A new technique is introduced to replace DOEs that are used for illumination in lithographic
projectors with polarization computer generated holograms (PCGHs) that produce both arbitrary
intensity and arbitrary polarization state in the illumination pupil. The additional capability of
arbitrary polarization state adds an additional degree of freedom for source-mask optimization.
The PCGHs are similar in design and construction to DOEs, but they incorporate polarizationsensitive
elements. Three experiments are described that demonstrate different configurations of
PCGHs deigned to produce a tangentially polarized ring. Measurements of ratio of polarization
and polarization orientation indicate that all three configurations performed well. Experimetns
are performed with visible (λ = 632.8nm) light.
Digital information can be encoded in the building-block sequence of macromolecules, such as RNA and single-stranded DNA. Methods of "writing" and "reading" macromolecular strands are currently available, but they are slow and expensive. In an ideal molecular data storage system, routine operations such as write, read, erase, store, and transfer must be done reliably and at high speed within an integrated chip. As a first step toward demonstrating the feasibility of this concept, we report preliminary results of DNA readout experiments conducted in miniaturized chambers that are scalable to even smaller dimensions. We show that translocation of a single-stranded DNA molecule (consisting of 50 adenosine bases followed by 100 cytosine bases) through an ion-channel yields a characteristic signal that is attributable to the 2-segment structure of the molecule. We also examine the dependence of the rate and speed of molecular translocation on the adjustable parameters of the experiment.
The reflectivity of the phase-change media of optical recording changes slightly upon the application of a weak laser pulse (i.e., a pulse of insufficient power to write/erase a mark), returning to its initial value at the end of the pulse. This behavior is shown to be due to the temperature-dependence of the optical constants of the phase-change layer.
In phase-change (PC) optical data storage, information bits are recorded as amorphous marks on a crystalline film of GeSbTe alloy (hereinafter referred to as GST). This is achieved by raising the local temperature of the film above its melting point (approximately 600°C) using a high power laser pulse, and allowing the film to cool down rapidly to below its glass transition temperature. The crystalline-to-amorphous transition (or vice-versa) is accompanied by a large change in the optical constants of the GST material, which provides a mechanism for optical readout. Thus, crystallization, melting, and amorphization of thin GST films are of fundamental significance in PC optical recording technology. Several such studies have been undertaken in the past, using a single laser beam to both trigger the transformation and monitor its progress. In the present paper we describe the results obtained in a novel, two-laser static tester, which allows real-time monitoring of the crystallization/amorphization processes both during the laser pulse and in the cooling period following the pulse.
As phase-change optical recording technology matures, partnerships emerge between companies to provide a complete optical data storage solution. A supplier of optical media and a optical disk drive supplier must exchange information, based on prototype evaluations, to establish media and drive specifications which optimize overall performance. For example, in the development of write strategies which result in acceptable jitter and media life, testing is important. But it can be very time-consuming to explore the effects of the many design parameters by iterating on media configurations in the laboratory. Therefore, simulation becomes an attractive option, if it (a) is verifiable using laboratory measurements, (b) requires a minimum number of media parameters, and (c) provides sufficient accuracy to enable good design decisions for both media and drive. For optimal jitter and media life, the simulation should point the way to a write strategy which precisely controls media temperature and cooling rate.
Gallstones have been classified as being cholesterol type and pigment type. The classification is important for diet control of the patient to avoid recurrence of the stone. Spectroscopy is a sensitive technique to determine the composition of the gallstone both in-vitro and in-vivo. this work deals with the fluorescence spectroscopy of gallstone. For fluorescence spectroscopic studies of gallstone, samples were excited with 5 mw of 488 nm line of argon-ion laser and spectra were recorded with a SPEX 1877E triplemate attached with a cooled PMT and DM3000R data acquisition system. Fluorescence spectra from pure cholesterol and bilirubin were also recorded for comparison. Different types of gallstones: mixed, cholesterol, pigment type were studied. All spectra exhibited a very broad band, 500 to 800 nm and sometimes two bands, depending on type of stone. Pure cholesterol shows three prominent fluorescence peaks at 513, 550, 583 nm along with two peaks at approximately 568 and 586 nm. Pure bilirubin shows prominent peak at 628 nm, without any Raman line. From fluorescence spectra different types of stones are identified. Different gallstones studied show a mixture of cholesterol and bilirubin types and the ratio of the two varies from one sample type to another.