摘要:

AbstractAn optical beam scanner with a variable phase waveguide can perform a high‐speed scanning into an arbitrary angle. Monolithic integration of the scanner with a light source can be realized by means of fabrication with semiconductor materials. However, in principle, the scanned beam has multiple peaks so that the maximum scanning angle and the power efficiency are limited.To relax the limitations and to improve the characteristics, the following methods are investigated in this paper: (1) a method to suppress the subbeams; (2) a method to increase the angle between the main beam and the subbeams; and (3) a method in which the entire envelope is scanned. The following results were obtained.(1) By chirping the waveguide spacing, the limitation of the scan angle due to the existence of the subbeams is removed.(2) By reducing the waveguide spacing and varying the widths of the adjacent waveguides so that the mode coupling between the waveguides is eliminated, the scan angle is increased.(3) Although the fabrication is difficult, the wavefront in the waveguide is tilted so that the envelope itself is scanned and the inherent limitation of the scan angle is eliminate

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750501

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe passive mode locking traditionally used frequently for generation of ultrafast optical pulses has a problem in generality and controllability although the method can generate short pulses. On the other hand, it is considered that the method based on electrooptic modulation cannot reduce the pulsewidth and the speed is slow even though the controllability is superior.This paper describes the research on the forced mode‐locking method for possible ultrashort and ultrafast properties and the external direct modulation pulse generation method, even though the highly controllable electrooptic modulation is used. First, the forced mode‐locking method is described in which the locking modulator (mode locker) with a pulse‐like transparency in itself and a deflector and a composite resonator are used.Next, a method is described in which short pulses on the order of subpicoseconds can be generated regardless of the laser bandwidth by means of the pulse‐generating modulator outside the laser cavity. (An example is a modified Fabry‐Perot modulator.) Further, an optical pulse synthesizer with a possibility of generating subpico‐second to several tens of femtosecond pulses is described in which the narrowband large signal electrooptic modulator and a deflector are used for generating optical sidebands with a wide optical bandwidth and they are combined for generation of arbitrary‐shaped optical pulse after the phase and amplitude are controlled. The concept is compared with the experiments. Some methods are still unde

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750502

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

年代:1992

数据来源: WILEY

摘要:

AbstractExcitons in a quantum well of a semiconductor exhibit large optical nonlinearity. Therefore, a quantum well of a semiconductor is regarded as a key to realizing a device which can control light using light. However, the lifetime of excitons, which are generated optically, is several nanoseconds to several tens nanoseconds. Therefore, the nonlinear optical effect including absorption saturation continues for the lifetime of the excitons.To shorten the lifetime of the excitons without disturbing the optical nonlinearity, a new superlattice structure is proposed called the “tunneling bi‐quantum well.” This structure uses the tunneling effect and measures the absorption recovery time. As a result, it was found that in a tunneling bi‐quantum well in a GaAs/AlGaAs system with a barrier width of 1.7 nm, the absorption recovery time was as short

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750503

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe Gaussian beam propagating in an inhomogeneous medium is analyzed based on the complex ray optics, and the analytical solution obtained is reported. It is assumed that the medium is inhomogeneous in the transverse direction and homogeneous in the longitudinal direction. A beam wave is assumed which propagates in such a medium with undulation. Its spot size is derived as a general solution. Further, by means of two examples, the spreading of the beam wave due to the dispersion is studied. The general solution obtained in this paper is the rigorous solution of the geometric optics.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750504

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

年代:1992

数据来源: WILEY

摘要:

AbstractA three‐dimensional (3‐D) nonstationary analysis method is proposed for the quasi‐phase‐matched (QPM) second‐harmonic generation in an optical waveguide with a periodic domain‐inversion structure. In this method, a 3‐D modeling of a waveguide‐type QPM is made possible by combining the mode coupling theory with the weighted‐index method (WIM) which is a highly accurate approximate analysis method for an optical channel waveguide. As an example of application, the effect of the channel dimensions on the conversion efficiency is studied for a proton‐exchanged LiNbO3waveguide with a rectangular‐shaped inverted domain. The actual domain‐inversion shape is expected to be different, depending on the type of substrate material and inversion process. The present method is also applicable to an arbitrary inverted‐domain shape. Hence, the method is considered to be extremely useful fo

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750505

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe equation widely known as the characteristic impedance of the waveguide is defined from the voltage in the cross section, wall current along the axial direction and Poynting vector. For the rectangular waveguide, the impedance has a form proportional to (b/a)λ. However, it is not possible to derive a correct reflection coefficient with this form of characteristic impedance. It has been predicted empirically by the present authors and others that the characteristic impedance connected directly to the reflection coefficient has a form proportional tobλg. However, investigation of the theoretical foundation has not been carried out clearly.In this paper, based on the fundamental differential equation describing the characteristics of the nonuniform waveguide, a transmission line equivalent to the waveguide is derived. By means of this transmission line, the forementioned characteristic impedance is proven to be theoretically correct. Here, this quantity is called the equivalent characteristic impedance.Based on this result, it is proved that there are several different procedures for the analysis of the characteristics of the tapered waveguide and that they all arrive at the same results. The theoretical results are verified by three different experiments. In addition, the applications of this equivalent characteristic impedance are described for the design of the connecting tapered waveguide and the quarterwave transforme

