Spaleniak, IzabelaJovanovic, NemanjaGross, SimonLawrence, JWithford, MichaelIreland, Michael2015-12-101 July 2019780819491510http://hdl.handle.net/1885/67211In this paper we present theoretical and laboratory results on integrated directly-written photonic lanterns with varying taper lengths. These lanterns convert seeing-limited light into multiple diffraction limited signals, in other words, a multimode signal into multiple single-mode signals. We investigated 19-channel structures which were written within a 30-mm-long glass block and designed to operate at 1550 nm. A single structure consisted of a multimode waveguide which transitioned into an array of single-mode waveguides and then back to a multimode waveguide utilizing cosine taper transitions. Based on simulations we found that transition lengths of 6 mm were sufficient to obtain throughput at a level of ∼95%. Fabricated devices showed losses (coupling and transition losses) at the level of 30% for injection F/# > 5 and taper lengths > 5 mm. We believe that such devices show great promise for future use in astronomy.Author/s retain copyrightKeywords: 1550 nm; Astrophotonics; Direct write; Fabricated device; Integrated photonics; Multi-mode waveguides; Multimode signals; Multiple diffraction; Photonic technologies; Single mode; Single mode waveguides; Single structure; Taper length; Transition length; Astrophotonics; Multimode waveguides; Photonic lanterns; Ultrafast direct write201210.1117/12.9252642016-02-24