Photonic Bandgap Structures Research Articles

High-sensitivity sensing based on intensity-interrogated Bloch surface wave sensors

A high-sensitivity sensing scheme based on Bloch surface wave is presented with the simple intensity interrogation configuration. The p-polarized electromagnetic surface wave is designed to be excited in a one-dimensional photonic crystal band-gap structure, and support a rather steep resonance dip, much sharper than that of the well-known surface plasmon resonance (SPR). Although the angular shift of this Bloch-surface-wave-based sensor is not as sensitive, the intensity measurement proves to be a more suitable scheme for Bloch surface wave based sensors, thanks to the sharpness of their resonance. Through detection of glycerol in water solution for different concentrations, the intensity sensitivity of our Bloch-surface-wave-based sensor significantly surpasses that of the conventional SPR-based sensors. Experimental results show that the sensor could achieve a detection limit as low as 7.5×10−7 refractive index units in a simple lab setup, which is much simpler than many of the much more complicated SPR-based platforms.

Anomalous transport of light in photonic crystal

Photonic crystal (PC) offers a powerful means to mold the flow of light and manipulate lightmatter interaction at subwavelength scale. In this paper, we review some recent theoretical and experimental work in our group on design and fabrication of microwave and infrared PC structures with the capability to achieve various anomalous transport behaviors of light. We discuss several microwave 2D PC and quasi-crystal structures that exhibit nearly isotropic equi-frequency surface (EFS) contours with effective refractive index equal to -1. In these structures, we can observe negative refraction induced focusing of microwave against a flat slab lens in non-near field regions. In comparison, if PC structures have anisotropic EFS contours in the lowest photonic band, only near-field focusing is expected. We move forward to high frequency infrared band and exploreremarkable dispersion properties of silicon 2D PC slab to achieve broad-band negative refraction and self-collimation transport of infrared light beam. We also explore the possibility to realize negative refraction and flat-lens focusing of light in 3D PC made from inverse opal. These studies show that PCs can offer a powerful route to manipulate various anomalous transport of light via photonic band gap and band structure engineering, which can be harnessed to build a wide variety of integrated optical devices for large-scale optical integration.

Extraction Length Determination in Patterned Luminescent Sol-Gel Films

Optimization of light emitting devices when light is trapped within the dielectric structures opens the question of the management of light propagation and of control of the directionality of extracted light. These phenomena are closely connected to the so-called extraction length of light propagating within the device, a parameter that is poorly discussed when considering the design and architecture of devices. In this work, a straightforward method for the measurement of the extraction length in the case of luminescent sol–gel films patterned with a 2D photonic bandgap structure is presented. Quantitative information usually obtained by spectro-angular measurements can be retrieved from simpler standard spectrometry, allowing discussion of the influence of pattern depth, which determines the extraction by the photonic structure as compared to other uncontrolled pathways such as diffusion from defects in the film coating. These assessments provide a quick and safe method for the quantitative evaluation of light extraction strategies toward a rational design of light emitting devices with optimized properties.

The properties of two-dimensional photonic crystals bandgap structure with rhombus lattice

The relative bandgap ωR of photonic crystals structure with rhombus lattice for both TE and TM modes is studied by the plane wave expansion method. Based on the analysis, a bending waveguide of U type can be easily obtained. The steady-state distribution of the electric field with ω=0.4765(a/λ) of TM mode is given by FDTD method and the transmission is obtained by FFT of the time domain field. All of the sufficient analysis shows the conceptual framework of the proposed rhombus lattice PCs and its great potential application in photonic integration circuit.

