The beam propagation properties of the high-powered Multi-Quantum-Well (MQW) laser diode (LD) are definitive elements in many application fields such as micro-processing, biomedical technique, and basic research, etc. In this study, the beam characteristics of a high-powered InGaAs/AlGaAs MQW-LD have been evaluated in both fast-axis and slow-axis. The multi-planar waveguide model and the non-paraxial second-order moment theory were used in analyses of the beam propagation features in the direction perpendicular to the active layer of a MQW-LD. The experimental results of the beam character measurement accord with those of the theoretical calculation very well for a sampled InGaAs/AlGaAs MQW-LD. The analysis approach is thought to be useful for design of the LDs and the other waveguiding optical devices.

A new extremely fast and high-power laser diode driver module is introduced, which is made of a fast high-power MOSFET and based on discharging capacitor. The main factors are analysed in theory, which determine the main performance of this kind of laser diode driver module. The whole performance of the laser diode driver module is simulated with SPICE module in detail, and the testing results of the produced laser diode driver module are described. The main methods to change the output peak power and current pulse width of the laser diode driver module are presented. The output peak power of the laser diode driver module is very high, which can reach 50 W. The output current pulse width of the laser diode driver module is very short, which is less than 8 ns. The laser diode driver module can directly drive many kinds of pulse laser diode in the market, and be used as the high performance transmitter driver module of time-of-flight ladar and laser range finder.

We present an optically pumped vertical external cavity surface emitting lasers using the semiconductor gain chip composed of quantum wells. The dependence of the spectrum of the output on the temperature of the gain chip was measured. The maximum output power reached 40mW at the wavelength of 1015.5nm with the pump power of 1.5W. The optical conversion efficiency reached 2.7%.

The attenuation of diode laser bar depends on the level of productive art and working condition, and the devices which attenuate quickly appear higher junction temperature and asymmetry of heat distributing. This paper introduces the research on the attenuation character of GaAs/AlGaAs diode laser bar, and obtains imitate curve of relation between PN junction voltage and junction temperature through plentiful experiments. At the same time, we draw the instantaneous thermal resistance through calculation. Based on the electrical method instantaneous thermal resistance and aging experiment, we have realized evaluating the attenuation character of diode laser bar without any damnify. Moreover, we have raised modification measure which based on analyzing the correlative art.

A single longitudinal mode and narrow line width external cavity semiconductor laser is proposed. It is constructed with a semiconductor laser, collimator, a flame grating, and current and temperature control systems. The one facet of semiconductor laser is covered by high transmission film, and another is covered by high reflection film. The flame grating is used as light feedback element to select the mode of the semiconductor laser. The temperature of the constructed external cavity semiconductor laser is stabilized in order of 10^-3°C by temperature control system. The experiments have been carried out and the results obtained ---the spectral line width of this laser is compressed to be less than 1.4MHz from its original line-width of more than 1200GHz and the output stability (including power and mode) is remarkably enhanced.

Semiconductor lasers are very different from other lasers because refraction variation can't be avoided when the gain is changed. Refraction variation can be introduced the theory of semiconductor laser by a dimensional parameter. This parameter is called linewidth enhancement factor (LEF). The value of LEF is very important for many aspects of laser behavior. The LEF characterizes the linewidth broadening and chirp due to fluctuation in the carrier density. A simple method to measure the linewidth enhancement factor of laser diodes is presented in this paper. The method uses the self-mixing effect at a weak feedback level. An optical beam is reflected and injected into the laser diode cavity by an external target, and is then mixed with the light inside the cavity, causing variations of the optical output power. The waveform of the optical power is determined by the feedback factor C and the LEF. A theoretical formula to compute LEF is proposed for the case when the feedback level C is smaller than 1. The experimental results show this method is feasible and simple when a laser diode operates at single longitudinal mode.

In this article, the laser performance of the 1300-nm In_0.4Ga_0.6As_0.986N_0.014/GaAs_1-xN_x quantum well lasers with various GaAs_1-xN_x strain compensated barriers (x=0%, 0.5%, 1%, and 2%) have been numerically investigated with a laser technology integrated simulation program. The simulation results suggest that with x=0% and 0.5% can have better optical gain properties and high characteristic temperature coefficient T0 values of 110 K and 94 K at the temperature range of 300-370 K. As the nitrogen composition in GaAs1-xNx barrier increases more than 1% the laser performance degrades rapidly and the T0 value decreases to 87 K at temperature range of 300-340 K. This can be attributed to the decrease of conduction band carrier confinement potential between In_0.4Ga_0.6As_0.986N_0.014 QW and GaAs_1-xN_x barrier and the increase of electronic leakage current. Finally, the temperature dependent electronic leakage current in the InGaAsN/GaAs_1-xN_x quantum-well lasers are also investigated.

