Avi Y Feldblum

Optical Interconnections Using Microlens Arrays

Free-space interconnection of widely spaced pixels may be implemented using microlenses, rather than conventional imaging. Advantages, problems, and studies of system capacity are discussed.

Refractive-diffractive micro-optics for permutation interconnects

Refractive and diffractive micro-optics are combined in monolithically fabricated array components for free-space permutation interconnects. Such space-variant optical interconnects are, e.g., of major importance for smart pixel architectures, which are proposed for photonic switching applications in telecommunication and data communication and for more general parallel information processing, for example, of images. The advantages of the considered optical concept and an experimental demonstration of a 2-D perfect shuttle interconnect with 8 x 8 optical channels are described. We also discuss the scaling behavior and the alignment and wavelength tolerances of the interconnect system.

Fabrication and measurement of fused silica microlens arrays

We report fabrication of refractive microlens arrays in fused silica (SiO2) with a variety of pitches, diameters, and focal lengths. Typical f-numbers range from f/1.5 to f/5. Melted photoresist lenses are made on a fused silica substrate, and etched into the SiO2 using reactive ion etching (RIE) by carefully controlling the etch ratio. Techniques for microlens testing and measurement are discussed.

Performance and measurements of refractive microlens arrays

Refractive microlens arrays with f numbers ranging from f/1 to f/5 have been fabricated using a melted photoresist technique. The photoresist surface profile has been accurately reproduced in the underlying SiO2 substrate using etching techniques. Surface profile and optical performance characteristics of these microlenses are reported. Spherical microlenses are shown to have nearly diffraction-limited performance.

Microlens array analysis using image processing techniques

In the field of photonics, there is an increasing need to couple arrays of optical fibers with arrays of receivers or transmitters. One method of doing this is by using micro-lens arrays on the same pitch as the active devices. This paper addresses the important concerns of focal point center-to-center accuracy and the coupling efficiency of these micro-lenses using computer image analysis. Although the image processing techniques used are conventional, their application to micro-lens testing presents a novel approach to determining manufacturing accuracy and lens coupling efficiency. Data on the behavior of the micro-lens can be gathered using the micro-lens array to image a laser beam through a relay lens and onto a CCD camera detector. This paper presents some preliminary experimental results and describes the algorithms that perform the following functions: (1) Using standard Ronchi rulings, calculate image scale and determine if geometric distortion caused by the relay lens is present in image data. (2) Find focal spots of multiple lenses in an image using region aggregation via recursive connectivity evaluation providing sub-pixel moment calculation. (3) Calculate lens coupling efficiency by summing the intensities of all pixels composing the focus spots and comparing them with similar data representing the light incident on the first surface of the lens.