Gold film-terminated 3-dimensional photonic crystals

Hybrid metal-dielectric photonic crystals assembled from an opal film coated by a gold film are designed in order to realize optical spectra that emanate from mixing Bloch modes in the opal and surface plasmon polaritons in corrugated gold films. The photonic crystal provides a spatial template for the gold film profile and modifies the electromagnetic vacuum in the vicinity to the gold layer. Reflectance spectroscopy was applied to deconvolute the plasmonic and photonic bandgap components in the optical response of hybrid crystals as opposite to their mixed appearance in the transmission spectra.     

Effect of dimensionality on the spectra of hybrid plasmonic-photonic crystals

Based on colloidal crystals of various dimensionality, hybrid metal-dielectric plasmonic-photonic heterocrystals have been prepared. It has been shown that the spectra of optical transmission of heterocrystals are mostly controlled by the sum of contributions of composing plasmonic and photonic crystals. At the same time, there are a number of phenomena caused by the mutual effect of heterostructure components, which lead to a deviation of observed optical properties from the linear superposition of responses of these crystals. In particular, it has been found that the anomalous transmission controlled by the plasmonic crystal decreases with increasing the dimensionality of the photonic crystal attached to it. At the same time, light reflection on a metallized surface changes light diffraction in photonic crystals and leads to Fabry-Perot oscillation amplification. It has been assumed that an intermediate layer is formed, in which Bloch modes of the photonic crystal and surface plasmon-polaritons of the plasmonic crystal are hybridized.     

Structural characterization of opal-based photonic crystals in the visible range

For structural characterization of periodic three-dimensional systems with submicron-scale lattice parameters (optical photonic crystals), is analogous to the use of visible light of x-rays. It is shown that specular reflectance and transmittance spectra of opal do indeed yield information on the lattice period and structural perfection of photonic crystals. Fiz. Tverd. Tela (St. Petersburg) 40, 648–650 (April 1998)     

Optical study of three-dimensional magnetic photonic crystals opal/Fe3O4

Optical and magneto-optical properties of three-dimensional magnetic photonic crystals, based on magnetite Fe₃O₄ embedded into an opal film matrix, are investigated in both transmission and reflection. A strong enhancement of the polar Kerr effect and a modification of the Faraday effect have been found near the photonic band-gap of about 1.8 eV. Unusual changes of hysteresis curves and their dependence on photon energy have been revealed in the spectral region where the magneto-optical effect reverses its sign. This phenomenon has been explained by two types of magnetite particles inside the opal matrix having different coercive fields and spectral behaviour.     

Raman Scattering in Three-Dimensional Photonic Crystals

The optical properties of three-dimensional photonic crystals associated with the form of reflection spectra from their surface (appearance of a forbidden gap in the energy spectrum) and with the specific features of Raman scattering are analyzed. Idealized models of the energy band structure of photonic crystals are studied. Expressions for the group velocity of photons with energy close to the forbidden gap are derived. Experimental results on the Raman scattering in photonic crystals based on artificial opal as well as in fused silica are discussed. Bands due to quantum-size effects (presence of nanoclusters in fused silica and nanoglobules forming the lattice of globular photonic crystals) were manifested in the spectra of inelastic light scattering. It is proposed to use photonic crystals for the creation of sensitive sensors of organic and inorganic substances using modern Raman techniques.     

Specific features of polarization anisotropy in optical reflection and transmission of colloidal photonic crystals

This paper reports on the measurements (in linearly polarized light) of the transmission and reflection spectra of colloidal photonic crystals with three-dimensional and one-two-dimensional photonic band structure, i.e., opal films and Langmuir-Blodgett crystals with a refractive index contrast of ∼1.5: 1.0. It has been shown that the polarization anisotropy is enhanced considerably in the diffraction resonance range both in transmitted and reflected light, and that the anisotropy in the resonance range can be as high as 99%. The interaction of photonic crystal eigenmodes has been found to affect the polarization anisotropy. The assumption has been made that the coincidence of the maxima in polarization anisotropy of the resonant and nonresonant light reflection in colloidal crystals originates from the disorder in their lattices. The generality of the results obtained is confirmed by the fact that the polarization anisotropy manifests itself in the same way in colloidal crystals with different lattice symmetries.     

Interference of additional modes in spectra of opal-like photonic crystals in the multiple diffraction regime

The mechanisms of formation of Bragg reflectance and transmittance spectra have been investigated for films of three-dimensional opal-like photonic crystals. Attention has been drawn to the fact that the spectra exhibit an additional short-period interference structure of the novel type due to the multiple Bragg diffraction of light. The spectra have been calculated in the framework of the dynamical three-wave diffraction model taking into account strong spatial modulation of the dielectric function. It has been found that short-period oscillations appear in the spectra due to the spatial quantization of additional modes with a low group velocity.     