The paper introduces a research on fiber coupled CW diode laser module. It works in a series connection other than parallel connection, which is done by other devices. Through the study and optimization on technology of heatsink insulate, narrowband reflector, exact coupling compound and collimation, we have secured 10~20W output power from fiber which have 100µm core diameter when the working current is only several ampere. Because the total junction capacitance in series connection is small, it is easy to carry out narrower pulse direct modulation .All of these characters make it more suit the arm equipment which use batteries to power supply. Especially in these fields such as laser beam riding guidance, active image and night vision system, it may have good foreground.

Polymer microfluidic chips have stimulated great instrests in the field of biochemical and medical analysis due to their low prices, easy fabrication and biocompatibility. Recently multilayer microfluidic chips have been fabricated by adhesive bonding to form 3-D multilayer laminate. However adhesive bonding may introduce pollution as well as complexity in coating. A bonding system with compact diode laser is introduced and a novel method based on transparent bonding line for multilayer microfluidic chips is developed. This bonding method is based on transmission laser microwelding technique. In this method, a special colorless dye as laser absorber, thus transparent polymer sheets can be stacked and bonded layer by layer. Initial results and bonding performance have demonstrate the feasibility of this method.

In this paper, we have designed a laser structure with separate confinement single quantum well (SCH-SQW )and have grown the laser structure by MOCVD .Moreover we have also fabricated broad area structure .The lasers are cleaved into bars and coated with high and low reflectivity films (approximate 95% and 5%).The measured results of the device show that its threshold current is 1.95A ,The CW output power is 2W ,and the peak wavelength of the device is 910nm±2nm .

Ultrafast intraband carrier dynamics strongly influence many important characteristics in bulk and quantum well lasers and amplifiers through Spectral-Hole Burning (SHB) leading to nonlinear gain effects. In Quantum Dot (QD) devices, where the inter-level relaxation times can be even longer than the intraband relaxation times in conventional devices, SHB effects should also be substantial. A number of promising applications of QD amplifiers in high-speed optical processing (Cross-Gain Modulation, for instance) are based on features of the carrier dynamics in QD structures. In the present paper, based on a density matrix approach, we develop a theory of SHB-based nonlinear gain in QD lasers and amplifiers, which can affect such important characteristics as the modulation bandwidth in QD lasers and the saturation power and pulse energy in QD amplifiers. We give an expression for the nonlinear gain in QD devices, and show how it depends, particularly, on the capture/escape and relaxation/excitation rates.

Semiconductor laser has the characteristic of high efficiency and small volume,which make it be the best illuminator in the night vision system so that increase the range of observation and improve the image quality of night vision system. But in bad weather, image qualitly will decline because of atmosphere's backward scattering which serious influence the laser beam. To solve this problem, We have studied how to control the working condition of semiconductor laser and make it form a pulse laser which according with range gating technology in night vision system. The result of study indicates that semiconductor laser is feasible as illuminator for night vision system.

Based on the rate equations and light propagation equations, a novel theoretical model of double-cladding erbium-ytterbium co-doped superfluorescent fiber source (SFS) in double-pass forward (DPF) configuration has been presented. By optimum choosing the fiber length and pump power, the characteristics including mean wavelength stability, threshold, output power, and bandwidth of the SFS are theoretically analyzed in details. The effects of the variation in pump wavelength on the system performance are also been investigated. The analysis results show that a double-cladding erbium-ytterbium co-doped SFS in DPF configuration may serve as light source for the navigation-grade fiber-optic gyroscope applications.

