1,721,325 research outputs found
DETERMINATION OF NONRADIATIVE RECOMBINATION COEFFICIENTS OF VERTICAL-CAVITY SURFACE-EMITTING LASERS FROM LATERAL SPONTANEOUS EMISSION
No full textA simple method to determine nonradiative recombination coefficients of vertical-cavity surface-emitting lasers is proposed and demonstrated. The dependence of the lateral spontaneous emission on the current density is used to determine the nonradiative recombination coefficients and the threshold carrier densities. In this scheme, the lateral spontaneous emission obtained from the nearest neighbor devices is analyzed. For 10-mu m diameter proton-implanted vertical-cavity surface-emitting lasers, the obtained nonradiative recombination coefficient is about 1.8 x 10(8) (-1), responsible for 25% of threshold current density. (C) 1995 American Institute of Physics.This work was supported by Opto-Electronics Research
Center
OPTICAL DISPERSION OF ALXGA1-XAS AT CRYSTAL-GROWTH TEMPERATURE
No full textThe authors thank Dr. Bun Lee, Gunho Lee, and Ingak
Hwang for helpful discussions
Trajectory planning and robust adaptive control for underactuated manipulators
No full textA stable, robust adaptive control method is proposed for underactuated manipulators in Cartesian space; Tt is considered that the passive joints have both no actuators and no brakes and thus swing freely
Dynamics and robust control of underactuated manipulators using brakes at passive joints
No full textA stable robust adaptive control method using the brakes equipped at passive joints is proposed for underactuated manipulators in joint space. It is considered that the passive joints have brakes instead of actuators
Bi-directional add/drop amplifier module for high-capacity WDM networks
No full textA bi-directional add/drop amplifier (BADA) module with a superior relative intensity noise (RIN) suppression capability has been realised based on a cost-effective dispersion compensation technique. A 14 x 10 Gbit/s bi-directional transmission over 200 km-long conventional SMF and channel-by-channel add/drop has been successfully demonstrated. The scalability of the BADA module is analysed
Very small oxide-confined vertical microcavity lasers with high-contrast AlGaAs-AlxOy mirrors
No full textWe report the photo-pumped lasing action from a very small oxide-confined 870-nm vertical microcavity lasers with high-contrast AlGaAs-AlxOy mirrors. The effective cavity length is as small as 0.37 mu m, and the oxide aperture size is 0.74 mu m, estimated from the blue-shift of lasing mode due to the lateral confinement. The observed blue-shift of the lasing mode is 13.4 nm, the largest one ever reported for vertical cavity lasers. The optical losses seem to be size-independent for these small microcavity lasers. Our results indicate the possibility of the ultimate microcavity of order of lambda(3).The authors thank M. J. Noble in AFIT/ENG for the helpful
discussions
Effect of carrier diffusion in oxidized vertical-cavity surface-emitting lasers determined from lateral spontaneous emission
No full textThe effect of carrier diffusion on threshold current is studied quantitatively for the oxide-aperturbed 780 nm vertical-cavity surface-emitting lasers (VCSEL) from the measured spontaneous emission, The oxide aperture size of 2-10 mu m is prepared and characterized, The diffusion coefficient of 4.6 cm(2)/s and the nonradiative recombination coefficient of 6.8x10(7)/s are obtained using the independence of the nonradiative recombination coefficient on the laser aperture size, The contribution of carrier diffusion loss is 42% of the threshold current for the 2 mu m VCSEL, The relative contribution of the diffusion becomes smaller for the larger devices as is expected. (C) 1997 American Institute of Physics.This work is supported by the research project for basic
science in KAIST
Adaptive variable structure controller with decreasing gain for nonlinear uncertain systems
No full textA novel adaptive variable structure controller (AVSC) is proposed for a class of nonlinear uncertain systems. The proposed method guarantees the occurrence of the sliding mode after the state hits the sliding hyperplane for the first time, even though the conventional AVSC could not achieve this. Furthermore, precise a priori knowledge of the bounds for the parametric uncertainties and external disturbances is not needed
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