Photonic Lantern Research Articles

“Photonic lantern” spectral filters in multi-core fibre

Fiber Bragg gratings are written across all 120 single-mode cores of a multi-core optical Fiber. The Fiber is interfaced to multimode ports by tapering it within a depressed-index glass jacket. The result is a compact multimode "photonic lantern" filter with astrophotonic applications. The tapered structure is also an effective mode scrambler.

Ultrafast laser inscription of a 121-waveguide fan-out for astrophotonics

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.

Nineteen-port photonic lantern with multimode delivery fiber

We demonstrate efficient multimode (MM) to single-mode (SM) conversion in a 19-port photonic lantern with a 50 μm core MM delivery fiber. The photonic lantern can be used within the field of astrophotonics for coupling MM starlight to an ensemble of SM fibers in order to perform fiber-Bragg-grating-based spectral filtering. An MM delivery fiber spliced to the photonic lantern offers the advantage that the delivery fiber guides the light from the focal plane of the telescope to the splitter. Therefore, it is no longer necessary to have the splitter mounted directly in the focal plane of the telescope. The coupling loss from a 50 μm core MM fiber to an ensemble of 19 SM fibers and back to a 50 μm core MM fiber is below 1.1 dB.

Ultrafast laser inscription of an integrated photonic lantern

We used ultrafast laser inscription to fabricate three-dimensional integrated optical transitions that efficiently couple light from a multimode waveguide to a two-dimensional array of single mode waveguides and back. Although the entire device has an average insertion loss of 5.7 dB at 1539 nm, only ≈0.7 dB is due to mode coupling losses. Based on an analysis which is presented in the paper, we expect that our device should convert a multimode input into an array of single modes with a loss of ≈2.0 dB, assuming the input coupling losses are zero. Such devices have applications in astrophotonics and remote sensing.

Photonic lanterns: a study of light propagation in multimode to single-mode converters

The "photonic lantern," an optical fibre device that has emerged from the field of astrophotonics, allows for a single-mode photonic function to take place within a multimode fibre. We study and evaluate the modal behaviour of photonic lanterns as well as the conditions for achieving low-loss between a multimode fibre and a "near-diffraction limited" single-mode system. We also present an intuitive analogy of the modal electromagnetic propagation behaviour along the photonic lantern transition in terms of the Kronig-Penney model in Quantum Mechanics.

Multi-mode to single-mode conversion in a 61 port Photonic Lantern

Efficient multi-mode (MM) to single-mode (SM) conversion in a 61 port splitter or "Photonic Lantern" is demonstrated. The coupling loss from a 100 microm core diameter MM section to an ensemble of 61 SM fibers and back to another 100 microm core MM section is measured to be as low as 0.76 dB. This demonstration shows the feasibility of using the Photonic Lanterns within the field of astrophotonics for coupling MM star-light to an ensemble of SM fibers in order to perform fiber Bragg grating based spectral filtering.

Astrophotonics and IR astronomy

Working in collaboration with industry, the University of Sydney, the Anglo-Australian Observatory and Macquarie University are developing new ‘astrophotonic’ solutions to problems in astronomical instrumentation. A key first step involves overcoming the limitations imposed by multimode (MM) optical fibres that have been used by astronomers for many years to transport or reformat light from the telescope focus to an optical spectrograph. These large-core MM fibres maximise light into an astronomical instrument but at the expense of propagating many unpolarized modes. Until recently, this has deterred the use of more complex in-fibre processing of the light since this is typically limited to single-mode (SM) propagation. A MM to SM converter, known as a ‘photonic lantern’, was first demonstrated by Leon-Saval et al. (2005). If the number of transverse modes equals the number of SM fibres, and if a gradual and adiabatic transition between the MM fiber and the ensemble of SM fibres can be achieved, lossless coupling can take place in either propagation direction. Noordegraaf et al. (2009) demonstrated an efficient 1 x 7 photonic lantern (1 MM input and 7 SM outputs) for the first time.

Efficient multi-mode to single-mode coupling in a photonic lantern

We demonstrate the fabrication of a high performance multi-mode (MM) to single-mode (SM) splitter or "photonic lantern", first described by Leon-Saval et al. (2005). Our photonic lantern is a solid all-glass version, and we show experimentally that this device can be used to achieve efficient and reversible coupling between a MM fiber and a number of SM fibers, when perfectly matched launch conditions into the MM fiber are ensured. The fabricated photonic lantern has a coupling loss for a MM to SM tapered transition of only 0.32 dB which proves the feasibility of the technology.

Astrophotonics: a new era for astronomical instruments

Astrophotonics lies at the interface of astronomy and photonics. This burgeoning field has emerged over the past decade in response to the increasing demands of astronomical instrumentation. Early successes include: (i) planar waveguides to combine signals from widely spaced telescopes in stellar interferometry; (ii) frequency combs for ultra-high precision spectroscopy to detect planets around nearby stars; (iii) ultra-broadband fibre Bragg gratings to suppress unwanted background; (iv) photonic lanterns that allow single-mode behaviour within a multimode fibre; (v) planar waveguides to miniaturize astronomical spectrographs; (vi) large mode area fibres to generate artificial stars in the upper atmosphere for adaptive optics correction; (vii) liquid crystal polymers in optical vortex coronographs and adaptive optics systems. Astrophotonics, a field that has already created new photonic capabilities, is now extending its reach down to the Rayleigh scattering limit at ultraviolet wavelengths, and out to mid infrared wavelengths beyond 2500 nm.