By using gain nonlinearity characteristics of semiconductor optical amplifier, an all-optical binary half adder at 10 Gbps is demonstrated. The half adder operates in single mechanism, which is XGM. The half adder utilizes two logic functions of SUM and CARRY, which can be demonstrated by using the XOR gate and the AND gate, respectively. In the XOR (A NOT B + NOT A B) gate, Boolean A NOT B is obtained by using signal A as a probe beam and signal B as a pump beam in SOA-1. Also, Boolean NOT A B is obtained by using signal B as a probe beam and signal A as a pump beam in SOA-2. By adding two outputs from SOA-1 and SOA-2, Boolean A NOT B + NOT A B (logic XOR) can be obtained. In the AND (AB ) gate, Boolean NOT B is firstly obtained by using signal B as a pump beam and clock signal as a probe beam in SOA-3. By passing signal A as a probe beam and NOT B as a pump beam through SOA-4, Boolean AB is acquired. By achieving this experiment, we also explored the possibilities for the enhanced complex logic operation and higher chances for multiple logic integration.

We have proposed a simple and convenient gain control scheme of the semiconductor optical amplifier (SOA) utilizing the amplified spontaneous emission (ASE) from the SOA itself. Based upon this scheme, an optical pulse active replicator using a SOA could be used for high-fidelity replication of short analog optical pulses. Taking into account the ASE noise, a numerical model of the SOA is developed to investigate the optical pulse recirculating propagation in the active replicator. Results indicate that the replicator is feasible and effective. Selecting appropriately operating parameters, such as the loss within the loop, the power of signal pulse and the front-end receiver electrical bandwidth, the replicator can generate a sequence of precise periodic optical pulse trains with low distortion and good SNR.

In order to realize the coupling of the crystal spectrum line, the wavelength output by the laser-diode must be adjusted to be accordant with the peak value absorbed by laser crystal in the solid laser of the laser-diode pump. In this paper, the finite element analysis (FEA) of the heat emission of the to-3 encapsulated laser-diode was researched and an accurate PI+Fuzzy temperature control system was developed. The refrigeration and the accurate temperature control of the high-power laser-diode was realized by the semiconductor refrigerator. Combined with fussy control and PI control, a full solid refrigerator of the laser-diode was developed. AT89C51 MCU and CRI^[1] fussy control arithmetic were used in this system. So the system has high temperature control precision and little chatting. The rate of change of the optical power peak value output by the laser-diode was less than 1%.

Currently in the initial stages of development, the endeavor aims to use satellite-to-satellite tracking laser interferometer-based optical technique, to document fluctuations in earth's gravitational field indicating other critical changes in the environment. This system must be able to measure infinitesimal changes in the relative velocity of the two satellites, using a laser light source, which oscillates at frequency stability better than 10-13 in the square root of the Allan variance. The constraints placed upon the system will ultimately require that the interferometer's light-source be small, lightweight, extremely efficient, durable, and possess high frequency-stability. Present-day technology of a laser diode possesses all of these characteristics, except the last and most critical one; frequency stability. So, our ongoing efforts are all focused on the search for a method of stabilizing the oscillation frequency of the satellite-to-satellite laser-diode light source. We used a Rubidium absorption line as a frequency reference of the frequency stabilization system and the "double optical feedback" method to narrow the laser diode's oscillation linewidth, in order to improve its frequency stability. We have measured the frequency, to determine its degree of stability, by comparing the "femtosecond optical comb generator"- and laser diode-frequencies.

Laser diode (LD) are playing more and more important role in a number of technical areas. However, due to LD's bad beam divergence, researchers have to use sophisticate optical systems to collimate or focus LD into other appliance. It is necessary to collimate laser diode. Whereas if the object is not ideal but with a limited dimension, no matter how to correct the radius, some aberrations may always remain. That is the collimation has a limitation. In this paper, we investigate the limitation for the asymmetric bi-convex lenses by ray tracing method with the help of Femat theory. And obtain the equations which analyze the limitation of the asymmetric bi-convex lenses. By programming the equations, we calculated and the limitation as a function of LD's beam dimension, index and the two radii of curvature of the asymmetric bi-convex lenses respectively. Keeping other conditions invariably and changing LD's beam dimension from 5mm to 150mm with a step of 5mm, we find that the limitation increases approximatively linearly with the increase of the beam dimension. Basing on the results of the calculation, we analyzed and plotted the limitation as a function of index and radii of curvature of the asymmetric bi-convex lenses in detail.

