Posted: March 16, 2010

Imperfections are perfect - implications for optical chip design

(Nanowerk News) Researchers from DTU Fotonik at Technical University of Denmark surprise the scientific world with their new discovery which, in the long term, may be used in, e.g., solar cells and quantum computers. Their findings will be published on 12 March 2010 in the prestigious international journal Science.
All over the world, intensive research is being conducted on how to use the smallest particles of light, photons, for communication applications. Where electronic technology makes use of microchips, optical communication uses the so-called optical chip.
how imperfections in a photonic crystal result in the localisation of light in a very small area
The figure shows how imperfections in a photonic crystal result in the localisation of light in a very small area. The red circles show the position of holes in an ideal structure. Random disorder has been introduced in this structure (compare the position of red circles to the actual holes (black) in the structure), which results in the localisation of light (orange areas).
On optical chips, a structure of holes is etched, and it is by means of these holes that the researchers try to control the photons’ movements on the chip So far, the aim has been to achieve a regular and ordered hole structure, and it has been the general conviction that disorder or imperfections in the hole structure reduce or simply destroy the functionality of the optical chip.
Disorder as a valuable resource
A group of researchers from DTU Fotonik has now turned everything totally upside down and demonstrated that disordered structures on optical chips may actually be an advantage. The researchers deliberately placed the holes on the optical chip irregularly, and this improved the chip. It has thus proved possible to capture and thus control photons very effectively on the ‘disordered’ chip. The discovery allows the production of a brand new type of optical chips where disorder is utilised as a valuable resource instead of being considered a limitation.
This finding is a major basic scientific breakthrough, which is published in the international journal Science on 12 March 2010.
The discovery may potentially be used in, e.g., solar cells and optical sensors or within quantum information technology. The dawning quantum information technology promises fundamentally new ways of coding and processing information, using the laws of quantum mechanics. This can, among other things, be used for 100% secure information exchange or, ultimately, for a quantum computer which can perform calculations far faster than the supercomputers of today.
The research group behind the discovery
The research has been conducted at the Department of Photonics Engineering at the Technical University of Denmark by a research group consisting of postdocs Luca Sapienza, Søren Stobbe and David Garcia, PhD students Henri Thyrrestrup and Stephan Smolka as well as Associate Professor and group leader Peter Lodahl.
Source: Technical University of Denmark (DTU)