Optical Tamm surface states are formed in 3-dimensional photonic crystals coated by thin metal films. These states
appear in registry with diffraction resonances and localize the electromagnetic energy in resonators formed by diffraction
mirrors of lattice planes and metal semishells. Tamm defect states provide the bypass for light in the spectral range of
photonic stop-bands and thus reduce the efficiency of the Bragg diffraction resonances. In spite of hidden nature of this
effect, its magnitude is comparable to the extraordinary transmission associated with tunneling of surface plasmon
polaritons, which are simultaneously excited at surfaces of corrugated metal film coating.
The retroreflection spectroscopy have been developed with the aim to investigate the spectra of light scattered at intrinsic defects of photonic crystals. Self-assembled 3-dimensional colloidal crystals, opals, have been investigated. Compared to conventional spectroscopies of reflected and transmitted light, which evaluate the rejected by photonic crystal light, the retroreflectance is designed to visualize the propagating eigenmodes of photonic crystals. The principal advantages of this method are the direct experimental evaluation of the stop-bandwidth and the quantitative estimate of defect concentration by the slope of the angle diagram of the scattered light intensity. The added value of this method is the independent evaluation of the periodicity and the effective refractive index of photonic crystals under interrogation by simultaneous observation of the angle dispersions of volume and surface resonances of the photonic crystal lattice.
Ordered and disordered monolayers of spheres were assembled on dielectric and metallized substrate using the Langmuir-Blodgett style technique. The coexistence of Mie and diffraction resonances was investigated. Experiments showed the weak dependence of diffraction resonances on the distance between spheres, but their gradual destruction with increasing disorder. In turn, Mie resonances appear along the increased light localization in the monolayer, but experience strong blue shift and gradual reduction of the magnitude along the increased isolation in the lattice. Calculation proved that hybridization of Mie resonances rapidly vanishes along the increase of the spacing between spheres and the hopping of excitations between spheres can be expected only in tightly packed arrays.
We prepared thin film opal crystals and studied their angle-resolved transmission spectra in linear and circular polarized light as a function of the incidence angle and the azimuth rotation angle. We also explored the polarization conversion in linear and circular polarized light. Based on the spectra analysis we ascribed the polarization conversion in opal photonic crystal to properties of the Bloch modes of 3-dimensional photonic crystal.
In order to realize the regime of strong coupling between Bloch modes of periodically structured dielectric and
surface plasmon polariton modes of corrugated metal film we prepared 2-dimensional slab hybrid plasmonicphotonic
crystals. Angle-resolved transmission/reflectance spectroscopy was used to assess the composition of
guided modes in such hybrid crystals. In the case of a monolayer photonic crystal encapsulated in a plasmonic
waveguide we achieved the splitting of major resonances, which was interpreted in terms of mode hybridization and
controlling the spatial localization of modes.
The transformation of 2-dimensional slab photonic crystal into 2-dimensional photonic glass was achieved by
gradually increasing the sphere spacing and by randomising the lattice. The materials were prepared by assembling
colloidal particles at the air/water interface using a Langmuir-Blodgett trough and the subsequent deposition on glass
substrates. Highly ordered monolayers were obtained by using colloids of one size, while use particles of two
different sizes and different partial concentrations allows to increase the spacing of the larger spheres and to
randomize the lattice. Changes in the spheres arrangements result in a change of in-plane light propagation from
band-like to hopping photon transport.
We prepared thin film colloidal crystals, namely, opals and Langmuir-Blodgett crystals, of different lattice constants
and coated them with 20, 50 and 100 nm thick gold films. Angle-resolved transmission spectra of these hybrid
nanostructures were obtained using linear polarized light over a spectral range of a photonic bandgap energy structure of
these colloidal photonic crystals. Up to 10 times transmission enhancement has been observed in specific spectral
intervals determined by the light coupling to surface plasmon polaritons in the metal film. At the same time these
hybrid nanostructures retain transmission attenuation bands inherited from a photonic crystal. The strong crosscorrelation
of the photonic bandgap and surface plasmon polariton properties was observed in the transmission spectra
of studied hybrids.
