Quantum entanglement and information processing via excitons in optically-driven quantum dots

We show how optically-driven coupled quantum dots can be used to prepare maximally entangled Bell and Greenberger-Horne-Zeilinger states. Manipulation of the strength and duration of the selective light-pulses needed for producing these highly entangled states provides us with crucial elements for the processing of solid-state based quantum information. Theoretical predictions suggest that several hundred single quantum bit rotations and Controlled-Not gates could be performed before decoherence of the excitonic states takes place.Comment: 3 separate PostScript Figures + 7 pages. Typos corrected. Minor changes added. This updated version is to appear in PR

Local optical spectroscopy of semiconductor nanostructures in the linear regime

We present a theoretical approach to calculate the local absorption spectrum of excitons confined in a semiconductor nanostructure. Using the density-matrix formalism, we derive a microscopic expression for the nonlocal susceptibility, both in the linear and nonlinear regimes, which includes a three-dimensional description of electronic quantum states and their Coulomb interaction. The knowledge of the nonlocal susceptibility allows us to calculate a properly defined local absorbed power, which depends on the electromagnetic field distribution. We report on explicit calculations of the local linear response of excitons confined in single and coupled T-shaped quantum wires with realistic geometry and composition. We show that significant interference effects in the interacting electron-hole wave function induce new features in the space-resolved optical spectra, particularly in coupled nanostructures. When the spatial extension of the electromagnetic field is comparable to the exciton Bohr radius, Coulomb effects on the local spectra must be taken into account for a correct assignment of the observed features

Single-frequency fiber laser at 880 nm

Single-frequency fiber lasers with extremely low noise and narrow spectral linewidth have found many scientific and practical applications. There is great interest in developing single-frequency fiber lasers at new wavelengths. In this paper, we report a single-frequency Nd3+-doped phosphate fiber laser operating at 880 nm, which is the shortest demonstrated wavelength for a single-frequency fiber laser thus far, to the best of our knowledge. An output power of 44.5 mW and a slope efficiency of 20.4% with respect to the absorbed pump power were obtained with a 2.5-cm-long 1 wt.% Nd3+-doped phosphate fiber. Our simulation results show that higher single-frequency laser output can be achieved with 1.5 wt.% or 2 wt.% Nd3+-doped phosphate fiber with mitigated ion clustering. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

SESAM Q-switched fiber laser at 1.2 mu m

Q-switched operation of a holmium-doped fluoride fiber laser at 1.2 mu m wavelength induced by a semiconductor saturable absorber mirror (SESAM) is reported. 650 ns pulses with 0.13 mu J pulse energy at a repetition rate of 260 kHz were obtained.This work is partially supported by NSF Engineering Research Center for Integrated Access Networks (#EEC-0812072) and Technology Research Initiative Fund (TRIF) Photonics Initiative of University of Arizona.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Half-Watt Tm3+-Doped Fluoride Fiber Laser at 785 nm

All-fiber single-transverse-mode laser oscillators operating at 785 nm were demonstrated by splicing a 0.1 mol% Tm3+-doped fluoride fiber with a core diameter of 4 mu m and a numerical aperture of 0.07 to a pair of silica fiber Bragg gratings. About 500 mW of continuous-wave single transverse mode laser output at 784.5 nm with a 3-dB spectral bandwidth of 0.2 nm was obtained by upconversion pumping a 3-m-long gain fiber at 1125 nm. Our experiments show that the ground-state absorption of Tm3(+ )at 785 nm is the origin of low efficiency in previous reports. The efficiency of this all-fiber laser can be improved by using a gain fiber with an optimized overlap between the laser, the pump, and the fiber core, and employing new pumping schemes that deplete the ground state sufficiently.NSF CIAN [EEC-0812072]; Technology Research Initiative Fund (TRIF); Photonics Initiative of University of ArizonaThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Solitonic supercontinuum of femtosecond mid-IR pulses in W-type index tellurite fibers with two zero dispersion wavelengths

We present a detailed experimental parameter study on mid-IR supercontinuum generation in W-type index tellurite fibers, which reveals how the core diameter, pump wavelength, fiber length, and pump power dramatically influence the spectral broadening. As pump source, we use femtosecond mid-IR pulses from a post-amplified optical parametric oscillator tunable between 1.7 μm and 4.1 μm at 43 MHz repetition rate. We are able to generate red-shifted dispersive waves up to a wavelength of 5.1 μm by pumping a tellurite fiber in the anomalous dispersion regime between its two zero dispersion wavelengths. Distinctive soliton dynamics can be identified as the main broadening mechanism resulting in a maximum spectral width of over 2000 nm with output powers of up to 160 mW. We experimentally demonstrated that efficient spectral broadening with considerably improved power proportion in the important first atmospheric transmission window between 3 and 5 μm can be achieved in robust W-type tellurite fibers pumped at long wavelengths by ultra-fast lasers