We propose a new approach to direct imaging of extrasolar planets: one-sided phase apodization. It is based on a discovery that an antisymmetric spatial phase modulation pattern imposed over a pupil or a relay plane causes diffracted starlight suppression sufficient for imaging of extrasolar planets. Calculations with specific square-pupil (side D) phase functions, such as φ(x,y)=a 1n[(1+ε)+2x/D(1+ε)+2y/D]/[(1+ε)-2x/D(1+ε)-2y/D], demonstrate annulling in at least one quadrant of the diffraction plane to the contrast level of better than 10~(-12), with an inner working angle down to 3.5λ/D (with a = 3 and ε = 10~(-3)). Furthermore, our computer experiments show that phase apodization remains effective throughout a broad spectrum (60% of the central wavelength) covering the entire visible-light range. Phase-only modulation has the additional appeal of potential implementation via active segmented or deformable mirrors, thereby combining compensation of random phase aberrations and diffraction halo removal in a single optical eletpent.
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