Combined analytical-finite difference time-domain full wave simulation of mode-locked vertical-extended-cavity semiconductor lasers (original) (raw)
Related papers
Semiconductor Lasers and Laser Dynamics II, 2006
We present a comprehensive description of electrically-driven vertical-external-cavity surface-emitting diode lasers (VECSELs) at 980 nm, mode-locked by saturable absorber mirrors. A novel partially-integrated time-domain model combines accuracy and flexibility, allowing for a semi-analytical stability analysis of the compoundcavity modes, tracking the mode-locking onset and an optimization analysis. The linear stability analysis of the compound-cavity modes indicates that single mode solutions exist and are stable only in a limited current range around threshold. Increasing the current above this current level leads to a multimode solution through a Hopf bifurcation. This bifurcation point is followed by a continuous transition leading from harmonic oscillations to fully-developed pulses that correspond to the mode-locked solution. We obtain stable, fully-developed modelocked pulses of few tens of picoseconds at 15 GHz repetition rate in good agreement with reported experimental results. We discuss the dependence of the mode-locking regimes on the reflectivity of the distributed Bragg reflectors, spot area of the spatial mode, and number of quantum wells in the emitter and absorber cavities. The optimization analysis reveals that, in order to favor the mode-locking onset, the effective coupling between the emitter and saturable absorber cavities has to be optimized through the standing wave pattern in the composite cavity and spot-area of the spatial modes.
Journal of The Optical Society of America B-optical Physics, 2003
Traditionally, one can calculate the update coefficients of the finite-difference time-domain algorithm at material interfaces by averaging the material properties of both sides, which leads to numerical inaccuracies of the reflection depending on the grid resolution. We propose a novel method to calculate the update coefficients such that the algorithm exactly fulfills the boundary conditions at a frequency of optimization, which allows a significant increase in grid spacing while limiting the numerical error. Using the proposed method, we reduced the computational expenses for the full-wave simulation of vertical-cavity surface-emitting lasers such that large structures can be treated without the need to exploit rotational symmetry. The method is demonstrated with the help of several examples.
Mode-locking dynamics in electrically driven vertical-external-cavity surface-emitting lasers
IEEE Journal of Quantum Electronics, 2000
We develop a novel description of electrically driven vertical-external-cavity surface-emitting semiconductor lasers (VECSELs) mode-locked by saturable absorber mirrors. Our approach is based on an analytical solution of the bidirectional traveling-wave equations for fundamental transverse mode operation. The resulting time-domain equations describe the evolution of the electric fields and carrier-densities at the quantum-well layers of the emitter and absorber structures which are coupled through delayed boundary conditions. For the design considered, we obtain stable mode-locked pulses of few tens of picoseconds at 15-GHz repetition rate in agreement with recently reported experimental results.
Simulation of passively mode-locked all-quantum-dot electrically-driven VECSEL
2018 35th National Radio Science Conference (NRSC), 2018
Passively mode-locked all-quantum-dot (QD) electrically-driven vertical external cavity surface-emitting laser (VECSEL) emitting at 1.3 μm is newly proposed at a repetition frequency of 45 GHz. The structure consists of QD-VECSEL (gain section) and QD semiconductor saturable absorber mirror (SESAM), which acts, also, as an output-coupler (OC). A time-domain travelling-wave model (TDTW) is used to simulate the proposed structure. The simulation results show the possibility of obtaining mode locking from the newly proposed structure, e.g., stable laser pulses can be obtained with a time width of 10 ps at a repetition rate of 45 GHz under specific laser structure parameters.
Finite element simulation of the optical modes of semiconductor lasers
physica status solidi (b), 2010
In the present article we investigate optical near fields in semiconductor lasers. We perform finite element simulations for two different laser types, namely a super large optical waveguide (SLOW) laser, which is an edge emitter, and a vertical cavity surface emitting laser (VCSEL). We give the mathematical formulation of the different eigenvalue problems that arise for our examples and explain their numerical solution with the finite element method. Thereby, we also comment on the usage of transparent boundary conditions, which have to be applied to respect the exterior environment, e.g., the very large substrate and surrounding air. For the SLOW laser we compare the computed near fields to experimental data for different design parameters of the device. For the VCSEL example a comparison to simplified 1D mode calculations is carried out.