Polarization anisotropy of the zero order forward-diffracted and the off-resonance transmitted light in the 3-dimensional
thin film opal photonic crystals has been numerically computed and experimentally measured. Studies of the
polarization anisotropy as a function of the incidence and azimuth angles of the incoming light have revealed strong
anisotropy changes at diffraction resonances and in the ranges of the multiple-band diffraction. The opposite sign of the
polarization anisotropy for different diffraction resonances has been observed. The cross-polarization coupling has been
measured and identified as one of the reasons for changing the anisotropy sign. The correlation of the lattice ordering and
the magnitude of the light polarization anisotropy has been demonstrated.
Photoluminescence spectra of the ZnO carcass of inverted opal have been examined in the conditions of the strong
lightto-structure interaction achieved by matching the photonic bandgaps of these photonic crystals to different parts of the
ZnO emission spectrum. Developing the bands of enhanced spontaneous emission associated with both the emission of
ZnO defects and the emission due to interband electron transitions has been observed. Interpretation has been given
taking into account the coupling of emission to eigenmodes of
3-dimensional photonic crystal and the nature of the
electron states involved in the radiative relaxation.
Heterogeneous 3-dimensional photonic crystals have been prepared by sandwiching self-assembled opal films and
forced-assembled Langmuir-Blodgett colloidal crystal films. Strong transformation of the transmission spectra of the
light traversing such hetero-crystals has been observed and interpreted in terms of the mismatch between eigenmodes of
these photonic crystals and subsequent strong scattering at the interface between these crystals. Direct measurements of
the spectra of forward scattered light have confirmed the peculiar character of the light scattering at the photonic crystal
Crystal ordering of opal-based self-assembled photonic crystals fabricated by vertical drawing deposition technique has
been examined by the angle-resolved transmission spectroscopy. Assuming that minima in transmission spectra register
the diffraction resonances occurring at different planes of the crystal lattice, the angle dispersions of these resonances
reflect the ordering of the crystal lattice. Since such dispersions obtained as a function of the angle of light incidence
cannot provide quantitative estimate of the crystal ordering without comparison to the adopted standard, we suggested to
analyse the diffraction resonances as a function of the lattice rotation. This method allows to quantify the lattice ordering
by the accuracy of the repetition of similar diffraction features upon the azimuth angle.
Crystal ordering of colloidal self-assembled photonic crystals fabricated by vertical drawing deposition
technique has been improved following application of acoustic noise vibrations. The scanning electron
microscopy has confirmed the improvement in the crystal order on the surface (111) plane and has
demonstrated that thin opal films crystallized under acoustic agitation consist of similarly oriented crystallites,
the characteristic transverse dimension of which is larger compared to that of sample grown without acoustic
field. Three-dimensional lattice arrangement of the opal crystal has been examined by means of laser
diffraction and optical transmission spectroscopy. Novel approach towards optical characterisation of the opal
crystallinity has been suggested.
We report on fabrication of high quality opaline photonic crystals from large silica spheres, self-assembled in hydrophilic trenches of silicon wafers by using a drawing apparatus with a combination of stirring. The achievements here reported comprise a spatial selectivity of opal crystallization without special treatment of the wafer surface, a filling of the trenches up to the top, leading to a spatially uniform film thickness, particularly an absence of cracks within the size of the trenches, and finally a good three-dimensional order of the opal lattice even in trenches with a complex confined geometry, verified using optical measurements. The opal lattice was found to match the pattern precisely in width as well as depth, providing an important step towards applications of opals in integrated optics. The influence of substrate structure on crystallization is also discussed.
