Chirping characteristic and frequency response of MQW opticalintensity modulator

The spectral linewidth enhancement factor and frequency responses of electro-absorption-type optical-intensity modulators, especially InGaAs/InAlAs MQW modulators, are described. A method of exactly estimating the value of the α factor is presented under the nonlinearity of extinction-ratio characteristics. For measuring the frequency response of modulators, the sideband strength of the modulated output light with an optical spectrum analyzer, is analytically compared with the microwave power of photodiode direct detection with an electrical spectrum analyzer     

Modulation characteristics of semiconductor Mach-Zehnder opticalmodulators

The transmission and chirp characteristics are described for two types of semiconductor Mach-Zehnder modulators, distinguished by the differential phase shift between the two arms of the interferometer in the unbiased state. The conventional modulator has a differential phase shift of 0 radians, while the π-shift modulator has a differential phase shift of π radians. The nonlinear dependence on the applied voltage of the attenuation and phase constants of the optical signal propagating in the p-i-n waveguide leads to different characteristics for the two modulators. The influence of the splitting ratio of the Y-junctions is considered for single-arm and dual-arm (push-pull) modulation formats. The π-shift modulator is shown to yield better transmission performance for 10 Gb/s systems compared to the conventional modulator     

MQW tuned semiconductor lasers with uniform frequency response

A tunable semiconductor laser with an intrinsically wideband uniform frequency response has been developed, using the quantum confined Stark effect in quantum well material as the tuning mechanism. A frequency response uniform within 3 dB from 20 kHz to 1.2 GHz was achieved, limited by the measuring system at low frequencies and by device capacitance at high frequencies. Analysis shows that with optimised tuning elements a uniform frequency response to over 50 GHz should be achievable with this technique     

Set and reset operation dependence on input light intensity of a side-light-injection MQW bistable laser

Dynamic set and reset operations of a side-light-injection MQW bistable laser are achieved using absorption saturation and gain quenching. As input light intensity increases, the turn-on and turn-off times decrease. The turn-on time is 200 ps when the input light peak intensity is 1 mW and the turn-off time is 2 ns when the input light peak intensity is 2100 mW.<>     

Ultrahigh-speed driverless MQW intensity modulator, and 20 Gbit/s, 100 km transmission experiments

An InGaArInAlAs MQW modulator with the low voltage of 1.5 V for 10 dB extinction ratio and 16 GHz bandwidth has been developed. This ultrahigh-speed modulator enables the modulator driver to be eliminated from the transmitter. 100 km transmission experiments have been carried out using either a 1 V peak to peak output monolithic-IC-driven modulator at 15 Gbit/s or a 2 V peak to peak output multiplexer-driven modulator at 20 Gbit/s. This is the first report on multigigabit operation of MQW modulators to the authors' knowledge.<>     

Saturation behavior of SF6at high pressure and laser intensity

An experimental study of the saturable absorption of SF6at high pressure with high incident laser flux is reported. Experiments with a high-pulse-power CO2laser show 15 orders of magnitude change in transmittance of SF6(17 torr pressure) at theP(16) CO2line and apparent saturation of the residual absorption atP(20) andP(22) CO2wavelength. Comparison of these results with behavior predicted by a four-level model yields reasonable agreement over certain intensity ranges.     

Frequency response of an MQW DFB laser injected with intensity-modulated TM-polarized light

The frequency response of a multiquantum-well (MQW) distributed-feedback (DFB) laser was measured by injecting intensity-modulated transverse-magnetic (TM)-polarized light. With low bias currents, the 3-dB bandwidth of the MQW DFB laser's frequency response was anomalously enhanced by injection of intensity-modulated TM-polarized light. The maximum 3-dB bandwidth, 16 GHz, was observed when the normalized bias current (I/I/sub th/-1) was 1. The 3-dB bandwidth behavior of the MQW DFB laser with TM-polarized light injection looks promising for high-speed lasing mode control of semiconductor lasers.<>     

