33 research outputs found
Three-dimensional microstructuring of yttrium aluminum garnet crystals for laser active optofluidic applications
The following article appeared in Applied Physics Letters 103.4 (2013): 041101 and may be found at http://scitation.aip.org/content/aip/journal/apl/103/4/10.1063/1.4816338We demonstrate three-dimensional microstructuring in a neodymium doped yttrium aluminum garnet (Nd:YAG) crystal. Spatially well-defined hollow microstructures deeply embedded within the material are shown to result from the creation of a pre-damage state within the Nd:YAG crystal network that is validated using luminescence and Raman analyses of the structures. This opens up the potential of fabricating next-generation optofluidic devices in optical gain materialsFinancial support from the Spanish Ministerio de Educación under the Programa de Movilidad de Recursos Humanos del Plan Nacional de IþDþi 2008/2011 for abroad postdoctoral researchers. This work was also supported by the Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (Project S2009/MAT- 1756) and by the Spanish Ministerio de Educación y Ciencia (MAT2010-16161
Observation of a localized flat-band state in a photonic Lieb lattice
We show experimentally how a non-diffracting state can be excited in a
photonic Lieb lattice. This lattice supports three energy bands, including a
perfectly flat middle band, which corresponds to an infinite effective mass
with zero dispersion. We show that a suitable optical input state can be
prepared so as to only excite the flat band. We analyse, both experimentally
and theoretically, the evolution of such photonic flat-band states, and show
their remarkable robustness, even in the presence of disorder.Comment: Accepted for publication in Physical Review Letter
Modulation-assisted tunneling in laser-fabricated photonic Wannier-Stark ladders
We observe Wannier-Stark localization in curved photonic lattices, realized
using arrays of evanescently coupled optical waveguides. By correctly tuning
the strength of inter-site coupling in the lattice, we observe that
Wannier-Stark states become increasingly localized, and eventually fully
localized to one site, as the curvature of the lattice is increased. We then
demonstrate that tunneling can be successfully restored in the lattice by
applying a sinusoidal modulation to the lattice position, an effect that is a
direct analogue of photon-assisted tunneling. This precise tuning of the
tunneling matrix elements, through laser-fabricated on-site modulations, opens
a novel route for the creation of gauge fields in photonic lattices.Comment: 5 pages. Comments are welcom
Optimisation of ultrafast laser assisted etching in fused silica
Observations of runout distances combined with velocity measurements suggest that “major” dry-mixed avalanches show a scale invariance to the total drop height HSC. This is in accordance to the proposed upper-limit envelope of the maximum velocity by McClung and Schaerer (2006). The observations are also supported by a simple scaling analysis using a simple mass block model on cycloidal and parabolic tracks (Gauer, 2018b), concluding Umax~ gHSC/2 . In this supplementary paper, a simple mass block model is presented that includes basic observations of major dry-mixed avalanches, such as mass entrainment and deposition, and that reflects this scale invariance. Almost all model parameters can principally be observed in the field. Model results are compared with a series of avalanche observations of runout and velocity and match well, considering that the model is a first order approximation
Controlled core-to-core photo-polymerisation – fabrication of an optical fibre-based pH sensor
The fabrication of fluorescence-based pH sensors, embedded into etched pits of an optical fibre via highly controllable and spatially selective photo-polymerisation is described and the sensors validated.</p
Development of integrated mode reformatting components for diffraction-limited spectroscopy
We present the results of our work on developing fully integrated devices (photonic dicers) for reformatting multimode light to a diffraction limited pseudo-slit. These devices can be used to couple a seeing limited telescope point spread function to a spectrograph operating at the diffraction limit, thus potentially enabling compact, high-resolution spectrographs that are free of modal noise