We have described an approach for miniaturizing spectroscopic devices by using the advantages presented by elastomeric based microfluidics and semiconductor detectors/emitters. Elastomers allow for both absorption and fluorescent spectroscopy in the visible range to be conducted on small volumes of solution and allow for easy integration with existing detectors such as CMOS imagers, CCD imagers, and silicon photodiodes. Results of some basic experiments are presented to demonstrate the effectiveness of the system. In addition, several ideas for emission sources are also discussed with their relevance yet to be determined.
The use of Micro-Electro-Mechanical Systems (MEMS) technology has opened the door for many applications. In particular, by exploiting the reconfigurability of optical surfaces fabricated with this technology, many sensor, communication and spectroscopic systems can benefit. The controlled re-direction of single or multiple optical input sources can lend itself to high throughput sample analysis or massively parallel optical connectivity. In addition, the change in a MEMS-based optical surface can result in a flexible spectral analysis of incoming radiation. We report on the recent advances in our projects which are focused on the design/simulation, materials processing and integration issues involved with the creation and optimized operation of such diffractive micro-arrays. In this presentation, the state of the art in such devices will be presented which will include the process flow associated with production, structural metrology, optical performance, and parallel switching capabilities of the systems. The use of numerous materials including polysilicon, silicon dioxide and selected polymers as structural layers has enabled the production of devices which can be tailored for specific, performance related applications. Examples to be presented include diffractive surfaces with substantial (1 cm x 1 cm) active areas as well as large arrays with sub-micron feature sizes. Functional integration of the prototype devices include optical interconnects, active spectroscopy and bio/chem diagnostic systems.
We have constructed a computed-tomography imaging spectrometer (CTIS) that uses two crossed phase-only computer generated holograms (CGH) as the dispersing elements. This imaging spectrometer collects the multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. Previous CTIS instruments require a single CGH dispersing elements which were designed with the freedom of adjusting each element in the cell profile independently during the design process. The CHGs for this instrument are designed as identical crossed gratings to model the design parameters of a crossed 1D addressable liquid crystal spatial light modulator. Future integration of a liquid crystal spatial light modulator allows for the possibility of optical preprocessing of tomographic images. The CGH disperser pair has been designed to maintain nearly equal spectral diffraction efficiency among a 5x5 array of diffraction orders and to minimize the diffraction efficiency into higher orders. Reconstruction of the (x,y,(lambda) ) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques.
Frequency stabilized diode lasers are key devices in many atom physics experiments and they are increasingly used in diverse metrological applications. Diminishing channel spacing in wavelength division multiplexing and requirement for worldwide interconnectivity motivates the study of diode laser stabilization at telecommunications wavelengths. In this paper recent development in diode laser frequency stabilization are briefly reviewed and recent research on frequency stabilized diode lasers conducted in the Metrology Research Institute of the Helsinki University of Technology is described. Special emphasis is on two compact diode laser based frequency standards at 633 nm, which are described in detail. This wavelength is especially interesting, as it is the most common wavelength in the realization of the definition of the meter. The first system is based on a solitary diode laser, which is forced to operate in a single mode using weak optical feedback from a closely mounted microlens. The properties of this system are sufficient for many practical applications, e.g. interferometry. The second system is base don a miniaturized external-cavity laser and demonstrates that the stability level of iodine-stabilized He-Ne lasers can be reached with iodine-stabilized diode lasers. A transmission grating in the Littrow configuration is used in this external-cavity laser, as it allows highly compact mechanical design without the problem of directional variation of the output beam while tuning the laser wavelength.
The tight tolerances imposed on photonic components for standardized integration into DWDM systems requires that some form of temperature stabilization must be incorporated. Frequently this involves the use of traditional temperature sensors integrated into a classic control-feedback scheme involving thermo-electric coolers. While easy to implement, such a scheme is hardly novel and may result in an inefficient use of electrical power. A technique using flexible thermal tape configured into packages applicable for thermal stabilization of DWDM compliant laser diode sources and tunable filters is described.
Advances in polymer and sol-gel derived hybrid materials have made possible to integrate optical structures including waveguides, sensors and structures used in passive alignment of optical devices on various type of substrates. Particular attention has been given to the fabrication of electro-optical printed circuit boards (EOPCB). Fundamental problems related to printed circuit boards (PCB) are the insufficient surface smoothness of common PCB substrate (FR4) and different coefficients of thermal expansion between the optical material and substrate. In order to resolve these problems sol-gel hybrid materials and cost effective spray-coating method are employed for the fabrication of optical structures on PCB. Surface roughness of the PCB's can be greatly reduced using additional layer under optical core material. This additional layer behaves also as an optical under-cladding layer. Optical properties of these used materials are determined and optical structures fabricated using these directly photopatternable materials are demonstrated.
