Photonic Quantum Wells Research Articles

Dipole–dipole interaction in nanoscale photonic quantum wells

AbstractThe dipole–dipole interaction (DDI) has been studied in photonic quantum wells are simulated from two photonic crystals say A and B. An ensemble of nanoparticles is doped within the quantum well layer. Nanoparticles are interacting with each other via DDI. The absorption spectrum has been calculated by using the time dependent Schrodinger equation method. A probe field is applied to measure the absorption spectrum. Numerical simulations for the absorption coefficient have been performed. It has been found that in the absence of DDI the spectrum has two peaks and a minimum at zero detuning. However, in the presence of the large DDI coupling both peaks disappear and a large minimum appears. This means that the positions and heights of peaks can be changed due to DDI interaction. This study can be used to make new types of optical devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

All‐photonic switching in nanophotonic quantum wells

AbstractWe have studied the absorption phenomenon in photonic quantum wells doped with an ensemble of three‐level nanoparticles. Photons are confined in the quantum well due to the band structure engineering. The bound states of the confined photon are calculated by using the transfer matrix method and it is found that the number of bound states in the quantum well depends on the size and the depth of the quan tum well. A probe lasers is applied to monitor the absorption spectrum. Nanoparticles are interacting with the bound photons within the quantum well. It is found that when the resonance energy of nanoparticles lies near the ground bound state, the system becomes transparent. These properties can be used to make new types of optoelectronic devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Omnidirectional and multi-channel filtering by photonic quantum wells with negative-index materials

We propose a type of photonic quantum well made of two different photonic crystals with negative- and positive-index materials. It is demonstrated by transfer matrix method that, omnidirectional and multichannel filtering can be achieved. Resonance tunneling modes, or the multi-channel filtering modes, are found to exist when a passband of the well photonic crystal is located inside the gap of the barrier photonic crystals. And for each passband of the well photonic crystal in the photonic bandgap of the barrier photonic crystal, the number of modes is the same as the number of periods in the well photonic crystals. Moreover, the modes are insensitive to the incident angle from 0 to 85 degrees and the scaling of the barrier photonic crystals at a certain range. Such structures are useful for all-direction receiving, sending, or linking-up of multi-channel signals in wireless-communication networks. And they can be applied in signal-detection systems to enhance signal-detection sensitivity.

Resonant modes and inter-well coupling in photonic quantum well with negative index materials

The transfer matrix method was used to study the resonant modes in photonic quantum well by stacking different photonic crystals consisting of positive index materials and negative index materials. The eigenfrequency equation for the resonant modes is derived. It is found that these resonant modes are omnidirectional, and the number of resonant modes is equal to the period number of photonic quantum wells. Moreover, the resonant modes become N-fold splitting in the N photonic quantum wells. The splitting intervals increase with the deceasing of photonic barrier thickness due to the coupling among the wells.

Controlling thermal radiation by photonic quantum well structure with zero-averaged-refractive-index gap

Based on Kirchoff's second law, we investigate the spectral-directional thermal emissivity of a photonic quantum well (PQW) structure with a zero-averaged-refractive-index (zero-n¯) gap coating on an absorbing substrate. It is shown that the thermal emission through tunneling modes having frequencies in the zero-n¯ gap is not only weakly dependent on the emission angle and polarization state but also insensitive to the unit-cell size scaling of the barrier photonic crystal. More importantly, the PQW structure promises the frequency-selective thermal emission for both TE and TM polarization states along a well-defined direction. This may result in designing thermal antennas.

Efficient transmission in cascaded photonic crystal waveguides via a strong coupling effect

A design of cascaded photonic crystal waveguide is proposed in this paper inspired by the work of Tang et al. [D. Tang, L. Chen, W. Ding, Appl. Phys. Lett. 89 (2006) 131120]. In contrast to a conventional waveguide source, a plane wave source is applied in the current design. We show that an efficient guide mode in the photonic band gap can be achieved. The same idea also works for a slight variation by defects introduction in the photonic crystal. Finally, the strong coupling effect present in the cascaded waveguides is demonstrated by an analogy with photonic quantum wells.

