Coherent all-optical switching by resonant quantum-dot distributions in photonic band-gap waveguides

Journal Article · Sat Dec 15 00:00:00 EST 2007 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.76.063814· OSTI ID:21140707

Vujic, Dragan; John, Sajeev ^[1]

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1. Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S-1A7 (Canada)

We study the detailed propagative characteristics of optical pulses in photonic band-gap (PBG) waveguides, coupled near resonantly to inhomogeneously broadened distributions of quantum dots. The line centers of the quantum-dot (QD) distributions are placed near a sharp discontinuity in the local electromagnetic density of states. Using finite-difference time-domain (FDTD) simulations of optical pulse dynamics and independent QD susceptibilities associated with resonance fluorescence, we demonstrate subpicosecond switching from pulse absorption to pulse amplification using steady-state optical holding and gate fields with power levels on the order of 1 milliwatt. In the case of collective response of QDs within the periodic dielectric microstructure, the gate power level is reduced to 200 microwatt for room temperature operation. In principle, this enables 200 Gbits per second optical information processing at wavelengths near 1.5 microns in various wavelength channels. The allowed pulse bandwidth in a given waveguide channel exceeds 0.5 THz allowing switching of subpicosecond laser pulses without pulse distortion. The switching contrast from absorption to gain is governed by the QD oscillator strength and dipole dephasing time scale. We consider dephasing time scales ranging from nanoseconds (low-temperature operation) to one picosecond (room-temperature operation). This all-optical transistor action is based on simple Markovian models of single-dot and collective-dot inversion and switching by coherent resonant pumping near the photon density of states discontinuity. The structured electromagnetic vacuum is provided by two-mode waveguide architectures in which one waveguide mode has a cutoff that occurs, with very large Purcell factor, near the QDs resonance, while the other waveguide mode exhibits nearly linear dispersion for fast optical propagation and modulation. Unlike optical switching based on Kerr nonlinearities in an optical cavity resonator, switching power levels and switching speeds for our QD device are not inversely proportional to cavity quality factors.

• OSTI ID: 21140707
• Journal Information: Physical Review. A, Vol. 76, Issue 6; Other Information: DOI: 10.1103/PhysRevA.76.063814; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
CAVITY RESONATORS
CRYSTALS
DIPOLES
LASER CAVITIES
LASER RADIATION
MARKOV PROCESS
NONLINEAR PROBLEMS
OSCILLATOR STRENGTHS
PERIODICITY
PHOTONS
QUALITY FACTOR
QUANTUM DOTS
RESONANCE
RESONANCE FLUORESCENCE
SIMULATION
STEADY-STATE CONDITIONS
TEMPERATURE RANGE 0273-0400 K
VELOCITY
WAVEGUIDES