Proposal of novel gain-levered MQW DFB laser with high andred-shifted FM response

A gain-levered multiple quantum well (MQW) distributed feedback (DFB) laser with high FM efficiency is discussed. The device consists of three sections with different bandgap energy. It can be fabricated by a selective area metalorganic vapor phase epitaxy (MOVPE) growth technique. Numerical analysis shows that a flat, red-shifted, and high FM efficiency of above 1 GHz/mA at 20-mW output power can be realized using the gain levering scheme     

高效率聚合物薄膜太阳能电池

本文评述了一种新发明的基于光合作用原理的太阳能电池发电概念。这种太阳能电池具有低的成本和高的理论转换效率。     

Strongly improved frequency response at high-optical input powersfrom InGaAsP compensated strain MQW electroabsorption modulators

InGaAsP MQW electroabsorption modulators with and without compensated strain were fabricated and tested. Compensated strain was employed to reduce the valence band discontinuity between the well and barrier, which decreased the heavy-hole carrier escape time. A short optical pulse coupled into the modulator was used to measure the enhancement in carrier escape time from strained compensated InGaAsP quantum wells, for the first time. As a result, the strained MQW sample demonstrated an improved frequency response when operated at high optical input powers and low fields     

Synthesis of photonic microwave filters based on external opticalmodulators and wide-band chirped fiber gratings

The synthesis of photonic microwave filters employing optical sources with modulation side-bands, as multimode optical sources, and chirped fiber gratings is addressed. A single wavelength laser externally modulated using electrooptical Mach-Zehnder modulators and electroabsorption modulators have been proved as optical sources with modulation sidebands. Microwave filter features such as wide range tunability, compactness, readily reconfigurable frequency responses and flexibility have been achieved and demonstrated for the proposed structure. Experimental results using both a dual-electrode Mach-Zehnder electrooptical modulator and an electroabsorption modulator as optical sources with modulation sidebands are provided to demonstrate the feasibility of this technique     

GaAs/GaAlAs多量子阱激子吸收谱

在10K至292K温度范围内测量了GaAs/GaAlAs多量子阱结构的激子吸收谱.观察到轻、重空穴对应的激子吸收峰(LH和HH)及台阶状态密度.研究了轻、重空穴激子吸收峰的能量间隔及激子吸收峰的温度特性.发现多量子阱样品的LO声子展宽系数为6.1meV,比体GaAs的展宽系数略小.样品用国产MBE设备生长,采用化学选择腐蚀技术除去GaAs衬底.     

应变多量子阱激光器的结构稳定性

通过计算应变多量子阱中的净应力和应变弛豫,讨论了激光器结构中应变多量子阱的稳定性。净应力是失配位错增殖的驱动力,是应变多量子阱稳定的重要判据。因此,用单结点模型计算了应变多量子阱结构中的净应力。计算结果表明,净应力的最大值在应变多量子阱结构中的位置与阱层和垒层的厚度以及阱层的失配有关,非应变垒层和盖层能在一定程度上稀释净应力。在此基础上,利用动力学模型计算了应变多量子阱的应变弛豫。     

Equivalent refractive index of MQW waveguides

In this paper, we have proposed some new numerical and semi-analytical methods for developing an equivalent three-layer model of an MQW waveguide. The waveguiding properties like effective index, field distribution, and fractional power within the core of the waveguide of these equivalent structures are compared with those of previously reported equivalent methods. These results are also compared with the results obtained from the exact multilayer analysis of the MQW waveguide. The waveguiding properties are accurately predicted by the semi-analytical method using variational analysis, and the computational effort is significantly reduced. The use of the three-layer equivalent is illustrated in obtaining an estimation of the waveguide losses and is used to study the effect of nonlinearity     

Common path differential intensity and phase profilometer using time division multiplexing

