Removal of surface-normal spot beam from on-chip 2D beam pattern projecting lasers

Abstract

Static arbitrary two-dimensional beam patterns have been demonstrated using on-chip size "integrable spatial-phase-modulating surface-emitting lasers," which use the band edge mode of a two-dimensional photonic crystal as an in-plane resonator, while the spatial phase of the lightwaves of the band edge mode are simultaneously modulated in a holographic manner by a local positional shift of holes from their lattice points. Meanwhile, the beam patterns include a spot beam in the surface-normal direction (0th-order beam), which corresponds to components of vertical diffraction of the band edge modes without spatial phase modulation. A promising method, used to remove the 0th-order beam, uses a structure that prohibits the vertical diffraction of band edge modes. For this purpose, we set the period of the virtual photonic crystal structure from the conventional Γ₂ band edge to the Μ₁ band edge, where vertical diffraction is prohibited. Moreover, the additional spatial phase modulation that cancels the in-plane component of the wavevectors of the lightwaves of the band edge modes at the Μ₁ band edge are also imposed to output the beam patterns vertically. As a result, we successfully demonstrated two-dimensional beam patterns without a spot beam in the surface-normal direction.