Photonic Band Gap Reservoir Research Articles

Threshold for formation of atom-photon bound states in a coherent photonic band-gap reservoir

We study the threshold for the formation of atom-photon bound (APB) states from a two-level atom embedded in a coherent photonic band-gap (PBG) reservoir. It is shown that the embedded position of the atom plays an important role in the threshold. By varying the atomic embedded position, a part of formation range of APB states can be moved from inside to outside the band gap. The direct link between the steady-state entanglement and APB states is also investigated. We show that the values of entanglement between reservoir modes reflect the amount of bounded energy caused by APB states. The feasible experimental systems for verifying the above phenomena are discussed. Our results provide a clear clue on how to form and control APB states in PBG materials.

Position Dependent Spontaneous Emission Spectra of a Λ-Type Atomic System Embedded in a Defective Photonic Crystal

We investigate the position dependent spontaneous emission spectra of a Λ-type three-level atom with one transition coupled to the free vacuum reservoir and the other one coupled to a double-band photonic band gap reservoir with a defect mode in the band gap. It is shown that, for the atom at the defect location, we have a two-peak spectrum with a wide dark line due to the strong coupling between the atom and the defect mode. While, when the atom is far from the defect location (or in the absence of the defect mode), the spectrum has three peaks with two dark lines due to the coupling between the atom and the photonic band gap reservoir with the largest density of states near the band edges. On the other hand, we have a four-peak spectrum for the atom at the space in between. Moreover, the average spontaneous emission spectra of the atoms uniformly embedded in high dielectric or low dielectric regions are described. It is shown that the atoms embedded in high (low) dielectric regions far from the defect location, effectively couple to the modes of the lower (upper) photonic band. However, the atoms embedded in high dielectric or low dielectric regions at the defect location, are coupled mainly to the defect modes. While, the atoms uniformly embedded in high (low) dielectric regions with a normal distance from the defect location, are coupled to both of defect and lower (upper) photonic band modes.

Position-dependent absorption-dispersion spectrum of a Λ-type three-level atom embedded in a defective photonic crystal

The position-dependent optical spectra of a Λ-type three-level atom embedded in a photonic crystal are studied by considering the double-band photonic band gap reservoir with defect modes in the band gap. It is shown that the number of absorption peaks, transparency windows and the slope of the dispersion curve can be modulated by adjusting the position of the embedded atom.

Controlled optical properties of a five-level atom embedded in photonic crystals with defect modes

The optical spectra of a five-level atom embedded in a photonic crystal are studied by considering the double-band photonic band gap reservoir with defect modes in the band gap. It is shown that some interesting phenomena such as absorption, transparency, normal or anomalous dispersion, and large amplification of a weak probe field can be observed by modulating system parameters.

Controllable Absorption and Dispersion Properties of an RF-driven Five-Level Atom in a Double-Band Photonic-Band-Gap Material

The probe absorption-dispersion spectra of a radio-frequency (RF)-driven five-level atom embedded in a photonic crystal are investigated by considering the isotropic double-band photonic-band-gap (PBG) reservoir. In the model used, the two transitions are, respectively, coupled by the upper and lower bands in such a PBG material, thus leading to some curious phenomena. Numerical simulations are performed for the optical spectra. It is found that when one transition frequency is inside the band gap and the other is outside the gap, there emerge three peaks in the absorption spectra. However, for the case that two transition frequencies lie inside or outside the band gap, the spectra display four absorption profiles. Especially, there appear two sharp peaks in the spectra when both transition frequencies exist inside the band gap. The influences of the intensity and frequency of the RF-driven field on the absorptive and dispersive response are analyzed under different band-edge positions. It is found that a transparency window appears in the absorption spectra and is accompanied by a very steep variation of the dispersion profile by adjusting system parameters. These results show that the absorption-dispersion properties of the system depend strongly on the RF-induced quantum interference and the density of states (DOS) of the PBG reservoir.

Effect of atomic position on the spontaneous emission of a three-level atom in a coherent photonic-band-gap reservoir

The effect of atomic position on the spontaneous emission and optical spectra of a three-level atom embedded in a photonic crystal was studied by considering the coherent two-band photonic-band-gap (PBG) reservoir. With the definite phase difference between the fields of the air band and dielectric band in this coherent PBG reservoir, we found that this coherent property grows stronger and results in the spectrum shift and the appearance of dark lines and kinks as the width of band gap gets smaller; and the variation of the atomic position leads to large shift of spectral peak. The averaged spectra of the system with an ensemble of atoms embedded in the dielectric region are blueshifted while those of atoms in the air region are redshifted. The spectra peaks can even shift more than 75% of the half width at half maximum. The feasible experimental systems composed of an ensemble of molecules (quantum dots or fluorescence dye) in photonic crystals are discussed.

