High-power 980-nm ridge waveguide laser diodes including an asymmetrically expanded optical field normal to the active layer

We propose a new ridge waveguide laser diode (LD) which supports an asymmetrically expanded optical field normal to the active layer in order to increase the maximum kink-free output power and reduce the aspect ratio of output beams. The dependence of maximum kink-free output power on facet reflectivity was analyzed from the viewpoint of the total optical power in the cavity. It was clarified that the maximum kink-free output power is influenced by the facet reflectivity which affects the refractive index changes of the ridge region via the total optical power in the cavity. More than 600 mW of maximum kink-free output power and an aspect ratio of less than 2.5 were achieved in experiments with 980-nm ridge waveguide LDs by means of this proposed new structure.     

Analysis of interior degradation of a laser waveguide using an OBIC monitor

We propose a novel optical-beam-induced current (OBIC) measurement technique for detecting the degradation in the interior of a waveguide. This technique uses an incident light with a wavelength longer than that of the band edge of the active layer. An OBIC scan image was obtained at a wavelength of 1.6 μm, which was 50 nm longer than the PL peak wavelength in the active layer of the degraded laser, and the OBIC became sensitive to some degradation when a long distance guided light was used. Furthermore, we confirmed that the degradation mechanism of the t^0.5 deterioration property is mainly governed by diffused defects at the waveguide other than those in the vicinity of the AR facet in a DFB laser.     

GaN基蓝紫光激光器的材料生长和器件研制

报道了国内首次研制成功的GaN基蓝紫光激光器的材料外延生长、器件工艺和特性.用MOCVD生长了高质量的GaN及其量子阱异质结材料,以及异质结分别限制量子阱激光器结构材料.GaN材料的X射线双晶衍射摇摆曲线(0002)对称衍射和(10(-1)2)斜对称衍射半宽分别为180″和185″;3μm厚GaN薄膜室温电子迁移率达到850cm2/(V·s).基于以上材料,分别成功研制了室温脉冲激射增益波导和脊型波导激光器,阈值电流密度分别为50和5kA/cm2,激光发射波长为405.9nm,脊型波导结构激光器输出光功率大于100mW.     

100-mW kink-free blue-violet laser diodes with low aspect ratio

400-nm-band GaN-based laser diodes (LDs) operating with a kink-free output power of over 100 mW and having a low aspect ratio of 2.3 have been successfully fabricated for the first time. A new ridge structure, in which the outside of the ridge is covered with a stacked layer of Si on SiO/sub 2/ and the ridge width is as narrow as 1.5 /spl mu/m, is applied to realize high kink-free output power with a wide beam divergence angle parallel to the junction plane. A new layer structure around the active layer is demonstrated to be quite effective for obtaining a narrow beam divergence angle perpendicular to the junction plane, maintaining low threshold current. Ten LDs with low aspect ratio have been operated stably for over 1000 h under 30-mW continuous-wave operation at 60/spl deg/C. Relative intensity noise measured under optical feedback with high-frequency modulation is as low as -125 dB/Hz. These results indicate that this LD is suitable for next-generation high-density optical storage systems.     

Fabrication of room temperature continuous-wave operation GaN-based ultraviolet laser diodes

Two kinds of continuous-wave GaN-based ultraviolet laser diodes (LDs) operated at room temperature and with different emission wavelengths are demonstrated.The LDs epitaxial layers are grown on GaN substrate by metalorganic chemical vapor deposition,with a 10×600 μm2 ridge waveguide structure.The electrical and optical characteristics of the ultraviolet LDs are investigated under direct-current injection at room temperature. The stimulated emission peak wavelength of first LD is 392.9 nm,the threshold current density and voltage is 1.5 kA/cm² and 5.0 V,respectively.The output light power is 80 mW under the 4.0 kA/cm² injection current density. The stimulated emission peak wavelength of second LD is 381.9 nm,the threshold current density the voltage is 2.8 kA/cm² and 5.5 V,respectively.The output light power is 14 mW under a 4.0 kA/cm² injection current density.     

