摘要:

AbstractSome error diffusion methods have been reported which are applied to amplitude quantize holograms, kinoforms, and trinary digital phase holograms. However, there is no method which is applied to binary digital phase holograms.This paper discusses improving reconstructed images with binary digital holograms using error diffusion methods in computer simulation. Consequently, it is clarified that error diffusion methods are effective, in general, in the range of reconstructed images not in contact with the diffused noise and the maximum ratio of an input domain is approximately 1:8.In the range of reconstructed image that does not contact with diffused noise, the error diffusion method gives a superior reconstructed image compared with any other encoding methods. Further, reconstructed images by computer simulation are verified and the deterioration factor in optical systems using optical experiments is eliminated.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes the basic items needed for design and simulation of optical integrated circuits and analysis tools for optical waveguides. Because the finite element method and beam propagation method are emphasized, the scalar wave approximation (which has been extensively used) is used in the discussion. In addition, using examples of analyses on various optical integrated circuits, the design and simulation technologies for optical integrated circuits will be introduced.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOptical communication systems are expanding from the conventional point‐to‐point system to the mesh‐type network systems for subscribers. As a result, the requirement for passive circuits such as optical divider, optical combiner, and optical switch is increased. Since optical waveguide‐type circuits have superior stability and mass producibility, they are considered important for construction of future optical communication systems.This paper describes development of the planar lightwave circuit (PLC) technology using the silica‐based waveguide on a silicon substrate. In the first half, the design technology of the silica‐based waveguide, the design and production examples of PLCs, and the system experiment examples are introduced. In the latter half, the latest tendency of high‐density integrated PLCs is emphasized based on the use of the high relative refractive index difference (high‐Δ) with a view to large‐scale PLC, and the characteristics of the high‐Δ waveguide and examples of its applications to high‐density integrated optical

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes the present status of LiNbO3optical waveguides with respect to the optical grade crystal, growth process, dc drift, and optical damage. In addition, the wideband optical modulators, QPM‐SHG blue light source and epitaxial growth of LiNbO3are reported. Optical grade crystals are needed for devices described in the foregoing and the requirements for such crystals have been proposed.The physics of optical waveguides has been understood and the relationship between the device properties and fabrication processes has been clarified. Methods to suppress the dc drift which has been one of the obstacles in practical applications of optical waveguides have been established. the solutions to minimize the optical damage in SHG devices have been found.Recently, drift‐free optical modulators and wideband optical modulators for 70‐GHz applications have been reported. Because of the rapid progress in polarization inversion technologies, SHG devices for blue‐light emission with an output power of 20 mW and a conversion efficiency of 600 percent/Wcm2have been developed. Solid‐state lasers formed by doping Er and Nd to crystals have been investigated. the research of growing an LiNbO3thin film to form an optoelectrical integrated circuit has been ca

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAn optical waveguide second‐harmonic genration (SHG) device in a quasiphase matched (QPM) system that obtains blue laser light from an infrared laser diode has shown promise. to obtain sufficient output power, it is necessary to understand how a high‐frequency conversion efficiency is attained in the SHG device. the technology for periodic inversion of the sign of the nonlinear optical constant is the key to full development of the QPM system. Most of the nonlinear optical crystals used for optical waveguide SHG devices in the QPM system are ferroelectric. In such crystals, self‐generated polarization is inverted so that the inversion of the sign of the nonlinear optical constant is carried out by polarization inversion. the authors have succeeded in forming a periodic inversion mechanism extremely ideal to the QPM by applying an external electric field in the device using lithium niobate. A conversion efficiency reaching 600 percent/W · cm2has been realized.Various polarization inversion methods are introduced herein. the QPM system optical waveguide SHG device is explained in which the polarization periodic inversion mechanism is formed by the applied electric field on the lithium n

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA new configuration of a ring resonator is proposed by using an Er‐doped silica‐based waveguide. Its laser oscillation and variable finesse were realized. to determine the Er concentration suitable for the Er‐doped waveguide ring resonator, the Er concentration dependence of the threshold pump power for laser oscillation in an Er‐doped waveguide ring resonator is analyzed numerically. It was found that an optimum Er concentration is in the range of 0.3 fc 0.5 wt.%. Further, from the actual measurement, it is confirmed that the gain of the silica‐based waveguide with Er doping concentration in this range is larger than the loss of the ring resonator. Then, an optimum coupling condition of the directional coupler is studied. It is found that a maximum value of 91 percent is obtained as the coupling ratio at a wavelength of 1.533 μm for a coupling length of 1.0 mm. Based on these investigations, an Er‐doped waveguide ring resonator with a circumferential length of 9.2 cm is fabricated. As a result, an Er‐doped waveguide ring laser is realized that has an oscillation center wavelength of 1.533 μm, a threshold value of 93 mW for the pump power and a slope efficiency of 0.3 percent. the oscillation modes of the realized ring laser are longitudinal multimodes with its free spectral range (FSR) of 2.2 GHz. the narrow line characteristics of an average line width of 200 kHz are found. From the results of the transmission spectral measurement, it is confirmed that the Er‐doped waveguide ring resonator works as a stopband‐type optical frequency filter. In addition, it is found that the finesse can be varied by controlling the pump power. Ma

