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

An imaging platform based on broadband coherent anti-Stokes Raman scattering (BCARS) has been developed which provides an advantageous combination of speed, sensitivity and spectral breadth. The system utilizes a configuration of laser sources that probes the entire biologically-relevant Raman window (500 cm-1 to 3500 cm-1) with high resolution (< 10 cm-1). It strongly and efficiently stimulates Raman transitions within the typically weak "fingerprint" region using intrapulse 3-colour excitation, and utilizes the nonresonant background (NRB) to heterodyne amplify weak Raman signals. We demonstrate high-speed chemical imaging in two- and three-dimensional views of healthy murine liver and pancreas tissues and interfaces between xenograft brain tumours and the surrounding healthy brain matter.

High-Speed Coherent Raman Fingerprint Imaging of Biological Tissues.

Supercontinuum generation, photonic crystal fiber

An efficient algorithm, which exhibits a fourth-order global accuracy, for the numerical solution of the normal and generalized nonlinear Schrodinger equations is presented. It has applications for studies of nonlinear pulse propagation and spectral broadening in optical fibers. Simulation of supercontinuum generation processes, in particular, places high demands on numerical accuracy, which makes efficient high-order schemes attractive. The algorithm that is presented here is an adaptation for use in the nonlinear optics field of the fourth-order Runge-Kutta in the Interaction Picture (RK4IP) method, which was originally developed for studies on Bose-Einstein condensates. The performance of the RK4IP method is validated and compared to a number of conventional methods by modeling both the propagation of a second-order soliton and the generation of supercontinuum radiation. It exhibits the expected global fourth-order accuracy for both problems studied and is the most accurate and efficient of the methods tested.

A Fourth-Order Runge–Kutta in the Interaction Picture Method for Simulating Supercontinuum Generation in Optical Fibers

We demonstrate supercontinuum generation in a highly nonlinear photonic crystal fiber with two closely lying zero dispersion wavelengths. The special dispersion of the fiber has a profound influence on the supercontinuum which is generated through self-phase modulation and phasematched four-wave mixing and not soliton fission as in the initial photonic crystal fibers. The supercontinuum has high spectral density and is extremely independent of the input pulse over a wide range of input pulse parameters. Simulations show that the supercontinuum can be compressed to ultrashort pulses.

Supercontinuum generation in a photonic crystal fiber with two zero dispersion wavelengths

The onset of supercontinuum generation in a photonic crystal fiber is investigated experimentally and numerically as a function of pump wavelength and intensity with 100-fs pulses Soliton formation is found to be the determining factor in the initial step The formation and behavior of a blueshifted, nonsolitonic component, emitted as the soliton evolves towards the stable regime, is investigated and the role of phase matching through higher-order dispersion is highlighted Good agreement between experiments and simulations is obtained

Initial steps of supercontinuum generation in photonic crystal fibers

We demonstrate spectral multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy based on a single Ti:sapphire oscillator and a nonlinear photonic-crystal fiber (PCF). The Stokes pulse is generated by spectral conversion of the laser pulse in a PCF. The pump pulse is either a highly chirped pulse or a pulse spectrally compressed in a PCF. A region of the Raman spectrum from 800to4000 cm−1 is accessible with two different PCFs. Spectral resolution improvement by 1 order of magnitude over a transform-limited pump pulse utilizing a chirped or spectrally compressed pump pulse is demonstrated. The CARS spectrum is distorted for short, chirped pump pulses. We show that the quality of the spectrum is significantly improved when using a spectrally compressed pump pulse.

Broadband multiplex coherent anti-Stokes Raman scattering microscopy employing photonic-crystal fibers

We report on the dispersion properties of a single mode, large core photonic crystal fiber. Using white light interferometry the fiber is found to have zero dispersion at 1064 nm

A photonic crystal fiber with zero dispersion at 1064 nm

We report on two orders of magnitude improvement of signal to noise ratio and enhanced tunability in photonic crystal fiber based CARS microscopy using an optimized photonic crystal fiber.

H.N. Paulsen

Papers

Supercontinuum generation in a photonic crystal fiber with two zero dispersion wavelengths

Initial steps of supercontinuum generation in photonic crystal fibers

Broadband multiplex coherent anti-Stokes Raman scattering microscopy employing photonic-crystal fibers

A photonic crystal fiber with zero dispersion at 1064 nm

Progress in CARS microscopy using photonic crystal fiber based light sources