Researchers demonstrate that an individual Mollow sideband channel of the resonance fluorescence from an InGaAs quantum dot can act as an efficient single-photon source. The central frequency of the bright and narrow sideband emission can be changed by laser detuning over a range spanning 15 times the emission linewidth.

Cascaded single-photon emission from the Mollow triplet sidebands of a quantum dot

We present a proposal to manipulate the Goos-H\"anchen shift of a light beam via a coherent control field, which is injected into a cavity configuration containing the two-level atomic medium. It is found that the lateral shifts of the reflected and transmitted probe beams can be easily controlled by adjusting the intensity and detuning of the control field. Using this scheme, the lateral shift at the fixed incident angle can be enhanced (positive or negative) under the suitable conditions on the control field, without changing the structure of the cavity.

/pdf/control-of-the-goos-hanchen-shift-of-a-light-beam-via-a-2etrxtxmkh.pdf

Control of the Goos-Hänchen shift of a light beam via a coherent driving field

The ability to prepare, optically read out and coherently control single quantum states is a key requirement for quantum information processing. Optically active solid-state emitters have emerged as promising candidates with their prospects for on-chip integration as quantum nodes and sources of coherent photons connecting these nodes. Under a strongly driving resonant laser field, such quantum emitters can exhibit quantum behaviour such as Autler-Townes splitting and the Mollow triplet spectrum. Here we demonstrate coherent control of a strongly driven optical transition in silicon vacancy centre in diamond. Rapid optical detection of photons enabled the observation of time-resolved coherent Rabi oscillations and the Mollow triplet spectrum. Detection with a probing transition further confirmed Autler-Townes splitting generated by a strong laser field. The coherence time of the emitted photons is comparable to its lifetime and robust under a very strong driving field, which is promising for the generation of indistinguishable photons.

/pdf/coherent-control-of-a-strongly-driven-silicon-vacancy-24p1hjof67.pdf

Coherent control of a strongly driven silicon vacancy optical transition in diamond

We describe the spectral characteristics of the radiation scattered by two-level atoms (quantum dots) driven by a strong external field, and coupled to a photonic crystal radiation reservoir. We show that in the presence of strong variations with the frequency of the photonic reservoir density of states, the atomic, Mollow, sideband components of the scattered intensity can be strongly modified. Consequently, a weak optical probe field experiences a substantial differential gain in response to slight variations in the intensity of an optical driving field. We suggest that these effects may be of relevance to all-optical transistor action in photonic crystals. Using a specific photonic crystal heterostructure, we suggest that an all-optical microtransistor based on photonic crystals may operate at less than $100\phantom{\rule{0.3em}{0ex}}\text{nW}$ switching threshold power. Collective $N$-atom effects substantially enhance this optical switching effect. Near the switching threshold intensity, collective effects are manifest in the ${N}^{2}$ scaling of the intensity spectrum (reminiscent of superradiance). Above and below this critical region, the gain spectrum widens (linearly with $N$). This correspondingly reduces the switching time scales of the atomic system in response to external fields. Furthermore, the quantum degree of second-order coherence exhibits unusual features. Scattered photons display a variable degree of antibunching as function of driving laser field intensity and the photonic density of states discontinuity. We analyze the effects of the inhomogeneous atomic line broadening on the amplification process. We show, using suitable photonic density of states engineering, that it is possible to select a narrow spectral range around the central frequency of the atomic frequency distribution over which amplification and switching occur. This is done either by spectral decoupling of the active elements from the electromagnetic field (through the introduction of band gaps at specified spectral locations) or through incoherent pumping to selectively saturate atoms outside the spectral region chosen for amplification.

/pdf/resonance-fluorescence-in-photonic-band-gap-waveguide-1arcfs1tw4.pdf

Resonance fluorescence in photonic band gap waveguide architectures: Engineering the vacuum for all-optical switching

A gain-assisted model is considered to study the Goos-H$\stackrel{\ifmmode \ddot{}\else \&#34;{}\fi{}}{\text{a}}$nchen (GH) shift behavior in the reflected and transmitted light. In this model, a probe light is incident on a cavity containing three-level dilute gaseous atomic medium. The atom-field interaction follows two-photon Raman transitions, and the dielectric susceptibility of the medium exhibits dispersion and gain properties [L. J. Wang, A. Kuzmich, and A. Dogariu, Nature (London) 406, 227 (2000)]. Under appropriate conditions, two gain peaks are observed with anomalous dispersion between the peaks, whereas normal dispersion can be observed at and around the gain maxima. The manipulation of the detuning associated with the probe light field which interacts with the intracavity medium during its propagation through the cavity can lead to a control over negative and positive GH shift in the reflected and transmitted light beam via the anomalous and normal dispersion of the medium.

Gain-assisted control of the Goos-Hänchen shift

We study the refractive index of a system of two-level atoms driven by a strong coherent external field. We show that this system can produce a large index of refraction accompanied by vanishing absorption

Index of refraction of a system of strongly driven two-level atoms

We investigate properties of a two-level atom coupled to a single cavity mode, and driven by a strong, in general off-resonance, external field. The cavity field is tuned to resonance with a Mollow sideband. We show that the steady-state atomic population may be highly (nearly totally) inverted, a phenomenon forbidden in semiclassical theory, and that a strong enhancement of the resonance fluorescence results. This system is suggested as an alternative approach to create the atomic inversion necessary for laser or maser generation without using additional atomic levels. We also investigate properties of the cavity field, derive an analytical expression for the photon number distribution in the good cavity or strong-coupling limit, and discuss the conditions under which this system acts as a single-atom dressed-state laser.

Atomic population inversion and enhancement of resonance fluorescence in a cavity.

We calculate the steady-state spectrum of resonance fluorescence from a two-level atom coupled to a single cavity mode and driven by a strong, in general off-resonance, external field. In the strong-coupling limit, each Mollow triplet component is split into a multiplet, whose detailed structure depends on the atom–cavity coupling, the cavity and spontaneous emission decay constants, and the photon-number distribution of the cavity mode. The dressed states for this system are identified, and the spectral features are interpreted in terms of transitions among these dressed states. In particular, we find that the central component of the central multiplet can have a strongly subnatural linewidth.

Steady-state resonance fluorescence spectrum of a two-level atom in a cavity

Spectrum of the one-atom dressed-state oscillator

We investigate the absorption and dispersion of a probe field by a two-level atom driven by a strong external field and coupled to a single cavity mode. For moderate atom–field coupling the absorption spectrum contains ultrasharp lines, and the real part of the linear susceptibility changes rapidly at the Mollow sideband frequencies. For large coupling the absorption and dispersion spectra split into multiplets whose structures depend on the photon-number distribution of the cavity field. A large index of refraction accompanied by vanishing absorption is predicted.

Tran Quang

Papers

Index of refraction of a system of strongly driven two-level atoms

Atomic population inversion and enhancement of resonance fluorescence in a cavity.

Steady-state resonance fluorescence spectrum of a two-level atom in a cavity

Spectrum of the one-atom dressed-state oscillator

Absorption and dispersion by a driven atom in a cavity