Passively modelocked surface-emitting semiconductor lasers
Physics Reports, 2006
This paper will review and discuss pico-and femtosecond pulse generation from passively modelocked vertical-external-cavity surface-emitting semiconductor lasers (VECSELs). We shall discuss the physical principles of ultrashort pulse generation in these lasers, considering in turn the role played by the semiconductor quantum well gain structure, and the saturable absorber. The paper will analyze the fundamental performance limits of these devices, and review the results that have been demonstrated to date. Different types of semiconductor saturable absorber mirror (SESAM) design, and their characteristic dynamics, are described in detail; exploring the ultimate goal of moving to a wafer integration approach, in which the SESAM is integrated into the VECSEL structure with tremendous gain in capability. In particular, the contrast between VECSELs and diode-pumped solid-state lasers and edge-emitting diode lasers will be discussed. Optically pumped VECSELs have led to an improvement by more than two orders of magnitude to date in the average output power achievable from a passively modelocked ultrafast semiconductor laser.
Passive Mode-Locking and Tilted Waves in Broad-Area Vertical-Cavity Surface-Emitting Lasers
IEEE Journal of Selected Topics in Quantum Electronics, 2015
We show experimentally and theoretically that an electrically biased 200 µm multi-transverse mode Vertical-Cavity Surface-Emitting Laser can be passively mode-locked using optical feedback from a distant Resonant Saturable Absorber Mirror. This is achieved when one cavity is placed at the Fourier plane of the other. Such non conventional optical feedback leads to the formation of two tilted plane waves traveling in the external cavity with opposite transverse components and alternating in time at every round-trip. Each of these plane waves gives birth to a train of mode-locked pulses separated by twice the external cavity round-trip, while the two trains are time shifted by a round-trip. A large portion of the transverse section of the device contributes to mode-locked emission leading to pulses of approximately 1 W peak power and 10 ps width. We discuss how inhomogeneities in the transverse section of the saturable absorber select the emitted tilted waves, thus leading to tunable emission over 4 nm.
A comprehensive circuit-level model of vertical-cavity surface-emitting lasers
Journal of Lightwave Technology, 1999
The increasing interest in vertical-cavity surfaceemitting lasers (VCSEL's) requires the corresponding development of circuit-level VCSEL models for use in the design and simulation of optoelectronic applications. Unfortunately, existing models lack either the computational efficiency or the comprehensiveness warranted by circuit-level simulation. Thus, in this paper we present a comprehensive circuit-level model that accounts for the thermal and spatial dependence of a VCSEL's behavior. The model is based on multimode rate equations and empirical expressions for the thermal dependence of the activelayer gain and carrier leakage, thereby facilitating the simulation of VCSEL's in the context of an optoelectronic system. To confirm that our model is valid, we present sample simulations that demonstrate its ability to replicate typical dc, small-signal, and transient operation, including temperature-dependent lightcurrent (LI) curves and modulation responses, multimode behavior, and diffusive turn-off transients. Furthermore, we verify our model against experimental data from four devices reported in the literature. As the results will show, we obtained excellent agreement between simulation and experiment.
Optical and Quantum Electronics, 2017
A generalized rate equation model is used to simulate the interrelated amplitude and frequency modulation properties of Electrooptically Modulated Vertical Compound Cavity Surface Emitting Semiconductor Lasers in both large and small signal modulation regimes. It is shown that the photon lifetime in the modulator subcavity provides the ultimate limit for the 3 dB modulation cutoff frequency. It is shown that there is an optimum design (number of periods) of both the intermediate and top multistack reflectors to maximise the large-signal modulation quality.