763长周期地震仪自动增光器设计

目前,我国地震基本台网已有30个台站配置了763长周期地震仪,由于没有自动增光点设备,致使在发生大地震时,大振幅的地震记录波形由于光照度不够而辩认困难,甚至无法辩认。为解决这一问题,根据本人多年来参加观测实践设计了一套自动增光器,现将该设计简介如下:增光器电路设计图(见图1),BG_1,BG_2,为两只焊接安装在一块约20×80mm左右的绝缘薄板上的光敏三极管,该板固定在一个弃置不用的废记录灯架上用螺丝拧紧,将灯架置于记录暗室中763滚筒前,紧贴聚焦板,使两光敏管紧换光缝下沿,两光敏管间距视触发幅度需要调节其宽度,通常约20mm左右。

Approximate Well Width and Optical Gain Formulas of 1 .555μm In_(1-x-y )Ga_y Al_x As Compressively Strained Quantum- Well Laser

Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary to an- alyze the well width,differential gain,transparency carrier density and the characteristic gain for an arbitrary com- position.Some useful empirical formulas are also presented.

Strongly Gain Coupled DFB Laser Monolithically Integrated with a Self Alignment Spot Size Converter

A new type strongly gain coupled (GC) DFB laser and a new type self alignment spot size converter (SA SSC) are proposed and successfully fabricated.The strongly GC DFB laser is monolithically integrated with the SA SSC with three step epitaxies.A high single mode yield and large side mode suppression ratio is obtained from the strongly GC DFB laser.A near circle far field pattern is obtained by using the SA SSC.

Gain and Noise Properties of Bidirectional EDFAs

The rate equation model is setup for the signal gain, pump absorption and output noise spectrum of bidirectional EDFA (Bi EDFA) including numbers of signals, pumps of arbitrary direction, amplified spontaneous emission (ASE) and inherent loss. The influence of erbium doped fiber length, input signal power, pump style and pump power on the gain characteristics of Bi EDFA is analyzed. Forward and backward noise figure for different pump style versus bidirectional input signal power is investigated.

Optimization for Top DBR’s Reflectivity in RCE Photodectector

The monolithic integration of vertical-cavity surface-emitting lasers (VCSEL) with photodetectors is very important in the application of free-space optical interconnects.Theoretical and experimental results on the resonant-cavity-enhanced (RCE) photodetector with VCSEL Structure are presented.The compatible requirement in input mirror reflectivity between the VCSEL and the RCE detector is achieved by precisely etching the top mirror.In this way,the RCE detector with relatively high quantum efficiency and necessary optical bandwidth has been obtained.[KH8/9D]

Array for 980nm Vertical Cavity Surface Emitting Diodes and Detectors

Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity of 4 8nm and high electroluminescence intensity of 0 7mW while injection current is 50mA.A 1×16 array of surface emitting light device is tested on line by probes and then used for module.The light detectors have wavelength selectivity and space selectivity.The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.

10Gb/s EML Module Based on Identical Epitaxial Layer Scheme

A 10Gb/s transmitter module containing an electroabsorption modulator monolithically integrated with a distributed feedback (DFB) semiconductor laser is fabricated using the identical epitaxial layer scheme.Gain-coupling mechanism is employed to improve the single mode yield of the DFB laser,while inductively coupled plasma dry etching technique is utilized to reduce the modulator capacitance.The integrated device exhibits a threshold current as low as 12mA and an extinction ratio over 15dB at -2V bias.The small signal modulation bandwidth is measured to be over 10GHz.The transmission experiment at 10Gb/s indicates a power penalty less than 1dB at a bit-error-rate of 10 -12 after transmission through 35km single mode fiber.

Optimization Design of Active Structure of Strained MQW DFB Lasers

The well number and the cavity length of 1.55μm wavelength In 1-x-y Ga y Al x As MQW DFB lasers are optimized using a simple model.A low threshold,maximum operating temperature of 550～560K,and high relaxation oscillation frequency of over 30GHz MQW DFB laser is presented.

