High-power, high-duty cycle and continuous wave operation of large-area monolithic 2D surface-emitting GaAlAs laser diode arrays mounted junction-down on microchannel heat exchangers have been demonstrated. Devices mounted don 2-mm-thick Cu heat spreaders were operated to peak output power densities of > 100 W/cm² at 35% duty cycles,a nd exhibited high power conversion efficiencies, and full width emission spectra of < 4nm. Arrays mounted on 1-mm-thick heat spreaders were operated under continuous wave operating condition to approximately equals 50 W/cm² power density levels. Silicon microchannel heat exchangers with a measured thermal resistance per unit are of 0.0324 degree(s)C cm²/W were used to removed up to 550 W/cm² of excess heat generated by the arrays.

The average power performance capability of semiconductor diode laser arrays has improved dramatically over the past several years. These performance improvements, combined with cost reductions pursued by LLNL and others in the fabrication and packaging of diode lasers, have continued to reduce the price per average watt of laser diode radiation. A low cost technique developed and demonstrated at LLNL for optically conditioning the output radiation of diode laser arrays has enabled a new and scalable average power diode-end-pumping architecture that can be simply implemented in diode pumped solid state laser systems (DPSSLs). This development allows the high average power DPSSL designer to look beyond the Nd ion for the first time. Along with high average power DPSSLs which are appropriate for material processing applications, low and intermediate average power DPSSLs are now realizable at low enough costs to be attractive for use in many medical, electronic, and lithographic applications.

Methods of reformatting the output of laser diodes and maintaining much of their intrinsic brightness are discussed. A commercial, fiber-coupled package is shown with a symmetric etendue and a brightness of 15 kW/(cm² sr). A symmeterized beam with a brightness of 200 kW/(cm² sr) is demonstrated by using a combination of a micro-lensed diode array and a lens array.

Reliable high-power GaInP/AlGaInP laser diodes with a maximum continuous wave (cw) output power of 2.1 W in the 690 nm band have been realized. The laser has a 100 micrometers - wide single stripe and an optimized separate-confinement heterostructure with a compressively strained multiple quantum well active region. The laser operated at a cw output power of 500 mW for 350 h at 20 degree(s)C with only a few percent increase in operating current.

We have investigated, via the beam propagation method, waveguide designs for wide window single-mode single-stripe lasers. The expanded window allows for higher power operation of the laser diode owing to the lower power density at the facets. Higher-order transverse mode suppression is achieved by incorporating a spatial filter in the waveguide that preferentially allows propagation of the fundamental mode. These devices can be fabricated using existing laser diode fabrication technologies such as reactive-ion-etching, native oxidation, or impurity- induced-disordering, and buried heterostructure processes. In our design and analysis of these devices we compare several expanding waveguides to determine the effects on mode selection. Additionally, the catastrophic optical damage power limit for these devices is expected to be significantly greater than for simple fundamental-mode single-stripe lasers.

The design of ridge waveguide semiconductor pump lasers poses particular simulation problems, since an accurate modeling of the electric and thermal effects and of the optical guiding capabilities is needed. We developed a model whose self-consistent application allows the evaluation of, among others, the threshold current of the lasing mode and the gain margin of the higher order modes, the P-I characteristic, the power coupled in the fiber, and the far field pattern. Particular attention is paid to the experimental verification of the transverse single mode operation region, and its evolution at high injection levels. The appropriate conditions for operation in the 150 - 200 mW single mode output power range have been found.

We investigate high-power InGaAsP/GaAs (0.77 - 0.83 micrometers ) buried heterostructure lasers grown by LPE technique. A redistribution of the output power in the far field pattern from higher-order modes into the fundamental mode was observed with a temperature increase in the range of 10 degree(s) - 70 degree(s)C. A theoretical model taking into account the affect of boundary recombination velocity on the mesa walls on the carrier concentration profile in the active region is proposed. Significant rise of the boundary recombination velocity with temperature was confirmed experimentally by comparing the temperature dependences of quantum efficiency in buried and stripe-contact (without mesa walls) lasers fabricated from the same wafers. As a result of these investigations, we propose a new laser design in which the carrier concentration profile is similar to that in a heated device. A narrow contact mesa stripe laser permits us to concentrate most of the pumping current in the middle of active region and, hence, to increase the overlap of the carrier concentration profile with the fundamental mode intensity. The optimal dimensions for single-mode laser were calculated.

