Helmut Zarschizky

Binary and multilevel diffractive lenses with submicrometer feature sizes

Binary and multilevel diffractive lenses with submicrometer feature sizes are realized on silicon and galliumphosphide wafers using CAD methods, direct write e-beam lithography, reactive ion etching, antireflection coating, and wafer dicing. Measurements prove aberration-free imaging and maximum diftraction efficiencies of 70% for lenses with high numerical aperture (NA) of 0.5. Comparisons to other miniature and micro-optical elements are carried out with respect to laser-to-single-mode-fiber coupling and show the competitive performance of the diffractive lenses. Arrays for 18-channel parallel receiver modules are fabricated in on-axis and off-axis versions. Optical crosstalk is estimated.

Optical multichannel parallel chip-to-chip data distribution

The design and the modelling results of an 8 channel parallel optical chip to chip interconnection consisting of a laser diode (LD) array, a single-mode waveguide (WG) array, and a photodiode (PD) array with 8 channels each are presented. The separation of the channels is 125 im, so the overall width of the 8 channel line is only I mm. The electronic and the optoelectronic components will be mounted on a silicon substrate wafer and the waveguides on a second silicon wafer which will be fixed upside down on the substrate. The LDs are envisaged to be AlGaAs singlequantum well types though the first implementation will be realized with conventional A1GaAs MCRW semiconductor lasers with a wavelength of 0.85 rim. The PDs are fabricated in standard silicon technology, the silica WGs with the flame hydrolysis technique and reactive ion etching. The trade off between large fabrication tolerances and the desired high coupling efficiencies is discussed. Mounting techniques for the LD- and PD-arrays are presented. A comparison between this optical interconnection and an equivalent electrical one is given.

Design and fabrication of synthetic lenses in silicon

We report on the design, calculation, and fabrication of binary and multilevel synthetic lenses realized in silicon. The diffractive patterns of the lenses are computer generated, direct E-beam written, and dry etched into the surface of silicon wafers. This paper describes the fabrication tools used and the techniques applied for the lens fabrication. The data processing as well as the efforts necessary for the electron beam writing are emphasized. Binary as well as multilevel elements are fabricated. First results are given for the performance of binary lenses in terms of diffraction efficiency, the efficiency of laser diode to fiber coupling, and the image quality of lenses.

Holographic optical elements for free-space clock distribution

Optical clock distribution is an attractive technique to avoid clock skew in highspeed digital systems. For short lengths free space distribution by holographic optical elements (HOE) has specific advantages. We will report on the requirements of the optical system in respect of necessary light power and its equipartition to the photoreceivers. We give an estimation for the maximum number for optical fanout con sidering especially ECL circuits. Specific system constraints lead to a certain layout for the whole arrangement. The realization of a distinct HOE type is carried out in form of a binary phase reflection HOE which is produced by dry etching of silicon. The measured diffraction efficiency is close to the theoretical limit.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Efficiency enhancement of diffractive optical elements by variable relief profiling

Diffractive optical elements (DOEs) are realized with various reliefs using e-beam lithography and existing methodes for the production of microelectronic components. Depending on the 3D-profile, diffraction efficiencies of more than 70% for DOEs with high numerical aperture of 0.5 were measured and aberration-free imaging was observed. In order to enhance the diffraction efficiency we present different methods for a flexible 3D-shaping of the resist mask for the dry etching process.

Design and fabrication of multilevel diffractive optical elements (DOEs) and holographic optical elements (HOEs)

Abstract In this report we describe the design, calculation and fabrication of binary and multilevel DOEs. In particular we pay attention to the direct write ebeam process and the pattern transfer into Si—substrates by reactive ion etching. First results can be given in terms of the diffraction efficiency and image quality of binary DOEs applied in test circuits for light coupling and free space light transfer with a multifunctional HOE.

Design, CAD-data generation and fabrication of diffractive lenses with submicron feature sizes

Binary and multilevel diffractive lenses with submicron feature sizes are realized on silicon wafers using direct electron beam lithography and reactive ion etching. The respective diffractive patterns of the lenses are computer calculated and the appropriate pattern data are generated with the help of a commercially available CAD tool. For enhanced efficiency the lens patterns have a three dimensional profile.

Multifacet diffractive mirror for optical clock signal distribution

Optical clock signal distribution has widely been discussed to be an attractive way to reduce the clock skew in high speed digital systems. For short interconnection lengths, especially for chip level clock distribution, free space systems using diffractive optical elements (DOEs) have specific advantages. The optoelectronic pathway described in this paper consists of a GaAs laser diode, a microetched silicon mirror, a facetted diffractive element, and silicon photodiodes. The key element of the clock distribution demonstrator is the diffractive element (the mirror), which matches set-up requirements like compactness, an off-axis geometry, and use of an unshaped laser diode beam. The diffractive mirror is computer generated, it is direct E-beam written and its diffraction pattern is dry etched into the surface of a silicon wafer. It is shown that the whole set-up meets the demands of alignment accuracy in an excellent way. This is achieved by the very good imaging characteristic of the DOE and by an alignment technique based on precision mounting of microetched silicon components.

Clock distribution using a synthetic HOE with multiple fan-out at IR-wavelength

We report about the design of an optical intrachip clock distribution using an IR-laser diode 1 ocated at one edge of an electronic chip and 4 on-chip photoreceivers, all components connected via a reflective HOE. The high divergence angle of the laser beam and its oblique incidence onto the HOE together wfth the 4 fan-out directions require HOE-feature sizes which are in the order of the operation wavelength X0.86 tm. This study considers both multiplex and multifacet computer-generated HOEs . The pattern complexity, the respective pattern resolutions, the beam rouung abilities and the spot quality of the focused output beams are discussed. A calculation method for the estimation of the alignment tolerances is explained and the results will show that our arrangement is feasible using mounting techniques based on micromechanics in preferential etched silicon.

Binary and Multilevel Diffractive Elements with Submicron Feature Sizes

Diffractive elements may be identified as miniaturised or micro optical components which affect an incoming beam of light by the laws of diffraction. In contrast to other micro optical components like refractive ball lenses and micro calottes or graded index lenses diffractive optics can be attributed as flat and in general aspheric optical elements which can perform multiple optical functions simultaneously.