R.W. van der Heijden

InP-based two-dimensional photonic crystals filled with polymers

Polymer filling of the air holes of indium-phosphide-based two-dimensional photonic crystals is reported. After infiltration of the holes with a liquid monomer and solidification of the infill in situ by thermal polymerization, complete filling is proven using scanning electron microscopy. Optical transmission measurements of a filled photonic crystal structure exhibit a redshift of the air band, confirming the complete filling.

Quantum Magnetoconductance of a Nondegenerate Two-Dimensional Electron Gas

Magnetoconductance measurements are reported for the low-density, two-dimensional classical electron gas formed on the surface of liquid helium. At strong magnetic fields, large deviations from the classical parabolic behaviour are observed. These deviations are described with a quantum-transport theory of scattering within broadened Landau levels.

The high-field Hall effect and magnetoresistance of electrons on helium

The diagonal and off-diagonal components of the resistivity tensor have been measured for the non-degenerate two-dimensional electron gas as a function of magnetic field. The Hall voltage varies linearly with the magnetic field, in fields up to the quantum limit. In contrast to the classical behaviour, a strong magnetoresistance is observed under quantising conditions. The observations are in agreement with the theoretically derived quantum transport magnetoresistivity tensor.

Photonic crystal cavity on optical fiber facet for refractive index sensing.

Using a micromanipulation technique, a planar photonic crystal nanocavity made from a thin semiconductor membrane is released from the host semiconductor and attached to the end facet of a standard single-mode optical fiber. The cavity spectrum can be read out through the fiber by detecting the photoluminescence of embedded quantum dots. The modified fiber end serves as a fiber-optic refractive index sensor.

Birefringence-induced mode-dependent tuning of liquid crystal infiltrated InGaAsP photonic crystal nanocavities

Mode-dependent shifts of resonant frequencies of cavities in liquid crystal (LC) infiltrated planar photonic crystals (PhC) are experimentally observed when the temperature is varied across the LC ordering transition. The shifts can be in opposite directions, even for two very similar nearly degenerate modes. The behavior is attributed to the different interactions of the modes with the two components of the refractive index of the LC infill and directly demonstrates that at least a substantial amount of the LC is oriented perpendicular to the PhC-hole axis.

Compact Mach-Zehnder interferometer based on self-collimation of light in a silicon photonic crystal

We demonstrate a compact silicon photonic crystal Mach-Zehnder interferometer operating in the self-collimation regime.The 2-D and 3-D simulation results, silicon membrane nanofabrication, near-field propagation and MZ output are discussed.

Temperature and electric field dependence of hopping transport in ion-implanted Si:As

Abstract The temperature and electric field dependence of the resistivity of thin layers of As-doped, not intentionally compensated, Si with concentrationsjust below that of the metal-insulator transition are reported. The temperature dependence gives evidence for variable range hopping with a coulomb gap in the density of states at the Fermi-level. From the field dependence of the resistivity, a characteristic length of ≈25 nm can be deduced, which is of the order of magnitude of the hopping length.

Diameter dependence of the thermal conductivity of InAs nanowires

The diameter dependence of the thermal conductivity of InAs nanowires in the range of 40-1500 nm has been measured. We demonstrate a reduction in thermal conductivity of 80% for 40 nm nanowires, opening the way for further design strategies for nanoscaled thermoelectric materials. Furthermore, we investigate the effect of thermal contact in the most common measurement method for nanoscale thermal conductivity. Our study allows for the determination of the thermal contact using existing measurement setups. The thermal contact resistance is found to be comparable to the wire thermal resistance for wires with a diameter of 90 nm and higher.

Photoluminescence enhancement in thin films of PbSe nanocrystals

Remarkable photoluminescence enhancement (PLE) in submonolayer films of PbSe nanocrystals (NCs) upon continuous illumination was observed. The intensity increase from films on InP substrates was highest in vacuum, while for films on Si/SiO2 substrates the PLE was stronger in air. The magnitude of the PLE was found to depend on the excitation intensity, being higher for a weaker irradiation power. The possible mechanisms behind the phenomenon of the PLE are discussed and it is suggested to originate mainly from charge trapping outside the NCs core.

Single wire configuration of electrons on a suspended helium film

A new technique to create and measure a single wire arrangement of electrons on helium is presented. Experimental results are reported for a 300 μm wide, 12 mm long channel.