arXiv subjects

G. S. Solomon

Publications and source records attributed to G. S. Solomon.

8 recordsLinked to original sources

arXiv2017

Quantum dot resonant-fluorescence linewidth narrowing and enhanced intensity

We study the processes in a quantum dot and its surrounds under resonant excitation with the addition of weak non-resonant light. We observe a decrease in inhomogeneous emission linewidth, as well as previously observed enhancement of resonant fluorescence (RF). Scanning excitation and detection frequencies, we distinguish between homogeneous and inhomogeneous broadening. Monte Carlo simulations model the enhanced RF only if we include charge-carrier loss from the quantum dot induced by the resonant laser. The cause of the linewidth narrowing is predominantly independent of the enhanced RF.

quant-ph↗

arXiv2009

Time-Integrated Evidence for Superfluorescence from Dense Electron-Hole Magneto-Plasmas in Semiconductor Quantum Wells

Cooperative spontaneous recombination (superfluorescence) of electron-hole plasmas in semiconductors has been a challenge to observe due to ultrafast decoherence. We argue that superfluorescence can be achieved in quantum-confined semiconductor systems and present experimental evidence for superfluorescence from high-density photoexcited electron-hole plasmas in quantum wells under high magnetic fields (> 20 T). At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. Changes in the linewidth, carrier density, and magnetic field scaling of the emission spectra correlate precisely with the onset of random directionality and are consistent with cooperative recombination. We further investigate the effects of spot size, temperature, and excitation geometry on the emission properties.

cond-mat.mes-hall↗

arXiv2008

Near-IR Subwavelength Microdisk Lasers

We report single-mode lasing in subwavelength GaAs disks under optical pumping. The disks are fabricated by standard photolithography and two steps of wet chemical etching. The simple fabrication method can produce submicron disks with good circularity, smooth boundary and vertical sidewalls. The smallest lasing disks have a diameter of 627 nm and thickness of 265 nm. The ratio of the disk diameter to the vacuum lasing wavelength is about 0.7. Our numerical simulations confirm that the lasing modes are whispering-gallery modes with the azimuthal number as small as 4 and very small mode volume.

physics.optics↗

arXiv2007

Tuning the shape of semiconductor microstadium laser

We presented a detailed experimental study on lasing in GaAs microstadium with various shapes. Unlike most deformed microcavities, the lasing threshold varies non-monotonically with the major-to-minor-axis ratio of the stadium. Under spatially uniform optical pumping, the first lasing mode corresponds to a high-quality scar mode consisting of several unstable periodic orbits. By tuning the shape of GaAs stadium, we are able to minimize the lasing threshold. This work demonstrates the possibility of controlling chaotic microcavity laser.

physics.optics↗

arXiv2007

The influence of a single quantum dot state on the characteristics of a microdisk laser

We report a quantum dot microcavity laser with a cw sub-microwatt lasing threshold, where a significant reduction of the lasing threshold is observed when a single quantum dot (QD) state is aligned with a cavity mode. The quality factor exceeds 15 000 before the system lases. When no QD states are resonant, below threshold the cavity mode initially degrades with increasing pump power, after which saturation occurs and then the cavity mode recovers. We associate the initial cavity mode spoiling with QD state broadening that occurs with increasing pump power.

cond-mat.other↗

arXiv2006

Control of lasing in fully chaotic open microcavities by tailoring the shape factor

We demonstrate experimentally that lasing in a semiconductor microstadium can be optimized by controlling its shape. Under spatially uniform optical pumping, the first lasing mode in a GaAs microstadium with large major-to-minor-axis ratio usually corresponds to a high-quality scar mode consisting of several unstable periodic orbits. Interference of waves propagating along the constituent orbits may minimize light leakage at particular major-to-minor-axis ratio. By making stadium of the optimum shape, we are able to maximize the mode quality factor and align the mode frequency to the peak of the gain spectrum, thus minimizing the lasing threshold. This work opens the door to control chaotic microcavity lasers by tailoring the shape factor.

physics.optics↗

arXiv2006

Cooperative Recombination of a Quantized High-Density Electron-Hole Plasma

We investigate photoluminescence from a high-density electron-hole plasma in semiconductor quantum wells created via intense femtosecond excitation in a strong perpendicular magnetic field, a fully-quantized and tunable system. At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. In addition, changes in the linewidth, carrier density, and magnetic field scaling of the PL spectral features correlate precisely with the onset of random directionality, indicative of cooperative recombination from a high density population of free carriers in a semiconductor environment.

cond-mat.other↗

arXiv2004

Dark-bright magneto-exciton mixing induced by Coulomb interaction in strained quantum wells

Coupled magneto-exciton states between allowed (`bright') and forbidden (`dark') transitions are found in absorption spectra of strained In$_{0.2}$Ga$_{0.8}$As/GaAs quantum wells with increasing magnetic field up to 30 T. We found large (~ 10 meV) energy splittings in the mixed states. The observed anticrossing behavior is independent of polarization, and sensitive only to the parity of the quantum confined states. Detailed experimental and theoretical investigations indicate that the excitonic Coulomb interaction rather than valence band complexity is responsible for the splittings. In addition, we determine the spin composition of the mixed states.

cond-mat.other↗