Number 103 (Story #3), November 17, 1992 by Phillip F. Schewe and Ben Stein AN ANTENNA MOUNTED ON A PHOTONIC CRYSTAL has been demonstrated by scientists at the MIT Lincoln Lab and Bellcore. Photonic crystals are the recently introduced structures that reject electromagnetic radiation lying in certain frequency ranges or "bands" in the same way that semiconductors reject electrons in certain energy bands. Elliott Brown of Lincoln Lab (617-981-4713) and his colleagues built a photonic crystal-antenna setup which can couple microwave radiation to devices on integrated circuits. This configuration allows integrated-circuit devices to receive microwave radiation, or conversely, convert electric current to microwave signals. The configuration traditionally used for this purpose, antennas on semiconductor substrates, transmits only a few percent of their total power into the air; the rest is radiated into the semiconductor. The Lincoln Lab-Bellcore antenna, which has a planar bow-tie geometry, has much higher efficiency because the photonic crystal on which it is mounted has a sizeable energy gap in the microwave region. (Optics & Photonics News, November 1992; also upcoming article in "Physics News in 1992," to be published by the AIP Public Information Division.)