Supercontinuum generation...

Optical supercontinuum
An optical supercontinuum is broadband coherent light generated when a short laser pulse causes a nonlinear effect in a material. It is unique in possessing both the spectral width of a conventional white light source and the coherence properties of a laser. A striking nonlinear process, it has many applications, the foremost being a new time standard which merited part of the 2005 Nobel Prize.

Fig. 1 – Supercontinuum generation in a photonic crystal fibre taper (Ti:Sapphire input)

Fig. 2 – Supercontinuum generation – low power threshold for spectral broadeneing in chalcogenide fibre tapers.

Supercontinuum research at CUDOS
Our aim is to understand and control the individual processes behind supercontinuum generation. We achieve this by modifying the waveguide properties longitudinally so that the pulse ‘feels’ different conditions as it evolves and spectrally broadens.

Fig. 3 – Femtosecond source for supercontinuum experiments

Highly nonlinear chalcognide fibre, drawn into a taper to increase power concentration in the glass allows for low power supercontinuum generation. The expertise at CUDOS in both chalcogenide glasses and fibre tapers provides a fertile ground for experiments in ultra-low threshold supercontinuum generation.

Fig. 3b - Chalcogenide taper SEM (left) and the supercontinuum generated from it (right).

Numerical studies of supercontinuum
We use numerical codes to assist in the design of longitudinally varying fibres for supercontinuum generation.

Fig. 4 – Simulation of supercontinuum generation in a chalcogenide taper. The top section shows the effect of two photon absorption on supercontinuum generation.

Nonlinear pulse propagation in ARROW fibers

We investigate femtosecond pulse propagation in a microstructured optical fiber consisting of a silica core surrounded by air holes which are filled with a high index fluid (ARROW-PCF geometry shown in Fig 1). Such fibers have discrete transmission bands which exhibit strong dispersion arising from the scattering resonances of the high index cylinders.

Fig. 5 Schematic of ARROW-PCF geometry. Inclusions have a higher index than the background.

Fig. 6 Experimental Setup. MO: Microscope Objective; AL: Achromatic Lens; FROG: Frequency Resolved Optical Gating

Fig. 7 Spectral evolution of the pulses as they propagate inside the ARROW-PCF. The average input power is fixed at 30 mW. Simulation results on left obtained from NLSE. Experimental results on righ retrieved from Frequency Resolved Optical Gating (FROG)

Publications

1. A. A. Sukhorukov, D. N. Neshev, A. Dreischuh, W. Krolikowski, J. Bolger, B. J. Eggleton, L. Bui, A. Mitchell, and Y. S. Kivshar
   "Observation of polychromatic gap solitons"
   Opt. Express 16, 5991-5996 (2008)
2. D. -I. Yeom, E. C. Mägi, M. R. E. Lamont, M. A. F. Roelens, L. Fu, and B. J. Eggleton
   "Low-threshold supercontinuum generation in highly nonlinear chalcogenide nanowires"
   Opt. Lett. 33, 660-662 (2008)
3. J. M. Dudley, G. Genty, and B. J. Eggleton
   "Harnessing and control of optical rogue waves in supercontinuum generation"
   Opt. Express 16, 3644-3651 (2008)
4. J. A. Bolger, F. Luan, D. -I. Yeom, E. N. Tsoy, C. M. de Sterke, and B. J. Eggleton
   "Tunable enhancement of a soliton spectrum using an acoustic long-period grating,"
   Opt. Express 15, 13457-13462 (2007)
5. Dragomir N. Neshev, Andrey A. Sukhorukov, Alexander Dreischuh, Robert Fischer, Sangwoo Ha, Jeremy Bolger, Lam Bui, Wieslaw Krolikowski, Benjamin J. Eggleton, Arnan Mitchell, Michael W. Austin, and Yuri S. Kivshar
   "Nonlinear Spectral-Spatial Control and Localization of Supercontinuum Radiation"
   Phys. Rev. Lett. 99, 123901 (2007)
6. E. C. Mägi, L. B. Fu, H. C. Nguyen, M. R. Lamont, D. I. Yeom, and B. J.
   Eggleton, "Enhanced Kerr nonlinearity in sub-wavelength diameter As2Se3
   chalcogenide fiber tapers," Opt. Express 15, 10324-10329 (2007)
7. D. -I. Yeom, J. A. Bolger, G. D. Marshall, D. R. Austin, B. T. Kuhlmey, M.
   J. Withford, C. Martijn de Sterke, and B. J. Eggleton, "Tunable spectral
   enhancement of fiber supercontinuum," Opt. Lett. 32, 1644-1646 (2007)
8. D. R. Austin, J. A. Bolger, C. M. de Sterke, B. J. Eggleton, and T. G. Brown
   Narrowband supercontinuum control using phase shaping
   Opt.Express 14, 13142-13150 (2006)
9. Eduard N. Tsoy and C. Martijn de Sterke
   Dynamics of ultrashort pulses near zero dispersion wavelength
   J. Opt. Soc. Am. B 23 2425-2433 (2006)
10. D. R. Austin, C. M. de Sterke, B. J. Eggleton, and T. G. Brown
    Dispersive wave blue-shift in supercontinuum generation
    Opt. Express 14, 11997-12007 (2006)
11. A. A. Sukhorukov, D. N. Neshev, A. Dreischuh, R. Fischer, S. Ha, W. Krolikowski, J. Bolger, A. Mitchell, B. J. Eggleton, and Y. S. Kivshar
    Polychromatic nonlinear surface modes generated by supercontinuum light
    Opt. Express 14, 11265-11270 (2006)
12. Fuerbach, P. Steinvurzel, J.A. Bolger, B.J. Eggleton
    Nonlinear pulse propagation at zero dispersion wavelength in anti-resonant photonic crystal fibers
    Optics Express 13, 2977-2987 (2005)
13. Fuerbach, P. Steinvurzel, J.A. Bolger, A. Nulsen, B.J. Eggleton
    Nonlinear propagation effects in anti-resonant high-index inclusion photonic crystal fibers
    Optics Letters 30, 830-832 (2005)
14. J. Nathan Kutz, C Lyngå, and B. J. Eggleton
    Enhanced Supercontinuum Generation through Dispersion-Management
    Optics Express 13, 3989-3998 (2005)