Planar-integrated Free-space Optics Research Articles

Planar-Integrated Optics and Microfluidics for Lab-on-a-Chip Systems

A planar integration platform for lab-on-a-chip systems is proposed. It evolves from planar-integrated free-space optics and includes planar microfluidics. Optical systems are folded into transparent wafers and can be fabricated with mask-based techniques. Fluidic actuation is achieved electroacoustically by means of Rayleigh-type surface acoustic waves that are generated with interdigital transducers on a piezoelectric wafer. Simple proof-of-principle demonstrators were constructed and experimentally tested. They contain a ring-shaped flow channel in which an arbitrary fluid can be set into circulation, and integrated free-space optical systems for microscopic brightfield and darkfield illumination, respectively. As piezoelectric material 128° y-cut LiNbO3 was used, the flow channel and the optical functions were realized in poly(methyl methacrylate) (PMMA).

Efficient Planar-Integrated Free-Space Optical Interconnects Fabricated by a Combination of Binary and Analog Lithography

Design, fabrication, and experimental testing of an integrated microoptical module for interconnection are reported. The systems integration is based on the concept of planar-integrated free-space optics. The module combines diffractive-reflective and refractive microoptics. The diffractive elements were fabricated by binary lithography and reactive ion etching. The refractive elements were made by analog lithography using a high-energy beam sensitive mask and replication in Ormocer. The fabricated module implemented a simple one-dimensional optical interconnect. Two versions were implemented for which insertion losses of approximately 8 and 4.5 dB were measured, respectively.

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.

Optical Interconnection and Clocking Using Planar-Integrated Free-Space Optics

Integration and miniaturization at the systems level are key requirements for photonics applications. Here, we describe the concept of planar integration of free-space optical systems and its use as an optical interconnection technology. Two specific applications will be considered, a parallel chip-to-chip interconnect and an optical clock distribution network.

Practical realization of massively parallel fiber–free-space optical interconnects

We propose a novel approach to realizing massively parallel optical interconnects based on commercially available multifiber ribbons with MT-type connectors and custom-designed planar-integrated free-space components. It combines the advantages of fiber optics, that is, a long range and convenient and flexible installation, with those of (planar-integrated) free-space optics, that is, a wide range of implementable functions and a high potential for integration and parallelization. For the interface between fibers and free-space optical systems a low-cost practical solution is presented. It consists of using a metal connector plate that was manufactured on a computer-controlled milling machine. Channel densities are of the order of 100/mm(2) between optoelectronic VLSI chips and the free-space optical systems and 1/mm(2) between the free-space optical systems and MT-type fiber connectors. Experiments in combination with specially designed planar-integrated test systems prove that multiple one-to-one and one-to-many interconnects can be established with not more than 10% uniformity error.

Compact discrete correlators with improved design

Optical correlators are of interest for a variety of signal processing tasks. In a recent paper [Appl. Opt. 39 (2000) 759–765], we described an approach to build discrete correlators for spatially incoherent signals using planar-integrated free-space optics. In that paper, input and output array were spatially interlaced in the same area. Here, we present an improved design with separated input and output.

Simulation of light propagation in planar-integrated free-space optics

A Fourier transform based beam propagation method is described to simulate light propagation in planar-integrated free space optics. Wide angle beam propagation is modified to minimize the required space-bandwidth product and the required computational load with suitable coordinate transforms. To model diffraction at perfectly conducting and dielectric surfaces the extended Kirchhoff approximation is employed. This model accounts for diffraction effects in typical configurations of planar integrated optics, where the thin element approximation fails to provide an accurate description.

Planar-integrated Talbot array illuminators

We demonstrate the planar integration of Talbot array illuminators designed to generate one-dimensional spot arrays. The array illuminator basically consists of a phase grating and a cylindrical diffractive lens integrated as a single diffractive optical element onto a transparent glass substrate. We discuss various design aspects, and we focus on problems typical for planar-integrated free-space optics like the tilted optical axis of the system. Experimental results and measurements, which were obtained from planar-integrated setups fabricated as surface-relief structures on a transparent glass substrate by use of standard photolithography, are included.