Novel properties of nanoscale organic–inorganic systems and photonic crystals — conducting polymers in nanoscale periodic structures,microcavities and photonic crystals

Conducting polymer/C₆₀and C₆₀doped conducting polymer/C₆₀heterojunctions have been fabricated and found to exhibit remarkably enhanced photoresponse due to the highly effective photoinduced charge transfer at the interface. In conducting polymer/C₆₀alkali metal nanoscale composite systems, multiphase superconductivity has been clarified and explained by taking the coupling of nanoscale grains by Josephson junctions into consideration. As examples of intramolecular organic-inorganic combined systems, unique electrical and optical characteristics have been revealed in oligosilanylene oligophenylene polymers. Electroluminescence has been demonstrated in organic-inorganic junction devices such as conducting polymer/porous Si and conducting polymer/diamond junctions. Conducting, polymer-based nanoscale multilayer systems have been studied utilizing molecular self-assembly method and novel photosensitive characteristics have been revealed. \indent Novel optical and electrical properties of conducting polymers infiltrated in a photonic crystal, synthetic opal made of SiO₂spheres of several hundred nm in diameter, and also a conducting polymer replica have been revealed. A clear diffraction pattern was observed in a photonic crystal infiltrated with conducting polymers, and transmission spectra are dependent on various ambient conditions. Their photoluminescence (PL) spectra, spectral narrowing of PL and lasing characteristics at relatively low optical excitation have also been clarified. Novel conducting characteristics of conducting polymers in a photonic crystal that was prepared by pyrolysis of a polymer replica of opal have also been observed.     

Optical properties of mesoporous one-dimensional photonic crystals

The systematic features in the reflectance spectra of broadband optical radiation from the surface of one-dimensional photonic crystals based on mesoporous structures are presented. The dispersion dependence for electromagnetic waves in the mesoporous one-dimensional photonic crystal is established. On its basis, reflectance and transmittance spectra are calculated for particular structures, and the microscopic parameters of the samples under study are determined. The developed theory is used to explain the shape of reflectance spectra in mesoporous photonic crystals based on silicon, quartz, and aluminum oxide.     

Quantized longitudinal exciton-polaritons in periodic metal–semiconductor nanostructures

We theoretically investigate the optical properties of one-dimensional photonic crystals composed of two alternating layers, namely a semiconductor film and a metallic one. The nonlocal optical response of the semiconductor is here described by using a resonant excitonic dielectric function, whereas the local response function of the metal film is modeled with Drude formula. We calculate optical spectra of the metal–semiconductor 1D photonic crystal for both s- and p-polarization geometries. In both cases the spectra exhibit a rich resonance structure due to the coupling of size-quantized excitons inside the semiconductor film with light. We show the difference between s- and p-polarization reflectivity as the angle of incidence is increased. In the p-polarization geometry, besides transverse exciton-polariton modes, longitudinal polarization waves are excited producing additional spectral resonances. The spectra become radically different when the frequency corresponding to the minimum of the first photonic pass-band is close to the exciton resonance, since such a frequency is distinct for s- and p-polarized modes. We also show how reflectivity spectra for both polarizations are modified with varying the metal filling fraction which controls the width of the gap below the lowest frequency band.     

Inverted yablonovite fabricated by the direct laser writing method and its photonic structure

Three-dimensional photonic crystals with an inverted yablonovite structure have been fabricated by the direct laser writing method based on the two-photon polymerization of a photosensitive material. The correspondence of the structure of the samples to the inverted yablonovite lattice has been confirmed by scanning electron microscopy. The photonic band structure of inverted yablonovite, as well as a number of related photonic materials with an fcc lattice, has been calculated. It has been found that the photonic properties of opal and yablonovite are opposite: the complete photonic band gap appears in inverted opal and direct yablonovite and is absent in direct opal and inverted yablonovite. A method for the fabrication of ideal three-dimensional photonic structures having the complete photonic band gap in the infrared and visible spectral ranges has been discussed.     

