Controlling the photoluminescence spectroscopy of quinacrine dihydrochloride by SiO_2 inverse opal photonic crystal

Manipulation of the photoluminescence spectra of light-emitting materials doped in three-dimensional （3D） inverse opal photonic crystals is investigated. Quinacrine dihydrochloride molecules doped highly ordered SiO2 inverse opal is successfully synthesized by co-assembly combined with double-substrate vertical infiltrate method. The quinacrine dihydrochloride-doped and-undoped SiO2 inverse opals each exhibit an apparent photonic band gap （PBG） in the visible light region. Significant suppression of the emission is observed when the PBG is overlapped with the quinacrine dihydrochloride emission bands. The mechanism of suppression effect of PBG in inverse opal on the fluorescence intensity of quinacrine dihydrochloride molecules is studied.     

Experimental study of the photonic band structure of synthetic opals at a low dielectric contrast

This paper reports on a comprehensive study of optical transmissivity spectra of synthetic opals as a function of the four major parameters of the observed photonic stop bands, namely, light beam orientation relative to the opal fcc lattice, light polarization, opal-filler dielectric permittivity contrast, and sample thickness. The measurements were performed under low opal-filler dielectric contrast conditions for the principal high-symmetry directions of the twinned fcc lattice of the opals. The experimentally determined dependence of the energy positions of photonic stop bands on the direction of the light wave vector is fitted well by the calculated dispersion relation of Bragg wavelengths in diffraction of light from the (hkl) fcc plane system.     

Optically excited secondary emission spectra of photonic crystals based on synthetic opals

The photonic dispersion, the group-velocity dispersion, the effective mass, refractive index, and the spectral distribution of the density of photonic states near the edge of the photonic stop band are numerically calculated in the one-dimensional model for photonic crystals based on synthetic opals. The fluorescence spectra of rhodamine 6G and 2,5-bis(2-benzoxazolyl)hydroquinone molecules infiltrated into a synthetic opal are measured. For both substances, it is observed that the spontaneous emission intensity in the range of the photonic stop band is appreciably suppressed. A blue shift of the fluorescence spectrum of rhodamine 6G molecules is revealed. Secondary emission of synthetic opals infiltrated with colloidal silver is observed in the Stokes range under excitation of opals by radiation at λ = 400 nm. The spectrum of the secondary emission is located in the range 450–590 nm, which contains the stop band and intervals near its edges.     

Spectroscopy of the photonic stop band in synthetic opals

The photonic band gap of opals has been studied experimentally from their optical transmission spectra as a function of the incident beam orientation in the opal crystal lattice. The measurements were carried out for all high-symmetry points on the surface of the Brillouin zone of an fcc lattice. The experimental dependence of the energy position of the photonic band gap on the light wave vector direction is well described by the set of theoretical relations developed for the stop bands originating from the Bragg diffraction of light on {111}-type planes of the twinned fcc lattice of synthetic opals.     

Multiple Bragg diffraction in low-contrast photonic crystals based on synthetic opals

The phenomenon of multiple Bragg diffraction in low-contrast photonic crystals based on synthetic opals has been studied both experimentally and theoretically. The transmission and reflection spectra of opal films near the K point of the Brillouin zone of the face-centered cubic lattice in s-polarization exhibit the effect of anticrossing of dispersion curves corresponding to the (111) and ([`1]11)(\bar 111) photonic stop bands. The effect of quasi-Brewster suppression of stop bands is clearly pronounced in p-polarization. The experimental data are analyzed using the calculation of the band structure of opal with the inclusion of the polarization of incident light.     

Optical and dielectric properties of nanostructured photonic crystals loaded by ferroelectrics and metals

The properties of new materials produced by loading artificial opals with different ferroelectrics (sodium nitrite, barium titanate, lithium niobate. etc.) are analyzed. The possibility of modifying the ferroelectric properties of materials by introducing them into pores of artificial opals is reported. The physical properties of artificial opals with pores loaded by conducting media (mercury, amorphous carbon, silver, gold, etc.) are studied. An analysis is made of the transmission and reflection spectra of broad-band radiation, which permit one to establish the characteristics of the stop bands as a function of the globule diameter, the type of ferroelectric or metal inserted into the opal pores, thermal annealing conditions, etc. The conditions favoring emission of slow electromagnetic waves in artificial opals are specified, and their characteristic properties are reported. The possibilities for increasing the efficiency of Raman and nonlinear optical processes in photonic crystals loaded by ferroelectrics and metals are analyzed.     

