Photonic Bandgap Structures Research Articles

Photonic band-gap resonators for high-field/high-frequency EPR of microliter-volume liquid aqueous samples

High-field EPR provides significant advantages for studying structure and dynamics of molecular systems possessing an unpaired electronic spin. However, routine use of high-field EPR in biophysical research, especially for aqueous biological samples, is still facing substantial technical difficulties stemming from high dielectric millimeter wave (mmW) losses associated with non-resonant absorption by water and other polar molecules. The strong absorbance of mmW’s by water also limits the penetration depth to just fractions of mm or even less, thus making fabrication of suitable sample containers rather challenging. Here we describe a radically new line of high Q-factor mmW resonators that are based on forming lattice defects in one-dimensional photonic band-gap (PBG) structures composed of low-loss ceramic discs of λ/4 in thickness and having alternating dielectric constants. A sample (either liquid or solid) is placed within the E = 0 node of the standing mm wave confined within the defect. A resonator prototype has been built and tested at 94.3 GHz. The resonator performance is enhanced by employing ceramic nanoporous membranes as flat sample holders of controllable thickness and tunable effective dielectric constant. The experimental Q-factor of an empty resonator was ≈ 420. The Q-factor decreased slightly to ≈ 370 when loaded with a water-containing nanoporous disc of 50 μm in thickness. The resonator has been tested with a number of liquid biological samples and demonstrated about tenfold gain in concentration sensitivity vs. a high-Q cylindrical TE012-type cavity. Detailed HFSS Ansys simulations have shown that the resonator structure could be further optimized by properly choosing the thickness of the aqueous sample and employing metallized surfaces. The PBG resonator design is readily scalable to higher mmW frequencies and is capable of accommodating significantly larger sample volumes than previously achieved with either Fabry-Perot or cylindrical resonators.

Superconducting metamaterials for waveguide quantum electrodynamics

Embedding tunable quantum emitters in a photonic bandgap structure enables control of dissipative and dispersive interactions between emitters and their photonic bath. Operation in the transmission band, outside the gap, allows for studying waveguide quantum electrodynamics in the slow-light regime. Alternatively, tuning the emitter into the bandgap results in finite-range emitter–emitter interactions via bound photonic states. Here, we couple a transmon qubit to a superconducting metamaterial with a deep sub-wavelength lattice constant (λ/60). The metamaterial is formed by periodically loading a transmission line with compact, low-loss, low-disorder lumped-element microwave resonators. Tuning the qubit frequency in the vicinity of a band-edge with a group index of ng = 450, we observe an anomalous Lamb shift of −28 MHz accompanied by a 24-fold enhancement in the qubit lifetime. In addition, we demonstrate selective enhancement and inhibition of spontaneous emission of different transmon transitions, which provide simultaneous access to short-lived radiatively damped and long-lived metastable qubit states.

Interference patterns of vortex beams based on photonic band gap structure.

We experimentally observe a vortex six-wave mixing (SWM), namely, enhanced four-wave mixing (FWM), signal with its orbital angular momentum transferred from a vortex probe via a photonic band gap (PBG) structure in a hot rubidium vapor cell. By analyzing spatial images and interference patterns, on the one hand, we demonstrate spatial shift and splitting of the images as well as shift of phase singularity for the probe transmission signal under the nonlinear phase of different dressing fields; on the other hand, we observe defocusing and shift of the images as well as shift of phase singularity for the reflected vortex SWM signal by scanning the frequency detuning of a related field. Moreover, we find the interference patterns of the vortex probe can be switched from parallel shape to spiral shape by changing its incident angle. Also, we further research the spiral interference patterns of the transmitted signal by scanning the probe detuning, observing that the number of forks changes with the detuning. We consider the transmitted signal as a combined beam of the linear probe and nonlinear FWM, which are separated under Kerr effect. It is the separation that causes the fork number to change with probe detuning. Our studies are useful for better understanding and manipulation of optical vortices and have wide applications in quantum communication and information processing.

