Simulations of mode-selective photonic lanterns for efficient coupling of starlight into the single-mode regime.

In ground-based astronomy, starlight distorted by the atmosphere couples poorly into single-mode waveguides, but a correction by adaptive optics, even if only partial, can boost coupling into the few-mode regime, allowing the use of photonic lanterns to convert into multiple single-mode beams. Corrected wavefronts result in focal patterns that couple mostly with circularly symmetric waveguide modes. A mode-selective photonic lantern is hence proposed to convert multimode light into a subset of single-mode waveguides of the standard photonic lantern, thereby reducing the required number of outputs. We ran simulations to show that only two out of the six waveguides of a 1×6 photonic lantern carry >95% of the coupled light to the outputs at D/r0<10 if the wavefront is partially corrected and the photonic lantern is made mode selective.

Modal analysis using photonic lanterns coupled to arrays of waveguides.

We present a new concept of an integrated optics component capable of measuring the complex amplitudes of the modes at the tip of a multimode waveguide. The device uses a photonic lantern to split the optical power carried by an N-modes waveguide among a collection of single-mode waveguides that excite a periodic array of at least N2single-mode evanescently-coupled waveguides. The power detected at each output of the array is a linear combination of the products of the modal amplitudes-a relation that can, under suitable conditions, be inverted allowing the derivation of the amplitudes and relative phases of the modal mixture at the input. The expected performance of the device is discussed and its application to the real-time measurement of modal instability in high power fiber lasers is proposed.