Scientists at the University of California, Berkeley have built what they claim is the world's smallest semiconductor laser, capable of generating visible light in a space smaller than a single protein molecule.
The breakthrough, detailed in the journal Nature, breaks new ground in the field of optics, and helps enable the development of:
- Nanolasers that can probe, manipulate and characterize DNA molecules;
- Faster optics-based telecommunications (think Verizon FioS);
- Faster and more powerful optical computing in which light replaces electronic circuitry.
The UC Berkeley team was able to squeeze light into the tiny space as well as keep its energy from dissipating as it moved along -- in other words, creating a laser.
"This work shatters traditional notions of laser limits, and makes a major advance toward applications in the biomedical, communications and computing fields," said Xiang Zhang, director at UC Berkeley of a National Science Foundation (NSF) Nanoscale Science and Engineering Center, and head of the research team behind the work.
It's commonly accepted that an electromagnetic wave -- which includes laser light -- can't be focused beyond the size of half its wavelength. Recently, research teams around the world have devised a way to compress light down to the scale of dozens of nanometers by binding it to the electrons that oscillate collectively at the surface of metals.
The interaction between the light and the oscillating electrons is known as "surface plasmons."
Since then, scientists have been working to construct surface plasmon lasers, but a primary hurdle is resistance from the metals, which dissipates the energy almost immediately.
Zhang's team stemmed the loss of light energy by pairing a cadmium sulfide nanowire -- 1,000 times thinner than a human hair -- with a silver surface separated by an insulating gap of 5 nanometers, the size of a single protein molecule.
That's a space that's 20 times smaller than the light's wavelength. Since most of the light energy is stored in the tiny non-metallic gap, loss is largely diminished.
Scientists hope to eventually shrink light down to the size of an electron's wavelength, which is about a nanometer, or one-billionth of a meter, so that the two can work together on equal footing.
"The advantages of optics over electronics are multifold," added Thomas Zentgraf, a post-doctoral fellow in Zhang's lab and another co-lead author of the Nature paper. "For example, devices will be more power efficient at the same time they offer increased speed or bandwidth."
The work is supported by the U.S. Air Force Office of Scientific Research and the NSF.