One-dimensional Photonic Band Research Articles

Variational Quantum Simulators Based on Waveguide QED.

Waveguide QED simulators are analog quantum simulators made by quantum emitters interacting with one-dimensional photonic band gap materials. One of their remarkable features is that they can be used to engineer tunable-range emitter interactions. Here, we demonstrate how these interactions can be a resource to develop more efficient variational quantum algorithms for certain problems. In particular, we illustrate their power in creating wave function Ansätze that capture accurately the ground state of quantum critical spin models (XXZ and Ising) with fewer gates and optimization parameters than other variational Ansätze based on nearest-neighbor or infinite-range entangling gates. Finally, we study the potential advantages of these waveguide Ansätze in the presence of noise. Overall, these results evidence the potential of using the interaction range as a variational parameter and place waveguide QED simulators as a promising platform for variational quantum algorithms.

Enhanced circular dichroism of sparse nanoobjects by localized superchiral optical field

The spectroscopic methods of circular dichroism (CD) is commonly used in analysing the chirality of molecules, which plays an important role in pharmaceutical compounds. However, the current methods require high sample density due to the weak CD effect of natural material, making it challenging to detect the signal of individual chiral molecule. In this work, we propose a technique to enhance CD signal of individual chiral molecule with the use of superchiral optical field, which is acquired by focusing a twisted radially polarized vortex onto a one-dimensional photonic band gap structure. Through adjusting the topological charge and the focusing angle of the illumination, a deep subwavelength optical field with full width at half maxima (FWHM) of 0.02λ and 22.4-fold superchirality factor enhancement can be generated. In addition, we demonstrate that up to 20-fold CD enhancement can be obtained by introducing 2 nm on-resonant chiral molecule into the superchiral optical field. This finding will have widely potential applications in CD spectroscopy and superresolution imaging for sparse subdiffraction chiral objects.

Design Method of Notch Filter Based on One-dimensional Photonic Crystal Band Structure

Design Method of Notch Filter Based on One-dimensional Photonic Crystal Band Structure

Characterization of photonic band resonators for DNP NMR of thin film samples at 7 T magnetic field

Polarization of nuclear spins via Dynamic Nuclear Polarization (DNP) relies on generating sufficiently high mm-wave B1e fields over the sample, which could be achieved by developing suitable resonance structures. Recently, we have introduced one-dimensional photonic band gap (1D PBG) resonators for DNP and reported on prototype devices operating at ca. 200 GHz electron resonance frequency. Here we systematically compare the performance of five (5) PBG resonators constructed from various alternating dielectric layers by monitoring the DNP effect on natural-abundance 13C spins in synthetic diamond microparticles embedded into a commercial polyester-based lapping film of just 3 mil (76 μm) thickness. An odd-numbered configuration of dielectric layers for 1D PBG resonator was introduced to achieve further B1e enhancements. Among the PBG configurations tested, combinations of high-ε perovskite LiTaO3 together with AlN as well as AlN with optical quartz wafers have resulted in ca. 40 to over 50- fold gains in the average mm-wave power over the sample vs. the mirror-only configuration. The results are rationalized in terms of the electromagnetic energy distribution inside the resonators obtained analytically and from COMSOL simulations. It was found that average of B1e2 over the sample strongly depends on the arrangement of the dielectric layers that are the closest to the sample, which favors odd-numbered PBG resonator configurations for their use in DNP.

The unique UV–Vis reflection features of the nacre of Hyriopsis cumingii shells, and its formation mechanisms

UV–Vis reflectance spectroscopy, combined with field emission scanning electron microscope (FE-SEM), was used to comparatively characterize nacre areas with milky-white and pink-violet coloration from the same Hyriopsis cumingii shell. Although the mean thicknesses of the aragonite platelets in the nacre from the pink-violet area were similar, the reflection spectra obtained from different locations within this area were not uniform. This indicated that the vivid color appearing on the inner surface of the shell was not completely derived from the one-dimensional photonic structure. We proposed that the absorption peak in the ultraviolet region was associated with carotenoids. The strength of the absorption peak increased with carotenoid concentration. The inner surface of the shell was not flat, leading to obvious frequency shifting in the reflection peak of the violet region. More importantly, our findings suggested that the vivid color of the inner surface of the shell was caused by the combined effects of organic pigment and one-dimensional photonic band. This present study advances our understanding of coloration mechanisms. Furthermore, we expect that our work may provide basis for further studies of pearl culture or quality grading and might inform further investigations of the design and synthesis of advanced functional materials for optical, biomedical, and mechanical applications.

