We have developed novel optical micro-electro-mechanical systems, (MEMS) and nano-electro-mechanical, (NEMS) optical components for applications including imaging, switching, and optical integrated circuits. This paper provides an overview of current optical MEMS/NEMS research projects in our integrated photonics laboratory at UCLA. Three optical MEMS/NEMS devices: a large, 1 mm diameter, scanning micromirror for imaging applications, an analog micromirror array for network switching applications, and a nanoscale photonic crystal switch for integrated photonic circuit applications will be described.
In this paper, we report the use of microelectromechanical system (MEMS) switches in development of a re-configurable optical add/drop multiplexer (ROADM). The implementation of MEMS switches enables fabrication of a highly integrated 16-channel ROADM having compact size, fast re-configuration time, low driving voltage and improved reliability. The dimensions of the die for the 2x2 crossover MEMS switch are 6.5mm x 6.5mm x 1.5mm. The insertion loss of the switch is less than 1 dB. The switching time is less than 3.3ms, and the driving voltage can be as low as 10V. Over 200 million cycles of switching have been achieved. The performance of the MEMS switch and the possibility of implementing the switch in a ROADM will be discussed.
This paper describes a potential application of silicon surface micromachined (SMM) mirrors to a space imaging application. We have developed micromirror arrays that can be individually addressed for potential use in a spectrometer planned for NASA's Next Generation Space Telescope (NGST), which will be launched later this decade. An array of micromirrors has been designed to replace a conventional fixed slit mask that is commonly used in spectrometer instruments. The fixed slit mask is used to select the desired portions of an incoming optical signal for analysis. These mirrors are designed to operate in two states, on and off, with the on position directing the signal into the instrument. Such an array of micromirrors can then be used as a "programmable" slit mask where portions of the incoming field of view can be selected in software.
Optical, electrical, processability, and film casting characteristics of various conductive cladding layers were investigated. The goal was to find conductive polymer cladding materials suitable for fabricating and optimizing waveguide electro-optic modulators. Using cladding material that is more conductive than the core material, the poling fields in the core will be maximized, realizing a maximum electro-optic coefficient, which reduces the operating voltage in waveguide electro-optic modulators. We found, however, that there are tradeoffs between absorption losses, conductivity, refractive index, materials processability and materials compatibility when using off-the-shelf materials.
It is well understood to be more difficult to operate an array of receivers simultaneously than individually, as sensitivity is degraded in the presence of simultaneous switching noise.1,2 In optoelectronic-VLSI applications, additional operability concerns exist due to the need to implement receiver circuits of reduced complexity due to physical space constraints and to bias and control receivers in groups. Operational yield refers to the percentage of receivers in a group that can simultaneously be operated successfully. Receivers in a group may be functional individually, but some may exhibit operational problems such as duty cycle distortion or stuck-at 1/0 behavior when operated as a group. The transfer characteristics of optically single-ended receivers can be sensitive to changes in biasing and control parameters. If a sensitive parameter is common to a group of receivers, operational yield can be compromised by problems caused by process variations in optoelectronic devices and in transmitter and receiver circuits, and non-uniformity in optical system power throughput. We present experimental and simulation-based analyses of operational yield for optically single-ended receivers in common bias and control groups. Architectures employing optically differential signaling are shown to facilitate approaches to alleviating operational yield problems.
Laser beam scanning has wide applications in laser printer, laser tracking, etc.. The previous phase coding method is the micro-lens array method, which is difficult to fabricate because of the extreme fine linewidth at the outer part of the array lens. We propose a new scanning method based on the Talbot phase coding method. The Talbot phase codes come from the natural phase codes of the self-imaging effect of a grating for array illumination. A pair of two complementary Talbot encoded phase plates is used to replace the previous micro-lens array. Compared with the previous microlens array method, this method overcomes the shortcoming of the extreme fine linewidth of the previous method by replacing the equal linewidth of the encoded phases. This method overcomes the shortcoming of the continuous phase levels requirement of the previous method by using a limited phase-level number. This method overcomes the shortcoming of the continuous movement of the previous method by taking the equal-step movement. Therefore, our design of Talbot encoded scanner is more easily fabricated with binary optics and more reliable in practical use.
