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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&ndash, 31 &micro, m). 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/cm2 was achieved in 31 &micro, m diameter microdisks operating uncooled. In microlasers with a diameter of 15 &micro, m, the minimum threshold current density was found to be 0.68 kA/cm2. 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 n+ GaAs substrate, whereas their individual addressing is achieved by placing them down on a p-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 present the design, fabrication, and characterization of a MEMS VCSEL which utilized a silicon on insulator wafer for the microelectromechanical system and encapsulates the MEMS by direct InP wafer bonding in order to improve the protection and control of the tuning element. This can enable more robust fabrication, a larger free spectral range, and bidirectional tuning of the MEMS element. The proposed device uses a high contrast grating mirror on a MEMS stage as the bottom mirror, wafer bondind InP with quantum wells for amplification and a deposited dielectric DBR. A tuning range of 40 nm and a mechanical resonance frequency of $>$ 2 MHz is demonstrated. We present design, fabrication, and characterization of an optically pumped MEMS VCSEL which utilizes a silicon-on-insulator wafer for the microelectromechanical system and encapsulates the MEMS by direct InP wafer bonding, which improves the protection and control of the tuning element. This procedure enables a more robust fabrication, a larger free spectral range, and facilitates bidirectional tuning of the MEMS element. The MEMS VCSEL device uses a high contrast grating mirror on a MEMS stage as the bottom mirror, a wafer-bonded InP with quantum wells for amplification and a deposited dielectric DBR as the top mirror. A 40-nm tuning range and a mechanical resonance frequency in excess of 2 MHz are demonstrated.

The feasibility of implementation of asymmetric barriers (ABs) made of common materials for completely aluminum-free diode lasers is studied. The ABs adjoining a low-dimensional active region on both sides aim to prevent bipolar population in the waveguide layers and thus to suppress parasitic recombination therein, which in turn would enhance the efficiency and temperature-stability of the device. Our search algorithm for appropriate AB materials relies on the minimization of undesired carrier flow (electrons or holes passing through the active region toward the p- or n-type doped cladding layer, respectively), while maintaining the useful flows of hole and electron injection into the active region. Using an example of an 808-nm GaInAsP laser, it is shown that the n- and p-side ABs can be made, for instance, of GaInPSb and GaInP, respectively. In such a laser, the parasitic recombination flux can be suppressed by a factor of 60 for electrons and 200 for holes. It is found that the contribution of the indirect valleys to the electron flow through the p-side AB can be significant and even decisive in some cases. The contribution of light holes to the transmission through the ABs can also be considerable. The optimal thicknesses of the AB layers are determined and the chemical composition tolerances are estimated for a given flux suppression ratio. Published by AIP Publishing.

We report on microdisk lasers based on GaInNAs(Sb)/GaAs(N) quantum well active region. Their characteristics were studied under electrical and optical pumping. Small-sized microdisks (minimal diameter 2.3 μm) with unprotected sidewalls show lasing only at temperatures below 220 K. Sulfide passivation followed by SiNx encapsulation allowed us achieving room temperature lasing at 1270 nm in 3 μm GaInNAs/GaAs microdisk and at 1550 nm in 2.3 μm GaInNAsSb/GaAsN microdisk under optical pumping. Injection microdisk with a diameter of 31 μm based on three GaInNAs/GaAs quantum wells and fabricated without passivation show lasing up to 170 K with a characteristic temperature of T0 = 60 K. publishedVersion

Light-current characteristic (LCC) of a novel type of quantum well (QW) lasers-QW lasers with asymmetric barrier layers (ABLs)-is studied. The ABLs (one on each side of the QW) prevent electrons from entering the hole-injecting side of the structure and holes from entering the electron-injecting side. The use of ABLs thus suppresses the parasitic electron-hole recombination outside the QW and eliminates the mechanism of sublinearity of the LCC in conventional lasers associated with this recombination and with the carrier capture delay into the QW. As a result, no matter how slow is the carrier capture into the QW, the LCC of an ABL QW laser is virtually linear. In an ABL laser containing indent layers between the QW and each of the ABLs (parasitic recombination still occurs in these thin layers), even in the case of slow capture of carriers into the QW, the LCC is also considerably more linear than in a reference conventional QW laser. (C) 2013 AIP Publishing LLC. Russia (Federation). Ministry of Education and Science - Agreement No. 8518

We fabricated and tested a quantum well laser with asymmetric barrier layers. Such a laser has been proposed earlier to suppress bipolar carrier population in the optical confinement layer and thus to improve temperature-stability of the threshold current. As compared to the conventional reference laser structure, our laser with asymmetric barrier layers demonstrates reduced internal optical loss, lower threshold current density at elevated temperatures, and higher characteristic temperature (143 vs. 99K at 20 degrees C). (C) 2012 American Institute of Physics. [doi: 10.1063/1.3676085] Federal Target Program "Scientific and Scientific-Pedagogical Personnel of Innovative Russia" (arrangement no. 1.5 "Team research led by invited scientists," Grant No. 02.740.11.5161) (FLASH) from the Danish Council for Independent Research Grant No. 274-09-0247 European Commission for funding through the Marie Curie Incoming International Fellowship (Project No. 252890)