Electron Injection Enhancement by Diamond-Like Carbon Film in Polymer Electroluminescence Devices

A diamond-like carbon （DLC） film is deposited as an electron injection layer between the polymer light-emitting layer（MEH-PPV） and aluminum （Al） cathode electrode in polymer electroluminescence devices （PLEDs） using a radio frequency plasma deposition system. The source material of the DLC is n-butylamine. The devices consist of indium tin oxide （ITO）/MEH-PPV/DLC/Al. Electron injection properties are investigated through I-V characteristics,and the mechanism of electron injection enhancement due to a thin DLC layer has been studied. It is found that： （1） a DLC layer thinner than 1.0nm leads to a higher turn-on voltage and decreased electroluminescent （EL） efficiency; （2） a 5.0nm DLC layer significantly enhances the electron injection and results in the lowest turn-on voltage and the highest EL efficiency; （3） DLC layer that exceeds 5.0nm results in poor device performance;and（4） EL emission can hardly be detected when the layer exceeds 10.0nm. The properties of ITO/MEH-PPV/DLC/Al and ITO/MEH-PPV/LiF/Al are investigated comparatively.

Gain Switch of an AlGaInP Red Light Semiconductor Laser Diode

We solve the single mode coupled rate equations by computer,simulate the behavior of a gain switch of an AlGaInP red light semiconductor laser diode,and find the characteristic of FWHM of pulses changing with the amplitude of modulation signal, the bias current, and the modulated frequency. On this basis, we conduct experiments. The experiment results accord with the simulations well.

Fluorescence Enhancement of Polyamine Derivatives of 1,8-Naphthalimide with Transition Metal Ions

A series of fluorescent chemosensors 1-3 were synthesized to detect transition metal ions. At the room temperature, fluorescence intensities of these chemosensors in acetonitrile without transition metal ions were found to be very weak, due to the process of the efficient intramolecular photoinduced electron transfer （PET）. However, after addition of the transition metal ions, the chemoscnsor 1-3 exhibits obvious fluorescence enhancement. Moreover, the intensity of the fluorescence emission of chemosensors increases significantly in the presence of Zn^2＋ and Cd^2＋. The fluorescent chemosensors with different polyamine as receptors show diverse affinity abilities to the transition metal ions and signal the receptor-metal ion interaction by the intensity change of fluorescence emission.

Theoretical Analysis of Gain and Threshold Current Density for Long Wavelength GaAs-Based Quantum-Dot Lasers'

Quantum dot gain spectra based on harmonic oscillator model are calculated including and excluding excitons. The effects of non-equilibrium distributions are considered at low temperatures. The variations of threshold current density in a wide temperature range are analyzed and the negative characteristic temperature and oscillatory characteristic temperature appearing in that temperature range are discussed. Also,the improvement of quantum dot lasers＇ performance is investigated through vertical stacking and p-type doping and the optimal dot density, which corresponds to minimal threshold current density,is calculated.

Accurate method for determining vibration temperatures, and gain limitation in pulse RF-discharge CO_2 laser

An accurate method of determining gain coefficients of pulse RF-discharge CO2 laser is developed, which involves the use of both the regular 00o1 and 00o2 laser transitions as probes of CO2 laser. The results indicate that the majority of transitions in discharge have anomalous gain coefficients under RF-discharge condition. This fact has not been generally recognized and the neglect of overlapping transitions can lead to errors in determining rotational temperature.

Gain Characteristics of Fiber Optical Parametric Amplifier

The theory model of fiber optical parametric amplifier (FOPA) was introduced, which is based on optical nonlinear effect. And then numerical simulation was done to analyze and discuss the gain spectral characteristics of one-pump and two-pump FOPA. The results show that for one-pump FOPA, when pump wavelength is near to fiber zero-dispersion wavelength(ZDW), the gain flatness is better, and with the increase of the pump power, fiber length and its nonlinear coefficient, the gain value will increase while the gain bandwidth will become narrow. For two-pump FOPA, when the pump central wavelength is near to fiber ZDW, the gain flatness is better. Moreover, by decreasing the space of two pumps wavelength, the gain flatness can be improved. Finally, some problems existing in FOPA were addressed.