Parallel synchronous digital links require tight control over inter-channel skew in order to obtain maximum performance. In parallel optical interconnects (POIs), inter-channel skew can arise from differences in optical and electrical path lengths as well as latency variations through transmitters and receivers. The receiver pre-amplifier is particularly susceptible to latency variation. In POI applications such as optoelectronic-VLSI, pre-amplifiers can exhibit variable latency and gain resulting from differences in optical power levels across the receiver array due to transmitter, laser, detector, or optical system non-uniformity. This establishes an input DC photocurrent and pre-amplifier operating point that varies across the array, resulting in gain and phase non-uniformity. We consider different receiver pre-amplifier designs and the susceptibility of their gain and phase delay uniformity to operating point variations. Feedback circuitry that stabilizes the pre-amplifier operating point is considered as a potentially robust approach for array-scale POI skew reduction. Optical ring oscillators are used to characterize the phase delay of different pre-amplifier designs by measuring the period of oscillation as a function of optical system power throughput.
A fully embedded board-level guided wave optical interconnection is presented to solve the packaging compatibility problem. All elements involved in providing high speed optical communications within a board are demonstrated. Experimental results on a 12-channel linear array of polymeric waveguides, thin film VCSELs (10 μm), and GaAs MSM photodetectors suitable for a fully embedded implementation are provided. By embedded approach, all the real estate of the PC board surface are occupied by electronics so that one only observes the performance enhancement due to the employment of optical interconnection without any interface problems between electronic and optoelectronic components. Thin film 1X12 linear array VCSEL and GaAs MSM detector were demonstrated and thermal management issue of the VCSEL in the fully embedded scheme was discussed.
Nowadays, in order to take advantage of fiber optic bandwidth, any optical communications system tends to be WDM. The way to extract a channel, characterized by a wavelength, from the optical fiber is to filter the specific wavelength. This gives the systems a low degree of freedom due to the fact of the static character of most of the employed devices. In this paper we will present a different way to extract channels from an optical fiber with WDM transmission. The employed method is based on an Optically Programmable Logic Cells (OPLC) previously published by us, for other applications as a chaotic generator or as basic element for optical computing.
In this paper we will describe the configuration of the OPLC to be employed as a dropping device. It acts as a filter because it will extract the data carried by a concrete wavelength. It does depend, internally, on the wavelength. We will show how the intensity of the signal is able to select the chosen information from the line. It will be also demonstrated that a new idea of redundant information it is the way of selecting the concrete wavelength. As a matter of fact this idea is apparently the only way to use the OPLC as a dropping device. Moreover, based on these concepts, a similar way to route signals to different routes is reported. The basis is the use of photonic switching configurations, namely Batcher or Bayan structures, where the unit switching cells are the above indicated OPLCs.
All-optical logic can avoid expensive demultiplexing back to electronics in telecommunications. The term all-optical is used to described processing in which all signal paths are optical whether used for control or information. Semiconductor optical amplifiers (SOAs) can perform all optical logic because they have nonlinearity, low latency, and require low power. We use highly accurate computer models to simulate and evaluate NOR and NXOR logic gates using SOAs. These elements can act as building blocks for advanced logic systems. For example, in previous publications we described an approach to constructing arithmetic units from optical logic elements.
High-speed operation of free-space optical interconnect for a three-dimensional optoelectronic crossbar switching has been analyzed. System architecture, transmitter and receiver design are presented. The effect of ghost talk caused by the superposition of the delayed reflections of the original signal due to the multiple propagation of the wave between the vertical-cavity surface-emitting laser (VCSEL) and metal-semiconductor-metal (MSM) detector has been analyzed. The study indicates that even in the presence of significant amount of ghost talk a high performance free-space optical interconnect can be realized in this system by employing a receiver architecture that allows for DC level adjustment of the signal at the input of the transimpedance amplifier stage.
Several circuits, the following two are denoted by (A) and (B), are needed for decoupling of lightwave circuits (LWCs) and for a future transfer function matrix (TFM) synthesis of LWCs. (A) Controller matrix of a feedback (FB) which is an optical network composed of (i) variable weighted distributed FBs, implemented by electro-optically tunable gratings at waveguides (WGs) and (ii) optical isolators (OIs) or (iii) switches, respectively, for the correct flow of the optical field in the network. The controller matrix may be generalized to include space-variable elements according to a step function by step-wise arranged electrodes at the substrate of the gratings.Another generalization is the introduction of several wavelengths by subsequently arranged gratings of different spacing at the WGs of the controller matrix. The inclusion of such controller matrices at several wavelengths into a WDM switch requires various frequency converters (FCs) for the non-blocking operation. (B) Optical differentiator with regard to the longitudinal space coordinate of a WG which is composed of (i) reflection-type Mach-Zehnder interferometers (RMZIs) arranged at a (ii) fish-bone WG pattern for the implementation of the parallel RMZIs. The interleaved organization of the arms in (ii) provides the approximate differentiation of the optical field in a WG. The application of (A) and (B) to the advanced control of couplers is proposed (derivative FB). The paper presents circuits and their principles rather than their evaluation. The final goal is the photonic integration of the presented decoupling circuits.
