Search query: laser diode thershold quasi-Fermi level

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author_names: Ding Li

Liefeng Feng

Wei Yang

Xiufang Yang

Xiaodong Hu

Cunda Wang
title: Redefinition the quasi Fermi energy levels separation of electrons and holes inside and outside quantum wells of GaN based multi quantum well semiconductor laser diodes
year: 2020

author_names: Dorin Dadarlat

Rodica M Candea

M Barlea
title: Majority carrier concentration and quasi Fermi level for Pb1 xSnxTe DH diode lasers
year: 1983

abstract: We show that the bifurcations between dynamical states originating in the nonlinear dynamics of an external cavity semiconductor laser at constant current can be detected by its terminal voltage V. We experimentally vary the intensity fed back into the gain medium by the external cavity and show that the dc component V(dc) of V tracks the optical intensity based bifurcation diagram. It is shown using computational results based upon the Lang Kobayashi model that whereas optical intensity accesses the dynamical state variable |E| V is related to population inversion carrier density N. The change in feedback strength affects N and thereby the quasi Fermi energy level difference at the p i n junction band gap of the gain medium. The change in the quasi Fermi energy level thereby changes the terminal voltage V. Thus V is shown to provide information on the change in the dynamical state variable N, which complements the more conventionally probed optical intensity.
author_names: Aakash A Sahai

B Y Kim

Daeyoung Choi

Alexandre Locquet

David S Citrin
title: Mapping the nonlinear dynamics of a laser diode via its terminal voltage.
venue: Optics letters
year: 2014

abstract: Analysis of spontaneous emission spectra of GaInP quantum well laser diodes above and below threshold show that the quasi Fermi level separation pins within the quantum wells but not throughout the whole device structure. By reproducing the temperature and cavity length dependence of the external differential efficiency using these measurements it is shown that a value of internal differential efficiency which is nonunity is due to current spreading and incomplete carrier injection and that the temperature dependence is due to the temperature dependence of the efficiency with which carriers are injected into the quantum well.
author_names: Peter M Smowton

Peter Blood
title: Fermi level pinning and differential efficiency in GaInP quantum well laser diodes
year: 1997

abstract: Signal monitoring characteristics of terminal voltage change across laser diode optical switches (LDSW) have been studied. The terminal voltage changes are caused by the photovoltaic effect in the OFF state and by the quasi Fermi level change in the ON state. The baseband frequency response characteristics are analyzed by small signal analysis and coincide well with the measured characteristics. The 6 dB down frequency response bandwidths are verified to be very wide in both the ON and OFF states.
author_names: Masahiro Ikeda
title: Signal monitoring characteristics for laser diode optical switches
year: 1985

abstract: Signal monitoring characteristics of terminal voltage change across laser diode optical switches (LDSW) have been studied. The terminal voltage changes are caused by the photovoltaic effect in the OFF state and by the quasi Fermi level change in the ON state. The baseband frequency response characteristics are analyzed by small sig nal analysis and coincide well with the measured characteristics, The 6 dB down frequency response bandwidths are verified to be very wide in both the ON and OFF states.
author_names: Nippon Telegraph
title: Signal Monitoring Characteristics for Laser Diode Optical Switches
year: 1985

abstract: Abstract Two dimensional semiconductors have emerged as promising candidates for next generation optoelectronics due to their excellent carrier transport and strong light matter interaction. Meanwhile, the feasibility of arbitrary van der Waals integration enables the construction of devices with designable interface properties. In this work, WSe2/WS2 heterostructures with type II band alignment were fabricated for high performance self powered photodetector and photovoltaics. Due to the ambipolar nature of WSe2, the junction property could be efficiently modulated with electrostatic doping. Under optimized gate voltage and 532 nm laser illumination, the heterojunction yields a high open circuit voltage of 0.58 V, the power conversion efficiency of 2.4% and external quantum efficiency of 50.2% The modulation of the photovoltaic response is demonstrated to be a combined effect of quasi Fermi level tuning at the interface and channel conductivity change. Moreover, the diode exhibits spectral photoresponse from visible to the near infrared region when it functions as a self powered photodetector. The photoresponsivity reaches 216 mA/W and the rise and fall time are 80 ms and 90 ms, respectively. This work not only advances our fundamental understanding of device physics in van der Waals solar cells but also uncovers the great potential applications of WSe2/WS2 heterojunction in solar energy conversion and photodetectors.
author_names: Pei Lin

Jinke Yang
title: Tunable WSe2/WS2 van der Waals heterojunction for self powered photodetector and photovoltaics
venue: Journal of Alloys and Compounds
year: 2020

abstract: Owing to the dependence of the difference of quasi Fermi levels on the carrier densities inside the diode, it is anticipated that, accompanying the appearance of an optical hysteresis loop on the P v (output power oscillation frequency) curve of a tunable external cavity semiconductor laser, a hysteresis loop of the voltage across (or current passing) the diode should be expected.
author_names: Yan Deng