We demonstrate the phase locking of a 12 X 12 two-dimensional surface emitting laser array to generate 1.4 W of output power in diffraction limited far-field. A phase contrast imaging system is used to measure array element phases and apply corrections to an intracavity liquid crystal array.

We have demonstrated the concept of scaling a large number of laser diodes to achieve high power with good beam quality. We have built a device which integrates 100 ridge waveguide amplifiers (1-D scaling) with a coherent optical signal distribution network and phase modulators on a 12.2 mm X 4.4 mm chip called a unit cell. We also achieved coherent combining from 200 waveguide amplifiers by stacking two unit cells (2-D scaling), and are currently working on stacking ten unit cells.

Semiconductor master oscillator power amplifier (MOPA) devices based on the resonant transmission properties of resonant-optical-waveguide (ROW) antiguided structures are shown to be promising candidates for stable, coherent, high-power sources. A novel mast oscillator for this type of MOPA is proposed: the three-core antiresonant reflecting optical waveguide (ARROW) diode laser. This device is also based on ROW antiguided structures and can easily be integrated with the power amplifier. Three-core ARROW lasers are shown to have large intermodal discrimination against unwanted modes, and when used as the maser oscillator of a ROW-MOPA, a uniform near-field, flat-phasefront, diffraction-limited beam output is obtained. Experimentally, 350 mW diffraction-limited beam operation has been demonstrated in ROW-MOPA devices without extremely low AR coatings.

A high-power monolithically integrated master oscillator flared power amplifier is demonstrated which operates at approximately 860 nm to an output power greater than 1.3 cw with a far field pattern consisting of a single, diffraction-limited lobe.

Semiconductor laser devices with tapered gain regions have recently generated much interest because they promise high output power with near-diffraction-limited spatial beam quality and good electrical to optical conversion efficiency. We report recent progress on two specific applications: a ring laser and a high- power erbium-doped fiber amplifier (EDFA). The ring laser operates unidirectionally in a single longitudinal mode with an output power of 170 mW and without a Faraday isolator. The high- power EDFA has an output power of 520 mW at 1.55 micrometers , the highest power reported to dates for an erbium-doped fiber amplifier using all semiconductor pump lasers. The common theme for both of these applications is the development of optical systems that produce high power in near-diffraction-limited collimated beams and efficient coupling into single mode optical fiber. We present an experimental procedure for quantitatively predicting the optical fiber power coupling efficiency. We have measured 64% power coupling efficiency measure fiber fact to power in the single-mode fiber, or 51% laser facet to power in the fiber, in good agreement with the predictions.

Recent progress on the monolithic integration of an index-guided single-lateral-mode preamplifier with a tapered semiconductor optical amplifier is reported. The suppression of the amplified spontaneous emission as a function of coupled input power and bias current is studied. With a coupled input power of only 1.2 mW, more than 1 W amplified output power is obtained at 810 nm, corresponding to 29-dB internal large-signal gain. The far-field pattern is dominated by a diffraction-limited single lobe. A new self-aligned dissipating grid, which improves the amplified- signal-to-total-output-power ratio from 72% to over 85%, is described.

Quantitative spectral analysis has been developed as an analytic tool for the identification and characterization of defects within the cavities of multilongitudinal mode semiconductor lasers. Unstressed lasers whose spectra suggest the presence of internal, manufacturing-related defects have failed at lower values of electrostatic discharge (ESD) stress than devices that are free of such defects. Lasers that have been selected with spectral analysis tend to fail only at the facets during ESD stress, suggesting that surface recombination and the associated optical absorption limit the stress performance. When the surface recombination velocity at the facets is reduced by passivation in aqueous solutions of ammonium sulfide, the laser failure voltage increases by more than a factor of 5 relative to unpassivated devices. The results of spectral analysis are compared with those of more conventional techniques, such as electroluminescence and low coherence reflectometry. We conclude by presenting recent results from spectral analysis during temperature cycling stress of low cost laser packages developed for fiber in the loop applications.

