A Terahertz Modulator

We’re all used to the changes in the properties of radio frequency systems as the frequency increases and the wavelength becomes shorter. The difference between the way an FM radio and a WiFi adapter behave with respect to their environments, for instance. But these are relatively low frequencies in the scheme of electromagnetic radiation, as you will be aware with ever shorter wavelengths those properties change further until eventually we are not dealing with something we’d describe as radio, but infrared light.

Terahertz waves are the electromagnetic radiation that lies in that area between radio frequencies and infra-red light. You might expect that since science has delivered so many breakthroughs in both radio and IR, we’d have mastered them, but so far very few devices capable of working at these wavelengths have been developed.

A Nature paper from a group at Tufts University holds the promise of harnessing terahertz waves for applications such as data transfer, for they have developed the first terahertz modulator. It takes the form of a section of slot waveguide between two conductors on a substrate, interrupted by what they describe as a two-dimensional electron gas. This is a very thin layer of electron concentration in an InGaAs region of a semiconductor sandwich that can be created or dissipated by electrical stimulus. This creation and removal of the electron layer has the effect of interrupting the flow of terahertz waves in the waveguide, making a functional modulator.

This isn’t something you’ll find on a hacker’s bench in the near future, but it’s no less exciting a development. One day it may deliver wireless data transfers at bandwidths we would now consider unimaginable, and you will wonder how we ever managed without it.

Unsurprisingly stories involving terahertz radiation are rare here. We recently had an SDR for terahertz frequencies, but it’s probably fair to say that it’s more fairly described as for infra-red. We’ll keep an eye out for further developments.

Via Phys.org.

14 thoughts on “A Terahertz Modulator

  1. This is not a modulator with terahertz bandwidth nor is it a modulator which can modulate terahertz frequencies, it is a modulator with 15GHz bandwidth which can interact with with a RF signal between 220-325GHz. It is a nice step forward in chip-scale electro-optic modulators, but is nowhere near the breakthrough that the HAD authors make it out to be since there are both faster and wider bandwidth terahertz/IR modulators which have already been demonstrated.

  2. As stated, “This isn’t something you’ll find on a hacker’s bench in the near future” , so what does such an article do here?
    Would be nice if HaD bloggers leave science article to scientific audience.
    They grasp only partially what they are talking about, and spread inexact information, just for the sake of filling up their ‘tube.

    Being an inaccurate proxy for serious articles published in scientific magazines does more harm than good to science !

    Stick to Arduinos, Neopixels, at least you mostly understand what the topic is.

    1. @rutigrem: You said, “Stick to Arduinos, Neopixels, at least you mostly understand what the topic is.”

      I strongly disagree. I am a highly qualified EE dealing daily with DC-to-Light communications technologies. And I found this post as pretty-much old news (as you did). However, I come to HaD to get a mix of interesting (and sometimes not so interesing) information (we can jump over what matters). On a site like HaD, you CANNOT expect Editorial expertise in ALL subjects. But you DO expect the posts will at-least try to cover a lot of different subjects (that’s why we come here!) HaD Editors are NOT experts in every field (so go EASY on them). But they do seem to select topics across a broad range of fields – to keep both newbies and and expert readers coming back. I come back to HaD; and so did you – So my conclusion is: HaD’s approach works.

      1. I’ve read that “are allowed to use “all” frequencies about 300 GHz” line several times myself. What I’ve always wondered.. is that really a ham specific privilege or does the FCC just not govern those frequencies.

        Decades ago I remember a project in Popular Electronics for a transmitter/receiver pair that operated in the low kHz. The article claimed that anything below 9KHz was free territory. I’ve tried to confirm this, having read parts 15, 97 and 47 as well as whatever frequency allocation guides I could find. I couldn’t find anything really that talked about frequencies that low at all.

        Does the FCC just regulate from 9KHz to 300GHz and anything outside those boundaries is free territory?

        Of course, even if so, I’m pretty sure that if your <9KHz signal started appearing in neighbors' audio amps or your terahertz signal started cooking the pedestrians that walk by your house something bad would happen to you.

  3. ok let me re word the question.

    if i was to build a wifi extender that can go for miles that is based on the idea of the ir remote extenders where it captures the wifi signal and modulates the 1.4 to 5 ghz signal with a say 1 thz carrier and beams it across town to some location on the other side of town and then unpacks the 1.4 to 5 ghz signal so the router there could get wifi on the opposite end of town would i need a license to transmit the signals?

    i would not think so since no one or at least no emergency dispatcher uses thz.

    1. You wouldn’t need a license, but THz would be terrible for a repeater. The absorption due to moisture is way worse than unlicensed 2.4 GHz even. Our sources are in the uW power range to begin with…you’d need something a wee bit stronger to get across the room with THz, let alone across town.

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