An optimized 650-nm AlGaInP multiple-quantum-well (MQW) laser, which has a compressively strained graded-index separate confinement heterostructure (GRIN-SCH), with improved characteristic temperature, is described. We theoretically show that the parabolic GRIN-SCH has a better carrier injection and smaller overflow than the conventional step-SCH for the AlGaInP LD under identical optical confinement. We have also calculated the electron distribution in the quantum wells for both GRIN-SCH-4QW and SCH-4QW at high temperature. The results indicate that the electron leakage to the p-cladding layer is greatly reduced if the GRIN-SCH-4QW structure is used. We have also compared the performance of LDs with different GRIN-SCH profiles and found that the parabolic GRIN-SCH is better than linear GRIN-SCH in terms of carrier confinement. We have further demonstrated the performance of AlGaInP LDs with four different structures (4-QW step-SCH, 5-QW step-SCH, 4-QW parabolic-GRIN-SCH and 5-QW parabolic-GRIN-SCH). Both theoretical and experimental results indicate that the laser diode with GRIN-SCH-4QW shows the best laser performance among the three structures. A characteristic temperature of 110 K has been demonstrated.

In this paper, a Vertical-Cavity Surface-Emitting Laser (VCSEL) of double oxide-confined regions is introduced. A direct coupling theoretical model in quasi-three-dimension for the gain-wave guide VCSEL has been created. With the finite-difference method, self-consistent solutions for the Poisson, injected current density, carrier concentration, optical field and thermal conduction equations were realized to study the electrical, optical and thermal fields characteristics of VCSEL with double oxide-confined regions or single oxide-confined region. The calculated results show that the structure of double oxide-confined regions in VCSEL has improved greatly the characteristics of lasers, and it provides a method of reducing threshold current and controlling high-order modes.

In this paper, an efficient numerical method is developed to solve the one-dimensional inverse nonlinear heat conductivity problem (INHCP). The method is proven absolute stability. It is more efficiently applied to determine the inner heat conductivity distribution by the measured surface temperature signals of some materials, such as semiconductor, steel, etc.

This paper introduces method of electrical noise evaluating of high-power fiber coupled diode laser. After photoelectricity conversion of output laser, We measure its electrical noise by analyse and test system. At the same time, we find out primary noise source through analysing 1/f noise, G-R noise and burst noise in the device systematically. Moreover we raise feasible advice on how to improve arts level and reliability of system after analysing relationship between noise and correlative arts. Experimental result shows that this method is effective and practicable .

The optical properties of the violet-blue InGaN quantum-well lasers with an emission wavelength of 400-480 nm are studied with a LASTIP simulation program. Assuming that the In_xGa_1-xN/In_yGa_1-yN heterostructure has a band-offset ratio of 7/3, our simulation results indicate that the use of an AlGaN blocking layer can help reduce the electronic current overflow, and the non-uniform carrier distribution in the quantum wells plays an important role in the laser performance. If the piezoelectric effect is taken into account, the lowest threshold current of the violet-blue InGaN quantum-well lasers is obtained when the number of InGaN well layers is two if the emission wavelength is shorter than 412 nm, and one if the emission wavelength is longer than 412 nm. At a laser wavelength of 478 nm, the slope efficiency of the InGaN single quantum-well laser is decreased by ~2.4% and that of the double quantum-well laser is decreased by ~13.9% when the thermal effect is taken into account.

A widely tunable, narrow-linewidth, simultaneous triple-wavelength oscillation erbium-doped fiber ring laser (EDFRL) has been developed. The EDFRL can produce double-wavelength oscillations with the same linear-polarization output, as well as another widely tunable wavelength oscillation with orthogonal linear-polarization from 1522.2 nm to 1595.9 nm. The long-term stability of the triple-wavelength output was observed with a high signal-to-noise ratio of larger than 40 dB. By using this EDFRL in combination with a 1550-nm semiconductor optical amplifier (SOA), an ultrabroad tunable wavelength converter is demonstrated with uniform efficiency and equalized optical signal-to-noise ratio (OSNR) over a 9.1 THz tuning range through four-wave mixing (FWM) in a SOA. This result is a significant improvement of both the conversion efficiency and the SNR as compared with the conventional FWM-based wavelength converters. We have also investigated the effect of both input power and wavelength of pump P2 on conversion efficiency and OSNR of the wavelength-converted signals

A study of the gain-switching process and output characteristics in a Nd:YVO₄ microchip laser end-pumped by a fiber-coupled laser diode (LD) is reported here. The gain-switched laser pulses with controllable repetition-rate from 1Hz to 4kHz and pulse width of 16 ns are obtained. To analyze the gain-switching dynamics of the LD end-pumped Nd:YVO₄ microchip laser, a theoretical model has been developed. The model is based on the rate equations of four-level systems and some practical physics conditions. Numerical simulations using the model illustrate the dependence of buildup time, pulse width and peak power of the gain-switched laser pulse on the pumping parameters. The experimental results coincide well with the theoretical analysis.

It is a difficult problem to collect the information of accident in the detection system of traffic information. The paper states the principle of scanning the vehicles along the road with semiconductor laser .We can judge the moving state of the vehicles by distance image which is got by laser beam scan. The moving state will be abnormal in case the accident happens. This paper present the forming technology of scanning beam by semiconductor laser and the principle of software to dispose the distance image. This technology may also apply to other relative fields.

Development of the optical non-destructive method and related experimental setup allowing interstitial oxygen-in-silicon "mapping" when doing in-process wafer control are described. Scanning translucent IR microscope principle has been used, in which a specific radiation source has been implemented-a solid-state tunable laser diode (TLD) on PbS-heterojunctions. This light source possesses a number of very useful features (small radiation-body size, very high spectral selectivity, high accuracy of single-mode positioning and fast mode-to-mode switching), which, in combination, allow building-up an efficient measurement procedure. Particularly, TLD allows implementation a new method enabling strong suppression of undesired interference effect of multiple beams reflected from front and back wafer's surfaces. It is shown that, when implementing double-wavelength scan procedure, not only oxygen concentration map may be derived from the data, but the info about the wafer thickness variations in the scanned area may be obtained simultaneously. The theoretical estimations are presented of the attainable limits of spatial resolution, concentration sensitivity and scan rates. The experimental setup is described realizing the method; experimental data are presented obtained by the new method demonstrating good agreement with the integrated values obtained by the standard method while possessing much better spatial resolution (~90..100μm for the present). Further improvements in the method’s parameters are discussed, as well as the perspectives for the method to be used in electronic industry.

A numerical design of a kind of novel distributed Bragg reflectors (DBRs) which is used in VCSEL with 808nm wavelength is reported. In this DBR, the short period superlattice (SPS) is used for the layers with high refractive index. First, the principle of the DBR with SPS is described, and the special features of the novel DBR are given. According to the literature, structure of this type can make the series resistance of VCSEL lower. Second, the numerical design of the DBR is performed by the characteristic matrix method. Third, the numerical simulation of the DBR is given. In accordance with the numerical simulation, the reflective spectrum of the DBR is similar to the traditional DBR. And, the conclusion is finally given. The results of numerical simulation to the DBR indicate that the SPS is well enough to act as the high refractive index layers in DBR. At the same time, because of its superior electrical properties, it is a promising way to obtain the DBR with lower series resistance.

The thermal effect of fiber-coupled laser diode (LD) end-pumped Nd:YAG high-repetition-rate solid laser during the optical pumping are the important factor which affects the laser output characteristic and the system integrated performance. Aiming at a 2 W fiber-coupled LD end-pumped Nd:YAG laser, starting with the thermal conduction function, the numerical value of temperature steady distributing in the laser crystal is calculated applying the finite element method (FEM). Then the thermal stress in the crystal is obtained by calculation. And thermal lens effect are counted and analyzed. The study establishes the base of optimizing the design of laser to reduce thermal effect and improve the stabilization of laser output.

The Al-free separate confinement hetero-structure (SCH) single quantum-well (SQW) lasers were grown by liquid phase epitaxy (LPE). For 100µm stripe laser with cavity length of 1mm, continuous wave (CW) output power of 4W, slope efficiency of 1.32W/A and far-field pattern of 11°×28°were obtained.

Sapphire is widely used material for blue emitting diode, laser diode devices, visible-infrared window and radome applications. Although there is a large mismatch in the lattice constants and thermal expansion coefficient between nitride and sapphire, sapphire is still known as the most commonly used substrate in the GaN device for its physical robustness and high temperature stability. The ensuing component performance is highly dependent on the quality of the surface processing. In this work the effects of mechanical polishing, chemo-mechanical polishing (CMP) as well as CMP and subsequent chemical etching on the properties of sapphire substrate surfaces has been studied. The sapphire substrates have been investigated by means of polarizing microscopy, atomic force microscopy (AFM), X-ray diffraction rocking curves (XRCs) and micro-Raman spectroscopy. The results show that CMP with subsequent chemically etching yields the best quality sapphire substrate surfaces. The optimized conditions to realize good substrate and smoother surface morphology have been obtained.