Long duration life tests of approximately 6,000 hours on AlGaAs single-mode lasers operating at 200 mW and 50 degree(s)C indicate that high reliability can be obtained under these conditions. The projected median life is 140,000 hr and MTBF is 100,000 hr. These results compare favorably with data from other material systems.

High output power and long-term stable operation have been realized in all-MOCVD grown 1.48 micrometers buried heterostructure lasers. For the purpose of high power operation, a diode with a cavity length of 1800 micrometers was mounted junction down. This diode shows the maximum output power of 310 mW at 25 degree(s)C, cw. A preliminary aging test is being carried on at a temperature of 50 degree(s)C with a constant light output of 100 mW for the diodes with cavity length of 900 micrometers and junction up configuration. Long-term stable operation over 3000 hrs and the estimated MTTF of 2.4 X 10⁵ hrs at 50 degree(s)C, 100 mW have been realized. As another advantage of the all-MOCVD process, the uniformity of the laser characteristics is also demonstrated. Lasers with a cavity length of 900 micrometers in junction-up configuration are assembled from a processed 2-inch wafer.

We studied local facet temperature near the active region of high power SCH SQW InGaAsP/GaAs (0.8 micrometers ) and InGaAs/GaAs (0.98 micrometers ) laser diodes (LD) along with their optical and degradational characteristics. It was shown that facet overheating with respect to the bulk temperature of the LD for current densities J < 2000 A/cm² was due to the absorption of intrinsic radiation of the LD and nonradiative recombination of nonequilibrium carriers at the mirror facets, while for J > 2000 A/cm² facet overheating connected with the surface leakage current was observed. Either mechanism may dominate in limiting the maximum optical power as well as increase the degradation rate of the LD.

Strained-layer In_xGa_1-xAs-GaAs-Al_yGa_1-yAs buried heterostructure (BH) quantum well lasers have been fabricated using three-step selective-area atmospheric pressure metalorganic chemical vapor deposition. Selective-area epitaxy is used to produce BH lasers involving only GaAs on GaAs regrowth, eliminating the detrimental effects associated with exposed Al_yGa_1-yAs found in other fabrication methods. Additionally, selective-area epitaxy provides in-plane bandgap energy control to fabricate BH devices with different wavelengths on the same wafer.

Fabry-Perot and distributed-feedback emission from strained InGaAs/InP quantum well lasers has been examined over a temperature range of 100 K to 315 K. The active layer contains two 12 nm wide In_0.75Ga_0.25As quantum wells. Fabry-Perot lasers, operating at 39 degree(s)C, showed cw emission at 2.0 micrometers . A threshold current of 40 mA and an external differential quantum efficiency of 10% were measured from a laser with 6 mW of cw light output. A linear wavelength tuning rate of 0.72 nm/K was measured from 100 K to 300 K. The characteristic temperature, T_o, of the threshold current, exhibits an abrupt decrease at 250 K, from T_o equals 136 K to T_o equals 56 K. A similar decrease in the characteristic temperature of the external differential quantum efficiency is observed. The decrease in T_o values at 250 K indicates the onset of an additional loss mechanism. Distributed feedback lasers were fabricated from the same wafer. They showed single mode output from 190 to 300 K with a side-mode-suppression ratio of about 20 dB. The wavelength was 1.95 micrometers at 0 degree(s)C and tuned at a rate of 0.13 nm/K. The current-tuning rate was -340 MHz/mA.

Low threshold current single quantum well InGaAs/GaAs lasers are fabricated by metalorganic chemical vapor deposition on a nonplanar substrate. By taking advantage of the growth rate and doping differences on different crystal facets during the growth, an almost- buried heterostructure laser is made by a single growth step. Threshold currents as low as 1.0 mA under pulsed operation and 1.2 mA under continuous-wave operation are obtained for uncoated lasers at room-temperature. The lasers showed high external quantum efficiency (80%). High reflection coated laser (95%/95%) has a cw threshold current as low as 0.28 mA.

