Abstract

Recent realization of diode-array end-pumped microchips¹ reveals a possibility of fabricating a single-frequency solid-state laser arrays. In contrast to fiber end-pumped Nd:YAG arrays,² the short cavity microchips provide a stable selection of the single longitudinal mode.³ The arrangement of a gain pixels in the form of a spatially periodic array with period p makes it possible to synchronize them by means of self-imaging,⁴ placing the output mirror at the distance being multiple of p²2λ from the active slice. The small value of self-phase modulation raises the threshold of transverse chaotic instabilities.⁵ A weak gain-guiding within the active slice offers the possibility of using a simple numerical model based on the Fox-Lee algorithm with a nonlinear mirror (rather than a coupled-mode model⁶) for calculation of the stationary eigenmodes of the system, taking into account transversely inhomogeneous gain saturation and thermal lensing. The validity of this model had been tested by the split-step FFT method.⁷ It was shown also by 1-D numerical modeling that such a system is sensitive to small transverse phase fluctuations that lead to the ramification of a wavefront on several domains where the wavefront is almost flat, but somewhat tilted; the waves emitted by this domain interfere in the far field, increasing the beam divergence beyond the diffraction limit.⁸

© 1994 IEEE