A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

Recent observations show that the probability of encountering an extremely large rogue wave in the open ocean is much larger than expected from ordinary wave-amplitude statistics. Although considerable effort has been directed towards understanding the physics behind these mysterious and potentially destructive events, the complete picture remains uncertain. Furthermore, rogue waves have not yet been observed in other physical systems. Here, we introduce the concept of optical rogue waves, a counterpart of the infamous rare water waves. Using a new real-time detection technique, we study a system that exposes extremely steep, large waves as rare outcomes from an almost identically prepared initial population of waves. Specifically, we report the observation of rogue waves in an optical system, based on a microstructured optical fibre, near the threshold of soliton-fission supercontinuum generation--a noise-sensitive nonlinear process in which extremely broadband radiation is generated from a narrowband input. We model the generation of these rogue waves using the generalized nonlinear Schrodinger equation and demonstrate that they arise infrequently from initially smooth pulses owing to power transfer seeded by a small noise perturbation.

Optical rogue waves

We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.

Optical properties of ZnO nanostructures.

Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

Rare-earth-doped diffusion bonded planar crystal waveguides have the potential to yield efficient, diode-pumped lasers and amplifiers. For the optimization of diode-pumped waveguides, stable, compact and mode-selective resonator- and gain structures are essential. For this purpose, we used a new modified cladding pump scheme for planar waveguides.

Cladding-pumped Yb:YAG planar waveguide laser

Controlling bundling and curl of carbon nanotubes permits ultrafast optical switching, which was demonstrated in a >500 nm near-infrated band by femtosecond mode-locking of three bulk lasers using one and the same saturable absorber.

Disentangling carbon nanotubes of broadland sub-100 fs optical switching

We present a 3-stage GaSe optical parametric amplifier based on a fs Cr:ZnS front–end generating idler pulses around 12 µm with sub-200 fs duration and energy of 65 µJ at a 1-kHz repetition rate.

LWIR OPCPA at 11.4 µm delivering 65 µJ femtosecond pulses at 1 kHz repetition rate

Erbium lasers emitting at ~2.8 µm according to the 4 I 11/2 → 4 I 13/2 transition are of practical interest for microsurgery, remote sensing and atmosphere pollution monitoring. Among the existing laser gain media for ~2.8 µm lasers, cubic rare-earth sesquioxides Er:A 2 O 3 (A = Lu, Y, Sc) appear promising due to their good thermal properties, low phonon energies and high Er 3+ doping levels [1] . The ceramic technology for sesquioxides offers lower synthesis temperatures (the melting point of Lu 2 O 3 is 2450 °C), and the possibility to fabricate in a more straightforward manner "mixed" materials [2] . We report on the synthesis, spectroscopy and first laser operation of a "mixed" ceramic Er:(Lu,Sc) 2 O 3 .

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Efficient Laser Operation of Transparent "Mixed" 7 at.% Er:(Lu,Sc) 2 O 3 Sesquioxide Ceramics near 2.8 µm

Mode-locking of the Yb:Sc2O3 laser with a saturable absorber mirror is demonstrated. The pump efficiency reached 47% in the picosecond regime and with dispersion compensation pulses as short as 230 fs were obtained at 1044.5 nm.

Uwe Griebner

Papers

Cladding-pumped Yb:YAG planar waveguide laser

Disentangling carbon nanotubes of broadland sub-100 fs optical switching

LWIR OPCPA at 11.4 µm delivering 65 µJ femtosecond pulses at 1 kHz repetition rate

Efficient Laser Operation of Transparent "Mixed" 7 at.% Er:(Lu,Sc) 2 O 3 Sesquioxide Ceramics near 2.8 µm

Highly-efficient mode-locked Yb:Sc2O3 laser