Recent progress on the use of liquid organometallic sources for replacing the group V compressed gases looks particularly encouraging. We have grown both strained and unstrained In_xGa_1-xAs_yP_1-y/InP and In_0.53Ga_0.47As/InP quantum well materials and devices in a non-hydride metalorganic chemical vapor deposition (MOCVD) system using liquid group V sources, tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP). Very low threshold current strained InGaAsP/InP quantum well laser diodes have been grown using TBA and TBP for the first time. Single 90 angstrom InGaAsP quantum well lasers emitting at 1.55 micrometers displayed threshold current densities of 121 A/cm² for a 1.6% compressively strained SQW, and 249 A/cm² for an unstrained SQW at a cavity length of 3500 micrometers . Unstrained ternary (In_0.53Ga_0.47As) single quantum well laser diodes exhibited extremely low threshold current densities (Jth equals 220 A/cm² for broad area devices 3.5 mm in cavity length). These values indicate that TBA and TBP are viable replacements for the more hazardous compressed gases, arsine and phosphine.

There is increasing interest in the use of visible emitting (formula available in paper) quantum well lasers for optical interconnections using polymer waveguides and this calls for the optimization of device structure for operation at a specific wavelength and usually at an elevated temperature. We concentrate on the mechanisms by which compressive strain modifies the threshold current in a regime where well composition (x) (strain) and quantum well width are adjusted to maintain a transition wavelength of 670 nm. In our model we assume a parabolic band structure, which is a reasonable approximation in this case since strain enhanced splitting of the valence bands is large, and we include the effects of monolayer fluctuations in well width and carrier-carrier scattering (where we calculate an energy and carrier density dependent lifetime). Using our model we examine the relative merits of various well composition (x)/well width combinations.

Lasers capable of greater than 20 GHz modulation rates are available today. Extending the usable frequency range can be accomplished with planar transmission line technology and broadband design techniques. Above about 25 GHz, planar transmission line approaches such as finline, dielectric image guide, and microguide should be considered. As for tackling microwave circuit designs, a combination of available approaches, design equations, and the Smith chart constitute the basic analysis and synthesis tools. As circuits increase in complexity, or greater accuracy is required, the use of computer-aided engineering software for optimization and even layout verification is often used to reduce laboratory time.

Gigabit fiber optic data links with transmission speeds of up to 2 Gb/s and distances of up to 2 km for multimode fibers were demonstrated using low-cost and short wavelength semiconductor lasers. The semiconductor laser used for high-speed fiber optic data links is a 780 nm device similar to those that are currently in high volume product in the compact disc (CD) industry. This suggests that a CD laser with multimode fiber and its simple receptacle package design may be more usable for the short-range nature of low-cost gigabit fiber optic link applications than has previously been considered to be practical.

Carrier transport and recombination dynamics are seen to be the intrinsic limitations to the performance of quantum well lasers. The carrier relaxation times as a function of quantum well width were measured in laser structures using a streak camera. Auger recombination rates were experimentally determined in compressively strained In_xGa_1-xAs/InGaAsP/InP quantum wells from the large signal modulation of single mode lasers. In order to overcome the intrinsic limitations in present semiconductor laser designs, a new device concept has been demonstrated: the tunneling injection quantum well laser, in which the carriers are injected into the active lasing subband by resonant and sequential tunneling. The highest 3 dB modulation bandwidth (12.5 GHz) and the highest differential gain (6 X 10^-16 cm²) for a single quantum well laser have already been demonstrated. To realize threshold currents of much less than 1 mA, quantum wire lasers are required. We present theoretical and experimental results on the performance characteristics of quantum wire lasers. The experimental structures are being realized in the In_xGa_1-xAs/GaAs system by MBE growth and regrowth and electron beam lithography.

We have fabricated 1.55 micrometers ridge waveguide DFB lasers consisting of p-doped, 1.5% compressive strained-layer all quaternary MQW active region by two-step MOCVD with a first-order grating located in the upper GRINSCH region. By optimizing the p-doped carrier concentration in the barrier layers, kL and detuning, the measured -3 dB bandwidth was 13 GHz with flat frequency response and very little RC roll-off in this structure. From RIN measurements, the intrinsic bandwidth was calculated to be 18 GHz. Furthermore, by changing the position of the grating to the MQW active region, partly gain-coupled DFB lasers were formed; these devices exhibit very stable single mode operation and narrow spectral linewidths. The -3 dB electrical bandwidth was measured around 22 GHz and the intrinsic bandwidth was estimated to be 28 - 30 GHz. Experimental results show that the devices have small wavelength chirps and clear eye patterns under 10 Gbit/s NRZ direct modulation.

