Fig. 1. Arrangement for obtaining an array of negatively coupled phase-locked lasers, forming first and second harmonics and their detection. It consists of three main parts: a degenerate cavity laser with an intra-cavity mask of holes so as to obtain a desired laser array geometry, a telescope with a KTP nonlinear crystal to obtain the second harmonics, and an arrangement to detect the near-field and far-field of the first and second harmonics.

Fig. 2. Two coupled lasers; (a) schematic illustration of phase shift doubling in the second harmonics, where an out-of-phase locking (π phase shift) in the first harmonics is converted into an in-phase locking (2π phase shift) in the second harmonics; (b) experimental intensity distributions for the near- and far- fields of first and second harmonics.

Fig. 3. Array of 334 coupled lasers formed in a square geometry; (a) schematic illustration of phase shift doubling in the second harmonics, where an out-of-phase locking (π phase shift) in the first harmonics is converted into an in-phase locking (2π phase shift) in the second harmonics; (b) experimental intensity distributions for the near- and far-fields of first and second harmonics.

Fig. 4. Array of 199 coupled lasers formed in a honeycomb geometry (a) schematic illustration of phase shift doubling in the second harmonics, where an out-of-phase locking (π phase shift) in the first harmonics is converted into an in-phase locking (2π phase shift) in the second harmonics; (b) experimental (left) and calculated (right) intensity distributions for the near- and far-fields of first and second harmonics.

Fig. 5. Array of 299 coupled lasers formed in triangular geometry, each laser with many longitudinal modes; (a) schematic illustration where summing of two longitudinal modes with vortex and antivortex phase distributions leads to an in-phase intensity distribution; (b) summing two longitudinal modes both with vortex phase distributions leads to antivortex phase distribution; (c) experimental (left) and calculated (right) intensity distributions for the near- and far-fields of first and second harmonics.