大功率量子阱远结半导体激光器

通过将下波导层掺杂为ｐ型,使半导体激光器的有源区与ｐｎ结分离,制作了大功率远结半导体激光器。该器件在老化期间表现出输出功率变大的趋势。理论分析表明,远结半导体激光器特殊的外延结构,决定了器件的阈值比正常器件的高,但是阈值受温度的影响较小,并且器件的退化机制转变为ｐｎ结的退化,这对于制作高可靠性、长寿命、低温度敏感性的半导体激光器具有重要意义。     

Statistical analysis of aging-induced degradation (or lifetime) variation in (Al, Ga)As/GaAs double-heterostructure lasers

Aging-induced degradation, defined as optical power decrease during constant current aging, is obtained for a number of (Al, Ga)As double-heterostructure lasers taken from sixty routinely grown wafers (20-30 devices per wafer). These aging characteristics are statistically analyzed wafer by wafer in correlation with initial laser parameters (or initial operating condition), i.e., CW threshold current, differential quantum efficiency, electrical resistance, nominal temperature sensitivity of threshold current, lasing wavelength, and driving current at aging. The multiple factor analysis evolved during this study reveals that degradation in average lasers can be substantially correlated to a new composite parameter defined as a linear combination of the above parameters. This fact suggests the feasibility of statistical estimation of laser degradation utilizing only the initial parameters. Of the parameters employed, driving current is revealed to be most strongly and commonly associated with laser degradation. To understand the role of driving current in causing lifetime scatters between individual lasers, a possible local heating model is developed. The lifetime scatters experimentally observed are well explained using this model.     

Degradation analysis in asymmetric sampled grating distributed feedback laser diodes

This paper presents the experimental observation of the degradation in asymmetric sampled grating DFB lasers by the accelerated life tests. Two degradation phenomena related to the electrical characteristics of LDs are observed during the tests. The first degradation phenomenon by increasing the reverse current is considered as a formation of leakage current path enough to prevent lasing operation in lateral blocking layer near active region of lasers. The second degradation phenomenon by decreasing the forward current is considered as activation of non-radiative Auger recombination process by thermal energy. It is also experimentally observed that the second degradation phenomenon is recovered after remained in room temperature with no electrical stress. Therefore, the criteria for LD reliability can be determined by observing the degradation of the reverse current–voltage characteristics.     

Degradation behavior of the active region and passive region in buried heterostructure (BH) distributed Bragg reflector (DBR) lasers

Changes in the threshold current and wavelength tuning characteristics due to the degradation of the active region and passive region in buried heterostructure (BH) distributed Bragg reflector (DBR) lasers are experimentally investigated. These changes are caused by the decrease in recombination carrier lifetime due to degradation. It is shown that the decrease in the carrier lifetime is mainly accelerated as a result of increased carrier density. This suggests that the degradation of the active region depends more strongly on the threshold current density than on the operating current. On the other hand, the degradation of the passive region is related to the injected current density, which affects the stability of the wavelength tunability of DBR lasers.     

Lasing wavelength changes due to degradation in buriedheterostructure distributed Bragg reflector lasers

Changes in the wavelength and lamp characteristics due to the degradation of distributed Bragg reflector (DBR) lasers are investigated and the lasers are confirmed to be reliable enough for application as the light sources in WDM systems. The change in wavelength characteristics is due to degradation of the DBR or phase control region and the change in lamp characteristics is due to the degradation of active region. These changes in the characteristics are caused by diminished recombination carrier lifetime. The wavelength stability is strongly correlated with the injected current density. The lamp characteristics is confirmed to be almost as stable as in conventional Fabry-Perot lasers. The applicability of DBR lasers as the light source for wavelength division multiplexing (WDM) systems is demonstrated for actual-use conditions     

Thermally accelerated degradation of 1.3 ?m BH lasers

An investigation has been made into the thermally accelerated degradation in ACC lifetests for 1.3 ?m BH lasers. The CW threshold current under high-stress aging has been evaluated at various temperatures. An increase in the CW threshold current was observed which could be represented as a combination of two linear variations. It was found that the rapid increase of the CW threshold current was dependent on the evaluation temperature, which could be an important parameter in assessing the degradation of InGaAsP lasers.     

On the degradation of InGaAsP/InP-based bulk lasers

Degradation of InGaAsP-InP-based buried-heterostructure bulk (BH-bulk) lasers has been studied by means of electroluminescence (EL), photoluminescence (PL), electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). Lasers with p/n as well as semi-insulating (SI) current-blocking layers were studied. The results show that moderate increases in the threshold current correlate well with formation of dark defects (DD's) (i.e., dark-line defects (DLD's) or dark-spot defects (DSD's), which cannot be distinguished in our case due to the narrowness of the laser stripe.) The DD's were found to be caused by dislocation loops. The dependence of threshold current increase on the number of DD's is explained in terms of a model which includes effects due to the DD's, as well as changes in the regions outside the DD's. The latter is found to be responsible for the major part of the threshold current increase. Values for the ratio between the carrier lifetimes inside and outside the DD's are presented, for the first time. In our lasers, strong degradation differs from moderate degradation in that DD's do not form during aging. The presence of dislocation loops only at the sidewalls of the active stripe in lasers with p/n current-blocking layers points to the sidewalls as being critical. The near absence of dislocation loops and the smaller increase in threshold current in SI lasers which have degraded strongly, compared to the strongly degrading p/n lasers, suggest that strong degradation is a synergistic combination of damage in the sidewalls and Zn indiffusion from the current-blocking layers     

