Optimization of Rowland circle mounts for grating demultiplexers and narrow-band spectrographs

A simple equation for the parameters of the Rowland circle grating mount is derived that ensures that the astigmatism and the meridional spherical aberration are stationary at the wavelength of correction. This is important in optimizing the design of grating multiplexers-demultiplexers and cross connects in wavelengthdivision multiplexed networks and high-resolution narrow-band spectrographs. An analysis of aberrations in three-dimensional and planar two-dimensional optical schemes is presented, and it is shown that in the wavelength range of 1530-1570 nm diffraction-limited performance can be achieved for 160 channels in a three-dimensional multiplexer-demultiplexer and for more than 800 channels for a planar free-space scheme.