Abstract: Lenses 1, 2, and 4 as an optical element having a power are cemented together in an optical axis direction. An optical filter 3 is sandwiched between the lenses 2 and 4. Optical elements neighboring each other are cemented together such that a positioning section which is disposed on a side surface of the optical element disposes an appropriate space in an optical axis direction and optical axes of optical elements align in a direction orthogonal to the optical axis. The cemented optical element arrays are cemented together and cut at a line for cutting operation. By doing this, it is possible to manufacture a small image pickup lens unit which can be used for an image pickup device in mass-production and in a low cost.

Abstract: Various optical elements with subwavelength structured surfaces have been developed. The periods of the subwavelength structures are too short to generate diffracted light waves. But the structures are equivalent to refractive index materials with form birefringence. Many new optical elements are realized using the artificial refractive indices of these subwavelength structures. Some typical elements are described here in the passive element regime, and fabrication methods of the elements are explained.

Abstract: Preface.Acknowledgements.Glossary of Abbreviations.Glossary of Symbols.1. An Introduction to Optical Communication Systems.2. Principles of Distributed Feedback Semiconductor Laser Diodes: Coupled Wave Theory.3. Structural Impacts on the Solutions of Coupled Wave Equations: An Overview.4. Transfer Matrix Modelling in DFB Semiconductor Lasers.5. Threshold Analysis and Optimization of Various DFB LDs Using the Transfer Matrix Method.6. Above-Threshold Characteristics of DFB Laser Diodes: A TMM Approach.7. Above-Threshold Analysis of Various DFB Lase r Structures Using the TMM.8. Circuit and Transmission-Line Laser Modelling (TLLM) Techniques.9. Analysis of DFB Laser Diode Characteristics Based on the Transmission-Line Modelling (TLLM).10. Wavelength Tunable Optical Filters Based on DFB Laser Structures.11. Other Wavelenght Tunable Optical Filters Based on the DFB Laser Structure.12. Conclusion, Summary and Suggestions.Index.

Abstract: A precise and effective technique for the design of bandpass resonant filters realized in a one-missing-row photonic-crystal waveguide by inserting proper defects along the waveguide is proposed. The main characteristics of photonic-crystal-based resonant filters are discussed and an application as channel-dropping filter is presented.

Abstract: Following the trend of increased integration in complementary metal oxide semiconductor (CMOS) image sensors, we have explored the potential of implementing light filters by using patterned metal layers placed on top of each pixel’s photodetector. To demonstrate wavelength selectivity, we designed and prototyped integrated color pixels in a standard 0.18-µm CMOS technology. Transmittance of several one-dimensional (1D) and two-dimensional (2D) patterned metal layers was measured under various illumination conditions and found to exhibit wavelength selectivity in the visible range. We performed (a) wave optics simulations to predict the spectral responsivity of an uncovered reference pixel and (b) numerical electromagnetic simulations with a 2D finite-difference time-domain method to predict transmittances through 1D patterned metal layers. We found good agreement in both cases. Finally, we used simulations to predict the transmittance for more elaborate designs.

Abstract: A display system is configured to produce a color image formed of a plurality of differently colored images and may include at least one light source that directs light along an optical path, and at least one filter having a given optical filter characteristic. The display system may be selectively operable in a first state in which the optical path does not pass through a first filter during production of the plurality of differently colored images to form a color image having a first optical characteristic, and in a second state in which the optical path passes through the first filter during production of the plurality of differently colored images to form a color image having a second optical characteristic different than the first optical characteristic.

Abstract: Using silicon-on-insulator-based silicon-wire waveguides with submicrometer cross sections, we constructed ultrasmall channel-dropping lattice filters for 1.5-microm infrared systems. The waveguide's low-loss bends with 2.5-microm radius reduce the total length of the filter to less than 100 microm and enlarge the free spectral range to more than 80 nm. The measured spectra show fine channel-dropping characteristics, and the results agree well with numerical predictions. Moreover, we have succeeded in tuning the dropping wavelength by adjusting the lengths of the delay lines.

Abstract: A three-dimensional imaging method and system illuminates an object to be imaged with a light pattern that is formed from two or more light sub-patterns. The sub-patterns can each encompass the visible light spectrum or can be spatially varying intensity sub-patterns that each correspond to a red, green, or blue component. The light pattern is generated by a slotted planar member or an optical filter.

