We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

https://science.sciencemag.org/content/sci/299/5605/358.full.pdf

Photonic crystal fibers

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

We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

Fiber grating sensors

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

Summary form only given. Modulation instability (MI) in Xe-filled kagome-style hollow core photonic crystal fibre (PCF) has recently been demonstrated experimentally using 500 fs laser pulses centred at λ = 800 nm with energies of a few μJ [1]. It is known that MI leads to the formation of fundamental solitons [2] with average amplitude and temporal width given by [3]: τ 0 = √2T 0 (ΠN), where T 0 is the duration of the input pulse, N = √(γP 0 T 0 /|β2|) the soliton order, γ the nonlinear coefficient, P0 the pump peak power and β 2 the group velocity dispersion. This means that τ 0 depends on N. The average temporal width of the solitons emerging from the instability can be arbitrarily set by suitable choice of gas pressure and pump pulse energy and duration. This theory is however only strictly valid within the approximations of the nonlinear Schrodinger equation; for few-cycle pulses a more complete model based on the full field equation must be used [4]. Using a statistical approach we explore numerically the differences between multi-cycle MI with a predicted soliton duration τ 0 > c/ λ ~2.7 fs, and sub-cycle MI τ 0 <; c/ λ ~2.7 fs. After running many simulations (~1000) for both cases we retrieve, at a given fibre position, the temporal location, duration and peak power of certain discrete peaks in the intensity envelope. For a predicted average soliton duration of 7 fs (multi-cycle regime) the simple analysis above works as expected (Fig. 1); N = 1 solitons are predominantly generated (dashed curve), the peak in the distribution of pulse durations being at 7 fs. Even after propagation over 3 dispersion lengths the distribution is maintained, as expected for solitons. The small deviations are likely to be due to higher order effects in these extremely short and broadband pulses.For a predicted average soliton duration of 1 fs, i.e., in the sub-cycle regime, we see that instead of an N = 1 distribution, the majority of pulses condense to a single state with duration 1.5 fs, two small distributions appearing along the N = 1 and N = 2 lines, corresponding respectively to half-cycle and single-cycle solitons (Fig. 2a). Upon propagation this state evolves , eventually converging to that in Fig. 2b. Remarkably, although the NLSE-based MI theory is not valid, MI-like break-up still occurs, leading to an incoherent train of pulses of duration 0.5 to 1.5 fs, with peak powers greater than 50 MW. A very broad supercontinuum is generated (Fig. 2c) and the numerical and experimental spectra agree extremely well, supporting the validity of the numerical model in this extreme case.

Modulation instability in the sub-cycle regime

We show that the efficient non-phase-matched anti-Stokes Raman generation observed in gas-filled hollow-core PCF can be explained by "phase locking" of the interacting fields leading to the establishment of a phase difference independent of the optical path.

Phase-locked anti-Stokes Raman generation in gas-filled hollow-core photonic crystal fibers

Optofluidic hollow-core photonic crystal fibers facilitate both efficient excitation of photochemical reactions and instantaneous feeding of the products into a mass spectrometer for rapid molecular structure determination using low sample volumes.

Optofluidic hollow-core photonic crystal fiber coupled to mass spectrometry for rapid photochemical reaction analysis

The quasi-Raman interaction between confined acoustic phonons and light in PCF is strongly altered by the introduction of a sub-wavelength hole running axially through the core. Coupling calculations and forward scattering spectra illustrate the effect.

Controlling Acousto-Optic Interactions in Photonic Crystal Fiber with Sub-Wavelength Core-Hole

We study, experimentally and theoretically, noise-seeded backward SRS in gas-filled hollow-core fibers. The spatio-temporal dynamics of the Raman coherence makes the backward Stokes signal stronger than the forward, despite a low backward/forward gain ratio.

Philip St. J. Russell

Papers

Modulation instability in the sub-cycle regime

Phase-locked anti-Stokes Raman generation in gas-filled hollow-core photonic crystal fibers

Optofluidic hollow-core photonic crystal fiber coupled to mass spectrometry for rapid photochemical reaction analysis

Controlling Acousto-Optic Interactions in Photonic Crystal Fiber with Sub-Wavelength Core-Hole

Noise-seeded Backward Stimulated Raman Scattering in Gas-filled Hollow-Core Fibers