To measure surface topography in the subnanometre range a new approach to obtain simultaneous differential phase and intensity scans from an optical profilometer/microscope is described. The proposed configuration achieves these objectives by multiplexing two interferometers in time. Optimum differential intensity and phase response are achieved without the compromise associated with previous systems.<>     

Operating characteristics of InGaAs-GaAs MQW hetero-nipi waveguidemodulators

We report frequency response measurements of optical MQW nipi waveguide modulators, observing a -3-dB bandwidth as high as 110 MHz. These devices have only 900-Å-thick intrinsic regions, and thus can achieve very high fields with modest reverse bias voltages. We also measured absorption modulation (32 dB) and a phase change figure of merit as low as V_π×L=0.8 V mm at a detuning of 115 meV below the photoluminescence peak. We compare ion-implanted selective contacts with traditional selective metal contacts     

Impact of PCS handoff response time

In a personal communications services (PCS) network, the network delay for a handoff request is limited by a timeout period. If the network fails to respond within the timeout period, the handoff call is forced terminated. We study the effect of the network response time on the performance (the call incompletion probability) of a PCS network. Our study indicates that at a small offered load, the network response time has a significant effect on the call incompletion probability. We also observe that the effect of the network response time is more significant if the mobile residence time distribution at a cell has a smaller variance     

wavelength dependent time development of the intensity of dye solution lasers

It has been observed that the intensity of laser emission from two different dye solution lasers (DTTC in DMSO and cryptocyanine in glycerol) reaches a maximum at the shortest wavelength in the emission band before it peaks at the longest. A simple model of dye solution lasers which explains this wavelength-time effect is presented. This effect can be interpreted to yield information on the rate of relaxation of internal energy of the dye molecule. The evidence suggests that, on the time scale of the laser action in these experiments (∼20 ns) the ground state of the dye molecule is inhomogeneously broadened. In addition, it is shown that certain other of the dye laser's properties may be understood by analysis of the solution's absorption and fluorescence spectra.     

Static and dynamic simulation for ridge-waveguide MQW DFB lasers

An efficient and versatile computer-aided simulator for the design and analysis of ridge-waveguide (RWG) multiple-quantum-well (MQW) distributed-feedback (DFB) lasers has been developed and is presented. This simulator combines spectral index method and Green's function-based transfer-matrix method (TMM) to deal with the transverse RWG MQW structure and longitudinal DFB structure, respectively. It is capable of simulating both static and dynamic behaviors for a variety of RWG MQW DFB lasers. The major difference from most of the existing models and analyses is that this simulator is capable of linking important device characteristics with practical material and geometrical parameters directly and self-consistently. For instance, the effects of lateral ridge width, vertical MQW layers and longitudinal nonuniformity are all explicitly included in the simulator. important laser characteristics, such as L-I curve, effective linewidth enchancement factor, static lasing wavelength shift, spectral linewidth, facet-power spectrum, AM and FM modulation responses, dynamic-wavelength chirping, as well as longitudinal photon and carrier distribution, can be predicted based on material and waveguide parameters. Therefore, this simulator may be used as an efficient and versatile tool for the systematic exploitation and optimization of a wide range of practical RWG MQW DFB lasers. Analysis of a λ/4 shifted SCH RWG MQW DFB laser is performed to illustrate the capability of this simulator     

InGaN多量子阱面发射微盘激光器的理论研究

为了实现半导体微盘磁光器的单模面发射,设计了一种以ＩｎＧａＮ多量子阱为有源层,ＣａＮ外延层为覆盖层的半导体微盘激光器。通过对ＧａＮ覆盖层进行图形刻蚀,可以对不同的角模式进行有选择的增益,由此实现选模。用有效增益因子加电介质盘的模型对实际微盘结构进行简化,并根据此模型计算微盘外的远场分布,并进上步计算有效增益因子。分析表明,这种结构能够实现ｍ＝１角模式的面发射。