Three-dimensional Colloidal Photonic Crystals Research Articles

Anomalous Fluorescence Enhancement from Double Heterostructure 3D Colloidal Photonic Crystals--A Multifunctional Fluorescence-Based Sensor Platform.

Augmenting fluorescence intensity is of vital importance to the development of chemical and biochemical sensing, imaging and miniature light sources. Here we report an unprecedented fluorescence enhancement with a novel architecture of multilayer three-dimensional colloidal photonic crystals self-assembled from polystyrene spheres. The new technique uses a double heterostructure, which comprises a top and a bottom layer with a periodicity overlapping the excitation wavelength (E) of the emitters, and a middle layer with a periodicity matching the fluorescence wavelength (F) and a thickness that supports constructive interference for the excitation wavelength. This E-F-E double heterostructure displays direction-dependent light trapping for both excitation and fluorescence, coupling the modes of photonic crystal with multiple-beam interference. The E-F-E double heterostructure renders an additional 5-fold enhancement to the extraordinary FL amplification of Rhodamine B in monolithic E CPhCs, and 4.3-fold acceleration of emission dynamics. Such a self-assembled double heterostructue CPhCs may find significant applications in illumination, laser, chemical/biochemical sensing, and solar energy harvesting. We further demonstrate the multi-functionality of the E-F-E double heterostructure CPhCs in Hg (II) sensing.

Plasmonic Resonance-Induced Effects on Stopband and Emission Characteristics of Dye-Doped Opals

Three-dimensional colloidal photonic crystals containing a fluorophore, and fabricated by inward growing self-assembly method, are infiltrated with gold nanoparticles of 5-nm diameter. The effects of localized surface plasmon resonance of gold nanoparticles on the stopband of the photonic crystal are investigated by tuning the reflection band to overlap with the plasmonic band. Interestingly, reflection spectra of gold-infiltrated PhC show a clear suppression in the reflection band around the stopband center at higher angles of incidence due to the efficient coupling between the plasmon and photon modes inside the crystal. The resonant absorption appears only when there is a significant overlap between the stopband and the plasmonic resonance. The role of plasmonic resonance towards the enhancement of emission at the band edges is also discussed from the experimental results on the dielectric and metallo-dielectric photonic crystals.

Self-assembly and magnetically induced phase transition of three-dimensional colloidal photonic crystals

Charged superparamagnetic colloidal Fe(3)O(4)@SiO(2) core-shell particles were chosen as model dipolar soft spheres to study their crystallization and magnetically induced phase transition in suspensions. The 3D colloidal crystals feature excellent magnetically responsive photonic properties with strong diffraction, fast response and wide tunability.

Hybrid Colloidal Plasmonic‐Photonic Crystals

We review the recently emerged class of hybrid metal-dielectric colloidal photonic crystals. The hybrid approach is understood as the combination of a dielectric photonic crystal with a continuous metal film. It allows to achieve a strong modification of the optical properties of photonic crystals by involving the light scattering at electronic excitations in the metal component into moulding of the light flow in series to the diffraction resonances occurring in the body of the photonic crystal. We consider different realizations of hybrid plasmonic-photonic crystals based on two- and three-dimensional colloidal photonic crystals in association with flat and corrugated metal films. In agreement with model calculations, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tuneable functionality of these crystals.

Angular dependence of the intensity of light beams diffracted by colloidal crystals

An experimental and theoretical analysis of the angular dependence of the diffracted light beams emerging from three-dimensional colloidal photonic crystals is herein presented. Diffracted beams are identified according to their associated reciprocal-lattice vectors, and their intensities are obtained as a function of the zenithal and azimuthal incidence angles. Significant changes in the beam intensities are observed for large zenithal incidence angles as the azimuthal angle is varied. This phenomenon is related to the excitation of new resonant modes inside the photonic crystal which cannot be observed under normal incidence conditions.

Highly monodisperse vinyl functionalized silica spheres and their self-assembled three-dimensional colloidal photonic crystals

A one-step method was presented for the controlled synthesis of highly monodisperse vinyl functionalized silica spheres (VFSSs), which could be self-assembled into three-dimensional (3D) fcc colloidal photonic crystals on a horizontal glass slide by a gravity sedimentation process. One precursor (vinyltriethoxysilane) and one solvent (water) were used in the experiment. The size of VFSSs could be adjusted from 420 to 650 nm with relative standard deviation below 2% by controlling the dripping speed of diluted ammonia catalyst, without changing the concentration of precursor/catalyst. SEM and TEM images illustrate the copiousness in quantity and the uniformity in size/shape of the VFSSs. 29Si nuclear magnetic resonance (NMR) spectrum confirms the surfaces of VFSSs have abundant vinyl groups (–CH CH 2) which connect to the silicon atoms. Optical characterizations of the transmission spectra reveal that the periodic arrays exhibit a photonic band gap in the (1 1 1) direction of the fcc lattice in consistent with the Bragg diffraction theory. This work has also been extended to prepare other monodisperse surface-modified silica spheres and fabricate organic functionalized colloidal templates.

Experimental investigation of the slow light and superluminal effects in high-quality three-dimensional colloidal photonic crystals

We investigated by time-of-flight technique the slow light and superluminal effects in high-quality three-dimensional （3D） colloidal photonic crystals （PCs） with opal structure, fabricated by pressure controlled isothermal vertical deposition technique. They produce high transmission in the pass bands and sharp band edges due to low volume density of defects and dislocations. The variation of the group velocity across the short-wavelength band edge was measured. Group velocity as low as 0.43c was observed near the band edge while group velocity as high as 1.34c was found in the band gap. We have also simulated the transportation of ultrashort pulses through 3D PCs and compared the simulation results with the experimental ones.

Industrial application of three-dimensional colloidal photonic crystals made in space

Three-dimensional colloidal photonic crystal can be utilized as optical pulse control devices for ultra-short laser pulses as short as a few tens of femtosecond. Using a recently developed colloidal crystallization method, a few centimetre sized single colloidal crystals were made. By shining femtosecod laser pulses onto one hundred micrometer thick colloidal crystal, we confirmed a pulse shape change clearly. Under a collaborative project within Japan Aerospace Exploration Agency, we have grown such colloidal photonic crystals at the international space station, successfully. Optical and mechanical properties of the colloidal photonic crystal will be discussed in more detail to figure out their industrial high power laser application.

Pressure controlled self-assembly of high quality three-dimensional colloidal photonic crystals

A concise pressure controlled isothermal heating vertical deposition (PCIHVD) method is developed, which provides an optimal growing condition with better stability and reproducibility for fabricating photonic crystals (PCs) without the limitation of colloidal sphere materials and sizes. High quality PCs are fabricated with PCIHVD from polystyrene spheres with diameters ranging from 200nmto1μm. The deep photonic band gap and steep photonic band edge of the samples are most favorable for realizing ultrafast optical devices, photonic chips, and communications. This method makes a meaningful advance in the quality and diversity of PCs and greatly promotes their wide applications.

Weak photonic band gap effect on the fluorescence lifetime in three-dimensional colloidal photonic crystals

The photonic band gap (PBG) effect on the fluorescence lifetime of molecules in three--dimensional colloidal photonic crystals is studied theoretically by means of a full vectorial quantum electrodynamics. In these colloidal systems where the refractive index contrast is as low as below 1.2, the PBG-induced lifetime variation is found to be below $5%.$ Our theoretical simulations can help to distinguish the pure PBG effect on the observed fluorescence lifetime variation from other effects such as complex electronic and chemical interactions that can occur in condensed-matter materials.