provides a convenient method to create transparent, robust, highrefractive index nanostructures compatible with a wide variety of substrates.

Efficient diffractive optical elements in chalcogenide glass layers fabricated by direct DUV laser writing

Direct laser writing with high power densities at a wavelength of 244 nm is applied to the patterning of surface relief diffractive optical elements (DOEs) with submicron features in thin chalcogenide layers of different compositions. The topology of created features in dependence on exposure conditions is investigated. Potential and limitations of this technique for the fabrication of efficient DOEs for applications from the visible to the near infrared spectral region are discussed on the basis of examples.

Nanostructuring of organic and chalcogenide resists by direct DUV laser beam writing

A direct writing DUV laser lithography system was used to write surface relief gratings into an organic positive DUV resist and into amorphous chalcogenide layers. For both material groups feature sizes down to 160 nm with aspect ratios of two and more were realised. The nanostructures in chalcogenide layers emerge directly during the writing process, without any development or etching process.

New laser pattern generator for DUV using a spatial light modulator

A new breed of pattern generators for photomasks using spatial light modulator (SLM) technology with many architectural similarities to that of a modern stepper is under development. The SLM, having an array of individually addressed micromirrors, is illuminated by an excimer DUV laser pulse and imaged onto the surface of a photomask. A stage moves the photomask to a new position and the SLM is reloaded with a new portion of the pattern, followed by a new exposure. The complete pattern is stitched together at a high rate. Analog modulation of each pixel provides an address grid satisfying the requirements of the industry roadmap without speed penalty. The new SLM technology has the resolution to rival that of e-beam pattern generators, yet provides the productivity of laser patterning due to the massive parallel exposure strategy.

Fiber-optic probes with improved excitation and collection efficiency for deep-UV Raman and resonance Raman spectroscopy

The ability of ultraviolet resonance Raman spectroscopy (UVRRS) to determine structural, environmental, and analytical information concerning low-concentration aqueous biomolecules makes it a powerful bioanalytical and biophysical technique. Unfortunately, its utility has been limited by experimental requirements that preclude in situ or in vivo studies in most cases. We have developed the first high-performance fiber-optic probes suitable for long-term use in pulsed UVRRS applications in the deep- UV (DUV, 205-250 nm). The probes incorporate recently developed improved ultraviolet (IUV) fibers that do not exhibit the rapid solarization and throughput decay that previously hampered the use of optical fibers for delivering pulsed, DUV light. A novel 90 degrees mirrored collection geometry is used to overcome the inner-filtering effects that plague flush-probe geometries. The IUV fibers are characterized with respect to their efficacy at transmitting pulsed, DUV laser light, and prototype probes are used to obtain pulsed UVRRS data of aromatic amino acids, proteins, and hormones at low concentrations with 205-240-nm pulsed excitation. Efficient probe geometries and fabrication methods are presented. The performance of the probes in examining resonance-enhanced Raman signals from absorbing chromophores is investigated, and the optimal excitation wavelength is shown to be significantly red-shifted from the maximum of the resonance Raman enhancement profile. Generally applicable procedures for determining optimal experimental conditions are also introduced.