Spectra of the light scattered in the heterogeneous photonic crystal based on the thin triple-film opal, which was prepared by successive, convective force-assisted crystallisation of colloidal suspensions containing spheres of 374, 474 and again 374 nm in diameter, have been studied in the wavelength range of low order photonic bandgaps. If the ballistic regime of light propagation is preserved, the forward scattered light becomes the subject of the diffraction attenuation, whereas the backscattered light experiences both the diffraction enhancement and attenuation. A variety of possible configurations of scattered light measurements have been examined and corresponding spectra of scattered light have been compared with each other and with the spectra of transmitted and reflected light. The effect of the internal interfaces and the planar microcavity embedded in the photonic crystal upon the propagation of scattered light has been extracted.
Transmission spectra of thin opal films prepared by crystallisation in moving meniscus have been obtained in orthogonal polarisations in the wavelength range including the low and the high order photonic bandgaps. The anisotropy of light propagation in opal films has been studied as a function of the angle of light incidence, orientation of the opal lattice with respect to the light incidence plane, wavelength and polarisation of light. Clear correspondence between the spatial and the polarization anisotropy of light propagation has been demonstrated. The deviations of the opal film transmission from the commonly used model have been discussed.
Experimental and theoretical studies of the emission directionality diagrams of a perylene dye covering the inner surface of three-dimensional opal-based photonic crystals with incomplete photonic bandgap are reported. Directionality diagram of emission intensity is interpreted in terms of the spontaneous emission suppression by photonic band gap and the emission enhancement due to photon focusing phenomenon. A theoretical model is based on the classical analysis of an angular distribution of the radiated power of a point dipole.
The effect of photonic bandgap interface upon the light scattering was studied in hetero-opals consisting of two opal thin films with different lattice constant. It is shown that the weak scattering regime is preserved in thin hetero-opal films. By comparing scattering spectra of single and hetero-opal films recorded under reversing angles of light incidence and detection it was demonstrated that the interface scatters stronger the light at oblique incident angles. Squeezing of the scattering diagram of hetero-opals compared to single opal films is also assigned to the interface scattering.
The light reflectance in 3-dimensional metal-dielectric photonic crystals, assembled from polyelectrolyte-coated latex spheres and infiltrated after opal crystallisation with gold nanoparticles, has been studied. Development of the surface plasmon resonance bands of Au nanoshells along the increase of the Au nanoparticle concentration has also been observed, along with deviation of the diffraction resonance dispersion and formation of the specific excitation, which combines photonic crystal optical mode with surface plasmon resonance. For heavy nanoparticle loadings, the reentrant dielectric type behaviour of the metal-dielectric photonic crystal has been seen.
The light reflectance in 3-dimensional metal-dielectric photonic crystals assembled from polyelectrolyte-coated latex spheres infiltrated with gold nanoparticles prior or after opal crystallisation has been studied. Strong deviation of the optical reflectance of Au-opals from bare opals has been observed, including flattening of the diffraction resonance dispersion and topology dependence of surface plasmon bands. Depending on whether the infiltration was made before or after opal crystallisation, the plasmon reflectance shows different band central frequencies as well as band positioning as the function of angle. The strong alteration of shape of the reflectance spectrum has been demonstrated in the case of overlapping the diffraction and plasmon resonances.
A heterojunction between two 3-dimensional photonic crystals has been realized by interfacing two opal films of different lattice constants. The interface-related transmission minimum has been observed in the frequency range between two directional lowest-order bandgaps of the hetero-opal constituents. The interface transmission minimum has been modelled numerically and tentatively explained by formation of the standing wave across the photonic hetero-crystal due to matching of group velocities of optical modes in both parts at this frequency.
We review the status of 3D anisotropic crystals based on opal-semiconductor and opal-polymer nanocomposites with respect to controlling the spontaneous emission in space and frequency. An approach to grow photonic crystal structures form PMMA balls containing a laser dye is also presented. We show that depending mainly on the refractive index contrast and the choice of light emitter, photonic crystal effects manifest themselves in several forms. These are illustrated by choosing a suitable dopant for the polymer, such as laser dyes or rare-earth ions, under condition that their fluorescence should fall within the stop-band of the photonic crystals. The refractive index contrasts obtained are far from ideal and yet the impact of the anisotropic PBG is manifested unambiguously in, for example, the change of the density of states of photons and the directionality of the emission.