Abstract
We suggest an idea of data encoding scheme based on the switching from the ground state (GS) to excited state (ES) lasing in quantum dot (QD) lasers with increase in injection current. The ...groups of two bits are assigned to lasing spectra that comprise either one or both GS and/or ES lasing lines depending on injection current. We expect that the proposed encoding scheme can potentially combine some advantages of multilevel signaling and wavelength division multiplexing.
Modal absorptions in laser-like heterostructures containing InAs self-assembled quantum dots (QDs) and InGaAs quantum well-dots (QWDs) have been studied. The evaluation of photoresponse as a function ...of waveguide length has allowed us to determine per-layer modal absorptions of 69 and 13 cm -1 for the ground state optical transitions of QWDs and QDs, respectively. The values of the modal absorption can be used as a measure of the maximal (saturated) modal gain. To compare quantum heterostructures with different dimensionality we have introduced the layer gain constant, a parameter characterizing the light transmittance through the absorbing or gaining layer. We have shown that the QWD layer gain constant significantly exceeds quantum well and quantum dot ones.
We report on the fabrication and studies of Ø100 μm half-disk lasers with an active region based on InGaAs/GaAs quantum dots providing very high modal gain. Such resonators support whispering gallery ...modes propagating at the cavity periphery. The microlasers show directional light outcoupling: continuous-wave output power emitted from the flat side reaches 17 mW, which is about 7 times greater than the power emitted from the back semicircular side. Single-mode lasing in a wide range of the injection currents is observed. P-side down bonding of the devices onto Si-board allowed increasing the maximum optical power to more than 30 mW and the lasing was observed up to 93°C. The 3 dB modulation bandwidth of 4.6 GHz was measured likely being limited by RC-parasites.
We review epitaxial formation, basic properties, and device applications of a novel type of nanostructures of mixed (0D/2D) dimensionality that we refer to as quantum well-dots (QWDs). QWDs are ...formed by metalorganic vapor phase epitaxial deposition of 4–16 monolayers of InxGa1−xAs of moderate indium composition (0.3 < x < 0.5) on GaAs substrates and represent dense arrays of carrier localizing indium-rich regions inside In-depleted residual quantum wells. QWDs are intermediate in properties between 2D quantum wells and 0D quantum dots and show some advantages of both of those. In particular, they offer high optical gain/absorption coefficients as well as reduced carrier diffusion in the plane of the active region. Edge-emitting QWD lasers demonstrate low internal loss of 0.7 cm−1 and high internal quantum efficiency of 87%. as well as a reasonably high level of continuous wave (CW) power at room temperature. Due to the high optical gain and suppressed non-radiative recombination at processed sidewalls, QWDs are especially advantageous for microlasers. Thirty-one μm in diameter microdisk lasers show a high record for this type of devices output power of 18 mW. The CW lasing is observed up to 110 °C. A maximum 3-dB modulation bandwidth of 6.7 GHz is measured in the 23 μm in diameter microdisks operating uncooled without a heatsink. The open eye diagram is observed up to 12.5 Gbit/s, and error-free 10 Gbit/s data transmission at 30 °C without using an external optical amplifier, and temperature stabilization is demonstrated.
Material gain of InGaAs/GaAs quantum well-dots Gordeev, Nikita Yu; Maximov, Mikhail V; Payusov, Alexey S ...
Semiconductor science and technology,
01/2021, Letnik:
36, Številka:
1
Journal Article
Recenzirano
We study material gain of a novel type of quantum heterostructures of mixed (0D/2D) dimensionality referred to as quantum well-dots (QWDs). To evaluate the material gain in a broad range of injection ...currents (30-1200 A cm−2 per-layer) we studied edge-emitting lasers with various numbers of InGaAs/GaAs QWD layers in the active region and different waveguide designs. The dependence of the material gain on the current is well fitted by an empirical exponential equation similar to the one used for quantum dots (QDs) in the whole range of injection current densities. The estimated QWD transparency current-density-per-layer of 31 A cm−2 ranks between the values reported for quantum wells and QDs. The maximal QWD material gain as high as 1.1⋅104 cm−1 has been measured. The results obtained confirm specific gain properties of InGaAs QWDs making them promising active media for lasers, superluminescence diodes and optical amplifiers.
An InAs/InGaAs quantum dot laser with a heterostructure epitaxially grown on a silicon substrate was used to fabricate injection microdisk lasers of different diameters (15-31 µm). A post-growth ...process includes photolithography and deep dry etching. No surface protection/passivation is applied. The microlasers are capable of operating heatsink-free in a continuous-wave regime at room and elevated temperatures. A record-low threshold current density of 0.36 kA/cm
was achieved in 31 µm diameter microdisks operating uncooled. In microlasers with a diameter of 15 µm, the minimum threshold current density was found to be 0.68 kA/cm
. Thermal resistance of microdisk lasers monolithically grown on silicon agrees well with that of microdisks on GaAs substrates. The ageing test performed for microdisk lasers on silicon during 1000 h at a constant current revealed that the output power dropped by only ~9%. A preliminary estimate of the lifetime for quantum-dot (QD) microlasers on silicon (defined by a double drop of the power) is 83,000 h. Quantum dot microdisk lasers made of a heterostructure grown on GaAs were transferred onto a silicon wafer using indium bonding. Microlasers have a joint electrical contact over a residual
+ GaAs substrate, whereas their individual addressing is achieved by placing them down on a
-contact to separate contact pads. These microdisks hybridly integrated to silicon laser at room temperature in a continuous-wave mode. No effect of non-native substrate on device characteristics was found.
We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures ...where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of ∼22° FWHM (full width at half-maximum) in CW (continuous-wave) operation.
Abstract
An original design of ring semiconductor lasers based on InAs/InGaAs/GaAs quantum dots, promising for clock pulse generation, optical sensing, biological and medical applications, and ...microwave photonics, has been proposed and tested. Lasing was obtained at room temperature with a nominal threshold current density as low as 150 A cm
−2
. The output power in continuous wave mode was 45 mW.
Abstract
Half-disk lasers fabricated by cleaving initial full-disk lasers have an advantage of directional light outcoupling as well as increased output power and efficiency as compared to full-disk ...lasers of the same diameter. The continuous wave output power of a 200
µ
m diameter half-disk laser exceeds 70 mW. Quasi single-mode lasing with a high side-mode suppression ratio more than 20 dB is demonstrated for half-disk lasers of various diameters. A maximum 3 dB small signal modulation frequency of 4.9 GHz was measured for a 100
µ
m in diameter half-disk laser.
Abstract
Characteristics of a compact III–V optocoupler heterogeneously integrated on a silicon substrate and formed by a 31
µ
m in diameter microdisk (MD) laser with a closely-spaced 50
µ
m × 200
µ
...m waveguide photodetector are presented. Both optoelectronic devices were fabricated from the epitaxial heterostroctructures with InGaAs/GaAs quantum well-dot layers. The measured dark current density of the photodetector was as low as 2.1
µ
A cm
−2
. The maximum link efficiency determined as the ratio of the photodiode photocurrent increment to the increment of the microlaser bias current was 1%–1.4%. The developed heterogeneous integration of III–V devices to silicon boards by Au-Au thermocompression bonding is useful for avoiding the difficulties associated with III–V epitaxial growth on Si and facilitates integration of several devices with different active layers and waveguides. The application of MD lasers with their lateral light output is promising for simplifying requirements for optical loss at III–V/Si interface.
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