Laboratory demonstration of a broadband six-level phase mask coronagraph.

The six-level phase mask (SLPM) can he used in a focal plane as an efficient. coronagraph [Opt. Express 22, 1884 (2014)]. It has several advantages: high-contrast imaging in broadband with small inner working angle: easy fabrication at low cost by photolithography and reactive ion etching processes; easy implementation with no need of pupil apoditation. We present in this paper the first laboratory results demonstrating the high performance of a SLPM with an unobscured pupil. The on-axis attenuation reaches 2 x 10(-5) at lambda = 800 nm and is better than 10(-4) over a 10% spectral bandwidth and better than 10(-3) over a 20% bandwidth. Finally: the detection of a planet can he achieved down to 1 lambda/D. (C) 2018 Optical Society of America under the terms of the GSA Open AccessPublishing Agreement.