Structure optimisation of modern GaAs-based InGaAs/GaAs quantum-dot VCSELs for optical fibre communication

Abstract

Room-temperature (RT) continuous-wave (CW) performance of modern 1300-nm oxide-confined In(Ga)As/GaAs quantum-dot (QD) vertical-cavity surface-emitting diode lasers (VCSELs) taking advantage of many QD sheets is investigated using our comprehensive self-consistent simulation model to suggest their optimal design. Obviously, quantum dots should be as uniform as possible and as dense as possible to ensure high enough optical gain. Besides, our simulation reveals that efficient and uniform current injection into VCSEL active regions necessary to enhance excitation of the desired fundamental LP01 mode is accomplished in the VCSEL configuration with the broad-area bottom contact and the ring upper one as well as with the oxide aperture localized within the first period of the upper p-type DBR. The doping of the DBR mirrors is chosen as a compromise between their high enough electrical conductivity and low enough free-carrier absorption. The oxide aperture is additionally introducing the radial optical waveguiding. Moreover, our analysis has been concluded that VCSEL active regions should be composed of at least 9 QD sheets to acquire efficient RT CW operation. Furthermore, rather longer optical cavities are recommended in this case because localization of QD sheets should be adjusted to the anti-node positions of the optical cavity standing wave.

Time-Domain Travelling-Wave Model for Quantum Dot Based Vertical Cavity Laser Devices

“…Core refractive index is the refractive index of the layer material, while cladding refractive index is lower than that of the core because of the presence of the oxide layer with low refractive index. The core refractive indices of different materials are assumed to be 3.4109, 2.9514, 2.9185, 3.4504, and 3.4132 for GaAs, Al 0.9 Ga 0.1 As, Al 0.98 Ga 0.02 As, In(Ga)As (QW+QD) Layer, and Cavity (GaAs barrier & (QW+QD)), respectively [12]. The top mirror is terminated by air.…”

“…This stopband is much wider than the range of variation of the wavelength due to temperature change. Finally, the absorption loss coefficient in each layer of the device is assumed as follows [12]: 1.6457 cm −1 , 1.1861 cm −1 for (n-Al 0.9 Ga 0.1 As/n-GaAs), respectively. 0.85 cm −1 , 3.0428 cm −1 for (p-Al 0.9 Ga 0.1 As/p-GaAs), respectively.…”

“…In [11], finite-difference time-domain (FDTD) method is used together with QD Maxwell-Bloch equations to find electric field propagation and microscopic carrier dynamics. A complex model is presented in [12] to simulate room temperature threshold operation of GaAs-based QD VCSEL where the effective frequency method is used for optical modeling, and 3D finite-element method is used for both electrical and thermal modelings. A time-domain travelling-wave (TDTW) model is developed in [13] to describe the dynamic behavior of quantum-well (QW) based VCSEL.…”

VCSEL structures used to suppress higher-order transverse modes

“…They may emit not only (standard for arsenide devices) 850−nm radiation [4], but also ultraviolet one [5][6][7] with the aid of nitrides, the visible red 680−nm radiation [8] (phos− phide lasers) and even the 1.3−μm [9] and 1.55 μm [10] radi− ation used in a fibre optical communication. However in all of them, the problem with a mode selectivity is one of the most difficult to overcome.…”

GaAs/AlGaAs photonic crystals for VCSEL-type semiconductor lasers

“…Optical in− terconnection will be one major method to upgrade intercon− nect performance due to their advantageous high−speed data transfer capability in a small form factor with low crosstalk at high density. PhC VCSELs are promising light sources for optical interconnections due to very low power consumption [1][2][3] and strong discrimination of higher order modes which contributes to high−speed operation [4][5][6][7]. Furthermore, PhC VCSELs allow for high−density two−dimensional array, low crosstalk, and low production costs.…”