Facile fabrication of spherical photonic crystals microspheres with angle-independent fluorescent functionality

In this work, we report a facile way to fabricate fluorescent spherical photonic crystals (SPCs) microspheres for the first time. The SPCs microspheres immobilizing Photonic Bandgap (PBG) structure into a hydrogel framework, which can be used to uptake nanosized CdTe NCs particles based on their reversible volume phase transition behavior. Moreover, the resultant SPCs microspheres can not only monitor surrounding humidity, but also exhibit well integration of fluorescence and PBG color in a single structure. More interestingly, the photoluminescence (PL) spectra of fluorescent SPCs microspheres are angle-independent on the curved surface which would open a novel insight into the fabrication of multifunctional optical devices based on PBG and PL functionalities.

Experimental study of the evanescent-wave photonic sensors response in presence of molecular beacon conformational changes.

An experimental study of the influence of the conformational change suffered by molecular beacon (MB) probes-upon the biorecognition of nucleic acid target oligonucleotides over evanescent wave photonic sensors-is reported. To this end, high sensitivity photonic sensors based on silicon photonic bandgap (PBG) structures were used, where the MB probes were immobilized via their 5' termination. Those MBs incorporate a biotin moiety close to their 3' termination in order to selectively bind a streptavidin molecule to them. The different photonic sensing responses obtained toward the target oligonucleotide detection, when the streptavidin molecule was bound to the MB probes or not, demonstrate the conformational change suffered by the MB upon hybridization, which promotes the displacement of the streptavidin molecule away from the surface of the photonic sensing structure.

Computational screening of organic polymer dielectrics for novel accelerator technologies

The use of infrared lasers to power accelerating dielectric structures is a developing area of research. Within this technology, the choice of the dielectric material forming the accelerating structures, such as the photonic band gap (PBG) structures, is dictated by a range of interrelated factors including their dielectric and optical properties, amenability to photo-polymerization, thermochemical stability and other target performance metrics of the particle accelerator. In this direction, electronic structure theory aided computational screening and design of dielectric materials can play a key role in identifying potential candidate materials with the targeted functionalities to guide experimental synthetic efforts. In an attempt to systematically understand the role of chemistry in controlling the electronic structure and dielectric properties of organic polymeric materials, here we employ empirical screening and density functional theory (DFT) computations, as a part of our multi-step hierarchal screening strategy. Our DFT based analysis focused on the bandgap, dielectric permittivity, and frequency-dependent dielectric losses due to lattice absorption as key properties to down-select promising polymer motifs. In addition to the specific application of dielectric laser acceleration, the general methodology presented here is deemed to be valuable in the design of new insulators with an attractive combination of dielectric properties.

Pass-Band Characteristics of an L-Shaped Waveguide in a Diamond Structure Photonic Crystal

The conduction characteristics of a L-shaped waveguide in a diamond structure photonic crystal is investigated in this paper. The waveguides were fabricated with titanium dioxide ceramic via 3-D printing and sintering. The effects of the position and size of line defects on the transmission characteristics are first simulated using a finite-difference time-domain method. The simulated results show that, when the length of the rectangular defect equals the lattice constant, multiple extended modes are generated. When the centers of the single unit cell of the diamond structure and the line defect waveguide coincide, higher transmission efficiency in the line defect can be achieved. In addition, the corner of the L-shaped waveguide was optimized to reduce reflection loss at the turning point using the arc transition of the large diameter. Our experimental results indicate that L-shaped waveguides with an optimized photonic band gap structure and high-K materials can produce a pass-band between 13.8 GHz and 14.4 GHz and increase transmission efficiency. The computed results agree with the experimental results. Our results may help the integration of microwave devices in the future and possibly enable new applications of photonic crystals.

Spatial intensity distribution of controlled-NOT gate carrying orbital angular momentum via photonic band gap structure

By employing the different topological charges of a Laguerre–Gaussian beam as a qubit, we experimentally demonstrate a controlled-NOT (CNOT) gate with light beams carrying orbital angular momentum via a photonic band gap structure in a hot atomic ensemble. Through a degenerate four-wave mixing process, the spatial distribution of the CNOT gate including splitting and spatial shift can be affected by the Kerr nonlinear effect in multilevel atomic systems. Moreover, the intensity variations of the CNOT gate can be controlled by the relative phase modulation. This research can be useful for applications in quantum information processing.