Elaborate theoretical analysis has been done for the modulation characteristics of semiconductor 1aser and analytical expression has been deduced through the research of rate equation of semiconductor 1aser. A neural network model analyzing of the modulation characteristics of semiconductor laser is developed. Using the model, we find that the simulation result is well agreed with theoretical analysis result. Furthermore, a semiconductor 1aser is design by the model. The research shows that the method has significant direction for the design of semiconductor 1aser.

This paper introduces the inner structure principle and signal adjusting applications of programmable analogy device ispPAC which was manufactured by Lattice semiconductor company.It expounds the chip functions of agility,diverse amplification,smoothing and deamplification at length and discusses the design method of every function.

Based on the off-axis theory, by using the angular spectrum representation, the Fourier transform and the inverse Fourier transform, an inverse source model of a laser diode has been obtained. An accurate non-paraxial inverse source formulation is proposed by which the inverse source problem can be solved rigorously with the far-field measured data. So the accurate analytical solution to the source distribution can be obtained with the far-field intensity distribution, and then the parameters relating to the waveguide structure can be obtained.

Based on the off-axis theory, a further study of error analysis for the far field radiated from a small planar source is made and "sensitivity" and "sensitivity region" are discussed. Numerical results are also given to examine "sensitivity" and "sensitivity region" to the position of aberration tolerance. It is shown that "sensitivity region" is an important parameter to analyze and describe the far-field errors.

Based on the analysis of the beam output characteristics of laser diodes, using the generalized Collins integral, the propagation characteristics of Hermite-Gaussian beams passing through a gradient index lens is studied. The analytical expressions of intensity distribution is derived and numerical examples is illustrated. it furnished in analyzing physically the propagation properties of the beams of laser diodes.

Self-mixing interference effects in the LD pumped green laser under the threshold current are observed. The behaviors of laser under the threshold current are more like LED. Based on this, we put forward for the first time the idea that replacing the light source with LED. If so, the lifetime and price of this kind of interferometer, and also the cubage of the interferometer is reduced. The accurate threshold current of lasers can also be measured using this equipment. This will be great contribution to self-mixing interference effects and its applications.

With its study going deep into, the application field of semiconductor laser is increasingly broaden. But the asymmetry of far-field beam of semiconductor laser restricts its application. This article constructs a semiconductor laser current driving mode of high frequency and multi-wave. Through experiment, we present the best driving mode, which can uniform the far-field beam of semiconductor laser, and offer the result of the experiment at the same time.

A new self-mixing interference structure with compensatory cavity is proposed. The model of this structure is also established. With compensatory cavity, the defects of self-mixing interference signals, such as phase and environmental disturbance, can be improved. In addition, the range of distance measuring can be extended.

Self-mixing interference effects in the LD pumped green laser are observed. Then small disturbance theory is used for the first time to analysis the quantum behaviors in the laser. The cavity system without feedback is considered to be the initial status function, the influence of feedback is considered to be the disturbance. The interaction Hamilton is deduced finally.

With the development of science and technology, gunsight have made great progress. This paper introduces the working principle and structure of semiconductor laser gunsight that can be used day and night. The most excellence of which is that it can be used in the condition of zero illuminance. At the same time, we have developed an electrical cross line adjusting system which can lock goals easily. This kind of gunsight can be applied in the fields of the military, common security and civil affair.

The wurtzite Al_xGa_1-xN, In_xGa_1-xN, and Al_xIn_1-xN alloys are studied by numerical simulation based on first-principles calculations. For Al_xGa_1-xN the Vegard's law deviation parameter is 0.018 ± 0.001 Å for the a lattice constant and -0.036 ± 0.005 Å for the c lattice constant. For In_xGa_1-xN that is 0.047 ± 0.011 Å for the a lattice constant and -0.117 ± 0.026 Å for the c lattice constant. For Al_xIn_1-xN that is 0.063 ± 0.014 Å for the a lattice constant and -0.160 ± 0.015 Å for the c lattice constant The results indicate that the band gap bowing parameters obtained with the equilibrium lattice constant and with the lattice constants derived from the Vegard's law are 0.341 ± 0.035 eV and 0.351 ± 0.043 eV respectively for Al_xGa_1-xN, 1.782 ± 0.076 eV and 1.916 ± 0.068 eV respectively for In_xGa_1-xN, and 3.668 ± 0.147 eV and 3.457 ± 0.152 eV respectively for Al_xIn_1-xN.