Reliability of semiconductor lasers used in current communication systems and sensing equipment

The degradation mechanisms that had occurred – but that have now been largely suppressed or eliminated – in established consumer equipment and optical communication systems have also become problems in current optical fiber communication systems. This is due to the requirements of recently developed communication systems for semiconductor lasers, which operate at higher performance levels under severe environmental conditions. In addition, semiconductor lasers have now become important optical sources in new application fields such as sensing equipment, and these new applications have in turn brought new reliability problems to semiconductor lasers. In this paper, the degradation modes and reliability of semiconductor lasers are reviewed and discussed in association with recently developed optical sensing equipment and communication systems.     

5000小时室温连续激射GaAs/AlGaAs双异质结激光器

一、引言 半导体激光器采用双异质结构(DH),对有源层内的注入载流子及辐射光场进行限域,使得阈电流密度迅速下降为～1×10~3安培/厘米~2,1970年实现了室温连续激射。双异质结激光器是光纤通讯和精密测距的较理想光源,但急待解决稳定性和可靠性问题。自从对DH激光器退化机理有了比较清楚了解之后,激光器寿命基本上每年提高半个至一个数量级。到1976年美国Bell公司通过升温加速老化试验推断激光器寿命可望达到100万小时。也已采用多种方式制作各     

808 nm大功率半导体激光器的加速老化实验

对InGaAsP/GaAs有源区无铝的808 nm大功率半导体激光器进行了高温恒流加速老化实验,得到了器件在高温条件下的寿命,利用外推公式推算出激光器在室温条件下工作的寿命可超过30000 h.讨论了实验中出现的灾变退化现象,提出了防止灾变退化的几种方法.     

Effective screen for fast aging InGaAsP BH lasers using electrical derivatives

We report here the first use of electrical derivatives to predict threshold current degradation rates for InGaAsP, etched mesa BH lasers. Fast aging lasers are found to display a post-threshold I dV/dI temperature dependence which sets them apart from slow agers. This signature is explained in terms of a nonlinear current leakage path in the confinement layers. We propose the use of the I dV/dI temperature signature as a screen to eliminate fast aging lasers in high-reliability applications.     

Recombination enhanced annealing effect in AlGaAs/GaAs remote junction heterostructure lasers

New structure lasers, the remote junction heterostructure (RJH) lasers, are made to obtain information about slow degradation of AlGaAs/GaAs DH lasers. The RJH laser is characterized by the presence of a thin clad layer between the active layer and the p-n junction. During the LD and LED mode aging process, the RJH lasers showed a marked reduction of threshold current. This reduction was accompanied by increased spontaneous lifetime and pileup of defects at the p-n junction. From these observations, a model was proposed in which point defect generation in the active layer and defect motion toward the p-n junction during the aging are assumed. The rate equation was derived for concentration of the point defect, and the solution of this equation was compared with the experimental results with reasonable agreement. The parameters relating to the slow degradation were determined, and the ultimate life of conventional DH lasers was discussed using these parameters.     

808nm无铝材料激光器可靠性筛选的实验探讨

对８０８ｎｍ无铝ＩｎＧａＡｓＰ／ＧａＡｓ半导体激光器进行可靠性筛选实验,给出了器件老化前后的工作特性及其变化情况;讨论器件工作特性变化甚至失效的可能原因,并给出在进行器件的可靠性做初步的判定,认为工作电流的变化率小于１％时是可靠的器件。     

The characterization and functional reliability of 45 Mbit/s optical transmitters containing MBE-grown lasers

We have characterized the performance and studied the functional reliability of 45 Mbit/s lightwave transmitters containing proton-bombarded stripe lasers grown in a research environment by molecular beam epitaxy (MBE). We observe that these transmitters have superior performance compared to transmitters containing lasers of similar geometry grown in production facilities by liquid phase epitaxy (LPE), and subsequently processed using the same technology. The reliability data of over 10 000 h indicate that the functional lifetime of the MBE lasers will be limited ultimately by extinction ratio degradation in our circuit strategy. The origin of the degradation is the increase of the spontaneous light at the bias current.     