Enhancing fluorescence of tricolor fluorescent powders by silica inverse opals

Silica inverse opal photonic crystals (PCs) were fabricated by using a sacrificial polymer template method, and were characterized by scanning electron microscopy and reflection spectra. The fluorescence of tricolor fluorescent powders has been enhanced obviously by silica inverse opals as the emission wavelengths of the tricolor fluorescent powders are in the range of stop bands of the inverse opal PCs, which demonstrates that the PCs will be efficient and selective reflection mirrors. A promising application of the strategy would be in novel effective lighting devices. PACS 42.70.Qs; 78.55.-m; 78.55.Mb; 78.68.+m; 78.67.-n An erratum to this article can be found at     

Resonant behavior and selective switching of stop bands in three-dimensional photonic crystals with inhomogeneous components

We demonstrate that, in contrast with the well-studied photonic crystals consisting of two homogeneous components, photonic crystals comprised of inhomogeneous or multiple (three or more) components may bring new opportunities to photonics due to the discovered quasiperiodic resonant behavior of their (hkl) stop bands as a function of the reciprocal lattice vector. A resonant stop band cannot be switched off for any permittivity of structural components. Tuning the permittivity or structural parameters allows the selective on-off switching of nonresonant (hkl) stop bands. This independent manipulation of light at different Bragg wavelengths provides a new degree of freedom to design selective optical switches and waveguides. Transmission experiments performed on synthetic opals confirmed the theoretical predictions.     

Selective control of light beams in diffraction experiments on synthetic opals

This paper reports on an experimental and theoretical investigations of the possibility of selectively controlling the intensity of {hkl} diffraction reflections in synthetic opals. The calculations of the photonic stop-band width for low-contrast multi-component photonic crystals argue for a selective pattern of the vanishing of various {hkl} stop bands (and, accordingly, of the various {hkl} diffraction reflections) under variation of the dielectric permittivity of one of the components. Optical diffraction patterns have been studied visually and recorded in various scattering geometries with bulk opal samples illuminated by white unpolarized light. The experiments have made use of immersion spectroscopy, a method reducing essentially to successive measurements of diffraction patterns under variation of the dielectric permittivity of the liquid filler of the opal matrix. The {111} and {220} Bragg reflections have been observed to weaken noticeably at the filler permittivities matching very well with the values derived earlier from an analysis of transmission spectra.     

Complex interaction of polarized light with three-dimensional opal-based photonic crystals: Diffraction and transmission studies

Polarization characteristics of light interaction with the photonic crystal of a-SiO₂ synthetic opals were studied under the conditions of low dielectric contrast. We analyzed 3D diffraction patterns of monochromatic light and calculated optical transmission spectra of oriented samples. The diffraction patterns are found to change with the polarization of incident light, indicating a strong polarization dependence of photonic stop bands in synthetic opals. It is shown theoretically there exists a critical angle, θ_c, of the p-polarized light incident on the (h k l) crystal plane, at which the resonance contribution to Bragg diffraction vanishes.     

Spectroscopy of stop bands of globular photonic crystals filled with water

Reflectance spectra from the surface of artificial opals are measured at various globule diameters. A method for calculating the spectra of globular photonic crystals taking into account the globule size dispersion is proposed. The effect of the filling of opal with water on the spectral position of stop bands is revealed. Satisfactory agreement of theoretical results with experimental data was found.     

Propagation of polarized light in opals: Amplitude and phase anisotropy

The interaction of linearly polarized light with photonic crystals based on bulk and thin-film synthetic opals is studied. Experimental transmission spectra and spectra showing the polarization state of light transmitted through opals are discussed. A change in polarization is found for waves experiencing Bragg diffraction from systems of crystallographic planes of the opal lattice. It is shown that the polarization plane of the incident linearly polarized wave at the exit from photonic crystals can be considerably rotated. In addition, incident linearly polarized light can be transformed to elliptically polarized light with the turned major axis of the polarization ellipse. Analysis of polarization states of transmitted light by using the transfer-matrix theory and homogenization theory revealed good agreement between calculated and experimental spectra.     

Photonic band structure of 3D ordered silica matrices

The symmetry and orientation of a photonic lattice of 3D ordered porous silica matrices (synthetic opals) are determined by analysis of transmission electron micrographs. By optical transmission measurements the photonic band edges are mapped out at pointsLandKof the Brillouin zone. It is shown that modulating the refractive index of opal pores by filling them with liquids results in variation of the light attenuation length within the forbidden gap. To increase the refractive index contrast of the lattice, the pores of opals were filled with CdS. A dramatic decrease in attenuation length is observed for opal/CdS. The parameters of a photonic lattice with a ‘pseudo-gap’, that is, with a prominent depletion of the photonic density of states, are estimated.     

