Ultrafast All Optical Switching via Tunable Fano Interference

Abstract

Tunneling induced quantum interference experienced by an incident probe in asymmetric double quantum wells can easily be modulated by means of an external control light beam. This phenomenon, which is here examined within the dressed-state picture, can be exploited to devise a novel all-optical ultrafast switch. For a suitably designed semiconductor heterostructure, the switch is found to exhibit frequency bandwidths of the order of 0.1 THz and response and recovery times of about 1 ps. DOI: 10.1103/PhysRevLett.95.057401 PACS numbers: 78.67.De, 42.50.Gy, 42.50.Hz, 78.66.Fd Transmission and switching of data using all-optical devices is currently the ultimate goal of most telecommunication research. To build all-optical networking systems, optical analogues of existing microelectronics devices must clearly be found. Interesting proposals toward the realization of fast switches, for instance, have already been brought forward whereas important steps toward their actual implementation are now being made. Schemes based on dipole-dipole interactions [1], nonlinear Bragg diffraction [2], photonic band-gap materials [3], as well as those most recent ones based on quantum interference in atomic media [4 -7] all seem to be quite promising.This Letter describes a proof-of-principle study demonstrating that tunable tunneling induced quantum interference in asymmetric quantum wells can be exploited to devise an efficient new mechanism for ultrafast and broadband all-optical switching working at low temperatures (T 10 K). Unlike most familiar switching schemes based on photo-induced changes of the medium macroscopic refractive index [3] or other less usual ones based instead on virtual excitation of spin-polarized excitons [8] or on switchable mirrors made of thin polycrystalline films [9], this mechanism relies on quantum interference and hence it is quite sensitive. Quantum interference based phenomena such as, e.g., coherent population trapping [10], electromagnetically induced transparency [11], lasing without inversion [12], and light speed reduction [13] have recently attracted considerable attention. For many potential applications, solid-state solutions to implement these effects, first predicted and observed in dilute atomic media, are preferred and are now being sought after. In solid media [14] only few proposals followed the original idea of making use of quantum interference to devise an optical switch, first suggested [4] to work and recently observed [6] on a four-level atomic system.We investigate the steady-state and transient behavior of a weak probe light signal incident upon an asymmetric quantum well. The probe can be stopped in the presence of an external control switch beam but made instead to propagate with little absorption when the switch beam is off. The different response depends, respectively, on whether tunneling induced quantum interference is quenched or well developed. Such a control of quantum interference hinges on the creation of a new dipole allowed intersubband transition. Large pro...

Tunneling-induced giant Goos–Hänchen shift in quantum wells

“…For the present QW structure, the results turn out to be γ 2l 3.47 meV, γ 3l 4.13 meV, and γ 4l 0.8 meV. Finally, the term ζ ffiffiffiffiffiffiffiffiffiffiffiffiffiffi γ 2l · γ 3l p denotes a cross-coupling term between the states j2i and j3i coming from the tunneling to the electronic continuum [17][18][19][20][21][22][23][24]. Further, the term p ζ∕ ffiffiffiffiffiffiffiffiffiffiffiffi γ 2 · γ 3 p 0.83 represents the strength of Fano-type interference induced by the strong tunneling.…”

“…Simultaneously, these phenomena also are extended to a variety of applications [15,16]. Different from the mechanism of controlling GH shift based on photon-induced changes of the medium refractive index via coherent control beam [5][6][7][8][9], the mechanism of control GH shift is achieved here as a result of the tunneling-induced quantum interference [17][18][19][20][21][22][23].The schematic of a weak probe light incident upon a cavity containing semiconductor QWs in the configuration of four subbands is shown in Fig. 1.…”

Optical bistability in one-dimensional doped photonic crystals with spontaneously generated coherence

“…Semiconductor quantum well heterostructures can also be used in place of the defect layer in our system. Quantum coherence in the resonant tunneling can replace the SGC effect equivalently [41]. Due to the Hartmann effect the size of the heterostructures should not influence the speed of the OB operation.…”

Controllable Kerr Nonlinearity via Incoherent Pump Fields in Semiconductor Quantum Wells

“…The intensity of the Fano interference [35,41], defined by p = η/ √ γ 2 γ 3 , and the values p = 0 and p = 1 correspond to no interference (there is no negligible coupling between levels |2 and|3 ). This means that Fano interference does not generate) and perfect interference (no dephasing decay rates γ d ph i j = 0), respectively.…”