D. Schelle

Diffractionless propagation of light in a low-index photonic-crystal film

We experimentally demonstrate diffractionless propagation of light over 12 diffraction lengths in a two-dimensional photonic crystal film made of silicon nitride (SiNx). We show that self-guided beams may propagate for transverse electric (TE) and transverse magnetic (TM) polarized light but at slightly different frequencies. Three-dimensional calculations are used to optimize the structure for low loss and narrow beam operation in this low-index photonic crystals. Experimental and theoretical results are in good agreement.

High transmission and single-mode operation in low-index-contrast photonic crystal waveguide devices

We investigate photonic crystal films made of low-index glass materials. Polarization-sensitive waveguiding and single-mode operation (with losses as low as 1.7 dB/mm) have been observed in wide multimode photonic crystal waveguides after propagation of some millimeters. Furthermore, single-mode operation and transmission as high as about 50% per bend has been observed experimentally in low-index photonic crystal waveguide bends.

Highly efficient waveguide bends in photonic crystal with a low in-plane index contrast

We report on the realization and characterization of highly efficient waveguide bends in photonic crystals made of materials with a low in-plane index contrast. By applying an appropriate bend design photonic crystal bends with a transmission of app. 75 % per bend were fabricated.

Optical characterization of photonic crystal slabs using orthogonally oriented polarization filters

We present an experimental method for direct analysis of guided-mode resonances in photonic crystal slab structures using transmission measurements. By positioning the photonic crystal slab between orthogonally oriented polarization filters light transmission is suppressed except for the guided-mode resonances. Angle resolved transmission measurements with crossed polarizers are performed to obtain the band structure around the Gamma-point. Results are compared to mode simulations. Spatially resolved measurements in a confocal microscope setup are used for homogeneity characterizations. Stitching errors and inhomogeneities in exposure dose down to 1.3% in photonic crystal slabs fabricated by electron beam lithography are observed using this method.

Transmission measurements for the optical characterization of 2D-photonic crystals

The successful realization of devices based on two-dimensional (2D) photonic crystal structures relies on an accurate characterization of the properties of the fabricated nanostructured surface. Scanning electron microscope (SEM) images allow the verification of geometric parameters of fabricated 2D-photonic crystal structures such as the periodicity or the hole diameter. In order to investigate the optical properties of 2D-photonic crystals we realized an experimental setup for spectrally and spatially resolved transmission measurements at normal incidence. These measurements reveal the allowed modes of the photonic crystal at the Gamma-point. In contrast to transmission measurements in the plane of the photonic crystal, these measurements are independent of the lateral termination of the structure, since only the area of the photonic crystal is probed. The experimental setup allows for the characterization of microscopic structures of dimensions down to 50 micrometers in diameter. The setup can furthermore be utilized to characterize the spatial homogeneity of larger nanostructured surfaces. We present experimental results and compare them to photonic band structure calculations.

High resolution XUV Fourier transform holography on a table top

Today, coherent imaging techniques provide the highest resolution in the extreme ultraviolet (XUV) and X-ray regions. Fourier transform holography (FTH) is particularly unique, providing robust and straightforward image reconstruction at the same time. Here, we combine two important advances: First, our experiment is based on a table-top light source which is compact, scalable and highly accessible. Second, we demonstrate the highest resolution ever achieved with FTH at any light source (34 nm) by utilizing a high photon flux source and cutting-edge nanofabrication technology. The performance, versatility and reliability of our approach allows imaging of complex wavelength-scale structures, including wave guiding effects within these structures, and resolving embedded nanoscale features, which are invisible for electron microscopes. Our work represents an important step towards real-world applications and a broad use of XUV imaging in many areas of science and technology. Even nanoscale studies of ultra-fast dynamics are within reach.

Distribution and Emission Properties of Fluorescing Nanospheres on 2D Photonic Crystal Slabs

This paper investigates the quantum-optical interplay of photonic crystals (PCs) with localized emitters. Results show that the local density of states in the PC unit cell causes a position dependent modification of the spontaneous emission rate.

Spontaneous Emission Properties of Single Emitters in Planar Photonic Crystals

We investigate the quantum-optical interplay of two-dimensional (2D) planar photonic crystals with localized emitters. Due to the spatial variation of the photonic density of states in the photonic crystal unit cell the spontaneous emission properties dependent strongly on the location of the emitter. We infiltrate nanospheres doped with small dye molecules as localized probes into 2D hexagonal Nb2O5 photonic crystals. Using spatially resolved spectroscopy and time correlated single photon counting direct measurements of the spontaneous emission properties of single, localized emitters are performed

Spontaneous Emission Properties in 2D Photonic Crystals

This paper investigates the quantum-optical interplay of photonic crystals with localized emitters. Several emitter materials are evaluated for suitability in spectrum, lifetime variation, and photostability for infiltration in the photonic crystal. Theoretical calculations are also performed to predict the photonic band gap of different host materials

Highly dispersive photonic-crystal waveguides

We obtain both large group index and group velocity dispersion in a low-index contrast photonic crystal waveguide operated below the light cone. We present experimental results and compare with theoretical predictions.