Abstract: Porous materials with nanometer-scale structure are important in a wide variety of applications including electronics, photonics, biomedicine, and chemistry. Recent interest focuses on understanding and controlling the properties of these materials. Here we demonstrate porous silicon interference filters, deposited in vacuum with a technique that enables continuous variation of the refractive index between that of bulk silicon and that of the ambient (n ∼ 3.5 to 1). Nanometer-scale oscillations in porosity were introduced with glancing angle deposition, a technique that combines oblique deposition onto a flat substrate of glass or silicon in a high vacuum with computer control of substrate tilt and rotation. Complex refractive index profiles were achieved including apodized filters, with Gaussian amplitude modulations of a sinusoidal index variation, as well as filters with index matching antireflection regions. A novel quintic antireflection coating is demonstrated where the refractive index is smoothly decreased to that of the ambient, reducing reflection over a broad range of the infrared spectrum. Optical transmission characteristics of the filters were accurately predicted with effective medium modeling coupled with a calibration performed with spectroscopic ellipsometry.

Abstract: Wavelength-selective operation of an optical filter (add/drop) based on a contra-directional photonic crystal waveguide coupler is demonstrated. The waveguides are defined as line defects in a two-dimensional triangular photonic crystal fabricated in an InP/GaInAsP heterostructure. The device is characterized using the end-fire method for the drop functionality. The experimental data are in good agreement with the theoretical results predicted by finite-difference time-domain simulations.

Abstract: A composite material that includes a host matrix and a plurality of dispersed nanoparticles within the host matrix. Each of the plurality of nanoparticles may include a halogenated outer coating layer that seals the nanoparticle and prevents agglomeration of the nanoparticles within the host matrix. The invention also includes a process of forming the composite material. Depending on the nanoparticle material, the composite material may have various applications including, but not limited to, optical devices, windowpanes, mirrors, mirror panels, optical lenses, optical lens arrays, optical displays, liquid crystal displays, cathode ray tubes, optical filters, optical components, all these more generally referred to as components.

Abstract: This disclosure describes one-chip micro-integrated optoelectronic sensors and methods for fabricating and using the same. The sensors may include an optical emission source, optical filter and a photodetector fabricated on the same transparent substrate using the same technological processes. Optical emission may occur when a bias voltage is applied across a metal-insulator-semiconductor Schottky contact or a p-n junction. The photodetector may be a Schottky contact or a p-n junction in a semiconductor. Some sensors can be fabricated on optically transparent substrate and employ back-side illumination. In the other sensors provided, the substrate is not transparent and emission occurs from the edge of a p-n junction or through a transparent electrode. The sensors may be used to measure optical absorption, optical reflection, scattering or fluorescence. The sensors may be fabricated and operated to provide a selected spectrum of light emitted and a multi-quantum well heterostructure may be fabricated to filter light reaching the photodetector.

Abstract: We discuss the influence of optical and electrical filtering on the performance of beat-noise limited balanced and single-ended direct detection of return-to-zero differential phase-shift keying (DPSK). Our simulations, supported by 40-Gb/s measurements, show that balanced DPSK detection outperforms both its single-ended equivalent and ON-OFF keying by /spl sim/2.7 dB, with higher gains at narrower optical filter bandwidths.

Abstract: In this letter, a novel tunable and flexible photonic microwave filter architecture based on the use of laser arrays and the periodicity of N/spl times/N arrayed-waveguide-gratings optical response is proposed. Filter coarse and fine-tuning capabilities are experimentally demonstrated showing an excellent agreement with theory.

Abstract: Optical filters capable of single control parameter-based wide tuning are implemented and studied. The surface micromachined Fabry-Perot filter consists of two InP-air-gap distributed Bragg reflectors and shows a wavelength tuning of more than 140 nm using only a single voltage of up to 3.2 V at currents below 0.2 mA. The membrane-based filter is designed to block all wavelengths in the whole range of 1250-1800 nm apart from its transmission wavelength.

Abstract: We analyze theoretically the light transmission characteristics of corrugated long-period gratings formed in slab waveguides. The transmission spectra of the gratings show distinct rejection bands at specific wavelengths, known as the resonance wavelengths. We investigate in detail the phase-matching curves of the gratings, which govern the relationship between the resonance wavelength and the grating period. Thanks to the flexibility in the choice of the waveguide parameters, the phase-matching curves of a long-period waveguide grating can be different characteristically from those of a long-period fiber grating (LPFG), which implies that the former can exhibit much richer characteristics than the latter. Unlike an LPFG, the transmission spectrum of a long-period waveguide grating is in general sensitive to the polarization of light. Nevertheless, a proper choice of the waveguide and grating parameters can result in a polarization-independent rejection band. Long-period waveguide gratings should find potential applications in a wide range of integrated-optic waveguide devices and sensors.

Abstract: A tunable optical filter is provided that includes an array of independently tunable filter elements. Each of the elements is located along a different optical path that extends between an input and an output port. Optical assemblies for receiving an incident optical signal for providing a filtered optical signal are also provided. In one embodiment, polarization independent spectral filtering can be achieved. Wavelength selectable add/drop multiplexers and demultiplexers, dynamic gain equalizers and attenuators, optical channel blockers and branch filters, switches, and modulators are also provided. Furthermore, methods for constructing and operating filters consistent with this invention are also provided.

Abstract: A distance-measuring device, comprising a light source unit for emitting a distance-measuring light, a photodetection optical system, a projecting optical system for projecting the distance-measuring light from the light source unit to an object to be measured and for guiding the distance-measuring light reflected by the object to be measured to the photodetection optical system, and an internal reference optical system for guiding the distance-measuring light from the light source unit toward the photodetection optical system, wherein the light source unit can emit two distance-measuring lights having different spreading angles and having the same or almost the same wavelengths, and the photodetection optical system has an optical filter which transmits light components of narrower wavelength range of the distance-measuring light.

Abstract: This paper presents a micromachined in-plane tunable optical filter using the thermo-optic effect of crystalline silicon. The device was fabricated by a silicon deep reactive ion etching process with a silicon-on-insulator wafer and thermal oxide removal to improve the sidewall smoothness. Optical fibers could be horizontally aligned on the fabricated TOF device by exploiting in-plane device structures, which enable TOFs to easily connect with other optical components. Tunability of the TOFs was experimentally achieved through thermal modulation of optical path length by heating the silicon etalon. As the input voltage increases, a notch in the reflectance spectrum shifts to a longer wavelength with an average tuning sensitivity of 0.9 nm K−1 and a best bandwidth of 1.1 nm. The proposed device can be utilized for spectroscopy or optical communication.

Abstract: We have experimentally demonstrated a new optical signal processor based on the use of arrayed waveguide gratings. The structure exploits the concept of spectral slicing combined with the use of an optical dispersive medium. The approach presents increased flexibility from previous slicing-based structures in terms of tunability, reconfiguration, and apodization of the samples or coefficients of the transversal optical filter.

Abstract: We present an optical modulation and distribution scheme that incorporates subcarrier-multiplexed (SCM) transport with remote local oscillator (LO) delivery for a millimeter-wave (mm-wave) fiber-radio backbone driving a sectorized antenna interface. The proposed method is compatible with a standard wavelength-division multiplexing infrastructure with a 25-GHz channel spacing. We also characterize the profiles and bandwidths of the optical filters, which are essential for the adding and dropping of the 25-GHz signal block and the optical extraction of the LO signal. The placement of the LO signal within the 25-GHz band is investigated and its effect on the filter bandwidth requirements and system performance quantified. The performance of a ring incorporating the distribution scheme is evaluated via simulation. It is established that a compromise must be made between the feasibility of the required filters and the incurred penalty due to intermodulation distortions from adjacent blocks.

Abstract: A method for producing aperiodic gratings and waveguides with aperiodic gratings uses a simulated annealing process that starts with a random configuration of grating elements and iteratively computes a spectral response from a Fourier transform of the configuration of grating elements obtained in successive iterations. A cost function is computed as a convergence criterion. The aperiodic grating can be used, for example, as a filter in WDM applications.

