Nav: Home

Generation of random numbers by measuring phase fluctuations from a laser diode with a silicon-on-in

July 23, 2018

WASHINGTON -- Researchers have shown that a chip-based device measuring a millimeter square could be used to generate quantum-based random numbers at gigabit per second speeds. The tiny device requires little power and could enable stand-alone random number generators or be incorporated into laptops and smart phones to offer real-time encryption.

"While part of the control electronics is not integrated yet, the device we designed integrates all the required optical components on one chip," said first author Francesco Raffaelli, University of Bristol, United Kingdom. "Using this device by itself or integrating it into other portable devices would be very useful in the future to make our information more secure and to better protect our privacy."

Random number generators are used to encrypt data transmitted during digital transactions such as buying products online or sending a secure e-mail. Today's random number generators are based on computer algorithms, which can leave data vulnerable if hackers figure out the algorithm used.

In The Optical Society (OSA) journal Optics Express, the researchers report a quantum random number generator based on randomly emitted photons from a diode laser. Because the photon emission is inherently random, it is impossible to predict the numbers that will be generated.

"Compared to other integrated quantum random number generators demonstrated recently, ours can accomplish very high generation rates with relatively low optical powers," said Raffaelli. "Using less power to produce random numbers helps avoid problems such as excess heat on the chip."

Silicon photonics

The new chip was enabled by developments in silicon photonics technology, which uses the same semiconductor fabrication techniques used to make computer chips to fabricate optical components in silicon. It is now possible to fabricate waveguides into silicon that can guide light through the chip without losing the light energy along the way. These waveguides can be integrated onto a chip with electronics and integrated detectors that operate at very high speeds to convert the light signals into information.

The new chip-based random number generator takes advantage of the fact that under certain conditions a laser will emit photons randomly. The device converts these photons into optical power using a tiny device called an interferometer. Very small photodetectors integrated into the same chip then detect the optical power and convert it into a voltage that can be turned into random numbers.

"Despite the advancements in silicon photonics, there is still light lost inside the chip, which leads to very little light reaching the detectors," said Raffaelli. "This required us to optimize all the parameters very precisely and design low noise electronics to detect the optical signal inside the chip."

The new chip-based device not only brings portability advantages but is also more stable than the same device made using bulk optics. This is because interferometers are very sensitive to environmental conditions such as temperature and it is easier to control the temperature of a small chip. It is also far easier to precisely reproduce thousands of identical chips using semiconductor fabrication, whereas reproducing the necessary precision with bulk optics is more difficult.

Testing the chip

To experimentally test their design, the researchers had a foundry fabricate the random number generator chip. After characterizing the optical and electronic performance, they used it for random number generation. They estimate a potential randomness generation rate of nearly 2.8 gigabits per second for their device, which would be fast enough to enable real-time encryption.

"We demonstrated random number generation using about a tenth of the power used in other chip-based quantum random number generator devices," said Raffaelli. "Our work shows the feasibility of this type of integrated platform."

Although the chip containing the optical components is only one millimeter square, the researchers used an external laser which provides the source of randomness and electronics and measurement tools that required an optical table. They are now working to create a portable device about the size of a mobile phone that contains both the chip and the necessary electronics.
Paper: F. Raffaelli, P. Sibson, J.E. Kennard, D. H. Mahler, M. G. Thompson, J. C. F. Matthews, "Generation of random numbers by measuring phase fluctuations from a laser diode with a silicon-on-insulator chip," Opt. Express, volume 6, issue 16, pages 19730-19741 (2018).

About Optics Express

Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by The Optical Society and edited by Andrew M. Weiner of Purdue University. Optics Express is an open-access journal and is available at no cost to readers online at: OSA Publishing.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit

Media Contact:

The Optical Society

Related Laser Articles:

The sharpest laser in the world
With a linewidth of only 10 mHz, the laser that the researchers from the Physikalisch-Technische Bundesanstalt (PTB) have now developed together with US researchers from JILA, a joint institute of the National Institute of Standards and Technology and the University of Colorado Boulder, has established a new world record.
Biggest X-ray laser in the world generates its first laser light
European XFEL, the biggest X-ray laser in the world, has generated its first X-ray laser light.
Where does laser energy go after being fired into plasma?
An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde.
Over-the-counter laser pointers a threat to eyesight
Some laser pointers that can be bought over the counter are unsafe -- to the point that they can cause blindness.
Introducing the disposable laser
Since lasers were invented more than 50 years ago, they have transformed a diverse swath of technology -- from CD players to surgical instruments.
A laser for your eyes
A team of the Lomonosov Moscow State University scientists and the Belarusian National Technical University has created a unique laser, which is a compact light source with wavelengths harmless to the human eye.
New laser to shine light on remote sensing
A revolutionary new type of laser developed by the University of Adelaide is promising major advances in remote sensing of greenhouse gases.
Laser beams with a 'twist'
Using geometric phase inside lasers for the first time, researchers find a way to change the orbital angular momentum of laser beams.
New laser achieves wavelength long sought by laser developers
Researchers at the University of Bath, United Kingdom have created a new kind of laser capable of pulsed and continuous mid-infrared emission between 3.1 and 3.2 microns, a spectral range that has long presented a major challenge for laser developers.
New laser achieves wavelength long sought by laser developers
Researchers at the University of Bath, United Kingdom have created a new kind of laser capable of pulsed and continuous mid-infrared (IR) emission between 3.1 and 3.2 microns, a spectral range that has long presented a major challenge for laser developers.

Related Laser Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".