The Glass Ceiling: Limits of Silica. PCF: Holey Silica Cladding

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1 The Glass Ceiling: Limits of Silica Loss: amplifiers every km limited by Rayleigh scattering (molecular entropy) cannot use exotic wavelengths like 10.µm Breaking the Glass Ceiling: Hollow-core Bandgap Fibers Bragg fiber [ Yeh et al., 197 ] [ figs courtesy Y. Fink et al., MIT ] Nonlinearities: after ~100km, cause dispersion, crosstalk, power limits (limited by mode area ~ single-mode, bending loss) also cannot be made (very) large for compact nonlinear devices + omnidirectional white/grey = chalco/polymer = OmniGuide fibers silica Radical modifications to dispersion, polarization effects? tunability is limited by low index contrast High Bit-Rates Long Distances [ R. F. Cregan et al., Science 25, 1537 (1999) ] 5µm PCF [ Knight et al., 199 ] Compact Devices Dense Wavelength Multiplexing (DWDM) PCF: Holey Silica Cladding r = 0.45a light cone 2r n=1.4 State-of-the-art air-guiding losses a [Mangan, et al., OFC 2004 PDP24 ] above air line: guiding in air core is possible hollow (air) core (covers 19 holes) " (2!c/a) guided field profile: (flux density) air h lig tl in e" =!c [ figs: West et al, Opt. Express 12 (), 145 (2004) ] 3.9µm 1.7dB/km BlazePhotonics over ~ (2!/a) below air line: surface states of air core

2 State-of-the-art air-guiding losses larger core = more surface states crossing guided mode but surface states can be removed by proper crystal termination [ West, Opt. Express 12 (), 145 (2004) ] Hollow Metal Waveguides, Reborn metal waveguide modes OmniGuide fiber modes 100nm 20nm frequency " 13dB/km Corning over ~ [ Smith, et al., Nature 424, 57 (2003) ] 1.7dB/km BlazePhotonics over ~ [ Mangan, et al., OFC 2004 PDP24 ] 1970 s microwave Bell Labs wavenumber! wavenumber! modes are directly analogous to those in hollow metal waveguide An Old Friend: the TE 01 mode lowest-loss mode, just as in metal r E (near) node at interface = strong confinement = low losses non-degenerate mode cannot be split = no birefringence or PMD Suppressing Cladding Losses Mode Losses Bulk Cladding Losses Large differential loss TE 01 strongly suppresses cladding absorption (like ohmic loss, for metal) [ Johnson, Opt. Express 9, 74 (2001) ] 1x10-2 1x10-3 1x10-4 1x10-5 EH 11 TE # (µm)

3 Yes, but how do you make it? A Drawn Bandgap Fiber 3 1 find compatible materials Photonic crystal structural uniformity, adhesion, physical durability through large temperature excursions (many new possibilities) 2 Make pre-form ( scale model ) chalcogenide glass, n ~ 2. white/grey = chalco/polymer + polymer (or oxide), n ~ 1.5 fiber drawing High-Power Transmission at 10.µm (no previous dielectric waveguide) Log. of Trans. (arb. u.) Polymer ~ 50,000dB/m -3.0 waveguide losses < 1dB/m Transmission (arb. u.) [ B. Temelkuran et al., Nature 420, 50 (2002) ] -4.0 slope = db/m Breaking the Glass Ceiling II: Solid-core Holey Fibers solid core holey cladding forms effective low-index material R2 = 0.99 Can have much higher contrast than doped silica Length (meters) strong confinement = enhanced nonlinearities, birefringence, Wavelength(µm) (µm) Wavelength [ J. C. Knight et al., Opt. Lett. 21, 1547 (199) ]

4 Mode in a Solid Core small computation: only lowest-" band! (~ one minute, planewave) 2r n=1.4 a r = 0.3a flux density Endlessly Single-Mode [ T. A. Birks et al., Opt. Lett. 22, 91 (1997) ] at higher " (smaller #), the light is more concentrated in silica so the effective index contrast is less and the fiber can stay single mode for all #! fundamental mode (two polarizations) Band Diagram in Metallic Limit Band Gaps from Metallic Limit

5 Nonlinear Holey Fibers: Supercontinuum Generation (enhanced by strong confinement + unusual dispersion) e.g nm white light: from 50nm ~200 fs pulses (4 nj) Effective Area [ W. J. Wadsworth et al., J. Opt. Soc. Am. B 19, 214 (2002) ] Suppressing Cladding Nonlinearity Mode Nonlinearity* Cladding Nonlinearity Will be dominated by nonlinearity of air ~10,000 times weaker than in silica fiber (including factor of 10 in area) 1x10-1x10-7 1x10-1x10-9 * nonlinearity = $! (1) / P = % [ Johnson, Opt. Express 9, 74 (2001) ] TE # (µm) Holey Fiber PMF (Polarization-Maintaining Fiber) no longer degenerate with birefringence B = $!c/" = (10 times B of silica PMF) Loss = µm over 1.5km Can operate in a single polarization, PMD = 0 (also, known polarization at output) [ K. Suzuki, Opt. Express 9, 7 (2001) ]