Ultrafast laser inscription of a 121-waveguide fan-out for astrophotonics.
ABSTRACT Using ultrafast laser inscription, we report the fabrication of a prototype three-dimensional 121-waveguide fan-out device capable of reformatting the output of a 120-core multicore fiber (MCF) into a one-dimensional linear array. When used in conjunction with an actual MCF, we demonstrate that the reformatting function using this prototype would result in an overall through put loss of ≈7.0 dB. However, if perfect coupling from the MCF into the fan-out could be achieved, the reformatting function would result in an overall loss of only ≈1.7 dB. With adequate development, similar devices could efficiently reformat the output of so-called "photonic lanterns" fabricated using highly multicore fibers.
Full-textDOI: · Available from: Joss Bland-Hawthorn, Aug 13, 2014
SourceAvailable from: Sandra-Helena Messaddeq[Show abstract] [Hide abstract]
ABSTRACT: The photosensitivity of GeSx binary glasses in response to irradiation to femtosecond pulses at 800 nm is investigated. Samples with three different molecular compositions were irradiated under different exposure conditions. The material response to laser exposure was characterized by both refractometry and micro-Raman spectroscopy. It is shown that the relative content of sulfur in the glass matrix influences the photo-induced refractive index modification. At low sulfur content, both positive and negative index changes can be obtained while at high sulfur content, only a positive index change can be reached. These changes were correlated with variations in the Raman response of exposed glass which were interpreted in terms of structural modifications of the glass network. Under optimized exposure conditions, waveguides with positive index changes of up to 7.8x10−3 and a controllable diameter from 14 to 25 μm can be obtained. Direct inscription of low insertion losses (IL = 3.1 – 3.9 dB) waveguides is demonstrated in a sample characterized by a S/Ge ratio of 4. The current results open a pathway towards the use of Ge-S binary glasses for the fabrication of integrated mid-infrared photonic components.Optics Express 10/2014; 22(21):26103-16. DOI:10.1364/OE.22.026103 · 3.53 Impact Factor
IEEE Journal of Selected Topics in Quantum Electronics 01/2015; 21(1):401-413. DOI:10.1109/JSTQE.2014.2350022 · 3.47 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Spectroscopy is a technique of paramount importance to astronomy, as it enables the chemical composition, distances and velocities of celestial objects to be determined. As the diameter of a ground-based telescope increases, the point-spread-function (PSF) becomes increasingly degraded due to atmospheric seeing. A degraded PSF requires a larger spectrograph slit-width for efficient coupling and current spectrographs for large telescopes are already on the metre scale. This presents numerous issues in terms of manufacturability, cost and stability. As proposed in 2010 by Bland-Hawthorn et al, one approach which may help to improve spectrograph stability is a guided wave transition, known as a "photonic-lantern". These devices enable the low-loss reformatting of a multimode PSF into a diffraction-limited source (in one direction). This pseudo-slit can then be used as the input to a traditional spectrograph operating at the diffraction limit. In essence, this approach may enable the use of diffraction-limited spectrographs on large telescopes without an unfeasible reduction in throughput. We (and others) have recently demonstrated that ultrafast laser inscription can be used to realize "integrated" photonic-lanterns, by directly writing three-dimensional optical waveguide structures inside a glass substrate. This paper presents our work on developing ultrafast laser inscribed devices accept and reformat multimode light into a diffraction-limited slit.SPIE Astronomical Telescopes + Instrumentation 2014, Montreal (Canada); 06/2014