K. Richardson

PROGRESS ON THE FABRICATION OF ON-CHIP, INTEGRATED CHALCOGENIDE GLASS (CHG)-BASED SENSORS

In this paper, we review ongoing progress in the development of novel on-chip, low loss planar molecular sensors that address the emerging need in the field of biochemical sensing. Chalcogenide glasses were identified as the material of choice for sensing due to their wide infrared transparency window. We report the details of manufacturing processes used to realize novel high-index-contrast, compact micro-disk resonators. Our findings demonstrate that our device can operate in dual modalities, for detection of the infrared optical absorption of a binding event using cavity enhanced spectroscopy, or sensing refractive index change due to surface molecular binding and extracting micro-structural evolution information via cavity enhanced refractometry.

Glasses for Raman nonlinear optics

The Raman effect, by which light is frequency shifted by a vibrational mode, enters into a number of phenomena in nonlinear optics. Here, we summarize our progress in identifying glass materials with potentially useful Raman properties, methods for measuring the strength of the Raman effect and its spectral dependence, and the properties of a number of different families of glasses. Glasses with both larger peak Raman susceptibilities and larger bandwidths relative to fused silica are reported.

Femtosecond micro-machining of high index and photo-sensitive glasses in air

Summary form only given. It is well-known that micromachining with high intensity femtosecond pulses has significant advantages over nanosecond laser pulses including increased ablation rates although there are many complex interaction processes involved. They have been shown to be effective in creating microstructures in fused silica, particularly gratings. We are investigating the interaction of high intensity (/spl sim/10/sup 14/ W/cm/sup 2/) 110 fs laser pulses with a variety of glasses to determine their potential for detailed structural micro-fabrication in transparent media, and through analysis of the changes in material structure and chemical properties, assess the interaction processes involved.

Aging behavior of photo-induced As/sub 2/S/sub 3/ gratings

Summary form only given. Amorphous chalcogenide glass (ChG) films are candidates for passive and active photonic devices for applications in infrared integrated optical systems as they exhibit high transparency in the 1-10 /spl mu/m wavelength region, a large nonlinear refractive index, and low phonon energies. ChGs are photosensitive when exposed to bandgap energy (E/sub g//spl sim/2.35 eV for As/sub 2/S/sub 3/). Use of these photosensitive effects (photodarkening and photoexpansion) in ChGs, allows the creation of bulk waveguide structures, or the patterning of photoinduced relief gratings and guided wave structures in ChG films. The ultimate long-term stability of such optical elements relies on the generation of photo-induced structures which undergo limited structural relaxation with time. ChGs typically exhibit lower glass transition temperatures (T/sub g/) than oxide glasses and hence, can exhibit significant sub-T/sub g/ relaxation at, or near, room temperature. This relaxation can result in structural changes that modify the as-written glass structure and performance of the optical element. This paper reports results of Raman analysis of As/sub 2/S/sub 3/ films and gratings aimed at identifying specific bonding changes, which accompany the aging process.

Nearinfrared waveguide Raman spectroscopy of single and multilayer chalcogenide device materials

Waveguide Raman spectroscopy is employed to probe the microstructure of As-S-Se thin films. Correlations between chemical bonding and nonlinear optical properties are investigated.

Femtosecond micro-machining at atmospheric pressure near air-ionization threshold

Summary form only given. Femtosecond laser pulses are capable of producing very small features (on the order of 1 /spl mu/m) without significantly modifying the surrounding bulk material. Furthermore, it is well known that these pulses produce very smooth and deterministic features when compared with conventional laser processing. Since it is common for intensities to exceed 10/sup 15/ W/cm/sup 2/ during femtosecond ablation, several experiments have been performed at low pressures (<10/sup -3/ mbar) in order to avoid unwanted nonlinear reactions with the surrounding atmosphere. However processing in ambient atmospheric conditions would be preferable for femtosecond laser processing to be useful in commercial applications. We present a detailed study of femtosecond and subnanosecond ablation in glasses, ceramics, carbon composite, and metals in order to determine the influence of air on characteristics such as penetration rate and surface quality.