Observations of band structure and reduced group velocity in epitaxial GaN–sapphire 2D photonic crystals

We report experimental results for the band structure of 2-dimensional triangular photonic crystals of air holes in an epitaxial group III–nitride waveguide film. Surface coupling techniques enable the observation of sharp resonance dips in the transmission spectra due to a resonance phenomenon between the incident light and Bloch modes of the photonic crystal. The position of the dips has been measured as a function of angle of incidence and the photonic band structure has been successfully constructed by the measurement. Corresponding Bloch-mode group velocities have also been obtained. Received: 28 May 2001 / Published online: 23 October 2001     

红外区金属氧化物反蛋白石光子晶体的安德森定域化研究

根据Mie散射理论,在低浓度近似下,对中红外区由金属氧化物构成的反蛋白石光子晶体的禁带的存在区域,即光子定域化区进行了研究。发现在浓度为10%,此类晶体在中红外区将出现多个光子禁带区域,并且计算了影响定域化区域的各种因素。由此可知利用材料在剩余射线带内折射率小于1的特性,我们可以制备出中红外区和远红外区存在禁带的光子晶体。这一结果为反蛋白石晶体的研究提供了理论方法。     

中红外完全带隙Si反蛋白石光子晶体的制备与光学性能研究

通过溶剂蒸发对流自组装法制备SiO2胶体晶体,采用低压化学气相沉积法填充Si,制备得到Si反蛋白石(opal)三维光子晶体.采用扫描电子显微镜对Si反opal的显微形貌进行表征,采用平面波展开法理论模拟Si反opal的光子带隙,采用傅里叶变换红外光谱仪测试其光学性能.研究结果表明:Si在SiO2微球空隙内填充致密均匀,显微红外光谱测试的光子带隙反射峰位置及带宽与理论计算基本符合.变角度反射光谱测试表明,Si反opal沿不同角度入射时在中心波长3319nm处均存在明显的反射峰,证明其具有完全光子带隙,带隙位于中红外大气窗口区域.     

Spectra of secondary emission during generation of optical harmonics in globular photonic crystals

Secondary emission spectra of globular silica photonic crystals when their surfaces were exposed to laser pulses 250 fs long at a power density to 1 TW/cm² have been studied. Optical harmonics and plasma emission were detected in this case. For the opal matrix containing pores filled with air, in the reflection mode, the third optical harmonic with a conversion efficiency of ～10% arises. The highest conversion efficiency for exciting radiation with wavelengths of 1026 or 513 nm is implemented when the frequencies of the exciting radiation or the second harmonic are near the stop band edge. In globular photonic crystals filled with sodium nitrite or barium titanate ferroelectrics, the second optical harmonic is observed. The exciting radiation conversion efficiency to the second optical harmonic was a few percent and depended on the frequency of exciting radiation and photonic crystal globule diameters. It is found that the plasma emission intensity increases with the exciting radiation power density. The dependences of the intensity of the second and third optical harmonics on the pump intensity are constructed for various photonic crystal globule diameters.     

Features of the manifestation of a stop band in the spectrum of light diffracted at a glass-opal interface

The diffraction of light passing through a glass plate coated by an artificial opal film has been analyzed. It has been shown that the stop band of a photonic crystal is manifested against the background of the unchanged spectrum of reflected and refracted Bragg waves. The position of this stop band can be changed under a small change in the concentration of a number of substances filling the photonic crystal. The application of such an optical system as an optical chemical sensor has been demonstrated.     

The photonic analogue of the graded heterostructure: Analysis using the envelope approximation

We develop and deploy an envelope function formalism in order to study graded photonic crystals – periodic photonic media whose features vary continuously with position. We use the method to reduce the properties of the uniform crystals to the spectral position of their band edges and an effective mass-like term. These are employed within the Schrödinger-like equation derived herein to determine the behaviour of light inside a specific graded photonic crystal created using depth-dependent infiltration of an artificial opal.     

Study of domains in globular photonic crystals by bragg reflection of light

The spatial distribution of the intensity of light reflected from the surface of a globular photonic crystal prepared on the basis of artificial opal was studied. Using a CCD array as a selective radiation receiver and a special computer program, reflection spectra were measured for photonic crystal regions with different colors, referred to as color domains. An analysis of the obtained spectra allows estimation of the homogeneity of the irradiated surface of the photonic crystal, relative areas of color domains, differences in crystal structures of individual color domains, and crystal structure defects.     

Extremely low optical transmittance in the stopbands of photonic crystals

We demonstrate extremely low transmittance characteristics of photonic crystals (PhCs) with a finite thickness in specific photonic bandgaps (PBGs) through numerical simulation, and clarify its origin. Some of the PhCs support decaying Bloch eigenmodes, whose propagation constant (real part of the Bloch wavenumber) as well as their decay constant (imaginary part) changes with frequency inside the bandgap. Such a class of modes can interfere destructively at the exit end of the crystal depending on their round-trip phase change, which creates comb-like valleys in their transmission spectra.