Design of enhanced sensitivity gas sensors by using 1D defect ternary photonic band gap structures

In this paper, an approach to design enhanced sensitivity gas sensors by using one-dimensional (1D) defect ternary photonic band gap (PBG) material structure is demonstrated. It is shown that when the 1D defect binary PBG structure gas sensors are modified to 1D defect ternary PBG structure gas sensors, the sensitivity of the sensor enhances by 100%. Thus, by converting 1D defect binary PBG structures to 1D defect ternary PBG structures enhanced sensitivity gas sensors can be fabricated.

Enhancement in sensitivity of blood glucose sensor by using 1D defect ternary photonic band gap structures

This paper demonstrates a novel way to enhance sensitivity of a blood glucose sensor made up of one-dimensional (1D) defect binary photonic band gap (PBG) structure by converting it to 1D defect ternary PBG structure. On conversion of the structure from binary to ternary, the glucose concentration sensitive output transmission spectrum shift in the structure enhances by 25% and the sensitivity enhancement is 4.71 nm/RIU. Due to high sensitivity of 1D defect ternary PBG structure, fast and more accurate determination of concentration of glucose in blood can be achieved.

Improvement on reflectivity of tunable photonic band gap with spontaneous generated coherence

The photonic band gap is a spectral range which cannot propagate in a periodic optical nanostructure, that is, the structure itself has a “forbidden band”. It has been successfully applied to the filters, amplifiers, mixers, etc. As is well known, dynamically tunable photonic band gaps in cold atomic lattices are of great importance in various research fields. However, the photonic band gaps of a traditional photonic crystal are non-tunable because the periodic structure is determined once the photonic crystal is grown. On the other hand, a majority of previous researches focused on improving the reflectivity of photonic band gap, which can only keep approaching to 1. Due to the action of the vacuum of the radiation field, near-degenerate lower level has an additional coherence term, the spontaneously generated coherence term. In this paper, we consider a three-level ∧-type atomic system driven by a strong coherent field, a weak coherent field and an incoherent pump, in which the two ground states are of hyperfine structure. The one-dimensional photonic band gaps are formed by cold atoms trapped in a one-dimensional-ordered optical lattice and this system may create two photonic band gaps (PBGs). The trapped cold atoms have a Gaussian density distribution in each period as determined by the optical potential depth and the average atomic temperature. We investigate in detail how the reflectivities of the two PBGs are influenced by the coherent effect of spontaneously generated coherence. Then, we find that the reflectivities of the two band gaps can be significantly improved by the spontaneously generated coherence. The reflectivities of such two band gaps can be dynamically manipulated by varying the intensity of incoherent driving field and the relative phase between the probe field and the coupling field, which cannot be realized in a conventional ∧-type atomic system. Besides, by adjusting the parameters appropriately, the reflectivities of these two band gaps can be higher than 1, which is because probe field gain stems from the spontaneously generated coherence. In the future, photonic transport properties can be investigated in the three-dimensional atomic lattices and this work is meaningful for the optical routing, photodiode and transistor.

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.

Design and fabrication of energy efficient film based on one-dimensional photonic band gap structures

A photonic band gap structure of (SiO2/TiO2)5 with Ag system for energy efficient film was proposed theoretically and experimentally. The calculated transmittance spectra show high transmittance in the visible range, but ultra-low transmittance in the wavelength ranges of ultraviolet and infrared. Besides, the effects of the incident angle and two opposite directions on the optical characteristics were studied. The results demonstrate that the structure can simultaneously satisfy the demands of lighting and heat insulating as energy efficient window film. The cross-section morphology indicates that the sample has good periodicity in accordance with the design, whereas the experimentally measured transmittance spectra are well matched with the theoretical calculation.