We present experimental results showing a reduction of relative intensity noise (RIN) in partly gain-coupled InGaAsP/InP multiquantum-well DFB lasers. By comparing with conventional index-coupled lasers, it is found that even a small gain-coupling improves significantly the feedback insensitivity of DFB lasers. The mechanism of the RIN reduction and the less feedback sensitivity are believed to be a combined effect of the high relaxation frequency and heavy damping rate, the stronger internal mode discrimination, the facet reflectivity immunity, and the flatter carrier distribution in the gain-coupling structure.

Harmonic distortion in a semiconductor laser is described with the aid of a nonlinear differential equation for the photon density, derived from the rate equations. Analytical results are obtained by linearization, and curves are presented showing the fundamental, second-order harmonic and third-order harmonic IM and FM responses. The present development provides a significant improvement in the third-order harmonic characteristics. The comparison between Bessel functions analysis and the perturbation method is quite successful.

The advent of high power (> 10 Watts) 800 to 980 nm diode lasers, and medium power (1 to 10 Watts) 670 to 690 nm, and 1.8 to 2.1 micrometers diode lasers, has allowed diode lasers to enter the medical market. An overview of current, pending, and potential medical applications utilizing these lasers is presented.

Optical sensor systems have source requirements that can be significantly different from those of optical communications and other technologies that have generally driven the development of semiconductor sources. In this paper, we examine basic interferometric, polarimetric, and other sensors. Relevant semiconductor source data is reviewed to illustrate the impact of source characteristics on sensor performance. The effect of low-frequency amplitude and frequency noise on sensor precision is described. Errors in sensor calibration due to amplitude and wavelength drifts are discussed. Examples of sensor performance using typical source data illustrate these issues.

Over the last several years, it has become widely recognized that electromagnetic interference (EMI), electromagnetic Pulse (EMP), High-Intensity Radio Frequency (HIRF), and new threats, such as directed-energy weapons, can jeopardize the flight safety of vehicles equipped with Fly-By-Wire (FBW) systems, unless adequate shielding precautions are taken. This leads to weight penalties which can be avoided through implementation of Fiber-optic systems.

Near-infrared diode-laser-based systems using laser-absorption molecular spectroscopy can sensitively monitor atmospheric gases, pollutants, and toxic gases. They can also monitor trace gases on the human breath for medical diagnostics. The detection levels are equal to or less than parts per million. Sarnoff/SRI has made and tested room-temperature InGaAsP/InP DFB lasers operating at 1.39, 1.6, and 1.65 micrometers . All of these devices had output powers of 10 mW or more. The current-tuning rates varied from -580 to -1240 MHz/mA. The temperature tuning rate was about 0.1 nm/K for all devices. Continuous tuning ranges were 7 nm for the 1.39 micrometers lasers and 5 nm for the 1.6 and 1.65 micrometers lasers. We observed H₂O at 1.39 micrometers , CO and CO₂ at 1.6 micrometers , and CH₄ at 1.65 micrometers . We monitored the ratio of ¹³CO₂ to ¹²CO₂ on human breath samples as the initial step towards clinical trials for medical diagnostics.

In this paper we discuss the effects of incorporating carbon doping in semiconductor lasers. Data is presented that demonstrates that very high quality carbon doped epilayers for the fabrication of AlGaAs-GaAs and AlGaAs-GaAs-InGaAs quantum well lasers can be grown by solid source molecular beam epitaxy using a resistively heated graphite filament as a p-type dopant source. Also results are presented that indicate that the use of carbon instead of beryllium improves the contact resistance for refractory ohmic contacts.

The effect of zinc diffusion on the device performance of semi-insulating buried crescent (SIBC) lasers was analyzed by electron beam induced current and scanning electron microscope techniques. A novel liquid phase epitaxy regrowth technique has been developed to minimize the zinc diffusion into the iron-doped semi-insulating indium phosphide blocking layer. This technique has been demonstrated to improve the device performance of SIBC lasers.

