NTh2A.3.pdf Advanced Photonics Congress © 2012 OSA Supercontinuum generation with picosecond ultraviolet pulses in a solid-core photonic crystal fiber T. Sylvestre 1 , M. W. Lee 1 , A. R. Ragueh 1 , B. Stiller 1 , G. Fanjoux 1 , B. Barviau 2 , A. Mussot 2 and A. Kudlinski 2 1: Institut FEMTO-ST, Département d’Optique, Université de Franche-Comté, CNRS UMR 6174, F-25000 Besançon, France 2: Laboratoire PhLAM, Université de Lille 1, CNRS UMR 8523, IRCICA, 59655 Villeneuve d'Ascq, France Abstract: Black light supercontinuum generation is demonstrated as a result of picosecond pumping a solid-core photonic crystal fiber at 355~nm through the combined effects of intermodal four-wave mixing and cascaded Raman scattering. OCIS codes: 190.4370, 190.5650, 190.4005. The study of supercontinuum (SC) generation in photonic crystal fibers (PCF) continues to be an area of active research, motivated by many applications in bio-photonics, optical metrology, spectroscopy, and imaging. Although many previous reports on SC generation have used PCFs pumped with near infrared or visible lasers [1–5], studies of SC generation using UV laser have not yet been investigated. In this work, we report the observation of a broadband continuum spanning from 350 to 470 nm, i.e., in the black-light region of the electromagnetic spectrum, as a result of picosecond pumping a solid-core silica photonic crystal fiber at 355 nm. This was achieved despite both the strong absorption and large normal group- velocity dispersion (GVD) of silica glass in the UV. Further investigations reveal that the continuum generation results from the interplay of intermodally phase-matched four-wave mixing and cascaded Raman scattering. In our experiment, we used a standard solid-core silica PCF similar to those usually used for SC generation when pumping at 1064 nm in the small anomalous dispersion regime [4]. It has a triangular lattice with pitch and holes diameters of 3.88 µm and 2.73 µm, respectively. Its zero-dispersion wavelength is 1044 nm. At 355 nm, our PCF exhibits a large normal GVD dominated by material dispersion (D=-1720 ps/nm/km). In addition, the PCF carries several propagation modes at 355 nm that have been numerically identified as the LP 01 , LP 11 and LP 31 modes using a finite element method. Fig. 1. Left Top : (a) Output spectra for increasing input power from 0.5 to 4 mW showing black- light continuum generation in the UV-A-visible from 350 nm up to the blue at 470 nm in a 30 m- long silica PCF pumped at 355-nm with 300-ps Q-switched pulses. Left bottom : (b) Output spectra in shorter fiber samples showing the FWM sidebands (blue) and cascaded Raman scattering (red and green) responsibles for SC generation. Right images show respectively the UV (c) and visible (d) parts of the continuum, the optical mode output (e), and the modal distribution of the continuum showing the FWM sidebands (f) generated in the fundamental LP 01 and in the higher-order LP 11 mode for phase-matching reasons, and all the FWM and Raman sidebands (g). (a) (b) (c) (d) (e) (f) (g)