Resolution Characteristics of GaAs/GaAlAs Transmission Photocathode

The resolution characteristic of GaAs/GaAlAs transmission photocathode is an important parameter in third generation intensifiers. The modulation transfer function of GaAs/GaAlAs transmission photocathode is derived from a simple two-dimensional diffusion equation. The theoretical resolution characteristic of a 2 μm thick GaAs/GaAlAs transmission photocathode is calculated. The relationship between resolution and parameters in GaAs/GaAlAs transmission photocathode is discussed. A conclusion is shown that one can design the GaAs/GaAlAs transmission photocathode for maximum quantum efficiency, since the sacrifice in the resolution doesn't limit system performances.

Hybrid WDM/TDM PON system employing an all-optical wavelength converter

A new hybrid WDM/TDM passive optical network （PON） implemented by using all-optical wavelength converters （AOWCs） is proposed. The AOWCs are based on the cross-gain modulation （XGM） effect of the semiconductor optical amplifier （SOA）. Moreover, the feasibility of this sys- tem is experimentally demonstrated by evaluating the impacts of the optical wavelength conversion, time domain waveforms, eye diagrams and bit-error-rate （BER） in AOWC. The results show that the proposal will be a promising solution for the next generation access networks.

Interfacial state induced ultrasensitive ultraviolet light photodetector with resolved flux down to 85 photons per second

We present an ultrasensitive ultraviolet （UV） detector based on a p-type ZnS nanoribbon （NR）/indium tin oxide （ITO） Schottky barrier diode （SBD）. The device exhibits a pseudo-photovoltaic behavior which can allow the SBD to detect UV light irradiation with incident power of 6 × 10^-17 W （-85 photons/s on the NR） at room temperature, with excellent reproducibility and stability. The corresponding detectivity and photoconductive gain are calculated to be 3.1 × 10^20 cm.Hz1/2.W^-1 and 6.6 × 10^5, respectively. It is found that the presence of the trapping states at the p-ZnS NWITO interface plays a crucial role in determining the ultrahigh sensitivity of this nanoSBDs. Based on our theoretical calculation, even ultra-low photon fluxes on the order of several tens of photons could induce a significant change in interface potential and consequently cause a large photocurrent variation. The present study provides new opportunities for developiphigh-performance optoelectronic devices in the future.

Design of a transversal equalizer for electronic dispersion compensation in optical communication links

A programmable transversal equalizer for electronic dispersion compensation(EDC) in optical fiber communication systems is developed.Based on the SiGe technology with a cut-off frequency of 80 GHz,the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps,which ensure that the equalizer can work at the bit rate of 10 Gb/s.With different tap gains,the forward voltage gain of the transversal equalizer varies,which demonstrates that the equalizer has various filtering characteristics such as low pass filtering,band pass filtering,band reject filtering,and notch filtering,so it can effectively simulate the inverse transfer function of dispersive channels in optical communications,and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion.The equalizer(including pads) occupies an area of 0.40 mm × 1.08 mm,and its total power dissipation is 400 mW with 3.3 V power supply.

All-optical ultra-wideband doublet signal source based on the cross-gain modulation in a semiconductor optical amplifier

We propose a novel scheme to generate the ultra-wideband (UWB) doublet signal pulse based on the cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). In the scheme, only an optical source and an SOA are needed. As there is only one wavelength included in the output doublet signal pulse, no time difference between the upper and down pulses is introduced during the transmission process. By using the software of Optisystem 7.0, the impacts of the optical power, the SOA current, the wavelength and the input signal pulse width on the generated doublet pulse are simulated and tudied numerically. The results show that when the pulse width of the input signal pulse is larger, the output signal pulse is better, and is insensitive to the change of wavelength. In addition, the ultra-wideband positive and negative monocycles can be generated by choosing suitable optical source power and SOA current.

Gain characteristics of a dual-pump fiber optical parametric amplifier with Raman effect

We investigate the pump-depleted model of a dual-pump fiber optical parametric amplifier(FOPA) with Raman effect.As bandwidth increases,the gain profile of the distorted FOPA would be impacted seriously.Under the widebands,especially when the pump separation is large,zero dispersion wavelength(ZDW) fluctuation is another factor which can not be neglected.Numerical simulations with these comprehensive factors are mainly analyzed to obtain their influence on gain characteristics.Saturated gain spectrum is also discussed in detail.