We have developed and tested an integrated fiber-optic coupled diode laser array module for use as a reliable pumping source for solid-state lasers, and rugged enough to withstand the nine `gs' acceleration of a military airborne laser experiment. This compact laser module has produced 12 watts of peak power in cw and pulsed operation modes. The output beam comes from a flexible, yet hardened, fiber-optic bundle. The laser has a footprint smaller than a 3' X 5' card. It has a built-in thermo-electric cooler to provide wavelength control, and integrated cooling channels that assure continuous use. The fiber-optic output has proven itself in beam pointing and positioning applications, including end-pumping of solid-state lasers and as an airborne beacon. In the later application this compact laser was bright enough to allow continuous aircraft tracking from 200 kilometers with a beam divergence up to 10 degrees.

Simple thermal management of large laser diode arrays can be accomplished by directly mounting laser diode material in a grooved substrate, This "Monolithic" assembly method dramatically simplifies the thermal path from the laser junction to the final user specified heatsink. For pulse width <lms, high density bar packing of 30 to 40 bars per cm is possible , pulse widths from 5 to 10 ms can be supported with packaging densities of 10 to 20 bars per cm and for those who need pure CW, typically 4 to 8 bars per cm arrays can be fabricated all while utilizing simple coolers. For those requiring the highest level of performance the "Bars in Grooves" packaging technology can be hybrid with, impingement, macro I micro channel or even pin type coolers. While Beryllium Oxide (BeO), Aluminum Nitride (AlN) and copper are typical base materials presently utilized for mount fabrication, it is only a matter of time before other very high thermally conductive material, such as diamond become commercially viable options ... The fabrication technology has the added benefits of precision location of emitters: for use with collimation lens. array repairability, bars can be removed and replaced. and requires minimum assembly fixturing, bars self align. and the technology scales both for array size and volume requirements.. The most important factor is that the "Bars in Grooves" assembly method produces laser diode arrays of the highest quality combined with the lowest cost!!

This paper describes as an alternative to the silicon technology the production, assembly, and performance of microchannel coolers in copper technology. A realization technique for these copper coolers is described for one specific cooler geometry with a stacked design of 5 microstructured copper plates. These 5 layers are bonded together by diffusion welding at a temperature near 800 degree(s)C. This bonding process allows the fabrication of 3 X 8 coolers in one step in which the 5 structured copper plates of a size of 100 X 150 mm² are bonded together. The structuring procedure is currently done by etching and laser machining. Microchannels with a width of 60 - 100 micrometers and a depth of 300 micrometers are used in the experiments as microstructures for better comparability to already existing theoretical and experimental results. A thermal resistance of 0.44 K/W of these copper coolers is demonstrated for a device with a 10 mm laser diode bar mounted on the front edge of the cooler. Experimental results for this configuration reach an average laser diode power of 71.5 Watts from one single bar with a footprint of 0.6 X 10 mm². The experimental results are compared to 3-D heat flow calculations.

Standardized laser test methods are necessary for valid comparison by customers of published results for both characterization tests and reliability tests. Although progress in standards has been made in the past five years, much more work remains to be addressed. The status of U.S. and international test standards is discussed and compared to Bellcore generic criteria. Background information is also provided on the nature of various standards organizations.

This paper describes the method used to develop an internal, company specification into a European standard, by cooperation, collaboration, and experience sharing across the industry. In so doing, it briefly outlines the structure of Standards bodies in Europe and demonstrates that with good will and a firm intent by all parties a document can be produced in acceptable timescales that allows the end customer to achieve the required degree of confidence in the product with an acceptable level of effort from the suppliers.

The availability of a reliable, non-hermetic InP based laser and associated monitor diode could provide the cost reduction needed for wide spread use of such lasers for two way broad band communication. Since there is little information available in the reliability of such devices in non-hermetic packages, a strategy for carrying out life testing in humid environments is presented. Accelerated aging tests can be used to assess the reliability of presently available devices and to discover the failure modes. Detailed failure analysis provides understanding of the physics and chemistry of the failure mechanism and leads to design and material improvements to prevent these failure mechanisms. The basic assumption underlying accelerated testing and the physical basis for the derivation of acceleration factors are discussed. Proper design of the accelerated test and selection of test conditions are essential for the derivation of useful temperature and humidity acceleration factors. These acceleration factors are determined from analyses of the time-to-failure as a function of both parameters. Finally, the possibility of condensation and its effects on a laser-monitor assembly are discussed.

