摘要:

AbstractConsiderable research and development have been done on semiconductor photonic integrated circuits in which various components such as a laser diode and other photonic devices were integrated.In this paper, a 1.55‐μm band wavelength division multiplexing (WDM) integrated light source for optical communication is developed and the results of the evaluation are described. Four‐channel laser sources were fabricated by integrating tunable semiconductor lasers and semiconductor optical modulators plus multiplexers, and the possibility of using a 2.5‐Gbit/s high‐density WDM optical transmission system is discussed.After analyzing the problems encountered in the fabrication of these photonic integrated components, the development of a bandgap energy‐controlling technique of quantum well structure using the selective metal oxide vapor‐phase epitaxial (MOVPE) growth, which is a better fabrication technique, is described. By using this technique, the difficult process of combining the waveguide with a different bandgap energy can be accomplished only by a one‐step crystal growing. This simplifies the components fabrication, and a high‐coupling efficiency of the waveguide between the integrated elements can be obtained.As an application example, the integrated light source was fabricated by integrating a tunable laser, distributed feedback (DFB) laser, and semiconductor optical modulator. Then the tunable characteristic and the extinction characteristic were verified. This simplifies the fabrication method of the previously difficult method of semiconductor photonic integrated circuits and clarifies the possibility of developing a high‐density

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760401

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe wavelength shift of laser diodes in a magnetic field has been known for a long time. However, most of the studies have been performed at very low temperatures in a strong magnetic field. An experiment is carried out using laser diodes which oscillate at room temperature and found that the wavelength shift changed significantly, being sensitive to an inner structure. Further, the wavelength shift occurred depending on a magnetic field direction.Previously, the wavelength shift was explained on the basis of the Landau level at very low temperatures in a strong magnetic field. However, such Landau levels are not formed in a relatively weak magnetic field at room temperature; and, thus, the present result cannot be accounted for by the existing theories.This paper describes the experimental results of various types of GaAlAs laser diodes and discusses the mechanism of the wavelength shift and the wavelength control.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760402

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

年代:1993

数据来源: WILEY

摘要:

AbstractA theoretical and experimental investigation is presented of injection locking on a semiconductor laser by coupling into nonlasing Fabry‐Perot modes.The very interesting behavior of intermodal injection locking is shown by the investigation of detailed locking characteristics. The analysis adopts a formulation similar to that of Lang in the injected mode, and the free‐running mode is expressed by the rate equation for the photon density.The theoretical analysis takes into account the dependence of the refractive index and of the peak gain wavelength on the carrier density and the spectral dependence of the gain function.The experimental results can be explained well qualitatively by the theoretical results. The locking range is located approximately around the center of detuning for the injection locking to a nonlasing mode as far as 18 mode spacings away from the free‐running mode. At the same time, the locking range is shifted toward the lower‐frequency side of detuning and has a symmetric tuning characteristic for that of several mode spacings as in the ordinary injection locking. The former is very useful in appl

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760403

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn erbium‐doped fiber laser with a nonlinear amplifying loop mirror pumped by 1.48‐μm laser diodes was fabricated. A 290‐femtosecond (fs) short pulse was obtained successfully from this laser. The oscillation wavelength was 1.56 μm and the output peak power was as high as 16 W when the pump power was 20 mW. The oscillation threshold was about 50 mW.However, once the laser started oscillation, it continued to oscillate even when the pump power was 10 mW. The repetition rate of the output pulses changed randomly from 5 MHz (fundamental repetition rate) to 2 GHz and could not be controlled. However, using a subring cavity with a length which is 1/nthat of the main cavity (nis an integer), a constant pulse repetition rate of 125 MHz was o

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760404

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

年代:1993

数据来源: WILEY

摘要:

AbstractConventional optical functional elements which utilize the magnetooptical effect induced by magnetostatic surface waves have been those of a thick film structure for a waveguide to excite a magnetostatic surface wave. Therefore, they can offer a single‐mode waveguide, leading therefore to a degradation of performance due to a coupling between higher‐order modes in the waveguide. Such a waveguide which can propagate only a single fundamental mode without lowering the interaction cross section can be fabricated by constructing a magnetic double‐layer film with two different refractive indices.This paper considers the case where the magnetostatic potential of the magnetostatic surface wave varies significantly near the surface. This structure provides further improvement in mode conversion efficiency and characteristics by adjusting the saturation magnetization of the film. A model for elements is proposed by which one can shorten an interaction length, and the calculated results are disc

