ETH Physicists Shine the Light From the World’s Smallest Laser, Measured at 30 Millionths of a Meter Long

ETH Zurich physicists have developed a new laser, and it is by far the smallest electrically pumped laser in the world and could one day revolutionize chip technology. The researchers have presented their development in the current issue of Science
World’s Smallest Laser
Image credit: ETH Pictures

From idea to successful implementation, the laser took Christoph Walther, a doctoral student in the group for the ETH Zurich Quantum Optoelectronics Laboratory, FIRST-Lab, just six months to develop.  The physicist, with four colleagues, had previously developed the smallest electrically pumped lasers in the world.
Much smaller than the wavelength
The laser’s length  is smaller than its wavelength. It measure 30 micrometers (or 30 millionths of a meter) long, eight microns high and has a wavelength of 200 micrometers. The laser is much smaller than the wavelength of the emitted light from it. Normally, a laser cannot be smaller than its wavelength. The reason: in a conventional laser light waves move the optical resonator to oscillate – like acoustic waves in the sound box of a guitar. This is a “walk” of light waves – in simple terms – between two mirrors back and forth. And this will only work if the mirror than the respective wavelength of the laser is bigger. Therefore, normal lasers are limited in size. While other researchers have already experimented in the border area, “…we are clearly gone under the previously known limit, as we have developed a completely new laser concept,” says Christoph Walther.
Inspired by the electronics
In the development of laser concept, Christoph Walther had teammates including Jérôme Faist, Professor and Director of the Institute for Quantum Electronics at ETH Zurich, who inspired the electronics of the laser. They used no optical resonator, as usual, but an electrical resonant circuit, consisting of a coil and two capacitors. In it, the light is “quasi-captured” and is amplified on the spot using an optical amplifier to excite self-sustaining electromagnetic oscillations.
As a result, the size of the resonator is no longer limited by the wavelength of light, but can in principle be arbitrarily reduced. This perspective makes lasers for the micro chip manufacturer especially interesting – as an optical alternative to transistors.  If researchers manage to converge the size of  micro-lasers with transistors then one day electro-optical chips could be built with a very high density on electronic and optical components,” said Christoph Walther. This could accelerate the exchange of data between microprocessors significantly.
Sources and contacts:
ETH Zurich 
Christoph Walther
Institute of Quantum Electronics
Tel +41 44 633 32 54
E-mail 

ETH Zurich
Media Relations
Tel: +41 44 632 41 41
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Publication: “Microcavity Laser Resonator Oscillating in Circuit-Based” C. Walther, G. Scalari, M. Amanti, M. Beck, J. Faist, Science, Vol 327, page 1495 (2010).