Jürgen Jahns

Planar integration of free-space optical components

In complex optical systems comprising many individual components, precise mechanical alignment becomes a difficult problem. We propose to integrate free-space optical components using planar technologies for their fabrication.

Two-dimensional array of diffractive microlenses fabricated by thin film deposition.

A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested. Each lenslet has a rectangular aperture and a size of 1.5 mm x 1.5 mm. The focal length of each lenslet is 47 mm. The array was produced by depositing thin films of silicon monoxide on a quartz glass substrate and by using photolithographic techniques. The performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP). The FZP pattern was implemented as a phase structure with eight discrete levels. The diffraction efficiency was measured to be 91%.

Crossover networks and their optical implementation

Crossover networks are introduced as a new type of interconnection network for applications in optical computing, optical switching, and signal processing. Crossover networks belong to the class of multistage interconnection network. Two variations are presented, the half-crossover network and the full crossover network. An optical system which implements both networks is proposed and demonstrated. Crossover networks can be implemented using the full space-bandwidth product of the optical system with minimal loss of light. It is shown that crossover networks are isomorphic to other multistage networks such as the Banyan and perfect shuffle.

Optical design of programmable logic arrays

Regular free-space interconnects such as the perfect shuffle and banyan provided by beam splitters, lenses, and mirrors connect optical logic gates arranged in 2-D arrays. An algorithmic design technique transforms arbitrary logic equations into a near-optimal depth circuit. Analysis shows that an arbitrary interconnect makes little or no improvement in circuit depth and can even reduce throughput. Gate count is normally higher with a regular interconnect, and we show cost bounds. We conclude that regularly interconnected circuits will have a higher gate count compared with arbitrarily interconnected circuits using the design techniques presented here and that regular free-space interconnects are comparable with arbitrary interconnects in terms of circuit depth and are preferred to arbitrary interconnects for maximizing throughput.

Planar packaging of free-space optical interconnections

Planar optics is an approach to build integrated free-space optical systems on single substrates. Computer-aided design, lithographic fabrication, and micro-bonding techniques are used to package the optics in a compact way. This paper reviews recent work on planar optics. It discusses various aspects of the fabrication, the design, and the application of planar optics as an interconnection technology for optoelectronic computing and switching systems. >

Array generation with multilevel phase gratings

The efficiency of phase gratings used for array illuminators can be improved by increasing the number of phase levels in computer-generated diffraction gratings. This is of interest to provide power to two-dimensional arrays of optical logic devices that are used for optical computing purposes. The theory and fabrication techniques are described, and the experimental performance of a four-level grating that produces a 5 × 5 array is presented.

Azimuthally polarized surface plasmons as effective terahertz waveguides.

Quite recently, it was found that metal wires can effectively guide terahertz radiation. Based on the fact that the absolute values of the relative permittivities of metals in the spectral region of terahertz radiation are huge, we here analyse the properties of this kind of waveguide and explain the related experimental results. In particular, we show that the observed waveguiding is due to the propagation of an azimuthally polarized surface plasmon along the wire. Some related aspects, such as the choice of metal and the slowly decaying modal field, are also discussed. In particular, we show that, if a copper wire with a radius of 0.45 mm is used, the attenuation coefficient is smaller than 2x10-3 cm-1 in the whole range of 0.1~1 THz.

Nonparaxial model for the focusing of high- numerical-aperture photon sieves

Recently, a paraxially individual far-field model was presented for the focusing and imaging analysis of pinhole photon sieves. By use of a local Taylor expansion of the integrated function of the Rayleigh-Sommerfeld diffraction formula, the small-size property of the individual pinholes, and the linear superposition principle, we extend this model to the nonparaxial case of high-numerical-aperture photon sieves. Some related problems, such as the validity range of this nonparaxial model and the selection conditions for the individual pinholes, are also discussed in detail.

Optical clock distribution using integrated free-space optics

Abstract The design and experimental results of an optical clock distribution system based on integrated free-space micro-optics are reported. Planar optical components such as lenses, beamsplitters, and mirrors, are monolithically integrated on a single glass substrate to provide a stable and compact system. A single input beam is split and distributed evenly to N output positions using a binary tree of beamsplitters. The experiment shown demonstrates the principle idea for a system with a fanout of eight. Theoretical considerations show that a fanout of 64 or larger is feasible.

Design and fabrication of high-efficiency beam splitters and beam deflectors for integrated planar micro-optic systems

High-frequency gratings with rectangular-groove profiles are used to generate high-efficiency beam splitters and beam deflectors. The effects of the grating design parameters, i.e., period, groove depth, duty cycle, number of phase levels, and polarization state (TE and TM) of the incoming signal, are considered. The case of the binary beam splitter grating is analyzed by using rigorous electromagnetic grating analysis. Fabrication techniques are presented in which three different lithographic techniques are considered (optical contact, deep-UV stepper reduction, and electron-beam direct write). Experimental results of 97% efficiency for the beam splitter grating and up to 80% for the beam deflector grating are reported.