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Patent abstract
A circular semiconductor laser, comprising a laser resonator with a planar active region, a first and a second waveguide layer defining the active region. The resonator has a shape defined by a circular perimeter, along which the first waveguide layer has a plurality of radial cuts forming a grating. The number of such cuts is a prime number, or an odd number that is a multiple of a prime number, called a prime number greater than or equal to five. This prevents the resonant modes from evolving outside the zone with the cuts, or at any rate with a non-zero component of the wave vector in the radial direction, and results in a pure whispering gallery mode of operation, with the maximum of the emitted radiation evolving in the vertical direction, i.e., orthogonal to the plane of the laser resonator, and without the radiation emitted by the laser evolving in the radial direction.