Influence of two-dimensional magnetic photonic quantum wells on resonant tunneling spectral character

The non-magnetic material closed photonic quantum well (PQW) and magnetic material PQW structures based on the non-magnetic material open PQW are proposed. The transmission spectra and the field distributions of these three PQW structures are calculated by finite-difference time-domain method, the quantized energy states are researched, and the feasibility of enhancing spectral intensity significantly by self-structure is disclosed. It is found that the optical transmittance of the magnetic PQW is close to 1, and the energy loss is less compared to non-magnetic PQW. Compared with the closed PQW structures, the device’s volume can be reduced, the degree of free regulation of the energy band project can be increased, and more photon bound states can be obtained. The results show that the open PQW is the traveling wave well, and its capability of capturing photons is weak. However, the closed PQW and the magnetic PQW are standing wave wells. Their capabilities for capturing photons are strong, while the light field gradient of the material PQW is bigger.

Second harmonic generations in aperiodic optical superlattices with finite width and in one-dimensional defective photonic crystals made of nonlinear optical materials

The characteristics of the second harmonic generations (SHGs) in homogeneous and inhomogeneous systems are investigated. We consider two kinds of structures: one is aperiodic optical superlattices (AOSs) with homogeneous linear susceptibility and the modulated second-order nonlinear susceptibility; the second is linear and nonlinear susceptibilities both the system with inhomogeneous. We derive a general solution of SHG for the AOS with finite lateral width and of SHG in considering the depletion of the pump light power. We carry out the design of AOSs by using simulation annealing (SA) algorithm and show that the constructed AOSs can implement multiple wavelength SHGs with identical effective nonlinear coefficient at the preassigned wavelengths of incident light. We observe great enhancement of SHGs in the one-dimensional photonic crystals (PCs) with defects consisting of multiple photonic quantum wells made of nonlinear material when the frequency of fundamental wave aims at one of the defect states. We also propose an effective design approach of aperiodically stacked layers of nonlinear material and air in terms of the SA method. The constructed structure can achieve multiple-wavelength SHGs at the preas-signed wavelengths.

Giant enhancement of second harmonic generation in multiple photonic quantum well structures made of nonlinear material

We present a general solution of second harmonic generation (SHG) in one-dimensional (1D) inhomogeneous systems. The structure consists of 1D multiple photonic quantum wells (PQWs) made of optical nonlinear material. The optimal arrangement of the polarization directions of the ferroelectric domains in multiple PQWs is determined by a simulated annealing method. We find that the conversion efficiency of SHG can be significantly enhanced when the fundamental wave frequency is aimed at one of the defect states. By tuning the polarization directions of the domains, the conversion efficiencies of “forward” and “backward” SHGs can be flexibly changed.

Coupling of one-dimensionally confined optical modes in porous silicon: Spectral observation and photonic-quantum-well description

Single and double photonic-quantum-wells (PQWs) have been fabricated, using refractive-index-modulated porous silicon multilayer structures. The one-dimensionally confined optical modes observed are consistent with those calculated using the transfer matrix method. While single PQWs exhibit atom-like discrete spectral features, molecule-like energy level splitting is accessible by combining two single PQWs into a double PQW structure. Similar to an electron in a double-quantum-well structure, the energy separation between the split ‘anti-bonding’ and ‘bonding’ photonic states can be ‘tuned’ by changing the strength of inter-well coupling.

INVESTIGATION OF PROPERTIES OF THE CONFINED STATES IN PHOTONIC QUANTUM-WELL STRUCTURES

We present a detailed investigation of the properties of the confined states in the photonic quantum-well (PQW) structures with the use of the transfer-matrix method. The influences of various physical and geometrical parameters of the systems on the characteristics of the confined states are systematically explored. The results show that the features of the confined modes can be engineered by adjusting system parameters. It may provide a useful way to control the merits of the defect modes in order to match the requirements in photonic or microwave devices.

CHARACTERISTICS OF DEFECT STATES IN ONE-DIMENSIONAL PHOTONIC CRYSTALS CONTAINING MULTIPLE PHOTONIC QUANTUM-WELLS

We calculate the omnidirectional dispersion spectrum for one-dimensional (1D) photonic crystals (PCs) inserting multiple photonic quantum-wells (PQWs) with the use of the plane-wave expansion method in combination with a supercell technique. We find that the localized defect modes significantly depend on the number of the PQWs and the configuration. This may provide a new way to engineer the dispersions of the composite PCs to meet the requirements of optical or microwave devices.

Resonant modes in quantum well structure of photonic crystals with different lattice constants

The resonant modes in a quantum well (QW) structure composed of three slabs of two dimensional (2D) photonic crystals with different lattice constants are analyzed with plane-wave-based transfer matrix method (TMM). It is found that the energy band of the well slab submerged into the band gap of barrier slab is discretized into quantized modes and the number of the resonant modes changes with the well slab thickness. A model structure of asymmetrical photonic QW consisting of two slabs of 2D photonic crystals with different lattice constants and one uniform dielectric slab in between is proposed and the resonant modes in it are investigated with the same method. A useful numerical simulation method for theoretical discussion as well as for practical application about photonic QW structure of photonic crystals with different lattice constants is proposed.

EVOLUTION OF THE BAND GAP STRUCTURES IN ONE-DIMENSIONAL PHOTONIC CRYSTALS WITH THE MODIFICATIONS OF THE STRUCTURES FROM PHOTONIC QUANTUM WELLS TO HETEROSTRUCTURES

We investigate the evolution of the band gap in one-dimensional (1D) photonic crystals (PC) with the gradual modifications of structural configurations from photonic quantum wells to PC heterostructures. The transmissive spectra are calculated with the use of scattering matrix method. We find that the transmissive spectra and confined states strongly depend on the structural configurations of samples.

The oscillation of the coherent light between photonic quantum wells with time-dependent coupling drive

We have derived the time-evolution of quantum states for a coupled photonic well system connected with two separate reservoirs by exact solution to a time-dependent Schrödinger equation. When the quantum wells are detached from the reservoirs, the oscillation of the coherent light between photonic quantum wells is studied. In this case, we obtain the condition that the light be localized in the lower-energy quantum photonic well and compare the difference between two resonance tunneling cases that the coupling drive is added adiabatically or the drive is switched on suddenly.

Photonic resonant transmission in the quantum-well structure of photonic crystals

A photonic quantum-well is constructed by sandwiching a uniform medium between two photonic barriers due to the photonic band gap mismatch, similar to electronic quantum well. The transmission coefficient is calculated by a plane-wave expansion method in combination with multiple-scattering techniques. The transmission peaks indicate that some photonic states exist in a quantized way, satisfying a quantized frequency relation. We also show that the finite photonic potential barrier plays different confined roles on the different photonic levels. The positions and number of the resonant peaks can be artificially tuned by varying the well width. By appropriately choosing the parameters of the well and barrier, a high-quality multichannel filtering can be achieved.

Resonance tunneling through photonic quantum wells

The band gap in photonic materials with periodic spatial modulation of refractive index greater than unity can actually be regarded as a potential barrier for photons. Similar to semiconductor quantum well systems due to the electronic band-gap mismatch, a photonic quantum well can be constructed by sandwiching a uniform medium between two photonic barriers. The transmission and reflection coefficients of light through the photonic quantum well are calculated by a modal expansion method with an R-matrix propagation algorithm. Resonance tunneling through the photonic quantum well structure is observed by varying either the well width or the frequency of incident light. Resonance peaks are found within the band-gap region, and indicate the existence of photon virtual states in the well.