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Maser: laser’s older cousin which could be going mainstream thanks to new study

The maser – “microwave amplification by stimulated emission of radiation” – has never seen as many uses as its well-known younger cousin, the laser. However, thanks to a new study from Imperial College London and UCL, we could soon see masers go mainstream – due to diamonds.

Researchers have created the first maser which can act continuously at room temperature. Before now, continuous masers required temperatures near absolute zero (-273°C) to function, with the only other maser operated at room temperature producing short bursts lasting less than a thousandth of a second; neither case is practical for most applications.

A maser is a beam of coherent electromagnetic radiation in the microwave frequency range (as opposed to lasers operating mostly within visible light frequencies). Producing masers relies on an element or molecule known as a gain medium, which – when induced into an excited energy state – releases electromagnetic radiation at a frequency specific to that element. When this process is contained inside a resonant cavity to contain the microwaves, a coherent beam can be created.

Researchers have created the first maser which can act continuously at room temperature

The key breakthrough in the latest study is the choice of gain medium: a synthetic diamond grown in a nitrogen-rich atmosphere. This diamond had carbon atoms knocked out of it using a high energy electron beam. After being heated, these “vacancies” could pair up with nitrogen atoms and form a defect known as a nitrogen-vacancy centre. When this diamond was placed inside a ring of sapphire to concentrate the microwave energy, surrounded by a copper cavity, and illuminated by green laser light, a maser was successfully made. Furthermore, the maser was able to operate continuously for up to 10 hours without any noticeable degradation in power.

This development suggests that masers could be used for new and exciting applications, where previously they were too impractical. The frequency of microwaves produced by masers is incredibly stable, making it well suited for high-precision uses. For example, masers are used in atomic clocks since their frequency can be measured very precisely and stays constant for a long period; similarly, they are used as low-noise amplifiers, boosting signals such as those used for deep space communication. The good thermal conductivity of diamond means that the maser could be pumped at a higher power than that demonstrated, increasing the intensity and stability of the maser. This may allow masers to be used in some entirely new ways, such as for medical imaging, security scanning and even remotely detecting explosives – following in the footsteps of the laser.


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