Adaptive phase-mask coronagraph with amplitude and phase modulation for high dynamic range synchronous detection: APM^2 coronagraph

We present a new Adaptive Phase Mask (APM) coronagraph design enabling Amplitude and Phase Modulation control (APM). The Adaptive Phase mask coronagraph is a technique proposed to provide both high dynamic and high angular resolution imaging of faint sources around bright objects. Discriminating faint sources from static speckles is a challenging problem. Our new system is based on synchronous demodulation that allows high dynamic range detection of a faint target immersed in a background. The APM^2 uses the coherence of speckles to discriminate them from proper companions, using the mask itself as the electric field modulator. Synchronous detection in the radio frequency range is used to side-step the effect of atmospheric turbulence and enable the detection of low amplitude signals. The APM^2 concept offers high dynamic range detection and provides a time- and cost-effective method to quantify the probability of presence of a faint object close to the central star.