HR-coated facet effect on the spectral characteristics of a three-section DBR tunable laser

High-relfection (HR)-coated facet effects on the spectral characteristics of a three-section distributed Bragg reflector (DBR) tunable laser are investigated theoretically, in which the output power emits to the DBR section. It is found that the output power to the DBR sectionP _DBR compared to the cleaved facet output powerP ₀ is nearly constant to some degree with increasing tuning current. Owing to the high-Q resonator, the HR-coated DBR laser showed a decrease in spectral linewidth. However, there is still linewidth broadening of the HR-coated DBR laser even though the rate of increase is smaller than that of the cleaved-facet DBR laser. In the case of output power emission to the DBR section, it is thought that the HR-coated effect can overcome the decrease in output power under frequency tuning, which is one of the most important drawbacks of DBR laser performance.     

The simulation of self-mixing interference effects in three-section DBR lasers

The self-mixing interference in three-section distributed Bragg reflector (DBR) lasers is analyzed based on the model of F-P cavity and coupling wave equation. The oscillating frequency and threshold variation are deduced. The influence of internal and external parameters on the output intensity and the inclination degree of waveform are discussed in simulation.     

A 10 Gb/s 1.5 μm Widely Tunable Directly Modulated InGaAsP/InP DBR Laser

We report 10 Gb/s data transmissions using a packaged two-section InGaAsP/InP distributed Bragg reflector(DBR) laser. The tunable DBR laser has a wavelength tuning range of 12.12 nm. The DBR laser has greater than 10.84 GHz 3-dB direct modulation bandwidth within the wavelength tuning range. The 10 Gb/s data transmissions are performed at up to a distance of 30-km.     

Wavelength stabilization of a distributed Bragg reflector laser diode by use of complementary current injection

We have demonstrated wavelength stabilization in an 821-nm AlGaAs three-section tunable distributed Bragg reflector (DBR) semiconductor laser diode (LD) that consists of active, phase-controlled, and DBR regions. We injected two separate, complementary currents into the active and the phase-controlled regions in the DBR-LD to suppress wavelength shift. This modulation method was applied to the LD fundamental wave in a second-harmonic-generation (SHG) laser, and the oscillating wavelength was maintained within the phase-matching acceptance range of the SHG device during modulation. A peak blue-violet light power of 62 mW was obtained for the ideal modulation waveform.     

Integrated waveguide Fabry-Perot microcavities with silicon/air Bragg mirrors

We demonstrate in-plane microfabricated Fabry-Perot cavities with cryogenically etched silicon/air distributed Bragg reflector (DBR) mirrors and integrated silicon-on-insulator rib waveguides. Several DBR configurations and cavity lengths were measured. Various devices exhibit Q=26963, FWHM=0.060 nm, finesse F=489, free spectral range FSR=81.7 nm, and DBR mirror reflectance R=99.4%. Thermo-optic tuning over 6.7 nm is also demonstrated.     

Circular grating DFB and DBR semiconductor lasers: threshold current analysis

The threshold current is analyzed for distributed feedback (DFB) and distributed Bragg reflector (DBR) semiconductor lasers with circular gratings. It is shown that in circular grating DFB lasers, the threshold current becomes minimum at a certain cavity radius, while in circular grating DBR lasers it increases monotonically as the active region radius increases.     

Self-aligned Coupled Waveguide Distributed Bragg Reflector Lasers

A novel self-aligned coupled waveguide (SACW) multi-quantum-well (MQW) distributed Bragg reflector (DBR) laser is proposed and demonstrated for the first time. By selectively removing the MQW layer and leaving the low SCH/SACW layer the Bragg grating is partially formed on this layer. By optimizing the thickness of the low SCH/SACW layer, a～80% coupling efficiency between the MQW gain region and the passive region are obtained. The typical threshold current of the SACW DBR laser is 39 mA, the slope efficiency can reach to 0.2 mW/mA and the output power is more than 20 mW with a more than 30dB side mode suppression ratio.     