Frequency stabilization of laser diodes is of vital importance for the exploitation of optical frequency-division multiplexing coherent transmission systems and high-resolution optical measurement application. The research of frequency standard in 1.5μm region becomes one of hot orientations in optical communication area. The molecules absorption frequency stabilization technology of Fibre Bragg Grating external cavity laser diode (FBG ECLD) is studied intensively. To overcome the shortcoming of traditional PID control, self-organized and self-adapted algorithm based on predictive estimate modelling is used. The algorithm adopts indirectness arithmetic, which estimates and improves on the modelling according to a suitable learning speed and gains perfect control effects. The algorithm which is adopted in embedded system can achieve high-resolution frequency stabilization within 5min warm-up without manual work.

We presented a diode end-pumped passively mode-locked Nd: YVO4 picosecond laser with a semiconductor saturable absorber mirror home made. Choosing a low-transmission output coupler and extending the cavity length suppressed the Q-switching mode-locked tendency in V-shaped cavity. We observed the pulse trains gone with a continuous background which was decreased with the decreasing of pulse repetition rate. The stable continuous mode-locked pulse was attained. The pulse repetition rate was 80.4MHz and the corresponding spectrum width was measured to be 0.15nm.

Optimization of a 1300-nm AlGaInAs/InP strained multiple quantum-well structure with an electron stop layer, which is located between the active region and the p-type GRIN-SCH layer, is studied numerically with a LASTIP simulation program. Specifically, the effect of the electron stop layer on the characteristic temperature and the temperature dependence of the slope efficiency are investigated. Various physical parameters at different operating temperatures are adjusted so that the threshold currents of the simulated laser structure can be matched to the results measured experimentally by Selmic et al. Our simulated results suggest that the AlInAs is a better material for the electron stop layer than the GaAsP. With the use of a p-type Al_0.5In_0.5As electron stop layer and an active region consisting of Al_0.175Ga_0.095In_0.73As(6 nm)/Al_0.27Ga_0.21In_0.52As(10 nm), a characteristic temperature of as high as 94.7 K is achieved for the 250-µm-long AlGaInAs/InP strained quantum-well laser under study.

In recent years, frequency stabilization technology of the external cavity laser diodes (ECLD) has developed rapidly. In this paper, an embedded system module that is adopted in the frequency stabilization circuit of ECLD is discussed, and an improved circuit of embedded system that is based on ARM core is presented. In this way, the reliability of frequency stabilization circuit system is increased, the power waste is reduced and the structure is simplified.

An all-optical full adder using semiconductor optical amplifiers has been demonstrated at 10 Gbps for the first time. The full adder consisted of XOR and NOR gates only utilizes the mechanism of cross-gain modulation. The full adder utilize two logic functions of SUM and CARRY, which can be demonstrated by using two XOR gates and four NOR gates, respectively. By passing signal A as probe signal and signal B as pump signal into SOA-1, Boolean A NOT B can be obtained. Also, by changing the role of signals A and B for SOA-2, Boolean NOT A B can be acquired. Addition of Boolean A NOT B and NOT A B results in NOT A B + A NOT B , which is Boolean expression of logic XOR. By passing this XOR signal and signal C into the second XOR gate with the same principle, SUM signal of the full adder can be obtained. The Boolean expression of SUM can be expressed as A # B # C . With the first three NOR gates, Boolean NOT(A+B), NOT(B+C), and NOT(C+A) can be obtained. With the addition of these outputs, Boolean NOT(A+B) + NOT(B+C) + NOT(C+A) can be formed. By injecting these outputs through the last NOR gate with clock signal, CARRY signal of the full adder can be realized. The Boolean expression of CARRY can be expressed as AB +BC +CA. The extinction ratio is about 6.1dB.