Direct gigabit modulation of injection lasers--Structure-dependent speed limitations

Samples of a large variety of quaternary 1.3- and 1.5-μm injection lasers were directly modulated at bit rates up to 2 Gbit/s using a drive circuit known to have a flat response up to speeds more than twice this high. The resulting optical signals were detected and analyzed for eye degradation and bit error rates. It was found that some lasers were capable of modulation at rates exceeding 2 Gbit/s without degradation while others exhibited significant eye closure at bit rates as low as 300 Mbit/s. A clear correlation was found between high-speed capability and the absence of a current blocking junction. That is, the lasers capable of the fastest modulation were of the simplest geometries: ridge guide and oxide stripe. Buried heterostructure (BH) and buried crescent (BC) lasers both showed significant speed limitations. The modulation bandwidths of the various lasers were also investigated using small-signal sinusoidal modulation and the measured half-power bandwidths were consistent with the large-signal modulation results. The shape of typical modulation transfer characteristics is consistent with a simpleRCrolloff withRCproducts of ≳ 400 ps for buried crescent lasers, ∼ 150 ps for buried heterostructure lasers, and < 60 ps for ridge guide lasers. These results apply also to samples which had been processed to form cleaved-coupled-cavity (C³) lasers for mode stabilization.     

Experimental tests of proposed mechanisms for gradual degradation of GaAs double-heterostructure injection lasers

Degradation rates of double-heterostructure GaAs lasers have been measured and found to vary superlinearly with the injected current density above threshold. The results are discussed in the context of the Gold-Weisberg phonon-kick and the extended Longini field-inhibited diffusion degradation mechanisms.     

Generation of short optical pulses in semiconductor lasers by combined dc and microwave current injection

We report picosecond pulse generation in low threshold buried optical guide lasers using combined direct and microwave current excitation. The pulse widths were obtained as a function of direct current for several levels of RF excitation using lasers 125 and 380 μm long. The pulses have a Gaussian shape with full widths at half maximum intensity ranging from 19 to 57 ps. The pulse widths were obtained from the second harmonic autocorrelation. The experimental results are in reasonable agreement with the theory of short pulse formation in sinusoidally modulated lasers. The pulse width decreases with increasing dc and microwave current, and decreasing laser length. The shortest pulses were obtained with a 125μm long laser using 0.25 W RF at 1 GHz and 35 mA de bias. Multiple pulses are emitted at high dc excitation levels. Using the above laser at the indicated current levels the emission consists of a burst of ∼10 pulses which are separated by 30 ps, and has an approximately exponentially decaying amplitude. Saturable absorption was introduced in the lasers by degradation and results in shortening the pulses. A comparison is made of the pulse widths obtained for sinusoidal microwave current modulation and for pulsed excitation where the excitation is obtained from a step recovery diode. Reduced pulse widths are obtained for short current pulse excitation.     

Degradation-robust 850-nm vertical-cavity surface-emitting lasers for 25Gb/s optical data transmission

Highly efficient fast vertical-cavity surface-emitting lasers (VCSELs) for the 850-nm spectral range, promising for the development of optical interconnections with a data transmission rate of 25 Gbit/s per channel, are fabricated and studied. Lasers with a selectively oxidized current aperture 6 μm in diameter demonstrate multimode lasing with a quantum efficiency of 35–45% and a threshold current of 0.5–0.7 mA in the temperature range 20–85°C. According to the results of small-signal frequency analysis, the maximum modulation frequency of the lasers exceeds 17 GHz, with the rate of its increase with current exceeding 9 GHz/mA^1/2, which provides VCSEL operation at a rate of 25 Gbit/s in the entire working temperature range. Endurance tests for 3000 h did not reveal any sudden degradation of the lasers. The optical power at working point and the threshold current changed relative to that at the beginning of the tests by no more than 5 and 10%, respectively.     

Degradation Behavior of 850 nm AlGaAs/GaAs Oxide VCSELs Suffered from Electrostatic Discharge

The effect of forward and reverse electrostatic discharge (ESD) on the electro‐optical characteristics of oxide vertical‐cavity surface‐emitting lasers is investigated using a human body model for the purpose of understanding degradation behavior. Forward ESD‐induced degradation is complicated, showing three degradation phases depending on ESD voltage, while reverse ESD‐induced degradation is relatively simple, exhibiting two phases of degradation divided by a sudden distinctive change in electro‐optical characteristics. We demonstrate that the increase in the threshold current is mainly due to the increase in leakage current, nonradiative recombination current, and optical loss. The decrease in the slope efficiency is mainly due to the increase in optical loss.     

Extensive Analysis of the Degradation of Blu-Ray Laser Diodes

This letter describes an analysis of the degradation of InGaN-based laser diodes. The influence of current, temperature, and optical power level on the degradation kinetics has been analyzed by means of a wide set of stress tests carried out under different operating conditions. We demonstrate the following: 1.) the degradation rate is strongly related to the operating current level; 2.) high-temperature stress does not determine significant degradation of lasers characteristics; and 3.) the intensity of the optical field does not significantly influence the degradation rate. Degradation process is found to be electrothermally activated and is ascribed to the increase of the nonradiative recombination rate in the active layer, with subsequent decrease of the efficiency of the devices.