E. Vekris

Towards the synthetic all-optical computer: science fiction or reality?

The global race for the optically integrated photonic chip is driven by the prospective that miniaturization of optical devices and enhanced chip functionality may revolutionize the manufacture of optical circuits, and the futuristic dream of the all-optical computer may come true. The aim of this article is to take a brief yet critical look at some developments in microsphere self-assembly of colloidal photonic crystals and their technological potential from the perspective of research results that have recently emerged from our materials chemistry group. The focus of the discussion centers on the provocative vision of the “colloidal photonic crystal micropolis”, Fig. 1, which depicts the direction in which the colloidal photonic crystal research of our materials chemistry group is heading. It is intended to bring to the forefront the pointed question of whether the most recent versions of colloidal photonic crystals and their integration on chips, developed in our laboratory, can rise to the stringent specifications of structural perfection and optical quality, functionality and complexity that will be demanded for photonic crystal optical devices and optical circuits touted for next generation all-optical chip and telecommunication technologies.

Tungsten inverse opals: The influence of absorption on the photonic band structure in the visible spectral region

We fabricate and characterize tungsten inverse opals for the visible and near-infrared spectral region. The influence of absorption in this spectral region and the resulting breakdown of the bandstructure are experimentally investigated in detail

Two-color pump–probe experiments on silicon inverse opals

We present time-resolved pump–probe experiments in a transmission geometry using off-resonant excitation on very high-quality silicon inverse opals. We show that the nonlinear optical response can drastically be modified by tempering of the sample. The as-grown samples are dominated by an absorptive response with recovery times as short as one picosecond. For the tempered samples, both the relaxation and the scattering times increase, leading to a prominent dispersive response. Based on simple calculations using the Drude model, we estimate corresponding refractive index changes as large as Δn=−0.5+i0.07.

Micro-Brillouin scattering from a single isolated nanosphere

Inelastic light scattering from a single isolated silica sphere, of diameter as small as 260nm, has been measured as a function of sphere size by micro-Brillouin spectroscopy. The feasibility of recording spectra of a sample as tiny as this, and for which only one particle is needed, further enhances the capabilities of Brillouin light scattering as a powerful investigative tool. Such measurements afford the evaluation of the elastic properties of single nanospheres and a determination of the size polydispersity of an aggregate of particles from the asymmetric broadening of its Brillouin spectrum. Unlike conventional Brillouin scattering from acoustic waves, what is observed here is the inelastic scattering from the eigenvibrations of a nanosphere.

Micro‐optical Spectroscopy of Stacking Faults in Colloidal Photonic Crystal Films

We report on direct measurements of the influence of stacking faults on the optical properties of thin colloidal crystal films. Spatially resolved micro‐optical spectroscopy is used to demonstrate that variations in the stacking sequence of close‐packed spheres give rise to unique optical spectra, which can be convoluted by large area spatially averaged measurements. FDTD simulations are in excellent agreement with the measured spectra.

Ultrafast all-optical switching with silicon inverse opals

We present ultrafast two-color pump-probe experiments on silicon inverse opals. A transient blue-shift of the stopgap leads to transmission changes up to a factor of five with relaxation times about 5 ps.

Buried linear extrinsic defects in colloidal photonic crystals

Photolithography combined with colloidal self-assembly enables linear defects to be embedded inside an opal film. Such defects can serve as templates for waveguides, and will allow colloidal PBG materials to be evaluated for integrated optics.