Nicolai Granzow

Supercontinuum generation in chalcogenide-silica step-index fibers

We explore the use of a highly nonlinear chalcogenide-silica waveguide for supercontinuum generation in the near infrared. The structure was fabricated by a pressure-assisted melt-filling of a silica capillary fiber (1.6 µm bore diameter) with Ga4Ge21Sb10S65 glass. It was designed to have zero group velocity dispersion (for HE11 core mode) at 1550 nm. Pumping a 1 cm length with 60 fs pulses from an erbium-doped fiber laser results in the generation of octave-spanning supercontinuum light for pulse energies of only 60 pJ. Good agreement is obtained between the experimental results and theoretical predictions based on numerical solutions of the generalized nonlinear Schrödinger equation. The pressure-assisted melt-filling approach makes it possible to realize highly nonlinear devices with unusual combinations of materials. For example, we show numerically that a 1 cm long As2S3:silica step-index fiber with a core diameter of 1 µm, pumped by 60 fs pulses at 1550 nm, would generate a broadband supercontinuum out to 4 µm.

Bandgap guidance in hybrid chalcogenide–silica photonic crystal fibers

We report a hybrid chalcogenide-silica photonic crystal fiber made by pressure-assisted melt-filling of molten glass. Photonic bandgap guidance is obtained at a silica core placed centrally in a hexagonal array of continuous centimeters-long chalcogenide strands with diameters of 1.45 μm. In the passbands of the cladding, when the transmission through the silica core is very weak, the chalcogenide strands light up with distinct modal patterns corresponding to Mie resonances. In the spectral regions between these passbands, strong bandgap guidance is observed, where the silica core transmission loss is 60 dB/cm lower. The pressure-assisted fabrication approach opens up new ways of integrating sophisticated glass-based devices into optical fiber circuitry with potential applications in supercontinuum generation, magneto-optics, wavelength selective devices, and rare-earth-doped amplifiers with high gain per unit length.

All-solid bandgap guiding in tellurite-filled silica photonic crystal fibers

We report all-solid bandgap-guiding fibers formed by pumping molten tellurite glass into silica-air photonic crystal fiber at high pressure. The spectral positions of the guidance bands agree well with multipole simulations and bandgap calculations. The micrometer-diameter tellurite strands are found to contain microheterogeneities (most probably originating from devitrification), which increase the fiber attenuation, although no evidence of crystallization is seen in the bulk tellurite glass. The technique offers a potential route to employing difficult-to-handle glasses, or glasses unsuitable for fiber drawing, in fiber-based amplifiers, modulators, filters, and nonlinear devices.

Midinfrared frequency combs from coherent supercontinuum in chalcogenide and optical parametric oscillation

We observe the coherence of the supercontinuum generated in a nanospike chalcogenide-silica hybrid waveguide pumped at 2 μm. The supercontinuum is shown to be coherent with the pump by interfering it with a doubly resonant optical parametric oscillator (OPO) that is itself coherent with the shared pump laser. This enables coherent locking of the OPO to the optically referenced pump frequency comb, resulting in a composite frequency comb with wavelengths from 1 to 6 μm.

Mid infrared supercontinuum generation in nanotapered chalcogenide-silica step-index waveguides

Chalcogenide glasses have nonlinear refractive indices ~200 times greater than fused silica, and offer windows of transparency extending far into the mid-IR. These properties make them interesting for supercontinuum (SC) generation at wavelengths beyond 2 μm. Various different waveguiding structures incorporating chalcogenide glasses have been reported in literature, including microstructured fibers [1] and fiber tapers [2].

Hybrid Fibers: An Innovative base for Plasmonics and Nonlinear Optics

By filling the holes of microstructured optical fibers with particular materials, we implement highly nonlinear chalcogenide-silica waveguides for mid-IR supercontinuum generation and plasmonic fibers showing hybridized plasmonics excitations with a sophisticated near field polarization.

Chalcogenide-silica fibers - a novel base for nanophotonic devices

In my presentation I will review our recent results on hybrid chalcogenide-silica waveguides with the focus on nanotapers, band gap guidance and mid infrared super continuum generation.

Nanophotonics inside hybrid optical fibers

In my presentation I will review our recent results related to nanophotonic hybrid waveguides in fiber form. I will discuss plasmonic hybridization of spiralling plasmons excited on metallic nanowires in photonic crystal fibers. I will also discuss the optical properties and fabrication of highly nonlinear chalcogenide-silica waveguides and their application in infrared supercontinuum generation.

Bandgap guidance in chalcogenidesilica photonic crystal fibers

We present a novel technique for realizing hybrid all-solid band-gap-guiding fibers [1] using chalcogenide and fused silica glass. The high refractive index contrast between the two materials gives rise to the formation of distinct band-gaps and pass-bands, resulting in a sequence of transmission bands at different wavelengths.

From plasmonics to supercontinuum generation: Subwavelength scale devices based on hybrid photonic crystal fibers

Photonic crystal fibers (PCFs) consist of arrays of micrometer-size hollow channels extending along the entire fiber length. A new approach to modify the optical properties and to improve the design flexibility of such fibers is to fill the air holes of the array by with different materials, realizing all-solid hybrid fiber structures. In this talk, recent results on silica PCF filled with noble metals, semiconductors or soft glasses are presented. Depending on the actual material being filled into the holes, we observed plasmonic excitations, Mie-resonances and photonic band gaps.