Design of a thermally tunable optical filter based on one-dimensional ternary photonic band gap material

Designof a tunable band pass filter using one dimensional ternary periodic refractive index profile has been presented. Design of the proposed filter is based on the model of Kronig–Penny in solid state physics. In this present filter, the desired wavelength regions can be tuned by altering the temperature or the incidence angle. A Ge/Si/air multilayer system is considered here. The refractive indices of Si and Ge layers have been taken to be functions of temperature as well as wavelength. Due to the dependence of refractive indices of Si and Ge on temperature, transmission characteristic of the structure changed, and this property has been exploited to shift the transmission band. Hence, the proposed ternary structure can be utilised to tune the pass bands by changing the temperature or the incident angle. Detailed analysis shows that ternary structure gives better performance than the binary structure in terms of tunability.

Study on planar concave diffraction grating with Bragg reflector facets

Based on the fact that Bragg reflection grating(BRG) is a special one-dimensional photonic crystal, we propose to apply the one-dimensional photonic crystal band gap theory to the design of Bragg reflection grating and then to make an analysis of its optical performance. According to the above band gap theory, FDTD solution is used to build the elliptical Bragg etched diffraction grating (EDG) based on the Rowland circle. We have studied the spectral characteristics for both TE and TM modes and the angle dispersion due to the variation of the incident angle, at the same time, the optical performances in the air dielectric type Bragg grating and the Al metallic line type Bragg grating are also made to compare with each other. It turns out that by choosing appropriate parameters the diffraction efficiency can be got more than 95% within the scope of 1.465-1.615 μm in both TE and TM modes, and the air dielectric type Bragg grating structure behaves better in the uniformity throughout the whole channel than in the Al metallic line type Bragg grating structure. When the incident angle varies from 30° to 60°, the angle dispersion in TM mode is larger than that in TE mode. This is the foundation of a new type of EDG wavelength division multiplexer with advantages of small size and high diffraction efficiency. It may have the potential to promote the development of high diffraction efficiency dense wavelength division multiplexer in the future.

Asymmetric one-dimensional photonic crystal for optical sensing in the visible spectral range

A gas sensor based on an asymmetric one-dimensional (1D) photonic band gap structure with one defect layer was designed and fabricated through layer-by-layer deposition of spin-coated poly methyl methacrylate (PMMA) and vacuum-deposited As2S3. Initially, the thickness variations, Δd, were determined of the thin films resulting from the poly methyl methacrylate exposure to chloroform vapor in the concentration range 100 – 9000 ppm. It was found that the value of Δd depends on the gas concentration and the exposure time. A two-layer structure was prepared consisting of PMMA and vacuum-deposited As2S3. Further, the permeability of thin As2S3 films to chloroform vapors was investigated. The asymmetric photonic structure consisted of 11 alternating layers of As2S3 and PMMA. The defect PMMA layer was located before the last high-refractive-index film of chalcogenide glass. The thickness of the defect layer of PMMA was pre-calculated so that the pass band be centered at the wavelength of 550 nm. An offset was observed of the position of the pass band to the larger wavelengths after exposure to chloroform vapor. The multilayered structure proposed is promising for optical sensor applications.

Magnetized plasma photonic crystals band gap

In this paper, the effect of the magnetic field on one-dimensional plasma photonic crystal band gaps is studied. The one-dimensional fourfold plasma photonic crystal is applied that contains four periodic layers of different materials, namely plasma1–MgF2–plasma2–glass in one unit cell. Based on the principle of Kronig–Penney's model, dispersion relation for such a structure is obtained. The equations for effective dielectric functions of these two modes are theoretically deduced, and dispersion relations for transverse electric (TE) and transverse magnetic (TM) waves are calculated. At first, the main band gap width increases by applying the exterior magnetic field. Subsequently, the frequency region of this main band gap transfers completely toward higher frequencies. There is a particular upper limit for the magnitude of the magnetic field above which increasing the exterior magnetic field strength doesn't have any significant influence on the dispersion function behavior. (With an increase in incident angle up to θ1= 66°, the width of photonic band gap (PBG) changes for both TM/TE polarization.) With an increase in incident angle up to θ1= 66°, the width of PBG decreases for TM polarization and the width of PBG increases for TE polarization, but it increases with further increasing of the incident angle from θ1= 66° to 89° for both TE- and TM-polarizations. Also, it has been observed that the width of the photonic band gaps changes rapidly by relative difference of the two-plasma frequency. Results show the existence of several photonic band gaps that their frequency and dispersion magnitude can be controlled by the exterior magnetic field, incident angle, and two plasma frequencies. The result of this research would provide theoretical instructions for designing filters, microcavities, fibers, etc.

