Atomic Antenna Uses Lasers

If you think about it, an antenna is nothing more than a radio frequency energy sensor, or — more precisely — a transducer. So, it shouldn’t be a surprise that there could be different ways to sense RF that would work as an antenna. A recent paper in Applied Physics Letters explains an atomic antenna comprised of a rubidium vapor cell.

The interesting thing is that the antenna has no electrical components in the antenna, and can be located far away from the actual receiver. Instead of coax cables, the signal is read with a laser.

The experiment uses a 780 nm laser and a 480 nm laser to illuminate the sensor, which contains a corner reflector. The returned laser light changes based on the input signal at the antenna. That means, in theory, you could locate the antenna far away on a tower or mountaintop since the laser and sensing equipment don’t need to be close. The experiments had the sensor 10 m to 30 m away from the base station, but we’d imagine it would be possible to bridge larger gaps with some modifications.

The RF in question was in the 16 GHz – 20 GHz range. Unsurprisingly, the antenna cell is small, measuring 150 mm by 27 mm. The rubidium doesn’t require special temperatures. The lasers, too, aren’t anything unusual, producing just a few dozen milliwatts on each beam.

12 thoughts on “Atomic Antenna Uses Lasers

    1. Receive only. Transmit has to be able to handle the power-thermal requirements along with impedance matching of some kind. Receive is low hanging fruit and not especially interesting in itself.

  1. So translation – this is just POINT TO POINT link ?
    How is this superior to say a microwave hop ?
    Laser links have been around since the 60’s if recollection serves.

    What advantage does this offer over current solutions ?

    1. It’s not a link; it’s remote sensing with a passive component. Not a receiver that relays information. It’s a lot like those laser mics that pick up sounds from afar by aiming at anything reflective.

  2. Clever, interesting. Awful sensitivity though. Receive-only, obviously. I was skeptical, assuming that this only worked at the particular Rb resonance frequency, but they show that it’s actually broadband. Presumably in actual practice it will need to have cavity or other filters as a preselector to avoid being swamped by other parts of the EM spectrum.

    Similar things exist for EM field-to-optical transduction for use at the end of optical fibers, which are kind of neat for probing board-level EM fields, right down to DC.

    Another novel antenna with really interesting properties:

  3. I wonder if this is to create a false target for anything tracking absorption or perhaps just to enable wider triangulation in space.
    Imagine sending out tens of thousands of these as an array in space and using them as a virtual antenna telescope.

  4. Sounds like it all for the Ghz range, both feed and signal. If intent is for use in a microwave repeater or terminal end equipment, the periscope antenna also does the same thing without the technology, and I’ll bet the latter has a much better MDS.

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