Optical parametric amplification in one-dimensional photonic bandgap structures

In this paper, optical parametric amplification based on the degenerate four-wave mixing principle in a one-dimensional photonic bandgap (PBG) structure has been numerically studied. First, the multiple scale method was introduced to derive a complete set of nonlinear coupled-mode equations for a finite structure with different inhomogeneous nonlinear coefficients than those used in previous works. This finite structure is composed of 680 dielectric layers, which are alternating half-wave/eight-wave films. The wavelengths of the pump, signal, and idler pulses have been determined from the transmission spectrum, which was illustrated by using the transfer matrix method. The parametric interaction of the pump, signal, and idler pulses inside PBG structure has been numerically simulated by using the split-step Fourier transform method. The results of the simulation have shown that the intensities of the signal and idler have exponential growth with respect to the number of layers in the medium. Meanwhile, pump wavevector detuning directly affects the intensities of both pulses due to a band-edge phase-matching condition that might be achieved from only one optimal detuning parameter. Moreover, both the amplification gain and the conversion efficiency of the idler pulse have been shown to be dependent on the bandwidth of the pump pulse spectrum. A very narrow pulse, with a bandwidth much less than the relevant transmission peak, enables the highest amplification and conversion efficiency in this medium because the most efficient phase-matched condition occurs in this situation. Finally, the conversion efficiency grows exponentially with input pump intensity for several input signal intensities. Furthermore, the maximum conversion efficiencies directly vary with input signal intensity.

Non-Markovian Dynamics of Entanglement of three-level atom embedded in a 3D photonic band gap structure

Entanglement evolution for a classically pumped three-level atom interacting with an anisotropic structured reservoir is studied. We demonstrate that entanglement decay is much slower in the reservoir with the memory effects. This point is beneficial for the implementation of quantum computation in the non-Markovian environments. Unlike the free-space case, the unusual reservoir stimulates stationary entanglement with amplitude depends strongly on the relative phase between the control laser coupling the two upper levels and the pump laser pulse used to create an excited state of the atom in a coherent superposition of the two upper levels. An optimal stationary degree of entanglement is achieved for negative relative phase, where both detunings - from the upper band gap and driving laser - are the same. Moreover, a significant stationary degre e of entanglement is reached, for high detuned upper levels with the pump laser pulse, on resonant frequency near the edge of the PBG. For entanglement in stationary regime, the Rabi frequency of the control laser field exceeds the rate of entanglement degradation or e nhancement for tuned or detuned frequency from the band gap, depending on the relative phase value.

Novel All-Optical Liquid Photonic Crystal Router

A novel design of an easily and fully integrated terabit per second (Tbit/s) optical router is presented and analyzed using the finite difference time domain method. The proposed router consists of three photonic bandgap (PBG) waveguides with two nematic liquid crystal (NLC) layers. The suggested device can be used to divert the light beam to one of the three photonic crystal waveguides based on the biasing states of the two NLC layers. In this way, there are three different modes of operation where each one is used for routing data to the required direction. The suggested device offers crosstalk of 19 dB. In addition, the reported structure opens up the revenue for building multi-port optical routers through the use of a number of appropriately positioned NLC layers within the platform of PBG structure.

Ballistic charge transport in graphene and light propagation in periodic dielectric structures with metamaterials: A comparative study

We explore the optical properties of periodic layered media containing left-handed metamaterials. This study is based on several analogies between the propagation of light in metamaterials and charge transport in graphene. We derive the conditions for these two problems become equivalent, i.e., the equations and the boundary conditions when the corresponding wave functions coincide. We show that the photonic band-gap structure of a periodic system built of alternating left- and right-handed dielectric slabs contains conical singularities similar to the Dirac points in the energy spectrum of charged quasiparticles in graphene. Such singularities in the zone structure of the infinite systems give rise to rather unusual properties of light transport in finite samples. In an insightful numerical experiment (the propagation of a Gaussian beam through a mixed stack of normal and meta-dielectrics) we simultaneously demonstrate four Dirac point-induced anomalies: (i) diffusion-like decay of the intensity at forbidden frequencies, (ii) focusing and defocussing of the beam, (iii) absence of the transverse shift of the beam, and (iv) a spatial analogue of the Zitterbewegung effect. All of these phenomena take place in media with non-zero average refractive index, and can be tuned by changing either the geometrical and electromagnetic parameters of the sample,or the frequency and the polarization of light.

Optically tunable/switchable omnidirectionally spherical microlaser based on a dye-doped cholesteric liquid crystal microdroplet with an azo-chiral dopant

This paper presents an optically wavelength-tunable and intensity-switchable dye-doped cholesteric liquid crystal (DDCLC) spherical microlaser with an azo-chiral dopant. Experimental results present that two functions of optical control - tunability of lasing wavelength and switchability of lasing intensity - can be obtained for this spherical microlaser at low and high intensity regimes of non-polarized UV irradiation, respectively. If the DDCLC microdroplet is subjected to weak UV irradiation, azo-chiral molecules may transform to the bent cis state at a low concentration rate. The effect can slightly decrease the local order of LCs and thus the helical twisting power of the CLC in the microdroplet. As a result, the CLC pitch may become slightly elongated, which will cause the gradual red-shift of both omnidirectional PBG and lasing emission of the DDCLC spherical microdroplet. In contrast, when the microdroplet is subjected to strong UV irradiation, numerous azo-chiral molecules may simultaneously change to bent cis-isomers to seriously disarrange the helical texture of the CLC, which will quickly deform the PBG and deactivate the lasing emission of the microdroplet. Prolonged irradiation of a blue beam after strong UV irradiation may cause the cis azo-chiral molecules quickly convert back rod-like trans-isomers, which may then regenerate the CLC Bragg onion and PBG structures and reactivate the lasing emission of the microdroplet. Optical control of the DDCLC spherical microlaser is realized on a scale of seconds and minutes when UV irradiation is strong and weak, respectively. The 3D DDCLC spherical microlaser is a highly promising controllable 3D micro-light source or microlaser (e.g., all-optical 3D single photon microlaser) for applications of 3D all-optical integrated photonics, laser displays, and biomedical imaging and therapy, and as a 3D UV microdosagemeter or microsensor.

Investigation of one-dimensional photonic bandgap structures containing lossy double-negative metamaterials through the Bloch impedance

The Bloch impedance is studied and used to understand the properties of the absorption loss in one-dimensional photonic crystals (PCs) composed of air and metal-based double-negative metamaterials. We find that as the frequency increases across the zero-¯ n gap of the considered structures, the modulus of the Bloch impedance always decreases from a maximum to a minimum value. On the other hand, the frequency dependence of the phase angle of the Bloch impedance is greatly influenced by the ratio of the electric to the magnetic damping coefficient γe∕γm of the metamaterials. When the phase angle of the Bloch impedance reaches maximum inside the zero-¯ n gap, the impedance mismatch between the incident medium and the considered PC becomes greatest, the reflection will be strongest and a minimum absorption will be observed. As γe∕γm increases, the frequency corresponding to the minimum absorption shifts from the lower to the upper gap edge. We also show that the main characteristics of both the Bloch impedance and the absorption loss are insensitive to the geometrical parameters. Our study offers a valuable reference in the designs of zero-¯ n gap with optimized properties. © 2013 Optical Society of America

Mean-field optical bistability of two-level atoms in structured reservoirs

We consider N driven two-level atoms interacting with a structured reservoir. By dressing the collective operators within a semiclassical approach, we derive a master equation and a mean-field single particle effective Hamiltonian. This Hamiltonian describes the optical bistability phenomenon occurring in the relation between an input electromagnetic field and the effective output generated by the N atoms. The dissipative part of the master equation and the effective single-particle Hamiltonian contain new terms due the reservoir structure of modes. In plotting the output field amplitude and phase, for a structured reservoir, as function of the input amplitude, one verifies the bistable behavior in both. We illustrate our results for two structured reservoirs: one having a Lorentzian shape for the distribution of modes, and the second is modeled as a photonic band-gap structure.

Photonic bandgap via nonlinear modulation assisted by spontaneously generated coherence

A four-level double-ladder atomic system with two upper states coupled to the excited state by a standing-wave trigger field is explored to generate photonic bandgap (PBG) structure. With the assistance of spontaneously generated coherence (SGC) from the two decay pathways, we can obtain single or double fully developed PBG when the trigger field is far away from resonance or resonant. While in the absence of SGC, the atomic medium becomes strong absorptive to the probe field, and therefore the resulting PBGs are severely malformed or even cannot be opened up. Numerical results show that the PBG structure is originated from the third-order cross Kerr nonlinear modulation between the probe and trigger fields. This mechanism differs from the recent schemes based on linear modulation.

Adjustable YAG : Ce3+ photoluminescence from photonic crystal microcavity

Four different photonic bandgap (PBG) structures embedding a YAG : Ce3+ layer inside two three-period Bragg mirrors were prepared by sol–gel processing, forming Fabry–Perot microcavities whose defect peaks moved from red to green. Under irradiation of blue Ar+ laser light, the typical broad YAG : Ce3+ photoluminescence (PL) emission band was highly narrowed in these four samples, with the new position of the modified PL peaks corresponding to the resonance wavelength of each microcavity sample, while the simultaneous colour changes could be easily observed by the human eye. The adjustable range demonstrated here was wide enough to generate white light with colour temperatures from warm white (∼2700 K) to daylight white (∼5600 K), by mixing the modified PL with light from any usual blue LED excitation source. This result provides a novel technique to solve the red-deficiency problem in the white LED industry: instead of relying on the development of new phosphors, the well-known PL of YAG : Ce3+ can be conveniently adjusted by 1D PBG structures.

Design of ultra‐wide stop‐band DGS low‐pass filter using meander‐ and multilayer‐techniques

AbstractThis article presents a new dog‐bone defected ground structure (DGS) for low‐pass filter (LPF) applications with wide‐rejection band and low‐insertion loss in the pass‐band region.The prototype LPF consists of three dog‐bone cells in the ground plane with an open stub on the top layer acting as a compensated capacitor. The prototype LPF is then realized as a multilayer structure to enhance the filter response and reduce its size. The size reduction of the proposed multilayer LPF is about 34% more than the conventional one. The proposed filter has been fabricated and measured. Good agreement can be realized between the electromagnetic simulation and the measurement results. To minimize the difference between the simulation and measurement results, and at the same time to reduce the loss in the pass‐band region, a modification to the topology of the structure with the aid of the meander idea is used. The meander‐filter presents advantages of compactness, low insertion loss, and high out‐band suppression. The dog‐bone DGS cell is then used as a photonic band gap structure to minimize the coupling between two probe‐fed patch antennas and to improve the two antenna element array efficiency. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1276–1281, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27541

Calculation of wakefields in a 17 GHz beam-driven photonic band-gap accelerator structure

We present the theoretical analysis and computer simulation of the wakefields in a 17 GHz photonic band-gap (PBG) structure for accelerator applications. Using the commercial code CST Particle Studio, the fundamental accelerating mode and dipole modes are excited by passing an 18 MeV electron beam through a seven-cell traveling-wave PBG structure. The characteristics of the longitudinal and transverse wakefields, wake potential spectrum, dipole mode distribution, and their quality factors are calculated and analyzed theoretically. Unlike in conventional disk-loaded waveguide (DLW) structures, three dipole modes (${\mathrm{TM}}_{11}$-like, ${\mathrm{TM}}_{12}$-like, and ${\mathrm{TM}}_{13}$-like) are excited in the PBG structure with comparable initial amplitudes. These modes are separated by less than 4 GHz in frequency and are damped quickly due to low radiative $Q$ factors. Simulations verify that a PBG structure provides wakefield damping relative to a DLW structure. Simulations were done with both single-bunch excitation to determine the frequency spectrum of the wakefields and multibunch excitation to compare to wakefield measurements taken at MIT using a 17 GHz bunch train. These simulation results will guide the design of next-generation high-gradient accelerator PBG structures.