This paper introduces the usage of directly UV-photopatternable sol-gel based materials and the processing methods for the fabrication of binary diffractive optical elements. We designed and modeled a binary axicon - an optical element, which produces almost diffraction free beam in a specified distance from the element. We fabricated sol-gel based hybrid-glass materials and tailored their processing parameters to fit the demands of the axicon design. Resolution of 2 microns, film thickness of 850 nm, and certain morphological properties were required. The materials were derived from zirconium(IV)isopropoxide, methacrylic acid, and methacryloxypropyltritethoxysilane. We determined the morphological and line quality of the fabricated axicons as a function of the UV-irradiation dose. In addition, we measured the optical characteristics of the axicons in terms of the axial and radial intensity profiles. The reasons for the differences between calculated and measured values are discussed.
In order to enable optical storage in portable devices, a small optical drive building height and thus small sized objectives are needed. A small version of the DVR objective, having numerical aperture of 0.85 and operating wavelength (lambda) = 405 nm is required, in order to have sufficient storage capacity on a small sized disc. In this paper we present a miniaturised DVR objective made of plastic. It has a building height of only 1.335 mm, enabling optical storage for various mobile applications. Making the objective out of plastic eases the manufacturing and handling. Furthermore, the two element objective was designed to have low temperature dependence which was confirmed experimentally. Experiments with this objective showed that readout of a 25 GB RW 12 cm disc is possible. Furthermore, some considerations on the benefits and expected problems in miniaturizing the actuator are presented.
Though DVD becomes more and more popular, there are still millions of CD-R disk in using. The ability of reading both DVD and CD-R disk is necessary in compatible disk drive. Traditional optical pickup consists of different bulk components, which result in high cost, high difficulty in assembly and low reliability. Integration is a way to overcome these troubles. Based on planar optics, an integrated digital versatile disk (DVD)/compact disk recordable (CD-R) compatible optical pickup has been developed. In this device, the beams of two wavelengths follow different zigzag optical paths inside a few-mm thick glass substrate, which is used as a light guide. It is demonstrated that a beam combiner, a polarized beam splitter, a Fresnel prism, and a beam separator were integrated around a glass substrate, and such a planar optical pickup exhibited an excellent performance with high efficiency. It confirms that planar optics is an effective way to realize compatibility of DVD/CD-R.
There are many reasons that can degrade the image quality performance in a projection system, such as environment temperature, MTF of projection lens, structure of Lcd panel, EMI on the PCB and driver scheme... etc. Image quality is a function of all these parameters. In this article, the authors would like to estimate the image quality of a projection system under driver schemes and design parameters from the system point of view. The relationships between the voltage difference applied on liquid crystal (LC) cell and defect phenomenon are also revealed. This gives a clear-cut for different image defect (ex: flicker) and its causality. In the present time, ITRI/OES were modeling the LCOS Panel pixel with SpiceTM and ASAPTM for the estimation of image quality during the design of the optical engine.
BaTiO3 thin films were grown on Si (100) and UV transparent fused silica substrates by KrF (248 nm) excimer laser deposition. The analysis of thin films was performed using XRD, AFM, UV/VIS/NIR spectrometer and Nano-indenter to study general features of BaTiO3 thin films and to optimize deposition parameters. The XRD spectra of BaTiO3 films at 600 degree(s)C on Si (100) show polycrystalline peaks with a strongly preferential orientation. The surface imaging was taken by AFM and shows obvious grain boundary structures. The transmittance spectra for BaTiO3 films on UV fused silica were measured. The absorption increases rapidly below 380 nm. The effects of changing background O2 gas pressure and substrate temperature were studied. Finally, the hardness and Young's reduced modulus and scratch test of BaTiO3 films were measured using Nano-indenter system.
This paper discusses an all-optical switching device for routing signals in a WDM system based on a technique known as Electro-holography. The device features a photorefractive crystal with a hologram affixed in its crystalline structure. Upon receiving the correct stimulus, the device controls the index of refraction of the crystal and results in a diffraction of an input data signal to the correct output fiber based on the hologram's coding. When integrated in cross connect devices, WDM systems are projected to have faster response times and switching speeds resulting from the immense recording capabilities associated with an HOE.
In this paper we describe how finite difference time domain (FDTD) calculations can be used in the modeling of extremely short external cavity (ESEC) lasers used in modern optical data storage systems. We study the operation of direct semiconductor laser read/write heads that utilize either a conventional edge emitting laser or very small aperture laser. The storage medium is assumed to be a first-surface-recorded phase change (e.g. SGT) disc. The external cavity is formed between the laser's front facet and the disc. The length of the ESEC is typically 0.1 to 1.0 microns. By using FDTD we can study the behavior of the electric field in the ESEC in detail, taking into account the vector field effects resulting from the three-dimensional nature of the data marks and laser apertures. We calculate the distributions of electric field amplitudes, power flow and absorption in/near the external cavity. In addition, we calculate the effective reflectance spectrum of the ESEC and use this data as input into a phenomenological laser model to simulate the readout signal, i.e., the laser's output power and/or wavelength.