Characterization testing of monolithic, dual beam visible diode lasers operating at 670 nm (at 20 degree(s)C) is reported for AlGaInP lasers with a 50-micron channel separation. Of particular interest for use in the design of laser scanning systems is an understanding of the characteristic behavior of the thermal droop and thermal crosstalk between channels as heatsink temperature, laser drive current bias, and output power are varied. The thermal droop and thermal crosstalk are both found to decrease as the laser output power is increased. Additionally, the thermal droop and thermal crosstalk increase as the temperature of the heatsink increases. Characterization of the laser wavelength dependence on temperature and output power must also be considered in laser scanning system design. The dual beam laser wavelength was measured to change with temperature 0.17 nm/ degree(s)C. Laser wavelength at a constant laser case temperature was found to increase by 2 nm as the output power was increased from 1 mW to 15 mW.

We have witnessed a rapid advancement in optical fiber telecommunications in the last decade. The bit rate of early optical transmission systems in the late 1970's was 45 Mbit/s. By the m1d4980's, the transmission speed had been increased to rates ranging from 400 Mbitls to 560Mbit/s. More recently, SONET hierarchy, from OC- 1 , OC-3, OC-12, to OC-48 at 51.84 Mbitis, 1 55.52MbitJs, 622 Mbitls to 2.488 Gbitls respectively, has been the standard chosen by CCITT. The next SONET standard rate of OC-l92 at 10 Gbitis is now under consideration. Although laser transmitters at 10 Gbitls rate are still in the research and development stage, new products will be introduced in the marketplace to fuffill systems and networking needs in the near future. The singlemode optical fiber has a potential bandwidth of over 30 THz. In order to utilize this bandwidth, high density wavelength-division-multiplexing (WDM) has been considered. WDM can offer not only the increased usage of bandwidth, but also the flexibility of routing signals in a network by means of wavelength [11. In the last few years, the transmission distances have been increased dramatically due to the use of Er-doped fiber amplifiers. High power semiconductor lasers at either 0.98 tm or 1.48 .tm wavelengths are used for the pump. The powers into the amplifier required for both pump wavelengths are about 20 mW and 50 mW respectively. On the other hand, semiconductor opticai amplifiers are attractive for monolithic integration with lasers, waveguides, modulators, wavelength multiplexers and demultiplexers. For example multi-wavelength DFB laser arrays, as many as 20 wavelengths, have been integrated monolithically with wavelength combiners (star coupler) and optical amplifiers on InP substrate [2). These integrated multi-wavelengths DFB laser arrays have the advantage of easier wavelength control and lower cost per wavelength than the discrete DFB laser transmitters for WDM applications. Such photonic integrated circuits (PlC) can increase the functionality and reduce the optical fiber-to-device interfaces that are the main factor for the high cost of optoelect.ronic components. The fiber-to-device interface is also the major concern for component reliability.

Distributed feedback (DFB) semiconductor lasers are now widely used in long-haul high- capacity optical fiber transmission systems operating in the 1.3 micrometers and 1.5 micrometers wavelength windows, with direct modulation bit-rates up to 2.488 gigabit/s. Some form of link test over fiber is usually necessary to evaluate the dynamic performance of DFB lasers for potential application in actual systems, which requires considerable test time and equipment. Moreover, thermal considerations often dictate that this test be performed only after the chip is bonded to a heat sink and fully assembled. In this paper we present a study of the dynamic properties of DFB lasers at the chip level focusing on both side- and main-mode characteristics, using a simple technique which employs low duty cycle pulses. Our measurements were performed on some 1.5 micrometers DFB laser chips. To show the validity of the chip-level results, we followed up with measurements of the same chips after bonding to a diamond heat sink, and also after a burn-in period. For comparison, a more extensive link test over fiber was also performed on the same lasers.