The dynamics of carriers/excitons in as grown and annealed ZnO epilayers at room-temperature under high excitation densities were monitored by pump-probe(4.65/3.1 eV) differential reflectance transients on a time scale equal to 100 ps. The ΔR buildup showed a density-independent time delay of about 1.45 ps relative to the pump pulse, indicative of hot phonon effects, i.e., LO-phonon bottleneck, common to the as grown and annealed ZnO epilayers. Both appeared an initial fast ΔR decay with a time constant of about 20-25 ps due to rapid defect trapping. After the fast decay, the ΔR transient of the as grown ZnO became of sign reversal and turned to an induced absorption signal from defect levels with a decay time of several hundred picoseconds weakly dependent on excitation intensities. For the annealed ZnO, no change over in sign was observed on the slowly recovering component of ΔR, of which, in particular, the decay time was found to linearly depend upon carrier density. This finding, as confirmed by photoluminescence measurements, was attributed to a bimolecular recombination in terms of an exciton-exciton scattering in ZnO. These observations suggest that this unique pump-probe technique can provide a useful tool for understanding the defect physics of semiconducting materials.

At low light intensities (linear regime), the absorption coefficient is independent of the light intensity; however, at sufficiently high intensities, the absorption becomes a nonlinear function. In case that incident optical power is sufficiently high to saturate the absorption coefficient, the optical power which is not absorbed is transmitted to the next region in the absorption layer if the photodetector is in longitudinal structure. Therefore this type of light-absorption behavior would be critical in analyzing the nonlinearity of a traveling-wave photodetector (TWPD). The transmitted optical power is absorbed as a nonlinear function of absorption coefficient, and the generated photocurrent due to the saturated absorption also shows the nonlinear characteristics. In this paper, we calculated the photocurrent of a TWPD considering the effect of the absorption saturation caused by high input intensity, and compared with the results using the linear function of absorption coefficient. For a different incident optical power, the nonlinear characteristics of photocurrent are analyzed for two-tone input signals, and thereby the inter-modulation distortions (IMD's) and spurious-free dynamic range (SFDR) are obtained.

We present the first demonstration of the vertical-injection depleted optical thyristor-laser diode (VIDOT-LD) with InGaAs/InGaAsP multiple quantum well structure. The VIDOT-LD using the vertical-injection structure shows very good isolation between input and output signal. For the faster switching speed and the lower power consumption, we optimized the structure of a fully depleted optical thyristor (DOT) by the depletion of charge at the lower negative voltage. The measured switching voltage and current are 3.36 V and 10 μA respectively. The holding voltage and current are respectively 1.37 V and 100 μA. The lasing threshold current is 131 mA at 25°C. The output peak wavelength is 1570 nm at a bias current of 1.22 I_th and there is no input signal.

During some high precision measuring, the LD light beam on frequency modulating would be carried time marks using frequency, such as FMCW test system. In this system, the frequency is shifted usually by changing the injection current of a LD. In the same time, the intensity of the laser beam must be changed. This change have no use for the test. In our experiment, the intensity change can be controlled by a modulator through electronic circuits according to a high speed response detector. This is a closed-loop control system using opti-electronic method, but not a signal clipper. Then, the laser beam can be modulated on intensity through another modulator to carry available signal in the measuring system for another testing value.

We demonstrated a efficient 532-nm microchip laser with a conventional schematic pumped by a single-mode laser diode through a ball lens. An output power as high as 18.7 mW has been achieved for a 121-mW pumping power of the laser diode. We also investigated the temporal dynamic characteristic of the laser by numerically solving a set of rate equations.

Requirements for suitable communication systems with large capacity and high speed processing of information are rapidly on increase. Fiber-optic communication systems are presented for these requirements today. Modulation is one of the most important part in these system. Although many optical modulators already has been existed, for more high speed and performance we are interested in design of traveling-wave type electro-optic modulator which can be used for wide-band applications. Quantum dots(QDs) have long been expected to improve the performance of optical devices. Since their density of states due to the three-dimensional (3-D) carrier confinement behave as delta function, thus, QDs have the characteristics such as enhanced differential gain, suppressed thermal distribution of carriers, and a nearly zero alpha parameter at the peak gain. In this paper, we fabricated electro optic modulator using InAs/InGaAs columnar QD. The height of one QD is 4 nm and 10 periods of QDs are stacked including InGaAs capping layer. The peak wavelength of photoluminescence is 1260 nm at room temperature. The electrode of QD modulator is designed as Traveling-wave Mach-Zehnder type for high speed operation. And the microwave characteristics are simulated to design Traveling-wave QD modulator using Finite Difference-Time Domain method. Using simulation results, we fabricated Traveling-wave type quantum dot electro-optic modulator with varying the length of modulation region.