Photonic Crystal Fibers (PCFs) Laura Rossi 26-09-2006 Photon Physics final presentation

OUTLINE INTRODUCTION --> what are PCFs? FABRICATION METHODS PRINCIPLE OF LIGHT GUIDANCE APPLICATIONS WHY U SELECTED THE TOPIC - HOW U’VE USED THE MATERIAL OF THE COURSE FOR THE PRESENTATION+QUESTION ABOUT AN ISSUE U DID NOT UNDERSTAND TO START A DISCUSSION ON THE PRESENTATION

What are PCFs? new class of optical fibers hollow or solid core surrounded by an array of air-holes (photonic crystal)

Fabrication methods 1) EXTRUSION through a die 2) TUBE-STACKING Fiber drowing tower 2) TUBE-STACKING technique Most of them are made of silica extrusion used with other glasses materials J.C. Knight, Nature 424 (2003) 847-851 W.H. Reeves et al., Nature 424 (2003) 511-515

Two main types… Index guiding or Solid core PCFs Bandgap guiding or hollow-core PCFs CORE with lower refractive index CORE with higher refractive index Modified Total Internal Reflection (MTIR) Photonic Bandgap (PBG)

Light guidance INDEX GUIDING FIBERS TIR Modified Total Internal Reflection Solid core! PCF http://www.crystal-fibre.com/technology/technology_tutorial.shtm

Light guidance INDEX GUIDING FIBERS  a) Foundamental mode “trapped” inside the core b,c) Higher order modes can “escape” from the core b) Because of their transverse effective wavelenght is smaller d= hole diameter = interhole spacing SINGLE MODE GUIDING PCFs d/‹0.4 !!! P.Russel, Science 299 (2003) 358-362

Light guidance HOLLOW-CORE FIBERS Hollow Photonic Bandgap effect core! PCF

Light guidance HOLLOW-CORE FIBERS Periodic nanostructure designed to affect the propagation of electromagnetic waves Photonic Crystal Stop gap = interval of frequencies in which the light cannot propagate in a specific direction PC I0 I=I0 Band gap ≝ stop gap overlapping in all directions

Light guidance HOLLOW-CORE FIBERS PC LESS ABSORPTION LESS LOSS!!! Light traveling in air:

{ Applications amplifiers and lasers applications high power experiments on gases transport of atoms and particles { Ph.Roy et al.,C.R.Physique 7 (2006) B.Cowan et al.,Photonic crystal laser Accelerator structures, Stanford USA (2006) HOLLOW CORE PCF PARTICLE TRAPPING AND GUIDANCE IN A HOLLOW-CORE PCF. The van der Waals forces between the um-sized polystyrene particles (c) are broken by making them dance on a vibrating plate (a). The laser beam (b) captures them and entrains them into the hollow-core PCF The optical dipole forces of a laser beam prevent adhesion to the glass surface in order to obtain acceleration needed to overcome viscosity. VIBRATING PLATE THAT BREAKS VAN DER WAALS FORCES BETWEEN THE PARTICLES LASER BEAM P.Russel, Science 299 (2003) 358-362

SUPERCONTINUUM GENERATION Applications - nonlinear optics SUPERCONTINUUM GENERATION Light generators with high output power, broad and flat spectrum, tight focusing Ultrashort (femtosecond) laser pulses are coupled into the fiber, through standard microscope objectives, where the non-linear effects influence the pulse by broaden the narrow band laser radiation into a continuous spectrum (Fig.5).---In some applications, like interferometry or spettroscopy, these sources can, in addition to widen the spectral range over which measurements can be made, improve the signal-to-noise ratio and reduce the measurement time. Applied for: Optical coherence tomografy Optical frequency metrology and spettroscopy P.Russel, Science 299 (2003) 358-362 http://www.crystal-fibre.com/support/application_notes.shtm

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