Although there will always be intensity noise from a laser diode due to quantum effects, current fluctuations from the laser controller add additional noise. Noise spectra in the 0 - 150 MHz frequency range is presented for cw lasers powered by commercial controllers as well as by a simple, but well shielded battery supply. Various examples also are given to show the sensitivity of the noise level of the laser to small changes in wiring and grounding configurations. The laser diode user gains a familiarity with the magnitude of the intensity noise in this frequency range.

Research conducted in the early 1960s showed that the oscillation wavelength of a semiconductor laser shifted when exposed to a magnetic field. These experiments were conducted at very low temperatures and in very strong magnetic fields. We observed the wavelength shift toward a longer wavelength and the threshold current increase, in certain types of laser diodes in relatively weak magnetic fields at room temperature using recently developed Fabry-Perot type laser diodes. The shift mechanism, however, is not yet fully understood. We may assume that the presence of a magnetic field affects the current density in certain types of laser diodes, which in turn, affects the temperature around the active layer. This temperature change would then influence oscillation wavelength and threshold current. This means our measurement provides vital information about the current confinement characteristics of laser didoes.

In this paper the investigation of internal optical second harmonic generation (SH) of buried heterostructure (BH) InGaAs/AlGaAs strained quantum well laser diodes is performed for additional characterization of these devices which are capable of operating at high power densities as high as 3 MW/cm² at room temperature and 0.1 MW/cm² at 190 degree(s)C. The blue-green emission level is of the order of 10⁵ photons per second for laser diodes with 3micrometers active layer width at fundamental optical power of 2.0 mW. This relatively high SH intensity level makes it possible to observe the light spot in optical microscopes and to detect SH signal with a standard photon counting system in wide operation current and ambient temperature intervals. Variation of the SH signal at the constant fundamental harmonic (FH) power indicates that changes in the near field occur. SH far-field patterns of laser diodes reflect the effects of SH radiation spot size reduction in comparison with FH radiation spot size and FH waves nonlinear interactions in the waveguide material.

We have applied automated wafer scale testing methods to the characterization of arrays of vertical cavity surface emitting semiconductor lasers. The hardware and software for recording light versus current, current versus voltage, optical spectra, and high speed modulation performance are described.

Coolerless lasers meeting Bellcore technical advisory TA-TSY-000983 are needed for access applications. To this end, a parallel processing multi-temperature robotic tester (MTRT) for high volume dc characterization of semiconductor lasers over the temperature range -40 degree(s)C to +85 degree(s)C is presented. The cartridge based system is fully integrated with the device burn-in oven, allowing for automated testing and handling. The robot picks devices from a cartridge and places them in one of seven test pods, each independently temperature controlled and serviced by a stage with a photodetector, movable polarizer, and a fiber. The test pods measure dc, pulsed, polarized and non-polarized L/Is, V/Is, and optical spectrums of the devices at each temperature. The test software is multi- threaded and includes a custom task scheduler and mailbox system. This C software is three- tiered with a user-interface process, a test system process, and a database link process. All test specifications, device specifications, and device data are acquired from and stored back onto a remote database for data analysis and reporting. The database is also accessed via a 4GL user- friendly interface. An independent cartridge-based burn-in performs the automatic current control (ACC) burn-in cycles between tests and integrates into the robotic test system equipment. Together, the robot and the burn-in oven perform all process steps required between the post-bond and final test manufacturing stages.

Heterojunction bipolar transistors (HBTs) are capable of producing very high speed digital integrated circuits operating as high as 40 GHz. In this paper we introduce a potentially low cost technique of monolithically integrating in-plane lasers with HBT circuits. A multifunctional epitaxial structure is used which is essentially the same as that for a standard high-speed HBT with modifications made to allow for efficient light amplification. Unlike previous multifunctional epitaxial structures, compromise in the transistor's performance is minimal. The schematic energy band diagrams of the HBT/laser structure biased as an HBT and laser are depicted. Light amplification is achieved by forward biasing the HBT's base- collector junction. The optical gain media is placed in the GaAs collector and consists of strained InGaAs quantum wells (QWs). Under normal HBT operation, the base-collector junction is reverse biased and serves as a sink for electrons which have diffused across the base. To confine electronic carries to the gain region when this junction is forward biased, the subcollector and base consist of a wider bandgap AlGaAs relative to the GaAs collector.