High-power 660-nm GaInP-AlGaInP laser diodes with low vertical beam divergence angles

We present 660-nm GaInP-AlGaInP ridge multiple-quantum-well laser diodes (LDs) reliably operating at high output power over 200 mW at 70/spl deg/C not showing unstable higher order lateral modes owing to an adoption of a dry etching method instead of a conventional chemical wet etching for realizing steep ridge sidewalls. Employing an optimized two-step n-cladding layer LDs produced very narrow horizontal and vertical beam divergence angles of 8.6/spl deg/ and 15.3/spl deg/, respectively. To the best of our knowledge, this vertical beam divergence angle is the lowest value ever reported in high-power 660-nm LDs operating over 200 mW and is expected to play an important role in minimizing the coupling loss between LD and passive optical components in digital versatile disc system.     

Single contact optical beam induced currents

Semiconductor industry is continuously experiencing shrinking device features and a tremendous increase in the number of transistors in an integrated circuit (IC). The application of the optical beam induced currents (OBIC) technique in ICs is more difficult and mainly limited to a few transistors near the input–output pins of an IC. The single contact optical beam induced currents (SCOBIC) is a new device and failure analysis technique, that makes it possible to perform the similar OBIC technique on many transistor including internal junction on an IC. This is done by connecting the substrate or power pins of an IC circuit to the current amplifier. In contrast, in the OBIC technique, only the junction directly connected to the current amplifier is imaged. The implementation of the SCOBIC approach is discussed and experimental results which demonstrates the SCOBIC approach is presented. Application of the SCOBIC technique from the backside of an IC, which further enhances the technique, is also discussed.     

Improvement of catastrophic optical damage (COD) level forhigh-power 0.98-μm GaInAs-GaInP laser

We investigate improvement of catastrophic optical damage (COD) level for Al-free 0.98-μm ridge waveguide laser diodes (LDs) using the impurity induced layer disordering (IILD) process applied near the facets. The IILD is used for the purpose of forming transparent windows near both facets of the LDs utilizing its ability to increase bandgap energy of the GaInAs-GaInAsP strained quantum-well (QW) active layer. Improvement of the cod level by at least 1.65 times compared to the conventional LDs is obtained for the LDs with Si⁺ implantation followed by annealing at 900°C for 10 min     

Integrated AlGaAs two-beam LD-PD array fabricated by reactive ion beam etching

Monolitically integrated AlGaAs two-beam laser diode (LD)- photodiode (PD) arrays are described. LDs and PDs have etched facets fabricated by reactive ion beam etching (RIBE). LDs in the array exhibit threshold currents as low as 18 mA and external quantum efficiencies of more than 30% per facet. A PD can detect more than 20% of a light beam emitted from an LD facing it. Crosstalk between the two LD-PD columns (separated by 50 ?m), on the other hand, is suppressed to less than ?20 dB by an AlGaAs optical barrier (5 ?m thick) fabricated between them.     

A Simple and Color-Free WDM-Passive Optical Network Using Spectrum-Sliced Fabry–PÉrot Laser Diodes

We propose and demonstrate a simple and color-free wavelength-division-multiplexing passive optical network (WDM-PON) using spectrum-sliced Fabry-Perot laser diodes (F-P LDs). Due to its low front facet reflectivity (~0.1%), the F-P LD shows a broadband lasing spectrum and reduced mode partition noise. By utilizing multiple peaks that are separated by the free-spectral range of the cyclic arrayed waveguide gratings, the 16-channel WDM-PON is successfully demonstrated at 155 Mb/s.     

1.3-μm n-type modulation-doped AlGaInAs/AlGaInAsstrain-compensated multiple-quantum-well laser diodes

In this paper, we report the fabrication and characterization of 1.3-μm AlGaInAs/AlGaInAs laser diodes (LDs) with an n-type modulation-doped strain-compensated multiple-quantum-well (MD-SC-MQW) active region and a linearly graded index separate confinement heterostructure. The barrier in the MD-SC-MQW active region contains the 28 Å Si-doped modulation-doped region and two 29 Å surrounding undoped regions that serve to prevent the overflow of Si doping atoms into the wells. We investigate the threshold current density, infinite current density, differential quantum efficiency, internal quantum efficiency, internal optical loss, threshold gain (for the cavity length of 300 μm), and transparency current density as a function of doping concentration in the n-type AlGaInAs barrier for the 1.3-μm MD-SC-MQW LDs. The theoretical and experimental results show that the optimum doping concentration of doped barriers is 5×10 ¹⁸ cm^-3. With this optimum condition, the 3.5-μm ridge-striped LDs without facet coating will exhibit a lower threshold current and a higher differential quantum efficiency of 18 mA and 52.3% under the CW operation as compared to those of 22 mA and 43% for the undoped active region, respectively. In addition, a high characteristic temperature of 70 K, a low slope efficiency drop of -1.3 dB between 20 and 70°C, and a wavelength swing of 0.4 nm/°C for the LDs operated at 60 mA and 8 mW can be obtained in the LDs with doped barriers     

Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes

For the first time, the impact of longitudinal photon density distribution and longitudinal carrier density distribution on the spectral linewidth re-broadening effect in single-electrode 1.55-/spl mu/m distributed feedback (DFB) laser diodes (LDs) is investigated experimentally in details. By optimizing the front-to-rear facet power ratio, the nonuniformity of the photon density distribution along the laser cavity is reduced, hence reducing the degree of longitudinal spatial hole burning (SHB). Using this optimized value of front-to-rear facet power ratio, the degree of longitudinal SHB can be further reduced through reduction of the nonuniformity of the longitudinal carrier density distribution by increasing the cavity length. As a result, the local stimulated emission is reduced, hence reducing linewidth re-broadening caused by longitudinal SHB. The outcomes of this analysis is being used fruitfully to design high-power 1.55-/spl mu/m DFB LDs exhibiting very narrow spectral linewidth of approximately 1.3 MHz at an output power of 175 mW under continuous-wave operation.     

GaInAsP/InP lasers with monolithically integrated monitoring photodiodes fabricated by inclined reactive ion etching

Monolithic fabrication of a GaInAsP/InP laser (LD) with a monitoring photodiode (PD) is described. LDs and PDs have etched facets fabricated by inclined reactive ion etching (RIE). The etched LD facing facet PD is perpendicular to the junction plane and the etched PD facet facing LD is inclined by 55 degrees to the plane by the 'windward-leeward effect' of the inclined RIE. Therefore, coupling efficiencies between LDs and PDs are uniform because the multireflection effect of double mirrors does not exist for the LD-PD devices with inclined PD facets. Typical CW threshold current ranges from 20 to 30 mA and light output power from a single facet exceeds 15 mW at 25 degrees C. A PD can detect about 2% of the light beam emitted from an LD facing it.<>     

High-power and low-threshold-current operation of 1.3 μm strain-compensated AlGaInAs/AlGaInAs multiple-quantum-well laser diodes

Low-threshold-current and high-temperature operation of 1.3 μm wavelength AlGaInAs/AlGaInAs strain-compensated multiple-quantum-well laser diodes (LDs) with a linearly graded index separate confinement heterostructure also made up of AlGaInAs has been successfully fabricated. The threshold current density and differential quantum efficiency are 400 A/cm² and 22% for the as-cleaved broad-area LDs with a 900 μm cavity length, respectively. The calculated internal quantum efficiency, internal optical loss, and threshold gain are 23%, 6.5 cm⁻¹, and 45 cm⁻¹, respectively. The threshold current and slope efficiency at room temperature for the 3 μm-ridge-stripe LDs without facet coating are 12 mA and 0.17 W/A, respectively. The peak wavelength is at 1295 nm with an injection current of 60 mA. With increasing the temperature up to 100 °C, the threshold current will increase up to 41 mA. The characteristic temperature is around 78 K in the range from 20 to 60 °C and 56 K in the range from 60 to 100 °C. The wavelength swing varied with temperature is 0.43 nm/°C for the LDs operated at 60 mA and room temperature.     

Superluminescent diodes with bent waveguide

Superluminescent diodes are fabricated with a bent waveguide to prevent optical feedback. The bent ridge waveguide is formed with one end normal to the cleaved facet and the other angled at 7/spl deg/ from the facet normal. The spectral ripple of these devices is around 10% at 6 mW output power. The farfield pattern emitted from the angled facet is crescent-shaped. As the device is set up in an external-cavity configuration, lasing operation is observed regardless of the additional 10.8 dB bending loss introduced by the bent waveguide.     