Study of the diffraction grating designed based on the Bragg reflection structure

Based on the fact that Bragg reflection grating (BRG) is a special case of one-dimensional photonic crystal, we may apply the one-dimensional photonic crystal band gap theory to design the BRG. OptiFDTD is used to simulate both the width error and tilt angle error in BRG. It turns out that the diffraction efficiency will stay high at the 10% width error or the 10° tilt angle error of the Bragg grating. These indicate that the BRG has a high fabrication tolerance. One model of a Bragg diffraction double-grating in the Rowland circle structure is proposed based on the one-dimensional photonic crystal band gap theory for achieving the two-band spectral diffraction. Result shows that the diffraction efficiency of the two incident bands can be as high as 70% when the first set of Bragg grating periods is 6 layers while the second is 10. It is significantly higher than the traditional deeply etched diffraction grating. This is the foundation of a new type of EDG-WDMer with its advantages being of small size and high diffraction efficiency. It may have great potentiality for developing high diffraction efficiency dense wavelength division multiplexer in the future.

Theoretical and experimental evaluation of silicon photonic structures for enhanced erbium up-conversion luminescence

The enhancement of Er3+-based up-conversion for photovoltaics in multilayer porous silicon photonic structures is considered theoretically and experimentally. Transfer matrix simulations are used to assess the increased photonic density of states that results from the slowing of energy propagation at the short-wavelength edge of one-dimensional photonic band gaps. An indirect calculation of Er3+ absorption enhancement within slow-light modes is then used to illustrate an increase in absorption over the bulk value: the effective absorption coefficient is shown to increase by more than 22% over a broad spectral region and by more than 400% over a narrow region. Erbium-doped porous silicon photonic crystals are fabricated with the photonic band edge coincident with the I15/24→I13/24Er3+ transition. Challenges in fabrication are discussed. An angular-dependent photoluminescence measurement demonstrates emission intensity that varies non-monotonically with the position of the photonic band edge. A maximum of 26.6×enhancement of Er3+ emission intensity is observed for the 550-nm transition, with lower enhancement factors seen for longer wavelengths.

Optical bistability in one-dimensional photonic band gap structure with nonlinear graded-index defect layer

The transmission property of a one-dimensional photonic band gap structure with a nonlinear graded-index defect layer is investigated. Using the transfer matrix method, we find that such a composite structure exhibits a bistability that is strongly dependent on the gradation profile and the width of the nonlinear defect layer. The switching threshold values can be greatly reduced just by properly choosing the gradation profile and the width of the nonlinear defect layer.

Pancharatnam and total phases for one-dimensional photonic band gaps

We study the time evolution of the total and Pancharatnam phase of four-level atoms in the presence of a one-dimensional photonic-band-gap material. We obtain analytical and numerical results under certain parametric conditions and analyze the effect of a Kerr-like medium and the detuning parameter on the dynamics of the Pancharatnam phase for the initial atomic position. We observe an interesting feature of the Pancharatnam phase for the one-dimensional photonic-band-gap material.

Polarization multiplexed fluorescence enhancer using a pixelated one-dimensional photonic band gap structure

Fluorescence enhancement using photonic crystals can produce a significant improvement in the signal-to-noise ratio for single molecule and low molecule-concentration fluorescence imaging in biological and biochemical studies. In this Letter, a pixelated one-dimensional photonic band gap structure was designed to enhance both transverse electric and transverse magnetic polarizations through a spatially multiplexed photonic crystal resonance. The average enhancement of 15.6 and 17.9 fold were experimentally verified for the transverse and longitudinal fields on the same substrate. This device may be used as an optical platform for molecular orientation determination.

One dimensional photonic band gap material as an omnidirectional reflector

In this article, the reflection properties in one-dimensional dielectric-dielectric photonic band gap (PBG) structure have been studied. We have used SiO2 as material of low refractive index and Te as a high refractive index material. Reflectivity of proposed PBG structure is plotted as a function of wavelength and angle of incidence and omni-directional PBGs are computed theoretically. To obtain reflectance, we used transfer matrix method for solving Maxwell’s equations for electromagnetic wave in PBG structures. For a large range of frequency, the PBG structure is found to exhibit omni-directional reflection which can be exploited in devices such as optical resonators, mirrors, etc.