3D-M3: high-spatial-resolution spectroscopy with extreme AO and 3D-printed micro-lenslets.

By combining integral field spectroscopy with extreme adaptive optics, we are now able to resolve objects close to the diffraction limit of large telescopes, exploring new science cases. We introduce an integral field unit designed to couple light with a minimal plate scale from the SCExAO facility at NIR wavelengths to a single-mode spectrograph. The integral field unit has a 3D-printed micro-lens array on top of a custom single-mode multi-core fiber, to optimize the coupling of light into the fiber cores. We demonstrate the potential of the instrument via initial results from the first on-sky runs at the 8.2 m Subaru Telescope with a spectrograph using off-the-shelf optics, allowing for rapid development with low cost.

Computational optical imaging with a photonic lantern.

The thin and flexible nature of optical fibres often makes them the ideal technology to view biological processes in-vivo, but current microendoscopic approaches are limited in spatial resolution. Here, we demonstrate a route to high resolution microendoscopy using a multicore fibre (MCF) with an adiabatic multimode-to-single-mode "photonic lantern" transition formed at the distal end by tapering. We show that distinct multimode patterns of light can be projected from the output of the lantern by individually exciting the single-mode MCF cores, and that these patterns are highly stable to fibre movement. This capability is then exploited to demonstrate a form of single-pixel imaging, where a single pixel detector is used to detect the fraction of light transmitted through the object for each multimode pattern. A custom computational imaging algorithm we call SARA-COIL is used to reconstruct the object using only the pre-measured multimode patterns themselves and the detector signals.

Divide and conquer: an efficient solution to highly multimoded photonic lanterns from multicore fibres.

Photonic lanterns typically allow for single-mode action in a multimode fibre. Since their invention over a decade ago for applications in astrophotonics, they have found important uses in diverse fields of applied science. To date, large aperture highly-mulitmoded to single-mode lanterns have been difficult as fabrication techniques are not practical for mass replication. Here as a proof of concept, we demonstrate three different devices based on multicore fibre photonic lanterns with: 100µm core diameters; NAs = 0.16 and 0.15; and requiring 259 single-mode core system, specifically 7 multicore fibres each with 37 cores, instead of 259 individual single-mode fibres. The average insertion loss excluding coupling efficiencies is only 0.4dB (>91% transmission). This concept has numerous advantages, in particular, (i) it is a direct scaleable solution, (ii) eases imprinting of photonic functions, e.g. fibre Bragg gratings; and (iii) new approach for large-area optical fibre slicers for future large-aperture telescopes.

Multiplexed single-mode wavelength-to-time mapping of multimode light.

When an optical pulse propagates along an optical fibre, different wavelengths travel at different group velocities. As a result, wavelength information is converted into arrival-time information, a process known as wavelength-to-time mapping. This phenomenon is most cleanly observed using a single-mode fibre transmission line, where spatial mode dispersion is not present, but the use of such fibres restricts possible applications. Here we demonstrate that photonic lanterns based on tapered single-mode multicore fibres provide an efficient way to couple multimode light to an array of single-photon avalanche detectors, each of which has its own time-to-digital converter for time-correlated single-photon counting. Exploiting this capability, we demonstrate the multiplexed single-mode wavelength-to-time mapping of multimode light using a multicore fibre photonic lantern with 121 single-mode cores, coupled to 121 detectors on a 32 × 32 detector array. This work paves the way to efficient multimode wavelength-to-time mapping systems with the spectral performance of single-mode systems.

Characterizing the variation of propagation constants in multicore fiber.

We demonstrate a numerical technique that can evaluate the core-to-core variations in propagation constant in multicore fiber. Using a Markov Chain Monte Carlo process, we replicate the interference patterns of light that has coupled between the cores during propagation. We describe the algorithm and verify its operation by successfully reconstructing target propagation constants in a fictional fiber. Then we carry out a reconstruction of the propagation constants in a real fiber containing 37 single-mode cores. We find that the range of fractional propagation constant variation across the cores is approximately ± 2 × 10(-5).

Highly-efficient, octave spanning soliton self-frequency shift using a specialized photonic crystal fiber with low OH loss.

We report the first demonstration of efficient, octave spanning soliton self-frequency shift. In order to achieve this we used a photonic crystal fiber with reduced OH absorption and widely spaced zero-dispersion wavelengths. To our knowledge, this is the largest reported frequency span for a tunable, fiber-based source. In addition, we observe the generation of light above 2 µm directly from a Ti:Sapphire laser in the form of Cerenkov emission by the soliton when the red-shift saturates at the edge of the anomalous dispersion region.