Room temperature performance of low threshold 1.34-1.44-/spl mu/m GaInNAs-GaAs quantum-well lasers grown by molecular beam epitaxy

Room temperature lasing emission at 1.338 and 1.435 /spl mu/m with threshold current densities of 1518 and 1755 A/cm/sup 2/, respectively, is obtained in broad area GaInNAs-GaAs laser diodes (LDs) grown by molecular beam epitaxy. The 1.338-/spl mu/m LDs show a power output per facet up to 0.20 W/A, a characteristic temperature (T/sub 0/) of 78 K, and an external transparency current density (J/sub tr/) of 0.77 kA/cm/sup 2/. Increasing the lasing wavelength to 1.435 /spl mu/m results in a larger J/sub tr/ of 1.16 kA/cm/sup 2/ and a lower T/sub 0/ of 62 K, due to larger nonradiative recombination. However, the 1.435-/spl mu/m LDs still display a power output per facet up to 0.15 W/A, and a high internal quantum efficiency of 52%. These improved performances are achieved without the need to use strain compensation layers, Sb as a surfactant during the quantum-well growth, or a postgrowth thermal anneal cycle.     

低波长漂移的电吸收调制DFB激光器

采用端面有效反射率法,从理论上计算了单片集成电吸收调制DFB激光器（Electroabsorption Modulated DFB Laser,EML）的腔面反射率、耦合强度（κL）对其波长漂移的影响.同时在实验中通过改变腔面的反射率来验证计算结果.理论与实验的结果表明：为提高EML的模式稳定性,必须减小调制器一端的反射率,同时增加DFB激光器的κL.最终我们采用选择区域生长（Selective Area Growth,SAG）的方法,制作了低光反馈出光面的单脊条形EML,在2.5Gb/s的非归零(NRZ)码调制下,经过280km的标准光纤传输后,没有发现色散代价.     

Novel design procedure of broad-band multilayer antireflectioncoatings for optical and optoelectronic devices

A novel design procedure of broad-band multilayer antireflection (AR) coatings for optical and optoelectronic devices is proposed. The design algorithm is based on the optical admittance detuning, with the bandwidth of finite reflectivity as a new merit function. Coating structures consist of only two materials with nonquarter-wave thicknesses. Numerical mappings on the four-layer structure showed four optimizing regions where an optimized four-layer AR coating on 1.55 μm GaInAs-AlGaInAs MQW semiconductor laser facet was predicted to have a broad bandwidth of 106 mm for a reflectivity of less than 10^-5. TiO₂ and SiO₂ were electron-beam (EB) evaporated to form the four-layer AR coating on glass and InP substrates with an ion-beam assist and a real time in situ optical thickness monitor and experimentally verify its broad-band performance     

1.3μm高增益偏振无关应变量子阱半导体光放大器

采用低压金属有机化学气相外延法 (LP MOVPE)生长并制作了 1 3μm脊型波导结构偏振无关半导体光放大器 (SOA) ,有源区为基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱 (4C3T)结构 ,压应变阱宽为 6nm ,应变量 1 0 % ,张应变阱宽为 11nm ,应变量 - 0 95 % ;器件制作成 7°斜腔结构以有效抑制腔面反射。半导体光放大器腔面蒸镀Ti3 O5/Al2 O3 减反 (AR)膜以进一步降低腔面剩余反射率至 3× 10 -4以下 ;在 2 0 0mA驱动电流下 ,光放大器放大的自发辐射 (ASE)谱的 3dB带宽大于 5 0nm ,光谱波动小于 0 4dB ,半导体光放大器管芯的小信号增益近 30dB ,在 12 80～ 1340nm波长范围内偏振灵敏度小于 0 6dB ,饱和输出功率大于 10dBm ,噪声指数 (NF)为 7 5dB。     

200K高特征温度的1.3μm AlInGaAs应变单量子阱激光器

在20～80℃范围内连续工作条件下,非对称波导层结构的1.3μm AlInGaAs/AlInAs单量子阱激光器的特征温度为200K,这是目前国内报道的相同有源材料、相同发射波长的激光器中最高的特征温度值.因此AlInGaAs是长波长光纤激光器的理想有源区材料.研究表明非对称波导结构能降低光吸收,提高激光器的高温特性和COD阈值.