Andrey Zavalin

Surface-Enhanced Raman Spectroscopy Using Silver-Coated Porous Glass-Ceramic Substrates

Surface-enhanced Raman scattering (SERS) has been studied using a silver-coated porous glass-ceramic material as a new type of substrate. The porous glass-ceramic is in the CaO–TiO2–P2O5 system prepared by controlled crystallization and subsequent chemical leaching of the dense glass-ceramic, leaving a solid skeleton with pores ranging in size from 50 nm to submicrometer. Silver was coated on the surface of the porous glass-ceramic by radio frequency (RF) sputtering or e-beam evaporation in vacuum. SERS spectra of excellent quality were obtained from several dyes and carboxylic acid molecules, including rhodamine 6G, crystal violet, isonicotinic acid, and benzoic acid, using this new substrate. This new substrate showed a good compatibility with these molecules. The porous glass-ceramic with a nanometer-structured surface accommodated both test molecules and silver film. The absorbed molecules were therefore better interfaced with silver for surface-enhanced Raman scattering.

Achieving stabilization in interferometric logic operations

Interferometric systems with amplitude beam splitters can implement reversible operations that, on detection, become Boolean operators. Being passive, they consume no energy, do not limit the operating bandwidth, and have negligible latency. Unfortunately, conventional interferometric systems are notoriously sensitive to uncontrolled disturbances. Here the use of polarization in a common-path interferometric logic gate with and without polarization beam splitters is explored as an attractive alternative to overcome those difficulties. Two of three device configurations considered offer significant stability and lower drive modulator voltage as advantages over the previous systems. The first experimental tests of such a system are reported. Common-path interferometry lends itself to even more stability and robustness by compatibility with no-air-gap, solid optics.

Conservative Optical Logic Devices: COLD

Publisher Summary Conservative optical logic devices (COLD) aim at satisfying needs in niche markets. Where it is applicable, it has uniquely wonderful properties. This chapter describes COLD. Many integrated optical devices on silicon substrates have been developed and many more are being developed that combine small optical components on the same substrate as the electronics that operate them—a kind of best of both worlds approach. Those devices can be used for COLD. The most powerful COLD approach involves a digital light deflector (DLD). It can be made conservative, because it can build the DLD out of conservative operations, such as the Mach–Zehnder interferometer. The chapter focuses on the great deal of work on finding non-Boolean logics more amenable to COLD.

Zero-energy optical logic: can it be practical?

The thermodynamic “permission” to build a device that can evaluate a sequence of logic operations that operate at zero energy has existed and has been unsolved for about 40 years. Over the last four years, we have explored the possibility of a constructive proof. And we finally have found successfully such a proof and found that lossless logic systems could actually be built. It can only be implemented by optics. In this paper, the problems addressed are speed, size, and error rate. The speed problem simply vanishes, as it was an inference from the implicit assumption that the logic would be electronic. But the other two problems are real and must be addressed if energy-free logic is to have any significant applications. Initial steps in solving the size and error rate are addressed in more detail.

Simple online recognition of optical data strings based on conservative optical logic

Optical packet switching relies on the ability of a system to recognize header information on an optical signal. Unless the headers are very short with large Hamming distances, optical correlation fails and optical logic becomes attractive because it can handle long headers with Hamming distances as low as 1. Unfortunately, the only optical logic gates fast enough to keep up with current communication speeds involve semiconductor optical amplifiers and do not lend themselves to the incorporation of large numbers of elements for header recognition and would consume a lot of power as well. The ideal system would operate at any bandwidth with no power consumption. We describe how to design and build such a system by using passive optical logic. This too leads to practical problems that we discuss. We show theoretically various ways to use optical interferometric logic for reliable recognition of long data streams such as headers in optical communication. In addition, we demonstrate one particularly simple experimental approach using interferometric coinc gates.

C60 Clusters Self-Assembly in One-beam Optical Trap

Abstract : C(60) aggregated clusters up to 20 micrometer length were created on a glass surface within a solution inside of a gradient one-beam optical trap. It was possible to grow rod-shaped structures by motion of an optical trap parallel to the surface of the substrate. After the deposited structures became stable the solution was dried. By AFM measurements of the stable dried structures, it was shown, that aggregations have typical sizes of 5-15 micrometer X 1.5-2 micrometer, and thickness near 1.5 micrometer. The aggregations consist of thinner (30-100 nm diameter) rods, bundled together.