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750506

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

年代:1992

数据来源: WILEY

摘要:

AbstractTo cope with the deterioration of the yield of the memory LSI due to the microstructured design, this paper considers the centralized system‐level redundancy scheme, where, by providing the spare memory chip and the rescue control circuit to the semiconductor memory system, the fault is rescued in a centralized way. In this scheme, the fault bits are memorized in the nonvolatile memory for each word/bit line, and the normal and the spare memories are switched at the I/O terminal of the system by the parallel access.As the method of access to the spare memory, this paper proposes the indirect address input method, where the external address is converted by the control circuit, and the direct address input method, where the external address is directly used. In the former, the external address is converted into the internal address and the ratio of the spare memory to the normal memory decreases with the increase of the system scale, which is favorable to low‐cost applications.The method is applied to the 20‐Mbit file memory using partially good 1 MSRAM, and it is verified that the defect word/bit lines of up to 35 line/chip can be rescued, thereby improving the yield by approximately three times.In the latter method, the addresses to the normal and the spare memories are input simultaneously in parallel, which is favorable for the high‐speed operation. This method is applied to the 4‐Mbit memory module using partially good 4 MDRAM and it is verified that the defect can be rescued while minimizing the deterioration of the ac

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750507

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

年代:1992

数据来源: WILEY

摘要:

AbstractVLSI memories have been diversifying along with high density and high speed. With diversification, the evaluation test program also must handle each VLSI memory, and the efficiency of its generation is an important issue.In this paper, to evaluate diversifying VLSI memories, a program structure is described which can create evaluation test programs quickly for semiconductor test equipment, especially memory testers. The test program presented herein has a module structure consisting of utility groups for evaluation, a main program, and subroutine programs which describe the specific test conditions for each VLSI memory. Also, it can handle the evaluation of various VLSI memories with minimum programming.As a result of using this program structure for the evaluation test programs for 16 kinds of VLSI memories, it has been confirmed that the program development time can be reduced to one‐fifth that of the conventional method and the evaluation time can also be reduced by one hou

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750508

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper describes an experimental 1.3‐μm, 1‐Mb BiCMOS DRAM, the first DRAM to use an ECL interface. The results are as follows: (1) quantitative analysis shows that direct sensing of a small read‐signal voltage on the data lines before amplification by the CMOS rewrite amplifier gives an access time 8 ns (up to about 30 percent) faster than conventional common input/output (I/O) sensing; (2) the bipolar cascode amplifier is characterized by the pulsed emitter‐bias current. Computer simulation and experiments show that its delay time is not sensitive to changes inVccat the rate of about 50 mV/ns; (3) a new bipolar ECL I/O circuit with a power‐switching function is shown to reduce the standby current of a 1‐Mb ECL chip to about one‐fifth that of an ECL chip without a power‐switching function; and (4) the experimental chip has an access time of 24 ns, power dissipation of 730 mW, and a chip area of 62.2 mm2under typical conditions ofVEE= −5.2 V,Ta= 25°C, output capacitanceCL= 10 pF and a cycle time of 70 ns, andnMOS/pMOS transistors with gate le

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750509

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

年代:1992

数据来源: WILEY

摘要:

AbstractPerformance evaluation of VLSI circuits has been studied widely following the progress of VLSI technology. In these studies, the amount of material as well as the wire routing lengths required for the VLSI layouts for sorting circuits, FFT circuits, interconnection circuits, and so on, have been discussed. These discussions are based on a fact that the wire routing controls the VLSI performance, but they all concentrate on conventional two‐dimensional (2‐D) VLSI circuits. By contrast, new integration technology, i.e., so‐called 3‐D VLSI technologies, have been developed to overcome the barriers to the progress of 2‐D integration technology.This paper discusses the performance evaluation of FFT circuits based on 2‐D VLSI technology as well as 3‐D VLSI technology. As the evaluation results, the amount of material can be reduced about oneO(N−1/2logN)‐th to oneO(N−1/2log−2N)‐th by using 3‐D construction rather than the conventional 2‐D VLSI circuit. Furthermore, the optimum FFT circuit based on theAT2complexity for 2‐D integrated circuits cannot always be an optimum circuit based on theV2T3complexity for 3‐D integrated circuits. Therefore, it will be necessary to reevaluate each circuit based on theV2T3complexity to fa

ISSN:8756-663X    

DOI:10.1002/ecjb.4420750510

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

年代:1992

数据来源: WILEY