Abstract: A novel MEMS-based tunable optical filter structure is presented which for the first time combines the advantages of an optimized filter shape function with tunability. Such a filter is essential for monitoring and reconfiguration of optical communication networks. The device is based on a Fabry-Perot interferometer employing multiple solid-state silicon cavities and dielectric Bragg mirrors. It is fabricated as a self-supporting membrane with thin film metal resistors using silicon MEMS technology.

Abstract: The design of optical communication networks with network switching elements operating in the optical domain requires careful system analysis and potentially stringent component requirements. We consider here network elements such as transparent optical cross-connects that demultiplex WDM signals, optically switch individual channels, and then multiplex the wavelengths together again before transmission into the next span. Network element optical impairments that can significantly degrade signal quality are in-band (same wavelength) crosstalk and signal distortion from filter concatenation effects. We examine tradeoffs between accumulated crosstalk and filter distortion in the context of the optical filters used in the network elements and demonstrate the balance that must be struck in the design of the filters and network system. As an example, we study a 10-Gb/s network with 50-GHz channel spacing, examining both nonreturn-to-zero (NRZ) and return-to-zero (RZ) modulation formats. In both cases, we find optimal filter bandwidths that minimize the total signal degradation measured in terms of Q penalty, including filter misalignment statistics and signal laser frequency offset. A model is developed to treat the statistical nature of filter misalignment and its effect on filter-generated in-band crosstalk. The optical node penalties suffered by RZ signals can be significantly higher than that of NRZ signals and must be considered when estimating overall system reach.

Abstract: Optical filters having at least two coupled whispering-gallery-mode (WGM) optical resonators to produce a second order or higher order filter function with a desired spectral profile. At least one of the coupled WGM optical resonators may be tunable by a control signal to adjust the filtering function.

Abstract: It is known that a doubly periodic guided-mode resonant grating (GMRG) filter has a broad angular selectivity with a narrow spectral bandwidth. This means that the doubly periodic GMRG filter operates for small beam diameter and grating area. This report describes the wave localization in the doubly periodic GMRG filter. We investigated the spread area of light waves in the waveguide layer and the accumulation of field energy by numerical simulation using the finite differential time domain (FDTD) method. Simulation results showed that, in the case of a doubly periodic GMRG filter with a Q factor of 600, the field energy is spread over an area 5 um in width, which corresponds to the expected value from the angular tolerance. And the magnitude of the field energy in the waveguide layer was Q factor times greater than the incident energy. On the other hand, a singly periodic GMRG filter with the same Q factor spread the field energy over an area 72 urn in width. This filter does not work for a small size structure or a small diameter light beam.

Abstract: Modulations imposed on a chaotic optical signal generated by a semiconductor laser can be suppressed by injecting the signal into another similar laser under conditions for chaos synchronization. This filter effect could be used to recover messages hidden in chaotic carriers for robust and secure communications. We use a numerical model to examine the filter properties and show that the filter can be described in terms of differences in characteristic transmission functions for imposed signal and chaotic carrier in the output of the synchronized laser. The filter effect is shown to be larger for lower frequencies and decreases as frequencies approach the relaxation oscillation frequency of the laser in the gigahertz regime, similar to the response of steady-state injection-locked lasers to small-signal modulation. The filter properties are confirmed in experiments using both single and multimode lasers.

Abstract: We demonstrate a digitally tunable microwave-photonic notch filter based on a differential group-delay module which produces a relative delay between two orthogonal polarizations. A maximum rejection level greater than 60 dB is obtained. The tunability of the filter is achieved through real-time electronic control of the relative delay time.

Abstract: A method of manufacture for optical spectral filters with omnidirectional properties in the visible, near IR, mid IR and/or far IR (infrared) spectral ranges is based on the formation of large arrays of coherently modulated waveguides by electrochemical etching of a semiconductor wafer to form a pore array. Further processing of said porous semiconductor wafer optimizes the filtering properties of such a material. The method of filter manufacturing is large scale compatible and economically favorable. The resulting exemplary non-limiting illustrative filters are stable, do not degrade over time, do not exhibit material delamination problems and offer superior transmittance for use as bandpass, band blocking and narrow-bandpass filters. Such filters are useful for a wide variety of applications including but not limited to spectroscopy, optical communications, astronomy and sensing.