Observation of whispering gallery modes through electron beam-induced deposition.

Surprisingly intense spectra of whispering gallery modes were observed in polymer microbeads after illumination with electrons in a scanning electron microscope and subsequent laser illumination and spectral analysis. It will be proposed that whispering gallery mode resonances became visible after local deposition of hydrocarbon material through electron beam-induced deposition. The illumination of deposited material with a near infrared laser generates a broad light spectrum, acting as a local "white light" source that couples, for favorable wavelengths, with the WGM sustained by the sphere. This facilitates a spectroscopic analysis of the WGM and provides the Q-factor and free spectral range for all investigated particles. The analysis by an integrated SEM and Raman micro-spectrometer offers a direct approach to the analysis of WGM resonators as they are, for instance, used in sensing.

Correlative SEM SERS for quantitative analysis of dimer nanoparticles.

A Raman microscope integrated with a scanning electron microscope was used to investigate plasmonic structures by correlative SEM-SERS analysis. The integrated Raman-SEM microscope combines high-resolution electron microscopy information with SERS signal enhancement from selected nanostructures with adsorbed Raman reporter molecules. Correlative analysis is performed for dimers of two gold nanospheres. Dimers were selected on the basis of SEM images from multi aggregate samples. The effect of the orientation of the dimer with respect to the polarization state of the laser light and the effect of the particle gap size on the Raman signal intensity is observed. Additionally, calculations are performed to simulate the electric near field enhancement. These simulations are based on the morphologies observed by electron microscopy. In this way the experiments are compared with the enhancement factor calculated with near field simulations and are subsequently used to quantify the SERS enhancement factor. Large differences between experimentally observed and calculated enhancement factors are regularly detected, a phenomenon caused by nanoscale differences between the real and 'simplified' simulated structures. Quantitative SERS experiments reveal the structure induced enhancement factor, ranging from ∼200 to ∼20 000, averaged over the full nanostructure surface. The results demonstrate correlative Raman-SEM microscopy for the quantitative analysis of plasmonic particles and structures, thus enabling a new analytical method in the field of SERS and plasmonics.

Photonic generation of stable microwave signals from a dual-wavelength Al2O3:Yb3+ distributed-feedback waveguide laser.

We report the fabrication and characterization of a dual-wavelength distributed-feedback channel waveguide laser in ytterbium-doped aluminum oxide. Operation of the device is based on the optical resonances that are induced by two local phase shifts in the distributed-feedback structure. A stable microwave signal at ~15 GHz with a -3 dB width of 9 kHz was subsequently created via the heterodyne photodetection of the two laser wavelengths. The long-term frequency stability of the microwave signal produced by the free-running laser is better than ±2.5 MHz, while the power of the microwave signal is stable within ±0.35 dB.

Highly efficient, low-threshold monolithic distributed-Bragg-reflector channel waveguide laser in Al2O3:Yb3+.

We report the fabrication and performance of a highly efficient, monolithic distributed-Bragg-reflector channel waveguide laser in ytterbium-doped aluminum oxide. The 1 cm long device was fabricated on a standard thermally oxidized silicon substrate and was optically pumped with a 976 nm laser diode. Single-longitudinal-mode and single-polarization operation was achieved at a wavelength of 1021.2 nm. Continuous-wave output powers of up to 47 mW and a launched pump power threshold of 10 mW resulted in a slope efficiency of 67%.

Ultra-narrow-linewidth, single-frequency distributed feedback waveguide laser in Al2O3:Er3+ on silicon.

We report the realization and performance of a distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a standard thermally oxidized silicon substrate. The diode-pumped continuous-wave laser demonstrated a threshold of 2.2 mW absorbed pump power and a maximum output power of more than 3 mW with a slope efficiency of 41.3% versus absorbed pump power. Single-longitudinal-mode and single-polarization operation was achieved with an emission linewidth of 1.70+/-0.58 kHz (corresponding to a Q factor of 1.14 x 10(11)), which was centered at a wavelength of 1545.2 nm.

Transition flow through an ultra-thin nanosieve.

The fabrication and gas flow characterization of an ultra-thin inorganic nanosieve structured by interference lithography and a bond-micromachining approach are reported. The nanosieve has been observed to exhibit transition gas flow behaviour around atmospheric pressure and ambient temperature. The small lip thickness (45 nm) of the nanopores with respect to their diameter (120 nm) helps in understanding pure transition flow by minimizing interactions between the molecule and inner pore wall. Due to the absence of these collisions, the transition flux is the superimposition of viscous and molecular fluxes without the need for higher-order slip correction. The nanosieve shows a flow selectivity of 3.1 between helium and argon at 20 mbar.