Contact:	Bob Nelson						For immediate release
		(212) 854-6580					November 12, 1997
		rjn2@columbia.edu



Columbia-SUNY Team Slices Magnetic Crystal;
Applications Seen for Miniaturized Optical Devices


	In laboratories at Columbia University, scientists are bonding light and 
electricity.
	They have taken the first important step toward creating a microchip that 
combines electronics and its optical equivalent, photonics.  The technology could 
simplify fiber optic communications and lead to the development of such 
miniaturized optical devices as tiny lasers and implantable medical sensors.
	The Columbia scientists, working with colleagues from the State University 
of New York at Albany, have bonded an ultra-thin sheet of magnetic garnet, a 
photonic material that transmits light in only one direction, to a semiconductor, a 
component of microelectric circuitry.
	"Ultimately, manufacturers will be able to combine optical and electronic 
capacity on the same silicon crystals, which are superior electronics platforms," 
said Richard M. Osgood, Higgins Professor of Electrical Engineering and 
professor of applied physics and co-author of the research.
	A crucial step was slicing an ultra-thin sheet - 9 microns, or millionths of 
a meter, thick - from the magnetic garnet crystal, the subject of a scientific 
paper published in the Nov. 3 issue of Applied Physics Letters.  Columbia has 
applied for a patent on the new technology.
	Professor Osgood and the co-inventor of the new technology, Miguel Levy, 
senior research scientist at Columbia, have already begun to receive requests for 
single-crystal magnetic garnet films from other laboratories around the world, 
for such diverse research applications as microwave electronics and optical
isolators.  Columbia is the only institution that can produce the thin films.
	The work took place at Columbia's Microelectronics Sciences Laboratory 
and at the Columbia Radiation Laboratory, both in the Fu Foundation School of 
Engineering and Applied Science.  The research group included two materials 
scientists at the State University of New York at Albany, Hassaram Bahkru and 
Atul Kumar, who assisted in processing the garnet used in the experiments at 
SUNY Albany's ion accelerator.
	"I'm excited that this technology can be used to build a whole new range of 
miniaturized systems, from medical sensors to ultra-small, powerful laser 
systems," Professor Osgood said.
	Miniaturized optical processors for fiber optic telecommunications are also 
possible.  Currently, optic messages travel by laser light to an isolator that 
prevents destabilization of the laser by outside interference, then to a modulator 
that imprints a signal, then to a multiplexer that combines signals of different 
wavelengths, each of which can carry a different message.  A similar system is 
required at the receiving end to decode the light message into sound or picture.
	"Right now, these are all very bulky devices," Dr. Levy said.  "If you could 
put all these optic circuits on a chip, it would be cheaper, more efficient and 
sturdier, and there has been a lot of research geared towards integrating these 
components.  Our work is an important step in this direction."
	Such integration between photonics and electronics had not been possible 
because garnet and other magnetic crystals cannot be grown on a semiconductor 
substrate.  Magnetic isolators cannot be made efficiently on any material other 
than magnetic garnets.  Thus the need to place garnet crystals on 
semiconductors, providing a bridge to an already mature technology, the 
researchers said.
	The Columbia research team fired high-energy beams of helium ions at a 
planar region that is just below the surface of the crystalline material, yttrium 
iron garnet (YIG), to loosen it from its substrate, gadolinium gallium garnet.  
They then applied chemicals to the region to cut the bonds entirely, slicing off an 
ultra-thin sheet of magnetic material from a single crystal.  The sample was then 
lifted off and bonded to a high-quality semiconductor.
	The goal of this effort is to make devices that allow light to go in only one 
direction on a fiber optic microchip, Professor Osgood said.  Light guides etched 
into the magnetic crystal, when exposed to a magnetic field, allow the light to 
travel in one direction only, making the light guide an effective routing device in 
an optic fiber network.
	The work is the result of a collaboration between Columbia and the 
University of Minnesota to create integrated photonic devices for use in fiber optic 
communications systems.  The collaboration is funded by the federal Advanced 
Research Projects Agency.

This document is available at http://www.columbia.edu/cu/pr/.  Working press may receive 
science and technology press releases via e-mail by sending a message to rjn2@columbia.edu.

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