E. I. Moiseev

Room Temperature Lasing in 1-μm Microdisk Quantum Dot Lasers

Lasing characteristics of InAs/InGaAs quantum dot microdisks with diameter varied from 1 to 6 μm were studied under optical pumping. The disks were fabricated with standard photolithography and two-step wet etching. We demonstrate room temperature lasing in the 1.29-1.32-μm wavelength range (ground-state transition) in microlasers as small as 1 μm in diameter. The microlasers demonstrate narrow linewidths (40-60 pm), low thermal impedance (85°C/mW), and low threshold powers (50-100 μW).

Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam are studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes, except for the fundamental radial one, is also demonstrated. The comparison of laser spectra measured at 78 K before and after ion beam etching for a microdisk of 8 μm in diameter shows a sixfold increase of mode spacing, from 2.5 to 15.5 nm, without a significant decrease of the dominant mode quality factor. Numerical simulations are in good agreement with experimental results.

Thermal resistance of ultra-small-diameter disk microlasers

The thermal resistance of AlGaAs/GaAs microlasers of the suspended-disk type with a diameter of 1.7–4 μm and InAs/InGaAs quantum dots in the active region is inversely proportional to the squared diameter of the microdisk. The proportionality factor is 3.2 × 10−3 (K cm2)/W, and the thermal resistance is 120–20°C/mW.

Lasing in microdisks of ultrasmall diameter

It is demonstrated by calculations and experimental results that room-temperature lasing can be obtained at the ground-state optical transition of InAs/InGaAs/GaAs quantum dots in optical microcavities with a record-small diameter of 1.5 μm. In 1-μm cavities, lasing occurs at the wavelength of one of the whispering-gallery modes within the band corresponding to the first excited-state optical transition.

Single-Mode Emission From 4–9-μm Microdisk Lasers With Dense Array of InGaAs Quantum Dots

A dense array of InGaAs quantum dots formed by MOCVD on a misoriented GaAs substrate has been used as an active medium of microdisk resonators of various types: a cylindrical disk, an undercut disk, and a suspended disk. Single-mode room temperature lasing in a 9-μm microdisk laser is demonstrated with a dominant line around 1.13 μm. Impact of the resonator design on the lasing threshold and its temperature behavior is discussed.

Electrically pumped InGaAs/GaAs quantum well microdisk lasers directly grown on Si(100) with Ge/GaAs buffer

In this work we report, to the best of our knowledge, the first quantum well electrically-pumped microdisk lasers monolithically deposited on (001)-oriented Si substrate. The III-V laser structure was epitaxially grown by MOCVD on silicon with an intermediate MBE-grown Ge buffer. Microlasers with an InGaAs/GaAs quantum well active region were tested at room temperature. Under pulsed injection, lasing is achieved in microlasers with diameters of 23, 27, and 31 µm with a minimal threshold current density of 28 kA/cm2. Lasing spectrum is predominantly single-mode with a dominant mode linewidth as narrow as 35 pm.

Laser generation at 1.3 μm in vertical microcavities containing InAs/InGaAs quantum dot arrays under optical pumping

The fundamental possibility of achieving temperature stability of laser emitters of 1.3-μm spectral range exhibiting a vertical microcavity and an active region based on InAs/InGaAs quantum dots (QDs) is investigated. It is demonstrated that using an undoped hybrid vertical optical microcavity formed by a lower undoped semiconductor and an upper distributed dielectric Bragg reflectors allows obtaining laser oscillation up to a temperature of ~100°C at nearly constant threshold optical pump power for an active region consisting of QD layers under optimal spectral mismatch between the position of maximum gain of the QD ground state and the resonance wavelength.

Microdisk lasers based on GaInNAs(Sb)/GaAs(N) quantum wells

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.

Optical and electrical properties of silicon nanopillars

The electrical and optical properties of silicon nanopillars (Si NPs) are studied. Electron-beam lithography and reactive ion etching are used for the formation of ordered Si-NP arrays. The Si NPs with a diameter from 60 to 340 nm and a height from 218 to 685 nm are formed. The Si NPs are coated with a TiONx layer with a thickness of 8 nm for chemical and electrical passivation of the surface. Scanning electron microscopy and atomic-force microscopy are used to characterize the obtained structures. The Si-NP arrays acquire various colors when exposed to “bright-field” illumination. The spectra of reflection from the Si-NP arrays in the wavelength range 500–1150 nm are obtained.

3.5-μm radius race-track microlasers operating at room temperature with 1.3-μm quantum dot active region

We present detailed studies of optically pumped InAs/InGaAs quantum dot based racetrack microlasers with 3.5-μm bend radius operating at room temperature. Q factor over 8000 and room temperature threshold power in the mW-range were achieved in the racetrack microlasers with straight section length ranging from 0 to 4 μm. A systematic investigation of the influence of the racetrack straight section length on spatial distribution of optical modes is presented. The microcavity eigenmodes and electromagnetic field distribution calculated by means of three-dimensional numerical simulation demonstrate a good agreement with the experimental results obtained by micro-photoluminescence and scanning near-field optical microscopy. The racetracks demonstrate zigzagging behavior of the modes inside the cavity and the energy switching between the radial maxima in second-order modes. Higher-order modes are found to be suppressed in micro-photoluminescence spectra.