Approximate optical system model

An analytical development is presented for on-axis far-field irradiance in terms of an optical system that specifies a laser beam quality, an optical train with both linear and nonlinear phase aberrations (power driven), and a focusing telescope with jitter. It was found that the far-field intensity does not increase linearly with laser power, in fact it turns over and decreases as nonlinear, power-driven aberrations begin to dominate. The same phenomena causes the wavelength scaling to be less than 1/lambda(2) (with decreasing wave-length) for far-field irradiance.