Devices for optical connections by GRIN lenses have been reported in literature. In particular, two optical configuration designed for beam size control and light deflection by tapered GRIN lenses and for correction of astigmatic gaussian beams from laser diodes by anamorphic selfoc lenses are presented.
A new modified signed-digit (MSD) addition algorithm based on binary logic gates is proposed for parallel computing. It is shown that by encoding each of the input MSD digits and flag digits into a pair of binary bits, the number of addition steps can be reduced to two. The flag digit is introduced to characterize the next low order pair (NLOP) of the input digits in order to suppress carry propagation. The rules for two-step addition of binary coded MSD (BCMSD) numbers are formulated that can be implemented using optical shadow-casting logic system.
In the last few years, user requirements in data rate and bandwidth have grown enormously. A remarkable technological evolution has taken place in two major areas: transmission and interconnection networks. The role of photonic components and technologies in switched networks will mainly be determined by the enhanced functionality given by photonics, e.g., transparency, avoiding electronic bottlenecks. If switched data are kept in an optical format rather than electronic format, it allows the switch bandwidth to be as high as the fiber bandwidth. All-optical, space-division interconnects can be made using an acousto-optic beam deflector. The aim of this work is carry out an experimental analysis on the characteristics and behavior of an acousto-optic modulator (AOM) in order to determine its limitations for switching applications. Relevant parameters of the acousto-optic device have been derived from a theoretical study. This has allowed the identification of the parameters to be optimized in a switching application.
A major research area is the representation of knowledge for a given application in a compact manner such that desired information relating to this knowledge is easily recoverable. A complicated procedure may be required to recover the information from the stored representation and convert it back to usable form. Coder/decoder are the devices dedicated to that task. In this paper the capabilities that an Optical Programmable Logic Cell offers as a basic building block for coding and decoding are analyzed.
We have previously published an Optically Programmable Logic Cells (OPLC), for applications as a chaotic generator or as basic element for optical computing. In optical computing previous studies these cells have been analyzed as full-adder units, being this element a basic component for the arithmetic logic structure in computing. Another application of this unit is reported in this paper. Coder and decoder are basic elements in computers, for example, in connections between processors and memory addressing. Moreover, another main application is the generation of signals for machine controlling from a certain instruction.
In this paper we describe the way to obtain a coder/decoder with the OPLC and which type of applications may be the best suitable for this type of cell.
This paper presents an autonomous text and context-mining algorithm that converts text documents into point clouds for visual search cues. This algorithm is applied to the task of data-mining a scriptural database comprised of the Old and New Testaments from the Bible and the Book of Mormon, Doctrine and Covenants, and the Pearl of Great Price. Results are generated which graphically show the scripture that represents the average concept of the database and the mining of the documents down to the verse level.
In the previous paper  we demonstrated the usefulness of complex frequency scaling of Fourier Transform in identifying amount of rotation angle between two objects. Using the complex frequency scaling property of Fourier transform, an image and its Hilbert transform can be used to find the exact angle of rotation between the images . In order to find the correct angle between the two different images, we need to find the Hilbert transform of the function f(x,y) to construct an analytically extended function f'(x,y) . However, our approach does not perform satisfactorily for identification of rotation angle between two similar objects . A considerable amount of research has been performed on wavelet based signal processing by utilizing a pair of wavelet transforms where the wavelets form the Hilbert transform pair. In this paper we describe the design procedure based on spectral factorization in the generation of the Hilbert transform pair of wavelet bases. , , , . The one-dimensional wavelets are then used to generate two-dimensional wavelets. The two-dimensional wavelets thus generated are then used in the determination of correct angle between the images. The intention behind taking the above approach using the wavelets is to find if the wavelets help in discriminating the different images. In this paper we use the Hilbert transform pair of wavelet bases instead in constructing the analytically extended function. In generating the filter, orthogonal solutions are presented . The solution depends on the all pass filter having a flat delay response . We use the infrared images to validate our algorithm.
A novel uni-complex valued trinary associative model, which is implementable in the optical domain, is proposed. Retrieval of the stored pattern is accomplished using an threshold formula in the inner product domain. An algorithm to determine adaptive threshold formula for this trinary associative memory model is presented. The optimal threshold is chosen to yield the best performance. Different threshold parameters have been investigated to obtain the range of optimal threshold parameters. In order to validate our performance model, character recognition problem with noisy and noise-free data are investigated. Moreover, a bi-complex representation model for associative memory retrieval is presented and compared to previous methods.