人工欧泊填充InP后的形貌和反射谱特性

制备了人工opal晶体模板,运用MOCVD方法在SiO2人工opal球体间填充了高折射率的InP晶体,选择了MOCVD生长InP的有关参数.样品扫描电子显微镜及反射谱结果检测显示,InP晶体在二氧化硅间隙中的生长是均匀的,具有较好的结晶质量;高介电常数的InP的填充使人工欧泊光子晶体的光子禁带效应增强,反射峰移向长波长区.光学特性检测结果与理论计算值得到较好的符合.     

Low-temperature heat capacity and heat conductivity of single-crystal synthetic opals

The heat capacity at constant pressure (in the range 3–50 K) and the lattice heat conductivity (from 5 to 75 K) of a single-crystal synthetic opal are measured. It is shown that the heat capacity of the opal behaves at these temperatures in a way similar to porous amorphous materials. The data on the heat conductivity suggest that single-crystal opals can be related to a class of semicrystalline (partially crystallized amorphous) materials. However, because of specific features of their crystal structure, the opals form a nonstandard type of semicrystalline material which we termed semiamorphous.     

Bragg diffraction of light in synthetic opals

Three-dimensional light diffraction from the crystal structure, formed by closely packed a-SiO₂ spheres of submicron size, of samples of synthetic opals was visualized. The diffraction pattern of a monochromatic light beam was established to consist of a series of strong maxima whose number and angular position depend on the wavelength and mutual orientation of the incident beam and the crystallographic planes of the sample. The diffraction patterns were studied under oblique incidence on the (111) growth surface of the sample and with light propagated in the (111) plane in various directions perpendicular to the sample growth axis. The spectral and angular relations of diffracted intensity were studied in considerable detail in both scattering geometries. The experimental data are interpreted in terms of a model according to which the major contribution to the observed patterns is due to Bragg diffraction of light from (111)-type closely packed layers of the face-centered cubic opal lattice. The model takes into account the disorder in the alternation of the (111) layers along the sample growth axis; this disorder gives rise, in particular, to twinning of the fcc opal lattice.     

Multifrequency stimulated Raman scattering of light in liquid nitrogen infiltrated into 3D photonic crystals

Spectral characteristics of stimulated Raman scattering at least in synthetic opal matrices infiltrated with liquid nitrogen upon excitation by nanosecond laser pulses are studied. The effect of the stop band position on the generation efficiency of anti-Stokes components of stimulated Raman scattering up to the third order is demonstrated. The excitation threshold of stimulated Raman scattering in liquid nitrogen infiltrated into opals is significantly lower in comparison with the generation in bulk samples.     

Optical properties of 3D photonic crystals filled with CdSe/CdS quantum dots

We study 3D globular photonic crystals based on synthetic opals filled with semiconductor core/shell quantum dots CdSe/CdS by measuring the photoluminescence spectra. The spectra were obtained using 369, 384, and 408 nm LED light excitation and involving a pulse YAG laser operating at 365 and 266 nm. The study shows that the photoluminescence spectra of opal filled with CdSe/CdS changes sufficiently in comparison with spectra taken for pure opal and a reference colloidal solution of CdSe/Cds quantum dots in toluene. Such opals may be used to fabricate a narrow-band light sources.     

Optical characterization of synthetic opals

The results of a structural-optical characterization of synthetic opals are presented. Information on the growth-induced features of the opal structure was derived from an analysis of the position and width of the one-dimensional photonic band gap. The structure of the samples was found to vary substantially along the growth axis coinciding with the [111] direction of the fcc lattice. It was shown that the regions corresponding to early stages in the opal structure growth are typically strongly disordered, which manifests itself, in particular, in the crystallites being misoriented relative to the sample growth axis. It was concluded that the regions of synthetic opals most suitable for application as photonic crystals are those corresponding to later growth stages.     

Optics of globular photonic crystals

Recent experimental and theoretical results on the optical properties of globular photonic crystals coauthored by the author are presented. The dispersion relation for electromagnetic waves in a 1D photonic crystal that simulates the properties of a selected direction in the globular photonic crystal is calculated. The spectral ranges that are characterized by the anomalous slowing of electromagnetic waves in the photonic crystal and correspond to the stop-band edges are determined. A method for the measurement of the transmission and reflection spectra of the broadband radiation in photonic crystals is proposed. The method enables one to find the characteristics of the stop bands. The features of the secondary emission that emerges in opals due to the UV and visible excitation are reported. The conditions for the low-threshold lasing in opals filled with rareearth elements are presented. The experimental results on the induced-globular light scattering are demonstrated. Such a scattering implies the coherent excitation of vibrational states of the globules in a globular photonic crystal. A new phenomenon (slow light scattering) which involves the excitation of slow photons (slowtons) that correspond to the stop-band edges of the photonic crystal is observed. The conditions for the measurement of the slow light scattering in opals excited using the ruby and nitrogen lasers are experimentally determined. The experimental and theoretical results open up the prospects for low-threshold nonlinear optical processes in material media.