We have studied superluminescent diodes with simplified design and active region based on 5 or 7 layers of InGaAs/GaAs quantum well-dots (QWDs). Emission peaks of the individual QWD layers are shifted with respect to each other by 15–35 nm to provide as wide as possible emission line in a superluminescent mode with central wavelength of about 1 μm without significant spectral dips. For superluminescent diodes with the active region based on 5 and 7 QWD layers, the maximal value of full width at half maximum of emission spectrum was 92 and 103 nm respectively.

We have studied superluminescent diodes with simplified design and active region based on 5 or 7 layers of InGaAs/GaAs quantum well-dots (QWDs). Emission peaks of the individual QWD layers are shifted with respect to each other by 15-35 nm to provide as wide as possible emission line in a superluminescent mode with central wavelength of about 1 µm without significant spectral dips. For superluminescent diodes with the active region based on 5 and 7 QWD layers, the maximal value of full width at half maximum of emission spectrum was 92 and 103 nm respectively.

Рассмотрены тепловые и оптические свойства комбинированного отражателя, состоящего из слоя золота и распределенного брэгговского отражателя, составленного из чередующихся слоев In0.52Al0.48As/In0.53Ga0.47As. Показано, что можно достичь высокого коэффициента отражения при низком поглощении в металле и относительно малой суммарной толщине диэлектрического отражателя. Ключевые слова: вертикально-излучающий лазер, распределенный брэгговский отражатель, металлодиэлектрический отражатель, арсенид индия-алюминия, арсенид индия-галлия.

The thermal and optical properties of a combined (hybrid) metal–dielectric reflector comprising a gold layer and distributed Bragg reflector composed of alternating In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As bilayers are considered. It is established that a high coefficient of reflection of the hybrid structure can be achieved at low absorption in the metal and relatively small total thickness of the dielectric reflector.

AlGaAs/GaAs microdisk lasers with InAs/InGaAs quantum dots have been transferred to the surface of a silicon wafer using an indium solder. The microlasers have a common electric contact deposited on top of the residual n+-GaAs substrate and individual addressing is ensured by placing the microdisks with the p contact down onto separate contact pads formed on silicon. No effect of a non-native substrate on the electrical, threshold, thermal, and spectral characteristics has been established. The microdisks can operate in continuous-wave regime without forced cooling at a threshold current density of ~0.7 kA/cm2. The lasing wavelength is stable (<0.1 nm/mA) to the injection current.

The results of comparative analysis of the spectral and threshold characteristics of room-temperature injection microdisk lasers of the spectral range 1.2×× μm with different active regions, notably, InGaAsN/GaAs quantum wells or InAs/InGaAs/GaAs quantum dots are presented. It is found that microlasers of a comparable size with quantum wells possess a larger laser generation threshold when compared with microlasers with quantum dots. At the same time, the latter are characterized by a noticeably smaller fraction of emitted power corresponding to laser modes. The jump to lasing via an excited-state optical transition is also characteristic for them. Microdisk lasers based on InGaAsN alloy do not have these disadvantages.

The results are presented on a comparative analysis of the spectral and threshold characteristics of diode microdisk lasers operating at room temperature in a spectral range of 1.2xx μm with different active regions: InGaAsN/GaAs quantum wells or InAs/InGaAs/GaAs quantum dots. It was found that microlasers of a comparable size with quantum wells have higher lasing threshold compared to microlasers with quantum dots. At the same time, the latter are characterized by a noticeably smaller fraction of the radiated power with the laser modes. They are also characterized by a jump to excited-state optical transition lasing. The InGaAsN-based microdisk lasers lack these disadvantages.

AlGaAs/GaAs microdisk lasers with InAs/InGaAs quantum dots region were transferred onto a silicon wafer using indium bonding. Microlasers have a joint electrical contact put over a residual n+ GaAs substrate, whereas their individual addressing is achieved by placing them p-contact down to separate contact pads. No effect of non-native substrate on electrical resistance, threshold current, thermal resistance, and spectral characteristics was revealed. Microdisks lase in continuous-wave mode without external cooling with the threshold current density of 0.7 kA/cm2. Lasing wavelength remains stable (<0.1 nm/mA) against injection current increment.

The spectral, threshold, and power characteristics of a microdisk laser 31 μm in diameter with an active region based on InAs/InGaAs quantum dots, operating in the continuous-wave (cw) mode at room temperature are studied. The minimum threshold current density is 0.58 kA/cm 2 , the subthreshold linewidth of the whispering-gallery mode is 50 pm at a wavelength lying in the range of 1.26–1.27 μm. The total power emitted into free space reaches ~0.1 mW in the cw mode, whereas the radiation power of the whispering-gallery modes is ~2.8%.

The possibility of the formation of multilayer (30 layers) InAs/GaAs quantum-dot arrays with high structural and optical quality is demonstrated at small spacer-layer thicknesses (30–15 nm). In the case of decreasing the spacer-layer thickness to 15 nm, significant radiation polarization is observed, which points to the electron coupling of individual quantum dots due to tunneling.