D. Nau

Hydrogen sensor based on metallic photonic crystal slabs

A hydrogen sensor based on a metallic photonic crystal using gold and WO3 is presented. Hydrogen exposure influences the optical properties of this device by gasochromic mechanisms with a theoretical limit in the sub-1000-ppm-range.

Group velocity dispersion of tapered fibers immersed in different liquids

We investigate the group velocity dispersion of tapered fibers that are immersed in different liquids. Using the Sellmeier equations fitted from measured refractive indices of these liquids, we are able to analyze the dispersion characteristics of the tapered fibers in a tailored liquid environment. Theoretical results show a large span of slowly varying anomalous group velocity dispersion characteristics. This leads to potentially significant improvements and a large bandwidth in supercontinuum generation in a tapered fiber. This holds true as well for a range of new fiber materials.

1-GHz-repetition-rate femtosecond optical parametric oscillator

We report a 1-GHz-repetition-rate, low-pump-threshold, all-solid-state femtosecond optical parametric oscillator (OPO) based on periodically poled LiNbO3 and pumped by a GHz repetition rate Ti:sapphire laser. The OPO provides nearly transform-limited 65-fs-signal pulses tunable from 1160 to 1320 nm. The pump threshold is about 580 mW, and 43 mW signal power is obtained with 950-mW-pump power. Higher-order quasi-phase-matched sum frequency generation and second harmonic generation processes produce 10 mW blue light at 486 nm and 15 mW red light at 620 nm.

A hydrogen sensor based on metallic photonic crystal slabs

A hydrogen sensor based on a metallic photonic crystal using gold and WO3 is presented. Hydrogen exposure influences the optical properties of this device by gasochromic mechanisms with a theoretical limit in the sub-1000-ppm-range.

Linear and nonlinear optical properties of strongly coupled metal nanoparticles

Interaction of localized plasmons and propagating waveguide modes leads to strong coupling and polariton formation. These polaritons are the basis of nanoplasmonic effects in linear and nonlinear optics. Experiments, theory, and applications are presented.

Phase-resolved pulse propagation through metallic photonic crystal slabs: plasmonic slow light

We characterized the electromagnetic field of ultra-short laser pulses after propagation through metallic photonic crystal structures featuring photonic and plasmonic resonances. The complete pulse information, i.e. the envelope and phase of the electromagnetic field, was measured using the technique of cross-correlation frequency resolved optical gating. In good agreement, measurements and scattering matrix simulations show a dispersive behaviour of the spectral phase at the position of the resonances. Asymmetric Fano-type resonances go along with asymmetric phase characteristics. Furthermore, the spectral phase is used to calculate the dispersion of the sample and possible applications in dispersion compensation are investigated. Group refractive indices of 700 and 70 and group delay dispersion values of 90 000 fs2 and 5000 fs2 are achieved in transverse electric and transverse magnetic polarization, respectively. The behaviour of extinction and spectral phase can be understood from an intuitive model using the complex transmission amplitude. An associated depiction in the complex plane is a useful approach in this context. This method promises to be valuable also in photonic crystal and filter design, for example, with regards to the symmetrization of the resonances. This article is part of the themed issue ‘New horizons for nanophotonics’.

The influence of the disorder type on the optical properties of metallic photonic crystals

We present a quantitative analysis of the influence of disorder on the optical properties of metallic photonic crystals. Different disorder types are considered and the linear optical properties as well as the bandstructure are analyzed.

Photonic crystals with polymer waveguides for microforce detection

We present the fundamental concept and experimental results of a new optical sensor structure based on a 1D photonic crystal consisting of a polymer light waveguide, a cladding layer and a nanostructured gold layer. The polysiloxane layers are deposited by spin-coating and dip-coating, respectively. The gold nanostructure is deposited by DCmagnetron sputtering and structured by UV-laser lithography. The gold nanowires have a period of about 400 nm and cover an area of 5×5 mm2. This thin flexible structure shows high sensitivity to inclination and strain. Our method enables the fabrication of a new sensor for non-conducting measurement of strain, force, torque and angle.

Fano resonances in metallic photonic crystals

We demonstrate that interference of optical excitations of regularly arranged metallic nanodots on a waveguide shows spectral signatures of Fano resonances. The reason is coupling of localized particle plasmons and waveguide modes with different electronic continua

Spectrally and temporally resolved measurements of white light continuum generated in tapered fibers

Spectrally and temporally resolved crosscorrelation measurements of a white light continuum in tapered fibers created by 75 fs pulses at 800 nm show a transition from self-phase modulation to a break-up into several pulses.