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760405

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

年代:1993

数据来源: WILEY

摘要:

AbstractA discussion on a complex refractive index (n=nc″ ‐ jnc″) for a clad film of a thin‐film waveguide polarizer is presented. A guided light of a wavelength 0.5145 μm is chosen. Based on simulation result using a slab approximation, experimental results are discussed for SiN clad films. SiN films are fabricated onto a three‐dimensional waveguide as clad films with a waveguide width 20 μm. Five SiN films with differentnc″ (= 0.02, 0.07, 0.12, 0.16, 0.23) are examined for the performance characteristics. As a result,nc″ = 0.16 is found to be best for a TE mode transmission polarizer with an extinction ratio 27 dB and an insertion loss 6 dB. Also, for a TM mode transmission polarizer,nc″ = 0.07 is found to be most suitable where an extinction ratio is 26 dB and an inser

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760406

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe feasibility is examined of using the Miller phase‐compensation circuit to ensure the stability of the voltage limiter circuit in high‐density CMOS DRAMs. First, analytical expressions are obtained for the condition of stabilization to support the comprehensive circuit design and it is shown that both load capacity and load current affect the stability significantly. Second, by using the analytical expressions, parameters for the voltage limiter and the phase compensation circuit are calculated. By computer simulation and experiment voltage variations within the chip are evaluated when the internal circuit operates and external power supply voltage is changed. Results show that the voltage variation caused by the operation of the internal circuit is within 10 percent, resulting in no problem in practice.The voltage variation caused by the change in the external power supply voltage is 3 percent in the case of low‐frequency noise (tr,tf= 1μs) and is as large as 20 percent in the case of high‐frequency noise (tr,tf= 10 ns) and attention must be paid to the latter case in the circui

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760407

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

年代:1993

数据来源: WILEY

摘要:

AbstractDifferential capacitive accelerometers have been fabricated using silicon micromachining, and a capacitance‐detection circuit and hybrid two‐wire sensing system have been realized.The features of the differential capacitive accelerometer are the small influence of both acceleration at other axes and temperature and in restrained parasitic capacitance due to the concentration of efforts on the structural design of the sensor. The sensitivity of the sensor depends on the residual stress in beams supporting the weight.By careful design of the capacitance‐detection circuit, the effect of both power supply voltage and temperature is small while the output signal of the sensor can be obtained from the current flowing in the two wires for power s

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760408

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe partial‐response maximum likelihood (PRML) system currently is investigated for practical applications as a modulation/demodulation scheme for digital magnetic recording equipment.This paper proposes a construction of the bit synchronizer by complete digital signal processing. The operational principle is verified by experiment. The proposed bit synchronizer is composed of the decision‐feedback digital PLL and the interpolator. The decision‐feedback digital PLL receives the data‐asynchronous sampled signal sequence as the input, which is the result of sampling by the fixed clock of two samples/bit, and regenerates the clock. The interpolator calculates the signal value at the data point indicated by the phase of the decision‐feedback digital PLL output. The result is given to the Viterbi decoder.By applying the proposed scheme, the PRML demodulator from the equalizer to the Viterbi decoder can be realized as a digital signal processing circuit, which operates synchronously with the single fixed master clock. A PRML demodulator is constructed based on the proposed bit synchronizer, and the operational principle is verified by an experiment using a magnetic disk device. The bit‐error rate less than 10−6is obtained for the channel bit ra

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760409

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

年代:1993

数据来源: WILEY

摘要:

AbstractDiode decoders are often used in ultrahigh‐speed memory. The AND gate in this type of decoder consists of several diodes and the output voltage of the decoder varies depending on the number of conducting diodes. Although this variation in the output level is an important problem, it has not yet been studied in detail. This paper describes the mechanism of this effect and shows how it affects the performance of the decoder. The parasitic capacitance of the output node, the deviation of the output voltage, and the operating speed are compared for three kinds of diode decoders: a downward diode decoder, an upward diode decoder, and Schottky barrier diode (SBD) decoder, using 0.8‐μm SICOS (sidewall base contact structure) technology. It is shown that the upward diode decoder provides the highest performance. This high performance is demonstrated using the upward diode detector in a 64‐

ISSN:8756-663X    

DOI:10.1002/ecjb.4420760410

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

年代:1993

数据来源: WILEY