Shooting Lasers through Fibres

Directing lasers with "perfect mirror"
technology; © MIT/Yoel Fink

Now "perfect mirror" technology is being used to shoot a laser through a spaghetti-thin, flexible fiber to attack tumours and other diseased tissue in highly targeted, minimally invasive surgery.

The fiber originated with the "perfect mirror" created in 1998 by Yoel Fink, associate professor of materials science and engineering; John D. Joannopoulos, the Francis Wright Davis Professor of Physics; and Edwin L. Thomas, the Morris Cohen Professor of Materials Science and Engineering.

While the familiar metallic mirror is omnidirectional, which means it reflects light from every angle, it also absorbs a significant portion of the incident light. The new kind of mirror can reflect light from all angles and polarizations, just like metallic mirrors, but does so with much higher efficiency. In addition, the mirrors can be "tuned" to reflect certain wavelength ranges and transmit the rest of the spectrum, making them omnidirectional reflectors.

In 2002 a team from Fink's laboratory published an article showing that it was possible to form an omnidirectional perfect mirror into a "pipe" surrounding a hollow core. The mirror's creators then developed a process for making hollow-core fibers that are as thin as spaghetti and transport a beam of intense laser light for meters.

Less than two years later, the fiber was used for the first time in an experimental surgery at Wake Forest Hospital in North Carolina.

"I am very excited about this technology because it liberates me from the limitations of the traditional 'line-of-sight' laser beam," said Dr. Chris Holsinger of the University of Texas M.D. Anderson Cancer Center. "In the head and neck, with its complex 3-D anatomy, the ability to use the laser as I would manipulate a scalpel in three-dimensional space represents a dramatic step forward."

MEDICA.de; Source: Massachusetts Institute of Technology