Using numerical simulation, the search for designs of asymmetric barrier layers (ABLs) in a laser diode with a GaAs waveguide emitting at a wavelength of λ = 980 nm is carried out. A pair of ABLs ...adjoining the active region on both sides blocks undesired charge-carrier flows and suppresses parasitic spontaneous recombination in the waveguide layers. Optimal designs of ABLs based on AlGaAsSb and GaInP for blocking electrons and holes, respectively, are proposed, which make it possible to reduce the parasitic recombination current down to less than 1% of the initial value. To suppress electron transport, an alternative structure based on three identical AlInAs barriers is also proposed. The GaAsP spacer layers separating these barriers from each other have different thicknesses. Due to this, the set of quasibound (resonant) states is formed in each spacer layer that is different from the set of states of the neighboring spacer layer. As a result, the resonant tunneling channels are blocked, and the parasitic electron flow is reduced by several tens of times in comparison with the case of spacers of identical thickness.
Gain saturation in a semiconductor optical amplifier with an array of quantum dots is studied analytically and by numerical simulation on the basis of an analysis of rate equations. It is shown that, ...at a moderate injection level, the saturation power increases in proportion to the current density, and then reaches its maximum value, limited by the rate of carrier delivery to the ground state and by the number of quantum dots interacting with photons. Expressions are proposed that allow explicit description of the dependence of the saturation power on current and its relationship with the internal parameters of the active region.
We demonstrate a record low threshold current density of 250 A/cm
2
in a quantum dot microdisk laser with a 31-μm diameter operating at room temperature in continuous wave regime without temperature ...stabilization. This low threshold current density is very close to the transparency current density estimated in broad-area edge-emitting lasers made of the same epitaxial wafer.
The linewidth enhancement factor (LEF) of an InAs/InGaAs quantum dot Fabry-Pérot laser in a wide wavelength range from 1110 to 1300 nm, including ground state (GS) and exited state (ES) bands, is ...studied. LEF spectra were derived from amplified spontaneous emission spectra measured below the threshold in the pulse regime. The ES optical transition is characterised by significantly lower values of the LEF (≤0.54) as compared to the GS (≥1.21). Moreover, a zero LEF is observed within the ES spectral band. At sufficiently high currents, a near-zero LEF (|α| ≤ 0.1) is achieved in a wide spectral interval from 1146 to 1175 nm, in which the optical gain is not less than 9 cm−1.
Virtual cavity in distributed Bragg reflectors Shchukin, V A; Ledentsov, N N; Kalosha, V P ...
Optics express,
2018-Sep-17, 2018-09-17, 20180917, Letnik:
26, Številka:
19
Journal Article
Recenzirano
Odprti dostop
We show theoretically and experimentally that distributed Bragg reflector (DBR) supports a surface electromagnetic wave exhibiting evanescent decay in the air and oscillatory decay in the DBR. The ...wave exists in TM polarization only. The field extension in the air may reach several wavelengths of light. Once gain medium is introduced into the DBR a novel class of diode lasers, semiconductor optical amplifiers, light-emitting diodes, etc. can be developed allowing a new type of in-plane or near-field light outcoupling. To improve the wavelength stability of the laser diode, a resonant cavity structure can be coupled to the DBR, allowing a coupled state of the cavity mode and the near-field mode. A GaAlAs-based epitaxial structure of a vertical-cavity surface-emitting laser (VCSEL) having an antiwaveguiding cavity and multiple GaInAs quantum wells as an active region was grown and processed as an in-plane Fabry-Pérot resonator with cleaved facets. Windows in the top stripe contact were made to facilitate monitoring of the optical modes. Three types of the optical modes were observed in electroluminescence (EL) studies under high current densities > 1 kA/cm
. Mode A with the longest wavelength is a VCSEL-like mode emitting normal to the surface. Mode B has a shorter wavelength, emitting light at two symmetric lobes tilted with respect to the normal to the surface in the direction parallel to the stripe. Mode C has the shortest wavelength and shifts with a temperature at a rate 0.06 nm/K. Polarization studies reveal predominantly TE emission for modes A and B and purely TM for mode C in agreement with the theory. Spectral position, thermal shift and polarization of mode C confirm it to be a coupled state of the cavity mode and near-field DBR surface-trapped mode.
In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are intended to prevent bipolar population of the waveguide layers, hence, to ...suppress parasitic recombination in them. A theoretical model of a laser with ABLs, based on rate equations which acknowledge undesirable carrier leakage inevitable in lasers of this type implemented in practice, is proposed. Solutions to equations are obtained for the steady-state case. By the example of an InGaAs/GaAs quantum-well laser (lasing wavelength λ = 980 nm), the effect of leakages through ABLs on the device characteristics is studied. The parasitic-flux suppression ratios
C
of ABLs which are required to prevent the adverse effect of waveguide recombination are estimated. In the case at hand, the effect of ABLs becomes appreciable at suppression ratios of
C
≥ 10
2
. To suppress 90% of the parasitic current,
C
should be 2.3 × 10
4
. The effect of ABLs on useful carrier fluxes arriving at the active region is also studied.
Abstract
Epi-side down bonding on a silicon substrate of AlGaAs/GaAs microdisk lasers is presented. A heterostructure with coupled large optical cavities enables location of an InGaAs quantum dot ...active region at a distance of ∼1
µ
m from the heterostructure surface. The thermal resistance was reduced to 0.2 and 0.1 K mW
−1
for disks of 30 and 50
µ
m in diameter, respectively. The maximum continuous-wave power limited by the thermal rollover is more than doubled after bonding.
A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide
p
–
i
–
n
photodiode with a light-absorbing region representing a multilayered array of quantum ...dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of –3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown.
The power of radiation in the continuous-wave mode of microdisk lasers with InGaAs/GaAs quantum-well dots hybrid integrated with a silicon substrate with the epitaxial side down using a ...thermocompression compound has been investigated. Because of a decrease in thermal resistance and suppression of self-heating, there is an increase in the current values at which power saturation and laser generation quenching occur, as well as an increase in the maximum power. In microdisks with a diameter of 19 μm, the largest value of the optical output power was 9.4 mW in the continuous-wave mode.
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