World’s First Continuous Room-Temperature Solid-State Maser

World’s First Continuous Room-Temperature Solid-State Maser. Credit: Thomas Angus / Jonathan Breeze, Imperial College London

The breakthrough means masers — the microwave version of lasers — could now be used more widely in a range of applications.

Masers (microwave amplification by stimulated emission of radiation), the older, microwave frequency sibling of the laser, was invented in 1954. However, unlike lasers, which have become widespread, masers are much less widely used because in order to function they must be cooled to temperatures close to absolute zero (-273°C or -459°F).

However, a new study from Imperial College London and UCL, published in Nature, reports for the first time a maser that can act continuously at room temperature.

In 2012, Imperial scientists demonstrated that a maser could operate at room temperature using the organic molecule pentacene. However, it produced only short bursts of maser radiation that lasted less than one-thousandth of a second. In any case, had the maser operated continuously, the crystal would likely have melted.

Now, Dr. Breeze and colleagues have used a synthetic diamond grown in a nitrogen-rich atmosphere to create a new maser that operates continuously.

The diamond before being placed in the sapphire ring. Credit: Thomas Angus / Jonathan Breeze, Imperial College London

Lead researcher Dr. Jonathan Breeze, from Imperial’s Department of Materials, said: “This breakthrough paves the way for the widespread adoption of masers and opens the door for a wide array of applications that we are keen to explore. We hope the maser will now enjoy as much success as the laser.”

Carbon atoms were ‘knocked out’ from the diamond using a high-energy electron beam, creating spaces known as ‘vacancies’. The diamond was then heated, which allowed nitrogen atoms and carbon vacancies to pair up, forming a type of defect known as a nitrogen-vacancy (NV) defect center.

The diamond is held inside a sapphire ring before the laser is used. Credit: Thomas Angus / Jonathan Breeze, Imperial College London

When placed inside a ring of sapphire to concentrate the microwave energy, and illuminated by green laser light, the researchers found that the maser worked at room temperature and importantly, continuously.

Co-author Professor Neil Alford, also from Imperial’s Department of Materials, said: “This technology has a way to go, but I can see it being used where sensitive detection of microwaves is essential.”

The maser is illuminated by green laser light. The red light is fluorescence from the NV centers. Credit: Thomas Angus / Jonathan Breeze, Imperial College London

The team who made the discovery says masers could be used in a range of applications such as medical imaging and airport security scanning. They have more traditionally been used in deep space communication and radio astronomy.

As well as medical imaging and airport security scanning, masers could play a pivotal role in improving sensors to remotely detect bombs, new technology for quantum computers, and might even improve space communication methods to potentially find life on other planets.

This work was funded by the UK Engineering and Physical Sciences Research Council and supported by the Henry Royce Institute.

The synthetic diamond was created and provided by Element Six.

Reference: “Continuous-wave room-temperature diamond maser” by Jonathan D. Breeze, Enrico Salvadori, Juna Sathian, Neil McN. Alford and Christopher W. M. Kay, 22 March 2018, Nature.
DOI: 10.1038/nature25970