Solid-state quantum optics with quantum dots in photonic nanostructures

AbstractQuantum nanophotonics has become a new research frontier where quantum optics is combined with nanophotonics in order to enhance and control the interaction between strongly confined light and quantum emitters. Such progress provides a promising pathway towards quantum-information processing on an all-solid-state platform. Here we review recent progress on experiments with quantum dots in nanophotonic structures with special emphasis on the dynamics of single-photon emission. Embedding the quantum dots in photonic band-gap structures offers a way of controlling spontaneous emission of single photons to a degree that is determined by the local light-matter coupling strength. Introducing defects in photonic crystals implies new functionalities. For instance, efficient and strongly confined cavities can be constructed enabling cavity-quantum-electrodynamics experiments. Furthermore, the speed of light can be tailored in a photonic-crystal waveguide forming the basis for highly efficient single-photon sources where the photons are channeled into the slowly propagating mode of the waveguide. Finally, we will discuss some of the surprises that arise in solid-state implementations of quantum-optics experiments in comparison to their atomic counterparts. In particular, it will be shown that the celebrated point-dipole description of light-matter interaction can break down when quantum dots are coupled to plasmon nanostructures.

High power breakdown testing of a photonic band-gap accelerator structure with elliptical rods

An improved single-cell photonic band-gap (PBG) structure with an inner row of elliptical rods (PBG-E) was tested with high power at a 60 Hz repetition rate at X-band (11.424 GHz), achieving a gradient of $128\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ at a breakdown probability of $3.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ per pulse per meter at a pulse length of 150 ns. The tested standing-wave structure was a single high-gradient cell with an inner row of elliptical rods and an outer row of round rods; the elliptical rods reduce the peak surface magnetic field by 20% and reduce the temperature rise of the rods during the pulse by several tens of degrees, while maintaining good damping and suppression of high order modes. When compared with a single-cell standing-wave undamped disk-loaded waveguide structure with the same iris geometry under test at the same conditions, the PBG-E structure yielded the same breakdown rate within measurement error. The PBG-E structure showed a greatly reduced breakdown rate compared with earlier tests of a PBG structure with round rods, presumably due to the reduced magnetic fields at the elliptical rods vs the fields at the round rods, as well as use of an improved testing methodology. A post-testing autopsy of the PBG-E structure showed some damage on the surfaces exposed to the highest surface magnetic and electric fields. Despite these changes in surface appearance, no significant change in the breakdown rate was observed in testing. These results demonstrate that PBG structures, when designed with reduced surface magnetic fields and operated to avoid extremely high pulsed heating, can operate at breakdown probabilities comparable to undamped disk-loaded waveguide structures and are thus viable for high-gradient accelerator applications.

Dispersion characteristics of 1D PBG structures composed of subwavelength dipole elements

In this article, an innovative approach for characterization of one dimensional photonic band gap (PBG) structures comprised of subwavelength dipole elements is presented.Through an efficient S- to T-parameters conversion technique, polarization sensitivity of the subwavelength cell element was exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrated that dispersion characteristics of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. The structure has potential application in orthomode transducer and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:611–615, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27378

Parametric Study of 1-D PBG Structures Composed of Subwavelength Dipole Elements

In this letter, an original approach for filter design using one-dimensional photonic band-gap (1-D PBG) structures composed of subwavelength dipole elements is presented. Through an efficient $S$ - to $T$ -parameters conversion technique, a detailed analysis is performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations.

Microfluidic generation of magnetoresponsive Janus photonic crystal particles

Janus particles with features of an anisotropic photonic band gap (PBG) structure and magnetic property have been achieved by phase separation and self-assembly of nanoparticles in microfluidic droplets. The resultant particles enable optical encoding and magnetically controllable motion, making them excellent functional encoded particles in biomedical applications.