First light-absorbing anti-laser built
NEW HAVEN, Conn. – More than 50 years after the invention
of the laser, scientists have built the world’s first anti-laser, paving the
way for novel technologies with applications in everything from optical computing
Scientists at Yale University created the device, in which incoming
beams of light interfere with one another in such a way that they cancel one another
out. Called a coherent perfect absorber (CPA), the device was built using silicon.
While conventional lasers use a gain medium, a semiconductor like
gallium arsenide, to produce a focused beam of coherent light, the anti-laser uses
a silicon wafer to act as its “loss medium.”
To demonstrate the anti-laser, the researchers focused two laser
beams with a specific frequency into the cavity containing the wafer. The light
waves were aligned by the wafer in such a way that they became trapped, bouncing
back and forth indefinitely until they were absorbed and transformed into heat.
The results were published in Science, Feb. 18, 2011 (doi: 10.1126/ science.1200735).
Because of experimental limitations, the team’s current
CPA, which measures 1 cm across, absorbs only 99.4 percent of incoming light. Theoretically,
the CPA could absorb as much as 99.999 percent of light and be as small as 6 µm.
While they were able to demonstrate the effect for near-infrared
radiation, they have determined that with some tweaking of the cavity and loss medium
in future versions, the CPA will be able to absorb visible light in addition to
the specific infrared frequencies used in fiber optic communications.
The scientists believe that one day the anti-laser could be used
as an optical switch, a detector or as other components in next-generation computing.
Additionally, it could be used in radiology applications for therapeutic or imaging
- The study of radioactive substances and high-energy radiations such as x-rays and g-rays.
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