Butt-Joint Monolithically Integrated DFB-LD/EA-MD Light Source for 10Gbit/s Transmission

This paper reports on the design,fabrication,and performance of an integrated electro-absorptive modulated laser based on butt-joint configuration for 10Gbit/s application.This paper mainly aims at two aspects.One is to improve the optical coupling between the laser and modulator;another is to increase the bandwidth of such devices by reducing the capacitance parameter of the modulator.The integrated devices exhibit high static and dynamic characteristics. Typical threshold current is 15mA,with some value as low as 8mA.Output power at 100mA is more than 10mW.The extinction characteristics,modulation bandwidth,and electrical return loss are measured.3dB bandwidth more than 10GHz is monitored.

Butt-joint regrowth method by MOCVD for integration of evanescent wave coupled photodetector and multi-quantum well semiconductor optical amplifier

We have realized integration of evanescent wave coupled photodetector(ECPD)and multi-quantum well(MQW)semiconductor optical amplifier(SOA)on MOCVD platform by investigating butt-joint regrowth method of thick InP/InGaAsP waveguides to deep etched SOA mesas.The combination of inductively coupled plasma etching and wet chemical etching technique has been studied to define the final mesa shape before regrowth.By comparing the etching profiles of different non-selective etchants,we have obtained a controllable non-reentrant mesa shape with smooth sidewall by applying one step 2 HBr:2 H_(3)PO_(4):K_(2)Cr_(2)O_(7)wet etching.A high growth temperature of 680℃is found helpful to enhance planar regrowth.By comparing the growth morphologies and simulating optical transmission along different directions,we determined that waveguides should travel across the regrowth interface along the[110]direction.The relation between growth rate and mask design has been extensively studied and the result can provide an important guidance for future mask design and vertical alignment between the active and passive cores.ECPD-SOA integrated device has been successfully achieved by this method without further regrowth steps and provided a responsivity of 7.8 A/W.The butt-joint interface insertion loss is estimated to be 1.05 dB/interface.

Experimental Investigation of Laser Welding Process in Butt-Joint Configurations

This paper presents an experimental investigation of laser welding low carbon galvanized steel in butt-joint configurations. The experimental work is focused on the effects of various laser welding parameters on the welds quality. The investigations are based on a structured experimental design using the Taguchi method. Welding experiments are conducted using a 3 kW Nd:YAG laser source. The selected laser welding parameters (laser power, welding speed, laser fiber diameter, gap between sheets and sheet thickness) are combined and used to evaluate the variation of four weld quality attributes (bead width, penetration depth, underfill and hardness) and to identify the possible relationship between welding parameters and weld physical and geometrical attributes. The effects of these parameters are studied using ANOVA to find their contributions to the variation of different weld characteristics. Plots of the main effects and the interaction effects are also used to understand the influence of the welding parameters. The results reveal that all welding parameters are relevant to bead width (BDW) and depth of penetration (DOP) with a relative predominance of laser power and welding speed. The effect of laser fiber diameter on penetration depth is insignificant. Typical gap-dependent weld shapes show that a small gap results in a narrower and deeper weld. Due to the standard sheared edge, an underfill between 5% and 10% occurs for no-gap experiments. The resulting hardness values are relatively similar for all the experimental tests.

Spotsize Converter Integrated DFB Laser Diode Using Selective Area Growth of MOCVD

The characteristics of thickness enhancement fact or and bandgap wavelength of selectively grown InGaAsP are investigated.A high thi ckness enhancement factor of 2.9 is obtained.Spotsize converter integrated DFB lasers are fabricated by using the technique of SAG.The threshold current is as low as 10.8mA.The output power is 10mW at 60mA without coating and the SMSR is 35.8dB.The vertical far field angle (FWHM) is decreased from 34° to 9°.The to lerance of 1dBm misalignment is 3.4μm vertically.

Sampled Grating DBR Lasers with 35nm Quasi-Continuous Tuning Range

We demonstrate a ridge waveguide sampled-grating distributed-feedback laser with quasi-continuous wavelength coverage over a 35nm range. The design is based on a 320nm-thick butt jointed passive waveguide optimized for carrier injection tuning. The butt-joint technology enable optimize the passive waveguide as well as active section. By tuning mirror sections,the laser provides 35nm tuning while maintaining 〉30dB sidemode suppression ratio.

Hybrid laser/arc welding of thick high-strength steel in different configurations

In this investigation, hybrid laser/arc welding （HLAW） was employed to join 8-mm-thick high-strength quenched and tempered steel （HSQTS） plates in the butt- and T-joint configurations. The influences of welding parame- ters, such as laser power, welding speed, stand-off distance （SD） between the arc of gas metal arc welding, and the laser heat source on the weld quality and mechanical properties of joints, were studied to obtain non-porous and crack-free fully-penetrated welds. The weld microstructure, cross- section, and mechanical properties were evaluated by an optical microscope, and microhardness and tensile tests. In addition, a finite element model was developed to investigate the thermal history and molten pool geometry of the HLAW process to join the HSQTS. The numerical study demon- strated that the SD had a paramount role in good synergy between the heat sources and the stability of the keyhole. For the butt-joint configuration, the results showed that, at a higher welding speed （35 mm/s） and optimum SD between the arc and laser, a fully-penetrated sound weld could be achieved. A non-porous weld in the T-joint configuration was obtained at a lower welding speed （10 mm/s）. Microstructural evaluations indicated that the formation of residual austenite and the continuous network of martensitic structure along the grain boundary through the heat affected zone were the primary reasons of the softening behavior of this area. This was confirmed by the sharp hardness reduction and failure behavior of the tensile coupons in this area.