Focal length dispersion compensation for field curvature

A wavelength router for receiving, at an input port, light having a plurality of spectral bands and directing subsets of the spectral bands to respective ones of a plurality of output ports, the wavelength router comprising:

• a routing mechanism having a substantially planar array of dynamically configurable routing elements, each of which is structured to direct a given spectral band to different output ports, depending on a state of such dynamically configurable routing element;
• and
• a free-space optical train disposed between the input port and the output ports providing optical paths for routing the spectral bands, the optical train including:
• a dispersive element disposed to intercept light traveling from the input port and to diffract it into a plurality of angularly separated beams corresponding to the plurality of spectral bands, the optical train being configured so that light encounters the dispersive element before reaching any of the output ports;
• and
• a first focusing element disposed with respect to the dispersive element and with respect to the substantially planar array of dynamically configurable routing elements such that dispersion in the focal distance of the first focusing element for different angularly separated beams compensates for field curvature aberration caused by the first focusing element.

An optical arrangement for receiving, at an input port, a light beam having a plurality of spectral bands and directing subsets of the spectral bands along optical paths to respective optical elements configured as a substantially planar array, the optical arrangement comprising:

• means for collimating the light beam;
• means for diffracting the collimated light beam into a plurality of angularly separated beams corresponding to the plurality of spectral bands;
• and
• means for focusing the angularly separated beams onto respective ones of the optical elements, such means for focusing disposed with respect to the means for diffracting such that dispersion in the focal distance of such means for focusing compensates for field curvature aberration caused by such means for focusing.

A method for directing spectral bands of a light beam having a plurality of such spectral bands along optical paths to respective optical elements configured as a substantially planar array, the method comprising:

• receiving the light beam at an input port;
• propagating the light beam from the input port such that it intercepted by a dispersive element;
• separating the light beam with the dispersive element into a plurality of angularly separated beams corresponding to the plurality of spectral bands;
• and
• focusing a subset of the plurality of angularly separated beams onto respective ones of the optical elements with a first focusing element disposed with respect to the dispersive element and with respect to the substantially planar array of optical elements such that dispersion in the focal distance for different spectral bands compensates for field curvature aberration.