Jianguo Chen

Dayi Li
title: Bistability of current passing diode of a tunable external cavity semiconductor laser
year: 2002

abstract: We present an efficient 3D simulation method for a nitride based visible light laser diode. The method involves the separation of the overall device simulation into coupled simplified models for the quantum wells, thep n junction, the bulk regions, and the thermal environment, each solved on a different mesh. I. SIMULATION PROCEDURE Drift diffusion simulation of complex 3D laser structures is a timeand resource intensive computational task. In order to accomplish a relatively fast 3D simulation of the laser diode, the laser simulation problem is separated into a set of subproblems, each of which can be solved on a different spatial domain [1] [2] The coupling between these sub problems is generally weak and can be restricted to a subset of the points on the larger domain. The sub problems are as follows, in order of increasing domain size: quantum well density of states, stimulated and spontaneous recombination in the k p approximation [3] p n junction recombination and optical gain in the quasiequilibrium approximation; bulk region carrier transport in the unipolar drift current approximation; optical mode calculation and a photon rate equation; thermal transport simulation using the continuity equation for heat flux. Each of these sub problems is described in more detail below. The quantum well density of states and recombination rates are calculated using a 6 band k *p solver including strain. The self consistent electric potential (including the bending due to piezoelectric and spontaneous polarization fields) is passed to thek *p solver from the quasi equilibriump n junction solver described in the next paragraph. The Hamiltonian is discretized using the real space finite difference procedure, and solved to obtain the eigenstates in the well. The bound state energies and wavefunctions are used in conjunction with the electron and hole quasi Fermi levels passed from the p n junction solver to calculate the dark recombination, spontaneous recombination, and optical gain of the quantum well. The p n junction is simulated using a set of parallel 1D models in the quasi equilibrium approximation. Each 1D model represents a patch of the p n junction, as shown in Fig. 1. The recombination and gain of a p n junction patch are calculated as follows. Starting from equilibrium, the strain and polarization of thep n junction region are calculated, and the nonlinear 1D Poisson equation with self consistent electron and hole concentrations is solved in the growth direction using the finite element discretization procedure [4] Although the p n junction requires fine spatial meshing, the use of 1D models greatly reduces the problem size, while neglecting current spreading in the active layer. The bias applied to the patch is increased in steps, and the electron and hole quasiFermi levels are assumed to be spatially invariant and equal to then side andp side Fermi levels, respectively. The nonlinear Poisson equation is solved again for each bias step. The dark recombination, spontaneous recombination, and optical gain of the active layer patch are calculated and stored in a look up table for a range of applied bias conditions and temperatures. This data is later used as described in the next paragraph. The carrier transport in the bulk regions of the device bounding the active region are modeled in 3D, in order to obtain current spreading and series resistance in complex laser diode structures. The drift continuity equation is solved for the majority carrier population using the finite element discretization procedure. At the boundaries of the p n junction region, the current through each p n junction patch is obtained from the recombination rates and optical gain from the lookup table described above, along with the photon number from the photon rate equation: j e(R R gNG) (1) whereR are the dark/radiative spontaneous recombination rates,N is the number of photons in the resonator, G andg are the modal gain and the overlap factor, respectively. The optical mode calculation, necessary to calculate modal overlap factors and the photon lifetime of the lasing mode, can be carried out using a variety of approaches, e.g. [5] The photon rate equation is given by many authors, e.g. [6] The thermal transport simulation is modeled using a thermal continuity equation [7] Heat generation due to Joule heating is calculated in the bulk regions, while the heat generation in the p n junction region is calculated from energy balance considerations: the total power dissipated in the p n junction region minus the power loss due to optical recombination. The thermal continuity equation is discretized using finite elements, and the mesh is a superset of the mesh used for bulk carrier transport. Self consistency between all the layers of models is achieved by iteration. The active layer and bulk transport are solved simultaneously using the Newton method [8] while the NUSOD 2009 Postdeadline Paper
author_names: Michael Povolotskyi

B J Connors

Benjamin Klein
title: Efficient multiscale simulation of InGaN laser diodes
year: 2018

abstract: We identify that the stimulated emission of GaN laser diodes (LDs) emerges far below the traditionally recognized threshold from both optical and electrical experiments. Below the threshold, the linear polarized stimulated emission has been the dominating part of overall emission and closely related to resonant cavity. Its intensity increases super linearly with current while that of spontaneous emission increases almost linearly. Moreover, the separation of quasi Fermi levels of electrons and holes across the active region has already exceeded the photon emission energy, namely, realized the population inversion.
author_names: Ding Li

Hua Zong

Wei Yang

Liefeng Feng

Juan He

Weimin Du

Cunda Wang

Ya-Hong Xie

Zhijian Yang

Bo Shen

Guoyi Zhang

Xiaodong Hu
title: Stimulated emission in GaN based laser diodes far below the threshold region.
venue: Optics express
year: 2014