S.R. Huisman

Extraction of optical Bloch modes in a photonic-crystal waveguide

We perform phase-sensitive near-field scanning optical microscopy on photonic-crystal waveguides. The observed intricate field patterns are analyzed by spatial Fourier transformations, revealing several guided transverse electric (TE) and transverse magnetic (TM) like modes. Using the reconstruction algorithm proposed by Ha et al. [Opt. Lett. 34, 3776 (2009)], we decompose the measured two-dimensional field pattern in a superposition of propagating Bloch modes. This opens new possibilities to study specific modes in near-field measurements. We apply the method to study the transverse behavior of a guided TE-like mode, where the mode extends deeper in the surrounding photonic crystal when the band edge is approached

Measurement of a band-edge tail in the density of states of a photonic-crystal waveguide

S.R. Huisman, ∗ G. Ctistis, S. Stobbe, A.P. Mosk, J.L. Herek, A. Lagendijk, 3 P. Lodahl, W.L. Vos, and P.W.H. Pinkse MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100, Copenhagen, Denmark FOM Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG Amsterdam, The Netherlands (Dated: December 21, 2013)

Programmable multiport optical circuits in opaque scattering materials

We propose and experimentally verify a method to program the effective transmission matrix of general multiport linear optical circuits in random multiple-scattering materials by phase modulation of incident wavefronts. We demonstrate the power of our method by programming linear optical circuits in white paint layers with 2 inputs and 2 outputs, and 2 inputs and 3 outputs. Using interferometric techniques we verify our ability to program any desired phase relation between the outputs. The method works in a deterministic manner and can be directly applied to existing wavefront-shaping setups without the need of measuring a transmission matrix or to rely on sensitive interference measurements.

Programming balanced optical beam splitters in white paint

Wavefront shaping allows for ultimate control of light propagation in multiple-scattering media by adaptive manipulation of incident waves. We shine two separate wavefront-shaped beams on a layer of dry white paint to create two enhanced output spots of equal intensity. We experimentally confirm by interference measurements that the output spots are almost correlated like the two outputs of an ideal balanced beam splitter. The observed deviations from the phase behavior of an ideal beam splitter are analyzed with a transmission matrix model. Our experiments demonstrate that wavefront shaping in multiple-scattering media can be used to approximate the functionality of linear optical devices with multiple inputs and outputs.

Observation of sub-Bragg diffraction of waves in crystals

We investigate the diffraction conditions and associated formation of stop gaps for waves in crystals with different Bravais lattices. We identify a prominent stop gap in high-symmetry directions that occurs at a frequency below the ubiquitous first-order Bragg condition. This sub-Bragg-diffraction condition is demonstrated by reflectance spectroscopy on two-dimensional photonic crystals with a centered rectangular lattice, revealing prominent diffraction peaks for both the sub-Bragg and first-order Bragg conditions. These results have implications for wave propagation in 2 of the 5 two-dimensional Bravais lattices and 7 out of 14 three-dimensional Bravais lattices, such as centered rectangular, triangular, hexagonal, and body-centered cubic.

Controlling the quality factor of a tuning-fork resonance between 9 and 300 K for scanning-probe microscopy

We study the dynamic response of a mechanical quartz tuning fork in the temperature range from 9 to 300 K. Since the quality factor Q of the resonance strongly depends on temperature, we implement a procedure to control the quality factor of the resonance. We show that we are able to dynamically change the quality factor and keep it constant over the whole temperature range. This procedure is suitable for applications in scanning-probe microscopy

Observation of nonlinear bands in near-field scanning optical microscopy of a photonic-crystal waveguide

We have measured the photonic bandstructure of GaAs photonic-crystal waveguides with high resolution in energy as well as in momentum using near-field scanning optical microscopy. Intriguingly, we observe additional bands that are not predicted by eigenmode solvers, as was recently demonstrated by Huisman et al. [Phys. Rev. B 86, 155154 (2012)]. We study the presence of these additional bands by performing measurements of these bands while varying the incident light power, revealing a non-linear power dependence. Here, we demonstrate experimentally and theoretically that the observed additional bands are caused by a waveguide-specific near-field tip effect not previously reported, which can significantly phase-modulate the detected field.

Experimental signature of a broad 3D photonic band gap in silicon nanostructures

Three-dimensional photonic crystals radically control propagation and emission of light [1, 2]. Photonic crystals are ordered composite materials with a spatially varying dielectric constant that has a periodicity of the order of the wavelength of light. In specific three-dimensional crystals, a common frequency range for all polarizations is formed for which light is not allowed to propagate in any direction, called the photonic band gap. It is an outstanding challenge to create these crystals and experimentally demonstrate the photonic band gap.

Experimental observation of sub-Bragg frequency gaps in photonic crystals

Photonic crystals control light propagation at a fundamental level [1]. Photonic crystals are ordered composite materials with a spatially varying dielectric constant that has a periodicity of the order of the wavelength of light. Frequency gaps emerge for which light cannot propagate inside such structure due to Bragg diffraction. These frequency gaps appear in experiments as stopbands. We have investigated stopbands in directions of high symmetry for two-dimensional photonic crystals. Surprisingly, we find a stopband below the first order Bragg condition. This result is valid not only for photonic crystals, but for wave propagation in periodic media in general. This has implications for crystallography, scattering of phonons and band gap formation.

A nanophotonic probe for quantum electrodynamics in random cavities

Disorder in photonic-crystal slab waveguides can cause localization of light [1, 2]. Sapienza et al. observed that the interaction of localized light with embedded quantum dots is so strong that it yields a considerable Purcell enhancement of the emission rate [3]. This coupling between emitters and these “random cavities” warrants a more detailed investigation.