Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fast, low-power, all-optical switch

04.05.2012
Switching light with light: only 140 photons are needed

An optical switch developed at the Joint Quantum Institute (JQI) spurs the prospective integration of photonics and electronics. What, isn't electronics good enough?

Well, nothing travels faster than light, and in the effort to speed up the processing and transmission of information, the combined use of light parcels (photons) along with electricity parcels (electrons) is desirable for developing a workable opto-electronic protocol.

The JQI (*) switch can steer a beam of light from one direction to another in only 120 picoseconds (120 trillionths of a second), requiring very little power, only about 90 attojoules (90 x 10-18 joules). At the wavelength used, in the near infrared (921 nm), this amounts to about 140 photons. These new results are being published in an upcoming issue of the journal Physical Review Letters (**).

The centerpiece of most electronic gear is the transistor, a solid-state component in which a gate signal is applied to a nearby tiny conducting pathway, thus switching on and off the passage of an information signal. The analogous process in photonics would be a solid-state component which acts as a gate, enabling or disabling the passage of light through a nearby waveguide, or as a router, for switching beams in different directions.

In the JQI experiment, prepared and conducted at the University of Maryland and at the National Institute for Standards and Technology (NIST) by Edo Waks and his colleagues, an all-optical switch has been created using a quantum dot (the equivalent of a gate) placed inside a resonant cavity. The dot, consisting of a nm-sized sandwich of the elements indium and arsenic, is so tiny that electrons moving inside can emit light at only discrete wavelengths, as if the dot were an atom. The quantum dot sits inside a photonic crystal, a material that has been bored with many tiny holes. The holes preclude the passage of light through the crystal except for a narrow wavelength range.

Actually, the dot sits inside a small hole-free arcade which acts like a resonant cavity. When light travels down the nearby waveguide some of it makes its way into the cavity, where it interacts with the quantum dot. And it is this interaction which can transform the waveguide's transmission properties. Although 140 photons are needed in the waveguide to produce switching action, only about 6 photons actually are needed to bring about modulation of the QD, thus throwing the switch.

Previous optical switches have been able to work only by using bulky nonlinear-crystals and high input power. The JQI switch, by contrast, achieves high-nonlinear interactions using a single quantum dot and very low power input. Switching required only 90 aJ of power, some five times less than the best previous reported device made at labs in Japan (***), which itself used 100 times less power than other all-optical switches. The Japanese switch, however, has the advantage of operating at room temperature, while the JQI switch requires a temperature of around 40 K.

Continuing our analogy with electronics: light traveling down the waveguide (the equivalent of the conducting pathway in a transistor) in the form of an information-carrying (probe) beam can be switched from one direction to another using the presence of a second pulse, a control (pump) beam. To steer the probe beam out the side of the device, the slightly detuned pump beam needs to arrive simultaneously with the probe beam, which is on resonance with the dot. The dot lies just off the center track of the waveguide, inside the cavity. The temperature of the quantum dot is tuned to be resonant with the cavity, resulting in strong coupling. If the pump beam does not arrive at the same time as the probe, the probe beam will exit in another direction

So, is this quantum-dot switch an "optical transistor"? Not quite, says JQI scientist Ranojoy Bose. "Our waveguide-dot setup can't yet be used to modulate a beam of light using only a weak control pulse of light---what we would call a low-photon-number pulse.

But Bose says he expects an improvement (reduction) in the number of photons needed to switch the resonant cavity on and off. In the meantime, the JQI switch represents a great start toward creating a usable ultrafast, low-energy on-chip signal router. "Our paper shows that switching can be achieved physically by using only 6 photons of energy, which is completely unprecedented. This is the achievement of fundamental physical milestones—sub-100-aJ switching and switching near the single photon level," Bose says.

(*)The Joint Quantum Institute is operated jointly by the National Institute of Standards and Technology in Gaithersburg, MD and the University of Maryland in College Park.

(**) "Low photon number optical switching with a single quantum dot coupled to a photonic crystal cavity," Deepak Sridharan, Ranojoy Bose, Hyochul Kim, Glenn S. Solomon, and Edo Waks. Physical Review Letters, in press.

(***) Nozaki et al., Nature Photonics, 2 May 2010.

Ranojoy Bose, rbose@umd.edu, 301-405-0030

A copy of the PRL paper can be obtained from Phillip F. Schewe, pschewe@umd.edu, 301-405-0989. http://jqi.umd.edu/

Phillip F. Schewe | EurekAlert!
Further information:
http://jqi.umd.edu/

More articles from Physics and Astronomy:

nachricht Supporting structures of wind turbines contribute to wind farm blockage effect
13.12.2019 | American Institute of Physics

nachricht Chinese team makes nanoscopy breakthrough
13.12.2019 | Chinese Academy of Sciences Headquarters

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Virus multiplication in 3D

Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.

For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Supporting structures of wind turbines contribute to wind farm blockage effect

13.12.2019 | Physics and Astronomy

Chinese team makes nanoscopy breakthrough

13.12.2019 | Physics and Astronomy

Tiny quantum sensors watch materials transform under pressure

13.12.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>