Early skin cancer detection sensor based on photonic band gap and graphene load at terahertz regime

Microwave, THz, and optical systems have been developed rapidly for biological detection and imaging in various applications such as skin cancer detection. In this paper, we have suggested special THz sensor based on split ring resonator to making a hot spot for electric field enhancement. In addition, we have utilized photonic band gap (PBG) structure to increase the electric field in the hot spot and we have revealed that this technique lead to enhance the maxima of the electric field more than 12% at the hot spot and the reflection coefficient (S21) value from − 22 to − 35 dB. In other words, we have tried to detect the cancer tissue based on reflection method and related frequency shift. Therefore, the sensor is studied in the existance and absence of the sample where the frequency shift is noticed as a detection factor. At last, the graphene loads are added to the structure and the maxima of the electric field are increased up to 25.3% for 1.96 THz at the hot spot in contrast to basic structure with the reconfigurable characteristic. The parametric studies are noticed to realizing the distortion effect on resonances and electric field.

Photonic band edge assisted spontaneous emission enhancement from all Er3+ 1-D photonic band gap structure

All Er3+ doped dielectric 1-D Photonic Band Gap Structure was fabricated by rf-sputtering technique. The structure was constituted by of twenty pairs of SiO2/TiO2 alternated layers doped with Er3+ ions. The scanning electron microscopy was used to check the morphology of the structure. Transmission measurements put in evidence the stop band in the range 1500 nm–1950 nm. The photoluminescence measurements were obtained by optically exciting the sample and detecting the emitted light in the 1.5 μm region at different detection angles. Luminescence spectra and luminescence decay curves put in evidence that the presence of the stop band modify the emission features of the Er3+ ions.

High sensitivity and label-free oligonucleotides detection using photonic bandgap sensing structures biofunctionalized with molecular beacon probes.

A label-free sensor, based on the combination of silicon photonic bandgap (PBG) structures with immobilized molecular beacon (MB) probes, is experimentally developed. Complementary target oligonucleotides are specifically recognized through hybridization with the MB probes on the surface of the sensing structure. This combination of PBG sensing structures and MB probes demonstrates an extremely high sensitivity without the need for complex PCR-based amplification or labelling methods.

Modulation of controlled-not gate using light beams carrying orbital angular momentum in a nonlinear atomic vapor

We propose and experimentally demonstrate a controlled-not gate with light beams carrying orbital angular momentum (OAM) through a degenerate four-wave mixing process via a photonic band gap structure satisfying the phase-matching condition. By employing the different topological charges of a Laguerre-Gaussian beam as a qubit in this nonlinear process, the controlled-not gate with OAM can be realized. Moreover, we investigate the evolution of the controlled-not gate, which can be modulated by the frequency and the power of the incident beam, i.e., under electromagnetically induced transparency conditions. The study results are useful for applications in quantum communication and information storage.

UHR RFID ring resonator-based tag antenna with photonic bandgap structure for metallic objects

Several recent works highlighted that metamaterial-based antennas are capable to function similar to large printed antennas. This paper presents a novel split-ring resonator-based UHF RFID tag antenna with photonic bandgap structure on metallic objects for high gain, which consists of two symmetrical C-shaped resonators with outer strip lines to feed split-ring resonator structure through implementing an inductively coupled feed approach placed on the top surface of Polytetrafluoroethylene substrate. The simulation results were verified by the presented method via enhancing the performance of tag antennas for metallic object.

Quasi-fractal PBG structures for Multi-Beam Devices

Quasi-fractal PBG structures for Multi-Beam Devices

Temperature control of the ultra-short laser pulse compression in a one-dimensional photonic band gap structure with nematic liquid crystal as a defect layer

We investigate numerically the controllable chirped pulse compression in a one-dimensional photonic structure containing a nematic liquid crystal defect layer using the temperature dependent refractive index of the liquid crystal. We consider the structure under irradiation by near-infrared ultra-short laser pulses polarized parallel to the liquid crystal director at a normal angle of incidence. It is found that the dispersion behaviour and consequently the compression ability of the system can be changed in a controlled manner due to the variation in the defect temperature. When the temperature increased from 290 to 305 K, the transmitted pulse duration decreased from 75 to 42 fs in the middle of the structure, correspondingly. As a result, a novel low-loss tunable pulse compressor with a really compact size and high compression factor is achieved. The so-called transfer matrix method is utilized for numerical simulations of the band structure and reflection/transmission spectra of the structure under investigation.