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe optical switch array is a key device for realizing photonic switching systems. A lossless and low crosstalk switch is the most desirable component of large‐scale switching systems which have more than 100 input/output ports. to realize such a switch monolithically, a carrier‐injection‐type optical single‐slip structure (S3) switch with traveling‐wave amplifier (COSTA) have been proposed. to realize the COSTA, a carrier‐injection‐type optical switch and an optical amplifier that are suitable for integration have been developed. First, a carrier‐injection‐type optical switch where the PN junction was formed by crystal growth was fabricated. It was confirmed that the characteristics of the device do not deteriorate during heating, which makes it suitable for integration. Next, the structure of an optical amplifier which can be integrated into the optical waveguide using the reactive ion etching (RIE) process was investigated. an optical amplifier that was integrated into a straight optical waveguide was fabricated, and it was confirmed that this amplifier could produce enough gain (internal gain of 25 dB) to compensate for the loss in the optical switch. Using these two basic techniques, a 4 × 4 COSTA was fabricated. With this 4 × 4 COSTA, fiber‐to‐fiber lossless (maximum gain of 5 dB) and extremely low crosstalk characteristics (ON‐OFF ratio of

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the search for a cause of modulated signal distortion of a GaAs power FET, an analysis is made for the frequency dispersion caused by the surface trap. First, the frequency dispersion characteristics of theVgs‐Idrelationship of the FET under a large signal operation are measured. It is found that theVgs‐Idcharacteristics at high frequencies are very different from the one at dc. It is found that the drain current decreases nearVgs= 0 V. Further, simulation is carried out for the intermodulation distortion using theVgs‐Idcharacteristics at the high‐frequency region. It is found that an increase in the nonlinearity of theVgs‐Idcharacteristic due to frequency dispersion is the cause of increased modulated signal distortion. From the measured temperature dependence of the frequency dispersion of the drain current, energy levels related to the dispersion are found to be 0.56 and 0.19 eV. Further, a comparison is made between SiN and SiO2surface passivation films. It is found that frequency dispersion is small and a low distortion characteristic can be obtained with the

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTo study methods for improvement of the intermodulation product of a traveling‐wave tube which amplifies multiple frequencies, the general mechanism was investigated by a large signal analysis. the origin of the intermodulation product is in the nonlinearity of the traveling‐wave tube. Previously, the phase nonlinearity has been considered important from the discussion of polynomial expansion of the amplitude and phase transfer functions.In this paper, the relationship between the intermodulation product and the phase nonlinearity is reevaluated theoretically and experimentally for various conditions. At the same time, the modulation components of the electron beam charge density are studied as a factor related directly to the generation of the intermodulation product. As a result, it was found that the fundamental component of the charge modulation components which is in phase with the circuit wave voltage best represents the tendency of the third‐order intermodulation pr

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractSemiconductor materials are suitable for monolithic photonic integrated circuits since they can realize almost all the necessary photonic functions such as light emission, light amplifications, light detection, light modulation/switching and optical waveguiding. Additionally, since the figure of merit of various physical effects used to realize the foregoing functions is large and since it is easy to arrange the spatial region to generate these effects into compact and convenient shape, it is advantageous for small size and high performance.The research and development of photonic integrated circuits utilizing semiconductors has an accumulation of history, knowledge, and technology, already spanning a quarter of a century. Although it has required a longer time before it becomes practical than the electronic integrated circuits, it has shown rapid progress since the end of 1980's. This is attributed to the combination of the driving force from the needs point of view based on the advances in semiconductor laser technology, introduction, and spreading of quantum well structures and evolution of processing technology such as epitaxial growth methods and the strong demand from the needs point of view toward all optical telecommunication networks where not only trunk lines but also switching nodes and subscriber lines use an optical wave.This paper reviews the present status of photonic devices and circuits obtained by monolithic integration of semiconductor element devices by classifying them into light emitters, optical switches, and combiners/splitters. Finally, the necessity of semiconductor integrated photonic systems is set forth toward the future.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420771110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY