In this paper, a 1.55 micrometers InGaAsP/InP partially gain- coupled DFB laser monolithically integrated with electroabsorption modulator is fabricated for the first time. The threshold current and the extinction ratio are 40 mA and 11 dB respectively.

The paper presents both numerical and experimental investigations on the behavior of 1.55 micrometers distributed feedback (DFB) laser diode (LD) driven by strong RF power. The picosecond dynamic response of gain-switched DFB LD can be analyzed by appropriate rate equations. The results of experimental research are generally in good agreement with the numerical calculations and the minimum pulse width is about 17 ps under 1 GHz, 20 dBm RF modulation.

High performance uncooled 1.55 micrometers InGaAsP/InP strained layer quantum well lasers grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) were reported in this paper. Whole MOCVD over growth method were applied in this work. The threshold currents of 5 mA and the highest lasing temperature of 122 degree(s)C were obtained.

1.3 micrometers strained-layer multi-quantum wells complex-coupled distributed feedback lasers with a wide temperature range of 20 to 100 degree(s)C are reported. The low threshold current of 10 mA and high single-facet slope efficiency of 0.3 mW/mA were obtained for an as cleaved device. The single mode yield was as high as 80%.

By using a recently modified LPE technique, extremely uniform InGaAsP/GaAs SCH SQW structure materials could be grown reproducibly. Single stripe lasers with 150 um emitting aperture generate 4.0 W in CW by improvement of waveguiding parameters and ohmic contact process.

Graded-index separate-confinement strained quantum well InGaAs/GaAs/GaAlAs lasers grown by metalorganic chemical- vapor deposition with carbon tetrachloride used as p-doped source for upper cladding layer and the capping layer are studied. By SIMS and electrochemical capacitance-voltage measurements, the desirable quantum well structure and the suitable doping and carrier concentrations profiles are found to be obtained. The grown crystals show good optical characteristics through the photoluminescence spectrum measurement of the upper cladding layer and the active layer. The oxide-stripe and the ridge waveguide stripe lasers are fabricated, the lower threshold current densities 160 A/cm² (uncoated) with 1500 micrometers long cavity are obtained. The differential quantum efficiency and the output power can be up to 0.4 W/A and 500 mw (uncoated).

For the first time, we report on the 980 nm InGaAs/GaAs/AlGaAs strained quantum well lasers with window structure in regions near the laser facet fabricated by impurity-free vacancy diffusion for quantum well intermixing. In the fabricating procedure, SrF₂ was used as a film suppressing the quantum well intermixing. 3 micrometers - stripe ridge waveguide lasers with window region of 25 micrometers at each end exhibit a high slope efficiency of 0.8 W/A and a threshold current of 20 mA. The characteristics are comparable with that of conventional lasers. Catastrophic optical mirror damage is not observed at thermal limited powers as high as 360 mW. Accelerated lifetesting at 100 mW and 50 degree(s)C shows devices to have good reliability.

In this paper, we adopted GaAlAs/GaAs SCH single quantum well wafer, which is grown by MBE, to complete one centimeter monolithic laser arrays, and two array structures were carried out on purpose to obtain cw and quasi-sw laser output respectively. In the experiment, by means of twice photoetching and chemical etching methods were used to isolate active regions to prevent photons from passing from one to another and amplified spontaneous emission. Results were presented for arrays which reach a maximum cw output power of 7 W perfacet and 50 W (200 microsecond(s) , 50 Hz) quasi-sw output, with lasing wavelength 806 - 810 nm.

In this paper, we report on the design, growth and fabrication of 980 nm strained InGaAs quantum well lasers employing novel material system of Al-free active region and AlGaAs cladding layers. The use of AlGaAs cladding instead of InGaP provides potential advantages in laser structure design, improvement of surface morphology and laser performance. We demonstrate an optimized broad-waveguide structure for obtaining high power 980 nm quantum well lasers with low vertical beam divergence. The laser structure was grown by low-pressure metalorganic chemical vapor deposition, which exhibit a high internal quantum efficiency of approximately 90% and a low internal loss of 1.5 - 2.5 cm^-1. The broad-area and ridge-waveguide laser devices are both fabricated. For 100 micrometers wide stripe lasers with cavity length of 800 micrometers , a low threshold current of 170 mA, a high slope efficiency of 1.0 W/A and high output power of more than 3.5 W are achieved. The temperature dependences of the threshold current and the emitting spectra demonstrate a very high characteristic temperature coefficient (T₀) of 200 - 250 K and a wavelength shift coefficient of 0.34 nm/ degree(s)C. For 4 micrometers - width ridge waveguide structure laser devices, a maximum output power of 340 mW with COD-free thermal roll-over characteristics is obtained.

A Q-CW laser diode drive based on microcontroller and sensor technology, using a power MOS FET as current amplifier is presented. It gives a exposition of hardware and software design according to special requirements of LD and custom of using instrument.

In order to enhance the conversion efficiency and output power of semiconductor lasers, extend its lifetime, the contact resistance has to be reduced. This paper introduces the recent results obtained about the semiconductor laser Ohmic contact experimental study. In our work, AuZn film was evaporated on to the P side of the laser epitaxial wafer, and AuGeNi on to N side. By choosing the optimum alloying temperature of 400 degree(s)C, we obtained the lowest contact resistance. After this process, AR and HR films were sputtered on to the two facets of the laser cavity. Finally, the following results were obtained for the laser performance: central wavelength (lambda) ₀ equals 808 nm, threshold current density J_th equals 300 - 470 A/cm², CW output power P equals 3W, resistance R equals 0.06 (Omega) (for a laser stripe of 150 micrometers , cavity length of 1 mm).

980 nm GaInAs/GaAs/GaInP separate-confinement heterostructure single quantum well lasers are fabricated by LP-MOCVD. The lasers exhibit threshold current density of 170 A/cm², output light power 2W in continuous wave, slope efficiencies of 0.91 W/A without mirror coating. The characteristic temperature T₀ is 330 degree(s)K.

It was observed that a twin-lobe like farfield appeared more obviously with larger stripe width of BA LD, also with increasing injected current, due to much more complicated lateral modes. As a consequence, a single-lobed farfield output of 2.0 W has been realized with BA InGaAsP/GaAs SCH SQW lasers (stripe width 150 um).

In this work, we report Al-free InGaAsP/GaAs separate confinement heterostructure single quantum well structures for lasers emitting at 808 nm are grown by enhanced liquid phase epitaxy. The highest continuous wave output power is 4 W for lasers with coated facts. The differential efficiency is 1.32 W/A. The record characteristic T₀ of the laser is estimated to be about 218 K between 10 degree(s)C and 40 degree(s)C from the temperature dependence of the threshold current density J_th.

In this paper, theoretical calculation results of dynamically thermal properties of high-power InGaAsP/InP stripe-geometry laser diode has been given based on the 2D thermal conduction model by means of finite difference. In this calculation, except for active layer heating due to nonradiative recombination and partial reabsorption of radiation, the radiative transfer of the spontaneous radiation through the wide-gap passive layers, the Joule heating is taken into account. At the same time, active region heat source is simplified as line heat source. Through the temperature profiles acquired by changing construction parameters and supplied power, we can see that temperature profiles have a certain relation with the construction parameters and supplied power. At last, the thermal resistance achieved by theory calculation compares with the laser diode thermal resistance achieved by measuring, the proportion of the crystal, the heat sink and the shell's thermal resistance is obtained. The calculation shows that a diamond film sandwiched between the crystal and the heat sink can improve the diode's thermal properties obviously.

A detailed operating characteristics of InGaAsP/GaAs separate confinement heterostructure single-quantum-well wide-stripe lasers emitting at 808 nm grown by liquid phase epitaxy is reported. The temperature dependences of the lasing wavelength (lambda) , the threshold current density J_th and differential quantum efficiency (eta) _d are studied. The effects of the cavity length L on the threshold current density J_th and the differential quantum efficiency (eta) _d are studied. The threshold current density J_th increases with increasing temperature T. But the increase of J_th with temperature T is slightly deviated from the exponential dependence. The data fitting of J_th with between 10 degree(s)C and 40 degree(s)C demonstrates a record characteristic temperature T₀ of 218 K, indicating a minor influence of temperature on J_th.

We have designed and fabricated the visible vertical-cavity surface-emitting lasers (VCSEL's) by using metalorganic vapor phase epitaxy. We use the 8(lambda) optical cavities with 3 quantum wells in AlGaInP/AlGaAs red VCSEL's to reduce the drift leakage current and enhance the model gain of AlGaInP active region. The structure has a p-type stack with 36 DBR pairs on the top and an n-type with 55-1/2 pairs on the bottom. Using micro-area reflectance spectrum, we try to get a better concordance between the center wavelength of DBR and the emitting wavelength of the active region. We used a component graded layer of 0.05(lambda) thick (x equals 0.5 approximately 0.9) at the p-type DBR AlGaAs/AlAs interface to reduce the resistance of p-type DBR. We use selective oxidation to define the current injection path. Because the oxidation rate of a thick layer is faster than a thinner one, we grown a thick AlAs layer close to the active region. In this way, we got a smaller active region for efficient confinement of injected carriers (the aperture area is 3 X 3 micrometers ) to reduce the threshold and, at the same time, a bigger conductive area in the DBR layers to reduce the resistance. WE employ Zn doping on the p-side of the junction to improve hole injection and control the Zn dopant diffusion to get proper p-i-n junction. At room temperature, pulse operation of the laser has been achieved with the low threshold current of 0.8 mA; the wavelength is about 670 nm.

Single mode 650 nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition was reported in this paper. Selected buried rigewaveguide were applied for single mode operation especially for DVD use. The operating temperature over 90 degree at CW output power 5 mW was achieved.

Based on the cavity quantum electrodynamics, the controllable enhancement of spontaneous emission in perpendicular direction by single quantum well embedded in a planar micro-cavity has been studied. The spontaneous emission spectra are obtained for different mirror reflectivity and cavity length when the carrier density is fixed. The results show that the spontaneous emission intensity can be enhanced by increasing the mirror reflectivity when radiation wavelength is about two times of the cavity length. The spectra can be changed by the micro- cavity structure and the quantum well parameters.

The behaviors of lateral propagating modes in the aperture and the oxidized regions are investigated numerically for selectively oxidized vertical-cavity surface-emitting lasers (VCSELs). The results show that the lateral propagating modes in the oxidized region are greatly affected by the oxide layer due to its low index, the modes are divergence for the VCSELs with sufficient thick double oxide layers. So the coupling between the modes in the aperture and oxidized regions is very weak, and we can expect that the lateral spontaneous emission is greatly affected in this case. Ignoring the contribution of the lateral spontaneous emission, we calculate spontaneous emission factor by counting the total number of the guided modes in selectively oxidized VCSELs with double oxide layers. The results agree very well with the reported measurements and are inversely proportional to the lateral index step.

We report our study on the optical properties and the disk mode pattern of InGaP microdisks. The semiconductor InGaP microdisks with radius of about 5 micrometers emitting at wavelength of 0.65 micrometers were fabricated on liquid phase epitaxial grown InGaP/AlGaAs/GaAs wafer on the substrate of (100)GaAs. The optical properties of InGaP microdisks were studied by photoluminescence, pump-probe femtosecond- transient reflectivity measurements. The strong enhancement of the PL intensity in the microdisks respect to that of the same un-patterned epitaxial wafer is obtained. In addition, the inhibition effect of the microdisks on the ultrafast decay of optical excited carriers is observed by the transient measurement. The fluorescence image of the InGaP microdisk is analyzed by a CCD fluorescence microscope system. Under the green light excitation, a bright red ring of fluorescence near the edge of microdisk is observed. The typical fluorescence intensity profiles as a function of radius in different microdisks are plotted out. As a result, the images reveal the optical disk mode pattern in our InGaP microdisks dominated by Whispering-Gallery modes and mixture with other modes.

Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 angstroms/50 angstroms GaN/Al_xGa_1-xN (x approximately 0.07) and 45 angstroms/45 angstroms In_xGa_1-xN/GaN (x approximately 0.15) multiple quantum well structures. Microdisks, approximately 9 micrometers in diameter and regularly spaced every 50 micrometers , were formed by ion beam etch process. Individual disk was pumped from 10 K to 300 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical properties of these microdisks have been studied by picosecond time-resolved photoluminescence (PL) spectroscopy. From cw PL emission spectra, optical modes corresponding to (1) the radial mode type with a spacing of 49 - 51 meV (both TE and TM) and (2) the Whispering gallery mode with a spacing of 15 - 16 meV were observed in the GaN-based microdisk cavities. The spacings of these modes are consistent with theoretical calculation. The implications of our results to III-Nitride microdisk lasers are discussed.

The advance of nanofabrication techniques allow us to realize microcavity lasers with an optical wavelength-size in one or three dimensions. In this work, the effect of microcavity to the optical pumping threshold is studied by using a simple two-level model. It is concluded that there are two factors that decrease the threshold of lasers, one is the transparency pump rate and the other is the additional pump rate while the latter is proportional to the reverse of (beta) , the spontaneous emission-coupling factor. InGaAs/InGaAsP/InP MQW microdisk lasers are fabricated by using nanofabrication techniques. The threshold pump power are 15 (mu) W and 170 (mu) W for disks with the diameter of 5 micrometers and 10 micrometers , respectively.

We research the probability of integrating a phase-only diffractive optical element (PDOE) with Vertical-Cavity Surface-Emitting laser. The slight variation of three parameters, i.e., beam waist width, wavelength and input Gaussian distribution are taken into consideration when we design the PDOE. Basing on the projected-onto-constraint- sets algorithm, a PDOE, which splits the image Gaussian beam into two equal intensity spots with the interval 30 micrometers between them at a certain plane, is designed. The simulation results show that the positions of two peaks keep stable and the width of them shifts slightly when the form of the incident wave shifts. The intensity distribution of wave field at the output plane can keep stable when the incident wavelength shifts between 0.66 micrometers and 0.68 micrometers , too. In addition, the corresponding results after the phase of PDOE being quantumlized is also shown.

The rare-earth Tb complex planar organic microcavity is successfully fabricated. It has a simple configuration which consists of Tb rare-earth complex [PMHP]₃Tb active thin film sandwiched by silver metal mirrors on a carefully polished quartz substrate. The thin film of Tb complex is prepared by Langmuir-Blodgett technique. By changing the monolayer number of L-B film, planar microcavities with different thickness of emitting medium are obtained. The modification of the spontaneous emission in this rare-earth Tb organic planar microcavity is demonstrated.

Among the attractive features of microcavity lasers for practical applications are the potential for reduced thresholds and the ability to design a mode structure with nearly ideal single mode operation. One of the most important parameters for semiconductor lasers is the linewidth. Generally the linewidth in semiconductor lasers is proportional to the inverse of the output power. In this work, we examine the lasing behavior of microdisk lasers, consisting of InGaP/InGaAsP/InP MQW structure, optically pumped at liquid nitrogen temperature by Ar ion laser. A decrease of threshold of the microdisk laser is observed. The linewidth of the lasing spectrum is measured at various pumping level. It turns out that the measured linewidth is broad and in the range of nanometer. The linewidth does not display the usual inverse power dependence, i.e., Schalow- Townes linewidth narrowing.

In this paper, a preliminary result for an iodine frequency stabilized tunable diode lasers at 633 nm is reported. The frequency stability of the diode laser was 2 X 10^-11, the tune ability was 10 nm and the line-width was 100 kHz. In addition, five groups of stronger hyperfine transitions of iodine molecule, which are available to be reference lines for diode laser frequency standard, beside the well-known transition R(127)11-5 at 633 nm region were observed by means of saturated absorption in the configuration of external iodine cell and their absolute frequencies were measured by a spectrum analyzer and a scanning Fabry-Perot cavity. The program for calculating the hyperfine structures and strength of transitions for rotational vibrational bands of iodine molecule was developed and the predictions for possible transitions around 633 nm including the transition strength are given.

We demonstrate 8 X 2.5 Gb/s OTDM data demultiplexing using a semiconductor laser amplifier in a loop mirror (SLALOM). The switching window of the SLALOM was set to 30 ps. Both all `1' and 2⁷ -1 pseudorandom codes were used for comparison. By an average control power of 1.6 mW the output signal extinction ratio was estimated to be 8 dB.

In this paper, a 2.2% doped Cr:LiSAF crystal with 1 mm in thickness is pumped by a 679 nm laser diode, and intracavity-doubled with NCPM KN crystal. Maximal output of TEMoo 3.15 mW of blue laser at 431.7 nm is obtained with the absorption power of 256 mW. The laser scheme shows a threshold of 96 mW and slope efficiency of 1.97%. Continuous-wave tunable output is demonstrated in the blue region of 423.4 - 445.5 nm through only changing temperature of KN crystal.

A new method of using a weak-feedback grating external cavity to improve the output characteristics of visible light semiconductor laser was studied and proved to be practical. The experiment has been conducted to apply this method on 650 nm semiconductor laser. A blazed grating is used as the external cavity mirror to narrow the linewidth and select frequency. Through turning the grating, we obtained laser output with single longitudinal mode and linewidth as narrow as 0.1 pm, of which the linewidth reduction rate is 9800. The tuning range of wavelength is about 5 nm out of 20 nm fluorescent spectrum, and the side mode suppression ratio is ideal. Confocal Fabry-Perot interferometer and spectroscopy were used to measure the linewidth and frequencies. Proposals to improve the experimental results are raised.

Liquid carbon tetrachloride (CCl₄) was used as dopants for the growth of p-type GaAs and AlGaAs materials by low pressure metalorganic chemical vapor phase deposition. Heavily carbon doped (1.9 X 10²⁰ cm^-3) GaAs and high quality p-type Al_0.3Ga_0.7As materials were obtained. Several key growth parameters, such as growth temperature (560 degree(s)C - 725 degree(s)C), V/III ration (20 - 150) and CCl₄ molecular flow (10^-7 mol/min- 10^-5 mol/min), were changed to investigate their influence on doping efficiency, growth rate and material properties. Electrochemistry capacity-voltage, Hall effect and photoluminescence methods were adopted to measure the electrical and optical properties. X ray double crystal diffraction method was used to study the relationships of carbon doping level and crystal lattice constant of epitaxial layers. On the basis of these research, carbon doped GaAs tunnel diode and high power GaAs/AlGaAs/InGaAs strain quantum well semiconductor laser structures were grown to qualify the carbon doped GaAs/AlGaAs materials comprehensively.

The operation principle of laser rotary encoders is expounded and the optical quadruple frequency technology used in laser rotary encoders is explained, and the design idea of optical system in (phi) 66 mm laser rotary encoder is mainly introduced, as well as the choice of principal devices.

The image from LD recording system with stripes is a very common phenomenon. The defects made the images blur and inseparable the gray scales. The article gives the principle and lots of actors generating stripes. Through careful analyses and discussion, the main cause of stripes is the optical system. Especially, the LD laser beam's uniformity that is inner the light aperture and the position of the light aperture's real image exerted a tremendous influence on stripes. Then, the article gives lots of methods to solve the problem. From mechanical structure to optical system, we discuss the components thoroughly. The uniform laser beam passes through the light aperture and fills it completely. The theoretical formula gives out the position change of the light aperture's real image. When we put these methods into action, the stripes almost disappear. In objective reality, the images meet the use.

The noise compensation method of APD photoelectronic sensor C30950E is studied in this paper. The noise theory and the compensation method of the constant false alarm rate are introduced, an APD noise compensation method controlled by a single chip microprocessor AT89C2051 is given.

Polarization independent semiconductor optical amplifiers are highly desirable for optical communication. In this paper, the influence of graded index waveguides on the gain difference between TE₀ and TM₀ modes of semiconductor optical amplifiers is studied in detail. A new numerical procedure called complex shooting method was proposed at first to solve the eigenvalues of waveguides with graded complex refractive index. The results show that a graded index waveguide will increase the polarization sensitivity of the modal gain while an unplanar waveguide can decrease it. A polarization independent semiconductor optical amplifier can be obtained by adopting an unplanar waveguide.

In terms of the parameter interpolation principle, calculations are performed for bandgaps and band offsets in strain-compensated In_zGa_1-zAs/In_xGa_1-xAs_yP_1-y multiple quantum well structures on InP. Relations between strains and material compositions in In_zGa_1-zAs wells and In_xGa_1-xAs_yP_1-y barriers are analyzed, and relative ranges of strains are evaluated. Bandgaps of In_zGa_1-zAs wells and In_xGa_1-xAs_yP_1-y barriers for heavy- and light-holes are studied, and relative ranges of bandgaps are estimated. Dependence of band offsets of conduction band and valence band for heavy- and light-holes on strain compensation between In_zGa_1-zAs wells and In_xGa_1-xAs_yP_1-y barriers is investigated, and variation of band offsets versus strain compensation is discussed. The computed results show that strains, bandgaps and band offsets are functions of material compositions, strain compensation changes the band offsets, and hence modifies the band structures and improves the features of strain- compensated multiple quantum well optoelectronic devices.

The paper reports a method of depositing SiO₂, SiN_x, a:Si, Si₃N₄ and SiO_xN_y dielectric thin films by electron cyclotron resonance plasma chemical vapor deposition (ECR CVD) on InP, InGaAs and other compound semiconductor optoelectronic devices, and give a technology of depositing dielectric thin films and optical coatings by ECR CVD on Laser's Bars. The experiment results show the dielectric thin films and optical coatings are stable at thermomechanical property, optical properties and the other properties. In addition, the dielectric thin film deposition that there is low leakage current is reported for using as diffusion and ion implantation masks in the paper. In the finally, the dielectric film refractive index can be accurately controlled by the N₂/O₂/Ar gas flow rate.

In this paper, the stability of strained MQWs in laser structure is discussed. The excess stress is the driving force of misfit dislocation multiplication and is a very important factor of strained MQWs stability. So we calculate the excess stress using the single-kink model. Our results show that the maximum position of excess stress is related to the barrier and well thicknesses and mismatches in the well(s). The lattice-matched barriers can dilute the excess stress. The capping layer can also dilute the excess stress in a certain degree. We then calculate the strain relaxation using the dynamic model of dislocations. In this model, the strain relaxation is driven by the excess strains. In this paper, the criteria of the stability of MQWs in laser structure is that the density of dislocations (or the strain relaxation) is less than a certain value. In this way, the barriers and capping layer are both important factors of MQWs stability. The method can be used to better the MQWs in laser structure.

Experimental results of disordering GaAlAs/GaAs MQW under different rapid thermal annealing (RTA) conditions are presented and discussed. Two kinds of novel device structures based on such technique are then proposed and fabricated. First, a laser diode with window regions for high power operation is designed and fabricated. The maximum output power of such a device shows an increase by 18% over laser diodes without window regions. Then a transverse mode controlled laser structure realized using RTA technique. A stable single transverse mode operation is obtained up to 4 times the threshold current.

Three-section semiconductor lasers are studied based on the ray method. An analytic expression of output power for the three-section semiconductor laser is derived. From this expression, threshold condition is also obtained. The relation between three-electrode semiconductor lasers and two-electrode semiconductor lasers is discussed.

A method of controlling chaos of a laser diode with all external optical feedback was proposed according to the principle of Pyragas method. Firstly, we added a team of optical feedback into the equations of laser diode with external optical delay-time feedback and analyzed the conditions in which the method can be used were given from theoretical analysis based on the coherence theory. Secondly, the maximum Lyapunov exponent (MLE) of the controlled system was computed and the ranges in which MLE was smaller than zero and the chaos was controlled were found. Finally, the attractor and the power spectra of the system were given. The efficiency of the method was proved by the computer simulation.

This paper clarifies superior external optical feedback resistant characteristics in partially-corrugated-waveguide laser diodes (PC-LDs), compared to conventional distributed feedback laser diodes (DFB-LDs). Based on a novel large single dynamic analysis by using the van der Pol equations in single-mode laser diodes (LDs), it is found that the external optical feedback resistance in single-mode LDs is dominated by the transient fluctuation of mirror loss (total net threshold gain), and depends on the grating phases at the cleaved facets. Theoretical results predict that in the PC-LDs, mirror loss is insensitive to the grating facet phases due to a unique waveguide, which consists of a corrugated waveguide near the antireflection-coated front facet and an uncorrugated waveguide near the high- reflection-coated rear facet. Therefore the variation of phase conditions for oscillation caused by the external optical feedback gives rise to a relative low transient fluctuation of the mirror loss that suppresses the positive feedback effect of mirror loss, as well as the optical output fluctuations. Furthermore, optimum-grating length, i.e. 150 micrometers for 250 micrometers cavity length, was derived by the calculations. The relative intensity noise (RIN) caused by external optical feedback was measured for PC-LDs with different grating length over a wide feedback level range from -40 dB to -20 dB. Experimental results show that, for the cavity length of 250 micrometers , the PC-LDs with a grating length of 150 micrometers have the most excellent external optical feedback resistant characteristics. The increase of RIN was suppressed to as low as -126 dB/Hz with the external optical feedback of -20 dB. These results agreed well with the theoretical analysis.

High power DFB laser emitting at 1550 nm wavelength is one of the key components for broadband supertrunk transmission systems. A CW optical power of 108 mW coupled into a polarization maintaining fiber was demonstrated from a high power InGaAsP/InP multi-quantum well DFB laser at 1550 nm wavelength. The laser also displays excellent high temperature performance, low noise, and narrow linewidth.

Analog fiber optic links can be used to transmit microwave and millimeter wave signals in applications such as cable TV, antenna remoting and active phased array. In this paper, we examine various issues pertaining to an integrated laser- modulator transmitter module for analog fiber optic links: (1) the performance requirements of the lasers, (2) the performance requirements of the electroabsorption modulator, (3) the bias control of the electroabsorption modulator.

The microwave optoelectronic oscillator (OEO) has been demonstrated on a breadboard. The future trend is to integrate the whole OEO on a chip, which requires the development of high power and high efficiency integrated photonic components. In this paper, we will present the design and fabrication of an integrated semiconductor laser/modulator using the identical active layer approach on InGaAsP/InP material. The best devices have threshold currents of 50-mA at room temperature for CW operation. The device length is approximately 3-mm, resulting in a mode spacing of 14 GHz. For only 5-dBm microwave power applied to the modulator section, modulation response with 30 dB resonate enhancement has been observed. This work shows the promise for an on-chip integrated OEO.

Aluminum-free laser diodes are InGaAsP/GaAs devices whose epitaxial layers do not contain aluminum. Studies comparing the GaAslAs/GaAs and InGaAsP/GaAs high power laser diodes allegedly indicate that aluminum-free lasers are more reliable due to a reduction of dark-line defects, sudden failures, and gradual degradation. The improved reliability of aluminum-free lasers is presumed to result from the elimination of oxidation of the aluminum-containing epitaxial layers of the laser facets. In this presentation, the performance and reliability of GaAlAs/GaAs and InGaAsP/GaAs high power laser diodes will be reviewed and compared. The present data shows that high reliable GaAlAs/GaAs lasers can be produced with good manufacturing practices.

High power semiconductor laser diodes have found their place in a wide variety of markets such as printing, pumping of solid state lasers, illumination, medical diagnosis, surgery, spectroscopy and material processing. In the past two years, the performance of the commercial available multi-mode semiconductor laser diodes has been elevated to a ultra high power level (continuous wave (CW) power density higher than 15 mW/micrometers -aperture for single emitter devices and 10 mW/micrometers -aperture per cm wide bar for monolithic arrays) as the result of breakthrough in device design, processing and packaging. We present in this paper record setting performance of these ultra high power devices in terms of CW power (> 10.6 W from 100 micrometers aperture, > 180 W from 1 cm wide array) and efficiency (wall plug-in efficiency 59%, differential quantum efficiency 87%). Reliability tests of these ultra high power devices indicates that these devices have equivalent to or better reliability than conventional lower power commercial devices. We will discuss the significance of these devices in enabling new applications and empowering current applications.

A novel near-infrared diode laser having sensitivity to change of absorption and refractive index at its surface- sensitive region is presented. This semiconductor laser utilizes an AlGaAs single quantum well structure emitting at a wavelength of 950 nm, and its dimensions are 1 mm X 0.5 mm X 0.2 mm. One of the cladding layers is thinned such that the evanescent wave in the quantum well interacts with a surface-sensitive region on the laser. A theoretical model of laser sensitivity toward changes in absorption of a dye- doped polymer coating is formulated. Experimental data using the surface-sensitive diode laser for sensing ammonia and adsorbed monolayers of molecular films are presented. The output power, threshold current and wavelength are shown to be affected by the changes in the adsorbed coating.

This paper presents a numerical design study of monolithically integrated microcavity detecting and emitting devices for applications in optical memory and interconnect systems. Combinations of 650 nm AlGaInP/AlGaAs resonant cavity light-emitting diodes and vertical cavity surface emitting lasers are examined. The device structures include resonant cavity p-i-n photodetectors embedded within distributed Bragg reflector mirrors. The photodetectors consist of an undoped quantum well absorbing layer positioned at an antinode of the resonant standing wave. Classical spontaneous and stimulated emission intracavity absorption models are developed to estimate the embedded photodetector spectral responsivity. This embedded photodetector configuration provides an effective means for studying the spontaneous and stimulated emission components of microcavity light emitting devices.

The coupled equations for describing nearly degenerate four- wave mixing in laser diodes subject to strong probe injection power are derived, taking into account the influence of pump depletion and carrier diffusion. The model can also be used to investigate the dependence of reflectivity efficiencies and bandwidth on the different parameters of the lasers and different signal injection powers in multisection laser diodes. The analysis will give opportunities for optimizing the parameters of mixing processes, cavity structure and input signal power.

Nearly degenerate four-wave mixing in Fabry-Perot laser diodes subject to strong probe injection power is investigated theoretically and experimentally. The measured reflectivity efficiencies of signal and conjugate waves demonstrate significantly different behaviors for strong signal injection power, compared to small probe injection power. Nearly uniform conversion efficiency of order 20 - 30 dB for frequency detuning up to 3 GHz is obtained at about 0.8 (mu) W launched probe power. These experimental measurements show good agreement with numerical simulations based on an advanced model taking into account the effects of pump depletion, carrier diffusion, gain saturation as well as gain compression.

A hybrid mode-locked semiconductor laser was demonstrated as a multi-wavelength light source for WDM networks. The laser simultaneously provides over 50 WDM channels spaced at 21.8 GHz (0.17 nm). Channel spacing is temperature independent and is determined by the modulating frequency applied to the absorber section of the laser, thus is very stable. The wavelength of the channels can be slightly tuned by injection current and/or temperature. We demonstrate dropping a WDM channel at a network node by using a Fiber Bragg Grating combined with a fiber coupler.

The continued need for increased bandwidth is driving the pursuit of both increased speed in TDM and more channels in WDM for fiber optic communication systems. Multiwavelength arrays of monolithic mode-locked DBR lasers are an attractive source for future high bit rate (100 - 800 Gb/s) optical communication systems. Monolithic mode-locked lasers in the colliding-pulse mode-locked configuration have been fabricated, with DBR end mirrors for wavelength selection. A continuous gain region has been employed for ease of fabrication and the elimination of multiple reflections within the cavity. Arrays containing up to 9 wavelengths have been fabricated, with all the wavelengths within the erbium-doped fiber amplifier gain bandwidth. An RF signal is applied to the saturable absorber for synchronization to an external clock and reduction of the phase noise. For a 4.6 mm cavity, short (< 10 ps) optical pulses at high (approximately 18 GHz) repetition rates have been achieved. Low single side-band phase noise values (-107 dBc/Hz 100 kHz offset) have been demonstrated, nearly equal to that of the RF source.

We have designed and fabricated the first multi-mode wavelength division multiplexer and demultiplexer (WDDM) based on axial graded index (AGRIN) lenses in conjunction with a volume holographic grating. The demonstration is made using a multi-mode fiber with a 50 micrometers core size. The diffraction-limited AGRIN lenses employed significantly increase the output coupling efficiency and reduce crosstalk when compared with the best homogeneous lens solutions previously reported. The volume holographic grating has a maximum diffraction efficiency of 92% at the center wavelength of 780 nm. An eight-channel WDDM device with a center wavelength of 780 nm and a channel separation of 4 nm is designed and demonstrated. The end-to-end insertion loss for each channel is between 2.8 and 3.8 dB. The maximum channel-to-channel crosstalk is -25 dB.

Optical CDMA is a complementary multiple access technology to WDMA. Optical CDMA potentially provides a large number of virtual optical channels for IXC, LEC and CLEC or supports a large number of high-speed users in LAN. In a network, it provides asynchronous, multi-rate, multi-user communication with network scalability, re-configurability (bandwidth on demand), and network security (provided by inherent CDMA coding). However, optical CDMA technology is less mature in comparison to WDMA. The components requirements are also different from WDMA. We have demonstrated a video transport/switching system over a distance of 40 Km using discrete optical components in our laboratory. We are currently pursuing PIC implementation. In this paper, we will describe the optical CDMA concept/features, the demonstration system, and the requirements of some critical optical components such as broadband optical source, broadband optical amplifier, spectral spreading/de- spreading, and fixed/programmable mask.

We demonstrate the realization of coupled opto-electronic oscillators (COEO) with different semiconductor lasers, including a ring laser, a Fabry-Perot laser, and a colliding pulse mode-locked laser. Each COEO can simultaneously generate short optical pulses and spectrally pure RF signals. With these devices, we obtained optical pulses as short as 6 picoseconds and RF signals as high in frequency as 18 GHz with a spectral purity comparable with a HP8561B synthesizer. These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.