Properties of the spontaneous emission of a driven four-level atom coupled to separate reservoirs

We investigate the spontaneous emission properties of a driven four-level atom coupled to separate reservoirs. Both the effect of the external field and the influence of the photonic bandgap reservoir on the atomic spontaneous emission are discussed. It is shown that a few interesting phenomena such as a laser-induced spectral narrowing dark line can be achieved and its physical understanding can be given by invoking the dressedatom approach.

Probe absorption spectra of a V-type atom embedded in PBG reservoir

In this paper, the probe absorption spectra of a V-type atom embedded in photonic band gap (PBG) reservoir have been investigated under conditions that quantum interference among decay channels is important. The effect of the probe polarization on the absorption amplitude and spectral structure is investigated in detail. Comparing with similar models located in vacuum reservoir studied earlier, the study here shows that the probe polarization has some different effects on the absorption spectra in PBG reservoir.

Spontaneous emission inhibition from a driven four-level atom in a photonic band gap material

Two models (an upper levels coupling model and a lower levels coupling model) of a four-level atom embedded in a double-band photonic crystal are adopted. The effect of spontaneous emission cancellation of such systems embedded in different reservoirs are investigated. Especially, the "trapping conditions" of such systems in photonic band gap (PBG) reservoirs are discussed for the first time. We also investigate the different quantum interference effects of the lower levels coupling model embedded in an isotropic PBG reservoir. It is interesting that when the trapping conditions are fulfilled, the additional peaks, which result from the contribution of the additional singularities of Laplace transform of the delayed Green function of the isotropic PBG modes, are eliminated.PACS Nos.: 42.50.Gy, 42.50.Ct, 42.70.Qs

Absorption Spectra of a Three-Level Atom Embedded in a PBGReservoir

We introduce the `decay rate' terms into the density matrix equationsof an atom embedded in a photonic band gap (PBG) reservoir successfully.By utilizing the master equations, the probe absorption spectra and therefractivity properties of a three-level atom in the PBG reservoir areobtained. The interaction between the atom and the PBG reservoir as wellas the effects of the quantum interference on the absorption of the atomhas also been taken into account. It is interesting that two differenttypes of the anomalous dispersion relations of refractivity areexhibited in one dispersion line. The methodology used here can beapplied to theoretical investigation of quantum interference effects ofother atomic models embedded in a PBG reservoir.

Quantum interference in absorption and dispersion of a four-level atom in a double-band photonic crystal

The probe absorption-dispersion spectrum of a double V-type four-level atom in a double-band photonic crystal is investigated. In the model used, the double V-type transitions are, respectively, coupled by the free vacuum modes and the photonic band gap modes, leading to the two possible types of quantum interference. Three types of zero absorption (transparency) appear in this model. In the first type, there exist two zeroes at the band edge frequencies in the case of isotropic photonic band gap. In the second type, a zero emerges at the middle frequency of two upper levels in the case that the quantum interference takes place in both V-type transitions. Finally, in the third type, a zero occurs at or around the middle frequency of two upper levels in the case that the quantum interference takes place only in the V-type transitions coupled to the free vacuum modes. Ultimately, the probe absorption-dispersion spectrum in the case of the single-band photonic band gap reservoirs compared to those of the double-band photonic band gap reservoirs. The results show that the dispersion property of the system depends on the two types of the quantum interference and the density of states of the photonic band gap reservoir.

Few-photon quantum electrodynamics in a structured continuum

We extend recent work on the discretization of photonic continua. A two-level atom is coupled to a photonic bandgap reservoir, which we model by a large number of discrete modes. The atom is also coupled to a defect mode inside the gap, which acts as a photon source that can pump the atom. Propagating the wavefunction of the system, we obtain results pertaining to the problem of two and three photons in the reservoir, for various states of the defect field. For a wide range of parameters we find that part of the total initial excitation remains trapped to the atom and the defect mode in the long-time limit, while the atomic population may exhibit inversion. We further investigate the dynamics of an atomic Dicke system, with transition frequencies at the edge of a photonic bandgap.

Thermally induced decay of the atom in a photonic bandgap reservoir

We investigate thermally induced partial decay of a two-level atom into a photonic bandgap reservoir in regimes when the atomic transition is tuned in the forbidden gap or at the band edge. The atom decays into a quasi-equilibrium state different from those given by the Boltzmann statistical distribution. We take values of physical parameters typical for Rydberg atoms and currently existing photonic crystals. We show that specific thermally induced transitions can be significant for such Rydberg atoms even at bandgap frequencies provided that there is a peak in the density of modes at the band edge. We point out a temperature sensitivity of microwave quantum optics devices based on photonic band structures due to temperature-dependent transitions and level shifts in regimes when important quantum transitions occur at energies near to band-edge frequencies.

Thermally induced decay of the atom in a photonic bandgap reservoir

Thermally induced decay of the atom in a photonic bandgap reservoir