Phase-locked laser array far-field normalization

The normalization of the far-field distribution from phase-locked linear arrays of evanescently coupled semiconductor diode lasers is evaluated. As the element number N→∞, the peak irradiance of the fundamental array mode tends to 81% of the peak irradiance of an array of in-phase equal-intensity diodes. It is also found that for N⩾10, the peak irradiance is proportional to 0.81 (1+1/N)N², and the diffraction-limited beamwidth is approximately 1.19 λ(N+1)S where λ is the vacuum wavelength and S is the array period. The far-field array factor is the same for an N-element array and an (N+1) S-wide cosine source as long as N⩾10