SPECTRALLY ADJUSTABLE FILTER
Spectrally filtering at least one input beam includes dispersing spectral components of at least one input beam at different respective angles in a spectral plane; changing at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components changes; receiving a plurality of the dispersed spectral components incident on a reflective surface at a location at which the central rays of each of the spectral components are incident at different points on the reflective surface; and tilting the reflective surface to select at least one and fewer than all of the received spectral components to be directed to a selected output path.
1 . An apparatus for spectrally filtering at least one input beam, comprising:
a spectrally dispersive element configured to disperse spectral components of at least one input beam at different respective angles in a spectral plane;
one or more optical elements configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components changes; and
a reflective surface configured to receive a plurality of the dispersed spectral components at a location at which the central rays of each of the spectral components are incident at different points on the reflective surface, and to tilt to select at least one and fewer than all of the received spectral components to be directed to a selected output path.
2 . The apparatus of claim 1 , wherein the one or more optical elements are configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components increases.
3 . The apparatus of claim 2 , wherein the dispersed spectral components diverge at a first maximum angular separation and the one or more optical elements are configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the spectral components diverge at a second maximum angular separation larger than the first maximum angular separation.
4 . The apparatus of claim 2 , wherein the dispersed spectral components diverge at a first maximum angular separation and the one or more optical elements are configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the spectral components converge at a second maximum angular separation larger than the first maximum angular separation.
5 . The apparatus of claim 1 , wherein the one or more optical elements comprise at least one prism.
6 . The apparatus of claim 1 , wherein the one or more optical elements comprise two lenses having different focal lengths, and wherein the two lenses are separated by a distance that is approximately the sum of the focal lengths.
7 . The apparatus of claim 1 , wherein the one or more optical elements are configured to change the transverse spatial extent of each of the dispersed spectral components such that the transverse spatial extent of the input beam incident on the spectrally dispersive element is larger than the transverse spatial extent of each of the plurality of dispersed spectral components incident on the reflective surface.
8 . The apparatus of claim 7 , wherein the transverse spatial extent of the input beam incident on the spectrally dispersive element is larger than the total transverse spatial extent of all the dispersed spectral components incident on the reflective surface.
9 . The apparatus of claim 7 , wherein the transverse spatial extent of the input beam incident on the spectrally dispersive element is at least about two times larger than the transverse spatial extent of each of the plurality of dispersed spectral components incident on the reflective surface.
10 . The apparatus of claim 1 , wherein the spectrally dispersive element is configured to disperse the spectral components at the different respective angles from a common spatial mode.
11 . The apparatus of claim 10 , further comprising one or more optical elements configured to expand the input beam provided to the spectrally dispersive element from a guided spatial mode of a waveguide to the common spatial mode incident on the spectrally dispersive element.
12 . The apparatus of claim 11 , wherein the reflective surface receives the plurality of the dispersed spectral components after at least two passes through the one or more optical elements configured to expand the input beam.
13 . The apparatus of claim 1 , wherein the reflective surface is configured to receive dispersed spectral components from multiple input beams, and to tilt to select at least one and fewer than all of the received spectral components of a given input beam to be directed to a corresponding selected output path.
14 . A method for spectrally filtering at least one input beam, comprising:
dispersing spectral components of at least one input beam at different respective angles in a spectral plane;
changing at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components changes;
receiving a plurality of the dispersed spectral components incident on a reflective surface at a location at which the central rays of each of the spectral components are incident at different points on the reflective surface; and
tilting the reflective surface to select at least one and fewer than all of the received spectral components to be directed to a selected output path.
15 . A system for monitoring spectra of spectral components of at least one input beam, comprising:
a spectrally dispersive element configured to disperse spectral components of at least one input beam at different respective angles in a spectral plane;
one or more optical elements configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components changes;
a reflective surface configured to receive a plurality of the dispersed spectral components at a location at which the central rays of each of the spectral components are incident at different points on the reflective surface, and to tilt to select at least one and fewer than all of the received spectral components to be directed to a selected output path; and
at least one detector configured to receive a spectral component directed to a selected output path.
16 . An apparatus for spectrally filtering at least one input beam, comprising:
a spectrally dispersive element configured to disperse spectral components of at least one input beam at different respective angles in a spectral plane;
one or more optical elements configured to change at least some of the angles of the propagation axes of the dispersed spectral components, at least one of the optical elements being located at a distance from the spectrally dispersive element that is less than the focal length of the at least one optical element; and
a reflective surface configured to receive a plurality of the dispersed spectral components, and to tilt to select at least one and fewer than all of the received spectral components to be directed to a selected output path.
17 . The apparatus of claim 16 , wherein the reflective surface is configured to receive a plurality of the dispersed spectral components at a location at which the central rays of each of the spectral components are incident at different points on the reflective surface.
18 . The apparatus of claim 16 , wherein the one or more optical elements comprise two lenses having different focal lengths, and wherein the two lenses are separated by a distance that is approximately the sum of the focal lengths.
19 . The apparatus of claim 16 , wherein the reflective surface is configured to receive dispersed spectral components from multiple input beams, and to tilt to select at least one and fewer than all of the received spectral components of a given input beam to be directed to a corresponding selected output path.
20 . An apparatus for spectrally filtering at least one input beam, comprising:
a spectrally dispersive element configured to disperse spectral components of at least one input beam at different respective angles in a spectral plane;
one or more optical elements configured to change at least some of the angles of the propagation axes of the dispersed spectral components so that the maximum angular separation among the propagation axes of the spectral components increases, and to change the transverse spatial extent of each of the spectral components to be smaller than the transverse spatial extent of the input beam incident on the spectrally dispersive element; and
a reflective surface configured to receive a plurality of the dispersed spectral components, and to tilt to select at least one and fewer than all of the received spectral components to be directed to a selected output path.
21 . The apparatus of claim 20 , wherein the one or more optical elements comprise at least one prism.
22 . The apparatus of claim 20 , wherein the one or more optical elements comprise two lenses having different focal lengths separated by a distance that is approximately the sum of the focal lengths.
23 . The apparatus of claim 20 , wherein the spectrally dispersive element is configured to disperse the spectral components at the different respective angles from a common spatial mode.
24 . The apparatus of claim 23 , further comprising one or more optical elements configured to expand the input beam provided to the spectrally dispersive element from a guided spatial mode of a waveguide to the common spatial mode incident on the spectrally dispersive element.
25 . The apparatus of claim 24 , wherein the reflective surface is positioned to receive the plurality of the dispersed spectral components after at least two passes through the one or more optical elements configured to expand the input beam.