Self-aligned Coupled Waveguide Distributed Bragg Reflector Lasers

A novel self-aligned coupled waveguide (SACW) multi-quantum-well (MQW) distributed Bragg reflector (DBR) laser is proposed and demonstrated for the first time. By selectively removing the MQW layer and leaving the low SCH/SACW layer the Bragg grating is partially formed on this layer. By optimizing the thickness of the low SCH/SACW layer, a-80% coupling efficiency between the MQW gain region and the passive region are obtained. The typical threshold current of the SACW DBR laser is 39 mA, the slope efficiency can reach to 0.2 mW/mA and the output power is more than 20 mW with a more than 30dB side mode suppression ratio.     

Transmission of 20 Gb/s PAM-4 signal over 20 km optical fiber using a directly modulated tunable DBR laser

We report 20 Gb/s transmission of four-level pulse amplitude modulation(PAM) signal using a directly modulated tunable distributed Bragg reflector(DBR) laser. Transmission distance over 20 km was achieved without using optical amplifiers and optical dispersion compensation modules. A wavelength tuning range of 11.5 nm and a 3 dB bandwidth greater than 10 GHz over the entire wavelength tuning range were obtained.     

Tunable DBR Lasers Fabricated by Selective Area Growth Technique

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　ＴｈｅｔｕｎａｂｌｅＤＢＲｌａｓｅｒｓｗｉｔｈｖａｒｉｏｕｓｇｒａｔｉｎｇｒｅｆｌｅｃｔｏｒｓｈａｖｅｂｅｅｎｆａｂｌｉｃａｔｅｄｔｏａｃｈｉｅｖｅｌａｒｇｅｔｕｎｉｎｇｒａｎｇｅａｎｄｓｔａｂｌｅｓｉｎｇｌｅｍｏｄｅｏｐｅｒａｔｉｏｎ[1,2 ] .Ｈｏｗｅｖｅｒ,ｔｈｅｓｅｄｅｖｉｃｅｓｃｏｎｔａｉｎｃｏｍｐｌｉｃａｔｅｄｇｒａｔｉｎｇｓａｎｄｗａｖｅｇｕｉｄｅｓ,ａｎｄｉｎｍｏｓｔｃａｓｅｓｔｈｅｙｈａｖｅｓｅｖｅｒａｌｔｕｎｉｎｇｅｌｅｃｔｒｏｄｅｓｏｐｅｒａｔｉｏ…     

Tunable DBR Lasers Fabricated by Selective Area Growth Technique

The tunable ridge waveguide distributed Brag g reflector (DBR) lasers grown by selective area growth and designed for WDM communication systems at 1.55 μm is reported. The threshold of DBR lasers is 62 mA and the output power is more than 8 mW; the isolation resistance between the active region and Bragg region is 30 kΩ; the tuning range is 6.5 nm which can provide 6 WDM channels with a 100 GHz spacing; in thetuning range, the single mode suppression ratio (SMSR) is more than 32 dB and the output power variation of different wavelengths is less than 3 dB.     

Dual-wavelength distributed Bragg reflector semiconductor laser based on composite resonant cavity

We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector (DBR) composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing (QWI) technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.     

Dual-wavelength distributed Bragg reflector semiconductor laser based on a composite resonant cavity

We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector (DBR) composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing (QWI) technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.     

波长可调谐取样光纤光栅激光器的输出特性研究

建立了具有两个取样周期略有不同的取样光纤光栅反射镜的Vernier波长调谐机制的光纤分布布拉格反射式激光器的数值仿真模型,对激光器的输出特性进行了分析. 研究了激光器输出特性随着激光器前后光栅反射镜波长以及前后光栅反射镜反射率的变化关系. 提出了对两取样光栅反射率的优化配置方案,可以使输出激光的边模抑制比有所提高;同时对波长调节方式也进行了探讨;进行了实验研究. 关键词： 取样光纤光栅 光纤激光器 波长可调谐激光器     

