Biomedical subjects

Matthias Gruber

Publications and source records attributed to Matthias Gruber.

5 recordsLinked to original sources

PubMed2006

High-reflectance composite metal coatings for planar-integrated free-space optics.

For planar-integrated free-space optical (PIFSO) systems high-reflectance thin-film coatings are crucial. Evaporated metal films are preferred for their relative technological simplicity. We propose a three-layer Al-Ag-Al coating composition that combines the high reflectance of Ag with the chemical passivity of Al and its good adherence to glass. Two special measures are taken to prevent delamination: one is an anchoring of the edges of the coating in narrow ditches that are etched into the substrate and the other is the use of an adhesive Al underlayer; to reduce absorption this underlayer is implemented only in sparsely distributed discrete areas. The optical properties of such composite coatings are investigated theoretically. The fabrication complexity is only slightly increased compared to PIFSO systems with one-layer Al reflectors. In experimental tests we verified a reflectance of approximately 98% and an adherence comparable to that of simple Al coatings.

Journal Article↗

PubMed2005

Achromatic optical fourier transformer with planar-integrated free-space optics.

We address the problem of achromatization of an optical system for the realization of planar-integrated, free-space optics. In particular we demonstrate an integrated optical Fourier transformation module that was achromatized for the visible spectrum by means of a diffractive lens doublet. The optical system design is studied by using the parabolic approximation of the scalar diffraction theory, including terms related to astigmatism. Based on the method of ABCD ray matrices, the optical specifications of the lens doublet are derived and the chromatic correction effect is quantified. For experimental confirmation the diffraction patterns of various grating structures are evaluated.

Journal Article↗

PubMed2004

Generalized confocal imaging systems for free-space optical interconnections.

A generalized confocal imaging system, which is composed of two confocal lenses and one field lens, is proposed for free-space optical interconnections. Unlike in a conventional 4-f system, both the object distance and the image distance can be almost arbitrarily chosen. This advantage is especially important for practical setups in which the object distance and the image distance cannot be designed to be the same. As a concrete example, we have designed and experimentally tested a planar-integrated micro-optical imaging system. The result is in good agreement with the theoretical prediction. Similarly to the conventional 4-f imaging system and the light-pipe imaging system, the system proposed here can also be used as one important part of a hybrid imaging setup.

Journal Article↗

PubMed2004

Multichip module with planar-integrated free-space optical vector-matrix-type interconnects.

Even in the semiconductor industry, free-space optical technology is nowadays seen as a prime option for solving the continually aggravating problem with VLSI chips, namely, that the interconnect technology has failed to keep pace with the increase in communication volume. To make free-space optics compatible with established lithography-based design and fabrication techniques the concept of planar integration was proposed approximately a decade ago. Here its evolution into a photonic microsystems engineering concept is described. For demonstration, a multichip module with planar-integrated freespace optical vector-matrix-type interconnects was designed and built. It contains flip-chip-bonded vertical-cavity surface emitting laser arrays and a hybrid chip with an array of multiple-quantum-well p-i-n diodes on top of a standard complementary metal-oxide semiconductor circuit as key optoelectronic hardware components. The optical system is integrated into a handy fused-silica substrate and fabricated with surface-relief diffractive phase elements. It has been optimized for the given geometrical and technological constraints and provides a good interconnection performance, as was verified in computer simulations on the basis of ray tracing and in practical experiments.

Journal Article↗

PubMed2002

Optimal suppression of quantization noise with pseudoperiodic multilevel phase gratings.

A comprehensive two-step approach to design staircase-type multilevel diffractive phase elements (DPEs) that generate arbitrary desired diffraction patterns with the highest possible accuracy is presented. First a preliminary periodic grating with an unconstrained phase delay and an optimized nonuniform amplitude profile is designed by means of a customized iterative Fourier-transform algorithm. Then this preliminary grating is subjected to a phase quantization in which strict periodicity is forgone in favour of the best possible preservation of the shape of the power spectrum yielding a final phase only DPE with only rudimentary periodicity. An arbitrarily high similarity between the diffraction patterns of the final DPE and the preliminary grating can be achieved independently of the number D of discrete phase delay levels as long as D > or = 3. The signal-to-noise ratio of the final DPE is close to the theoretical upper limit. These properties are confirmed in computer simulations and demonstrated in optical experiments. Pseudoperiodic DPEs may have applications in optical computing, optical communication and networking, optical authentication, or coherent laser coupling.

Journal Article↗