A microstrip photonic crystal bandgap device with a switchable negative epsilon plasma element

AbstractWe present a microstrip photonic bandgap (PBG) device with a switchable plasma element integrated into the patterned ground plane. A pulsed laser plasma is generated in one of the PBG cavity structures creating a medium having an effective negative permittivity in the 8–10 GHz frequency range due to the high plasma density ne = 1017 cm−3. The PBG structure consists of a linear array of seven cavities along the length of the microstrip manufactured by removing cylindrical portions of copper in the ground plane. The plasma is produced in the central cavity of the PBG array and recombines over times of several microseconds allowing for the characterization of the microstrip transmission over a range of plasma density. The results confirm a switchable transmission due to plasma interactions with the electromagnetic field within the PBG structure.

Quasiperiodic one-dimensional photonic crystals with adjustable multiple photonic bandgaps.

We propose an elegant approach to produce photonic bandgap (PBG) structures with multiple photonic bandgaps by constructing quasiperiodic photonic crystals (QPPCs) composed of a superposition of photonic lattices with different periods. Generally, QPPC structures exhibit both aperiodicity and multiple PBGs due to their long-range order. They are described by a simple analytical expression, instead of quasiperiodic tiling approaches based on substitution rules. Here we describe the optical properties of QPPCs exhibiting two PBGs that can be tuned independently. PBG interband spacing and its depth can be varied by choosing appropriate reciprocal lattice vectors and their amplitudes. These effects are confirmed by the proof-of-concept measurements made for the porous silicon-based QPPC of the appropriate design.

Investigation of pass-band characteristics in three-dimensional PBG structure with line defect

The pass-band characteristics of three-dimensional photonic band-gap (PBG) structure with line defect were investigated in this paper, which were fabricated with high-K TiO2 ceramic based on 3D printing technique and sintering process. The transmission characteristics were measured using transmission/reflection method and computed using FDTD method. Experimental results show that pass-band frequency of the waveguide between 13.5 and 14.7 GHz is within the band-gap of PGB structure (12.2–16.4 GHz) when the practical lattice constant of PBGs is 11.34 mm and practical aspect ratio is 0.296, and transmission efficiency is 80%, which increases by 60% than that of low-dielectric Al2O3 ceramic with transmission efficiency of 50%. Moreover, the computing results basically agree with the experimental results. These results indicate that waveguide of PBG structure with high-K materials will be able to obtain higher transmission efficiency, which will provide a method for adjusting transmission characteristics of PBG structure and promote PBG structure into the practical applications.

Modulated vortex six-wave mixing.

We have experimentally generated a vortex six-wave mixing (SWM) signal via a photonic band gap structure in a hot atomic ensemble. The output SWM carrying orbital angular momentum, transferred from a probe beam, has the interaction with the nonlinear effect in the multilevel atomic system. Our results show that a spatial SWM image can be modulated by the detunings and intensities of the related generating fields. Also, the nonreciprocal feature of the SWM signal is demonstrated. Such characteristics can potentially be used in information processing.

Fabrication of Colloidal Laves Phases via Hard Tetramers and Hard Spheres: Bulk Phase Diagram and Sedimentation Behavior.

Colloidal photonic crystals display peculiar optical properties that make them particularly suitable for application in different fields. However, the low packing fraction of the targeted structures usually poses a real challenge in the fabrication stage. Here, we propose a route to colloidal photonic crystals via a binary mixture of hard tetramers and hard spheres. By combining theory and computer simulations, we calculate the phase diagram as well as the stacking diagram of the mixture and show that a colloidal analogue of the MgCu2 Laves phase—which can serve as a precursor of a photonic band-gap structure—is a thermodynamically stable phase in a large region of the phase diagram. Our findings show a relatively large coexistence region between the fluid and the Laves phase, which is potentially accessible by experiments. Furthermore, we determine the sedimentation behavior of the suggested mixture, by identifying several stacking sequences in the sediment. Our work uncovers a self-assembly path toward a photonic structure with a band gap in the visible region.