Intermixing of quantum confined heterostructures, or quantum well intermixing (QWI), is an attractive alternative to regrowth and overgrowth techniques for realizing photonic and optoelectronic integrated circuits. Impurity free vacancy diffusion using SiO₂ dielectric cap is one of the promising QWI techniques. Silicon dioxide is known to induce outdiffusion of Ga and generate vacancies in GaAs- AlGaAs material during annealing. These vacancies, generated on the group-III sublattice, can be used to promote the diffusion of Al into a buried quantum well (QW) and the diffusion of Ga into the barriers and hence shift the QW band gap to higher energy by partially intermixed the quantum well.

We proposed and demonstrated a new type of quantum cascade laser based on interband transitions in InAs/GaInSb/AlSb type-II quantum wells. Contrary to the conventional heterostructure or quantum well lasers, this device takes advantage of recycling carriers from valence band back to conduction band for sequential photon emissions to achieve high quantum efficiency. So far, an external differential quantum efficiency exceeding 200% has been observed from 4- micrometers lasers under 1 microsecond(s) pulses and 0.1% duty cycle at 80 K. Under 5 - 10 microsecond(s) pulse lengths and 10% duty cycle, peak powers > 160 mW have been obtained, the corresponding internal quantum efficiency was deduced to be 220%.

A novel intersubband laser based on the inverted-effective- mass feature of valence light-hole subband is investigated. Such inversion is a result of the interactions between subbands, which is much stronger in valence band of most diamond and zinc-blend semiconductors. Unlike the conventional conduction-band intersubband lasers, the proposed laser does not require elaborate and delicate engineering of quantum wells (QWs). We consider GaAs/AlGaAs QW structures which give rise to several confined subbands including ground state heavy-hole subband (HH1) and light- hole subband (LH1). The inverted-effective-mass feature in subband LH1 emerges only in wide QW structures which produce closely spaced subbands in energy that are strongly coupled. The energy separation between subbands LH1 and HH1 is typically below the optical phonon energy in the THz range. Laser wavelength determined by this energy separation is 62 microns for a well width of 7 nm. The laser structure is designed to facilitate electrical pumping with a quantum cascade scheme consisting of multiple GaAs QWs isolated by AlGaAs barriers. Our calculation shows that with only a small fraction of the carrier population in the upper subband (LH1), it is still possible to achieve population inversion between the two subbands locally in k-space where the light-hole effective mass is inverted. Our result indicates that optical gain in excess of 150/cm can be achieved with a relatively small pumping current density on the order of 100A/cm².

Self-assembly effects in strained epitaxy have made it possible to grow high quality semiconductor dot structures. Recently several groups have shown good performance in quantum dot lasers. In particular for the In_0.4Ga_0.6As/GaAs quantum dot lasers differential gain of approximately 10^-14 cm² and modulation bandwidths of 7 - 8 GHz have been demonstrated. In this paper, we examine the electronic, optical and dynamic properties of self-assembled lasers. The formalism is based on an eight-band k.p model and a modified rate equations for quantum dots. A Monte-Carlo simulation is also done to compare with the rate equation results. Our results will focus on the following issues: (1) the role of cavity loss and quantum dot density in determining the position of the lasing peaks (i.e. whether ground state or excited state lasing with occur); (2) the dynamic response of quantum dot lasers and the gain compression factor due to Pauli exclusion principle.

The characteristics of high-speed quantum well and quantum dot lasers are described. It is seen that substantial improvements in small-signal modulation bandwidth are obtained in both 1 micrometers (48 GHz) and 1.55 micrometers (26 GHz) by tunneling electrons directly into the lasing subband. In quantum dots the small-signal modulation bandwidth is limited by electron-hole scattering to approximately 7 GHz at room temperature and 23 GHz at 80 K.

A high-yield and high-performance single longitudinal mode laser diode (LD) is essential for implementing a low-cost optical module for high capacity access networks. We have realized novel partially corrugated waveguide (PC) LDs and shown that they are cost-effective. Because of a unique resonance feature in a mirror loss profile, the PC-LD has higher yield in single longitudinal mode operation than that of a conventional distributed feedback (DFB) LD. The yield of the PC-LD with single-mode stability ((Delta) (alpha) L > 0.3) was theoretically predicted to be as high as > 65%, which is 1.5 to 2 times higher than that of a conventional DFB-LD. Side-mode suppression ratio was experimentally as high as 40 to 50 dB. Uncooled high-efficiency characteristics have been realized for a cavity with asymmetrical reflectivity facets. The threshold current and slope efficiency were 16 mA and 0.26 W/A at 85 degree(s)C. By introducing a spot-size converted waveguide with chirped corrugation, butt-coupling efficiency was improved by 3 dB higher than that of the conventional straight waveguide. Furthermore, excellent optical feedback resistant 622 Mb/s operation has been demonstrated over a wide temperature range of -40 to 85 degree(s)C. The power penalty was as low as 1 dB under the optical feedback level of -8.5 dB. Isolator-free 2.5 Gb/s-70 km transmission was also demonstrated. The PC-LDs with this performance are very promising for realizing cost-effective optical modules for use in high capacity optical access networks.