温度对Al0.5Ga0.5As/AlAs分布布喇格反射器的反射谱影响

采用光学传输矩阵理论对Al0.5Ga0.5As/AlAs材料分布布喇格反射器(DBR)进行理论研究,分析了－10℃到100℃的范围内,温度变化对不同DBR结构的反射光谱影响.结果表明：随着温度的升高,传统20周期DBR的反射光谱向长波长方向移动,速率约0.05 nm/℃,其中由线热膨胀系数带来的影响小于0.001 nm/℃.当传统DBR的周期数增大时,温度对DBR光谱反射率的影响在减小,同时DBR的反射谱峰值波长发生红移.为了降低温度对DBR反射光谱的影响,提出一种新型的复式DBR结构.分析指出：该复式DBR比传统DBR有更大的反射光谱半峰宽,基本能覆盖同温度的AlGaInP LED电致发光光谱,这对提高LED的出光效率有现实意义.     

Wavelength Tuning in the Two-Section Distributed Bragg Reflector Laser Fabricatedby Quantum-Well Intermixing

The two-section tunable ridge waveguide distributed Bragg reflector (DBR) lasers fabricated by strained InxGa1-xAsyP1-y. The threshold current of the laser is 51mA. The tunable range of the laser is 3.2nm and the side mode suppression ratio (SMSR) is more 38dB.     

Design of a monolithic tunable laser based on equivalent-chirp grating reflectors

A Vernier-tuned distributed Bragg reflector (DBR) semiconductor laser is an effective monolithic approach for wide wavelength tunability, at the expense, however, of costly electron-beam lithography during fabrication. In this Letter, a tunable laser design with equivalent-chirp based, flat-top envelope grating reflectors is proposed that can be implemented easily by conventional two-beam interference lithography. The principle is described, and a detailed design shows uniform output power (0.08 dB variation) and excellent side-mode suppression ratio (47 dB minimum) within a wide tuning range (>32 nm) through numerical simulation.     

Modeling of resistance characteristics of a continuously-graded distributed Bragg reflector in a 980-nm vertical-cavity surface-emitting laser

The resistance characteristics of a continuously-graded distributed Bragg reflector(DBR) in a 980-nm verticalcavity surface-emitting laser(VCSEL) are modeled in detail.The junction resistances between the layers of both the p-and n-DBR mirrors are analysed by combining the thermionic emission model and the finite difference method.In the meantime,the intrinsic resistance of the DBR material system is calculated to make a comparison with the junction resistance.The minimal values of series resistances of the graded p-and n-type DBR mirrors and the lateral temperature-dependent resistance variation are calculated and discussed.The result indicates the potential to optimize the design of the DBR reflectors of the 980-nm VCSELs.     

Simulation and fabrication study of porous silicon photonic crystal

The present work reports design and fabrication of porous silicon based one-dimensional (1D) photonic crystal. Distributed Bragg reflector (DBR) is a 1D photonic crystal composed of multilayer stack of high and low refractive index layers. Design of porous silicon DBR is a complex one and requires appropriate control in optical parameters of its constituent layers. In order to design DBR, two porous silicon single layer samples were fabricated using current density of 10 and 50 mA/cm². Optical characterization of single layer samples showed series of interference fringes. Reflective interferometric Fourier transform spectroscopy (RIFTS) method was employed to determine optical constants of porous silicon single layers. DBR simulation was carried out based on transfer matrix method. DBR was then fabricated using optical parameters obtained from RIFTS method. Reflection bandwidth of prepared DBR was found to be 216 nm, which is comparable to the simulated value of 203 nm.     

Absorption loss influence on optical characteristics of multilayer distributed Bragg reflector: wavelength-scale analysis by the method of single expression

Electrodynamical model of a classical distributed Bragg reflector (DBR) consisting of alternating quarter-wave layers of high and low permittivity is considered at the plane wave normal incidence. Reflective characteristics of DBR possessing absorption loss in constituting layers are analysed via correct wavelength-scale boundary problem solution by the method of single expression (MSE). Analysis of optical field and power flow density distributions within the lossy DBR structures explained the peculiarities of their reflective characteristics. Optimal configurations of lossless and lossy DBRs are revealed. Specific DBR structures possessing full transparency at definite number of layers are also analysed.