One of the major advantages of photonic crystals is miniaturization and on-chip, lithographic design of optical functional circuits.  So it is natural that there has been much interest in bringing gratings -- or any kind of dispersive optics -- onto the chip, so that light may be broken down easily into its constituent wavelengths for processing, and then recombined.

A photonic crystal superprism accomplishes this, but has been hampered by difficulty in collimating the dispersed light into different channels before the light diverges too much.  In a paper [1] that appears in this week's issue of Applied Physics Letters, Matsumoto et al. from the Yokohama National University in Japan solve the divergence problem by collimating the superprism output using a photonic crystal superlens.  This lens relies on the same mechanism as the grating and can thus be easily integrated on the same chip.  The news about this paper is not the superlens or supergrating -- each has been previously demonstrated -- but is the beautiful combination of the two.  This combination draws on a set of additional tricks, such as high-efficiency input couplers and chromatic corrections, that makes the completed device work quite nicely, and makes this paper read almost as a text-book example of the promise of integrated photonic crystal devices. 

[1]Takashi Matsumoto, Tomohiko Asatsuma, and Toshihiko Baba, Appl. Phys. Lett. 91, 091117 (2007)

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