Bacteria segmentation of particular species entails a challenging process. Bacteria shape is not enough as a discriminant feature, because there are many species that share the same shape. We present here two methods for tuberculosis image segmentation using the chromatic information. The first method is based on fuzzy segmentation of the color images based on the information that it is entailed in each separate chromatic histogram. The second method is a simple color filtering account by comparison of the inverse of the yellowish stained bacteria (blue channel) with the product of the other two chromatic channels. The third method is based on the extraction of image signatures by projecting logarithmic-polar mappings onto 1D vectors. This representation provides a very compact description of all image aspects, including shape, texture and color. An achromatic segmentation method is also presented based on the use of gray-level morphological operators only to the green channel. Finally we present the results of different autofocusing algorithms of stained tuberculosis images.
In this paper, a novel metric is defined that will allow one to compare the performance of 3-D pattern recognition systems. Any real object is inherently, three-dimensional. Therefore, any input object for an automated target recognition system should be ideally compared to the 3-D information about the object. The proposed metric captures the essence of such comparisons.
A two-step trinary signed-digit (TSD) multiplication technique based on digit grouping and smart pixel assignment is proposed. In this technique, the partial products are generated directly without recoding the TSD numbers. This nonrecoding based TSD multiplication technique results in significant reduction in the number of symbolic substitution rules employed in the algorithm. Several spatial encoding schemes are introduced and their relative performance in the presence of additive noise is discussed.
With the development of optical communication, the need of dynamic optical couplers, especially of Ν broad band couplers, becomes greater. Though some advanced fiber fusion techniques have been developed, they still have many shortcomings. We proposed a new 1×Ν dynamic coupler employing two even-numbered Dammann gratings. We divide a conventional Dammann grating into two complementary gratings. When there is no shift between them, they equal to a normal Dammann grating. The light that comes from the input fiber is diffracted into Ν spots with equal intensity and coupled into the Ν output fibers. When the two gratings have an accurate shift of a half-period, the total phase difference reduces to zero because of the complement. The light coming from the input fibers are coupled into the only one fiber which locates in the center. So they can work as a beam splitter or a combiner according to the relative shift between them. This approach has the clear advantage of realizing dynamic coupling of medium size of channels (e.g. 8×16) and is superior to the conventional methods particularly in very high Ν arrays. Experimental results of 1×8 optical dynamic coupler are presented in this paper.
An attempt is made to use the phenomenon of a two-phonon light scattering with direct transitions between all the optical modes in uniaxial single crystals for the implementation of acousto-optical logic-based device. The exact and closed analytical model for describing this strongly nonlinear phenomenon is developed. The feasibility of applying such an effect to perform an all-optical switching is analyzed in the paper presented. An opportunity for arranging two versions of key components for all-optical J-K flip-flops is revealed and algorithmically estimated.
In order to realize adaptive control of nonlinear big-lagged water location control system of drum boiler in thermal power plant, based on dynamic property analysis of the water supply course, a combination hybrid adaptive controller is designed in this paper. It includes a few hybrid adaptive controllers that parallel to work, the control signal is obtained by weighting the output signals of the few controllers, at same time, the method choosing weighed coefficients of the combination hybrid adaptive controllers is presented. Theoretical analysis and experiment result show the project is effective to solve inner disturbance, big-lag and pretense water location of the water location control system, and has quick adaptability and strong robustness. The results show that efficiency prospects for its further applications in power plant.
A 42-channel demultiplexer using a volume holographic grating formed in photopolymer medium for dense wavelength division multiplexing (DWDM) applications is experimentally demonstrated for the first time. A 3dB bandwidth of 0.18nm and channel crosstalk of -20dB for a 50GHz channel spacing, is reported.
This paper describes the separation of merged signals from a mass-selective chromatographic detector by means of an adaptive filtering technique. The technique is based on parallel feed-forward neural networks, which are trained to resolve the mass spectra of two merged chemical compounds. Specifically, the chemical mass spectra of the compounds ethyl benzene and xylene were used to evaluate a filter based on probabilistic neural networks (PNN). The results are that the PNN filter shows good noise rejection and is fast enough computationally to be utilized in real time. The filter technique has applications in on-line processing of environmental monitoring instrumentation data and direct processing of pixel spectral data, such as hyperspectral image cubes.