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Highly Directional Terahertz Laser Demonstrated 125

eldavojohn writes "A new paper published this week in the journal Nature Materials announces a successful demonstration of highly directional terahertz semiconductor lasers. You might not think it's a big deal that some Harvard and University of Leeds researchers (funded partially by the US Air Force) figured out how to better direct lasers; but this means the ability to see what's in someone's pockets and clothing, at a distance of possibly hundreds of meters, or farther. The big benefit is that they are lower in energy than X-Rays and are less invasive, since they cannot pass through water or metal. Coming soon to an airport near you or buzzing around on board a drone in civilian airspace?"
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Highly Directional Terahertz Laser Demonstrated

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  • PSA (Score:1, Informative)

    by JamesP ( 688957 ) on Sunday August 08, 2010 @04:10PM (#33182706)

    For non-visible wavelenghts (or anything near it) it's not a LASER it's a MASER []

  • Re:PSA (Score:5, Informative)

    by Daniel Dvorkin ( 106857 ) * on Sunday August 08, 2010 @04:25PM (#33182820) Homepage Journal

    The "M" in MASER stands for "microwave." The waves used here are non-visible, sure, but they're shorter than microwaves, closer to what's usually called infrared. And "laser," no longer capitalized, has entered the language as a word for any device that emits a beam of coherent EM radiation of whatever frequency -- thus you'll hear "IR laser," "X-ray laser," "gamma laser," etc. It would be pretty silly to insist on a separate word for each frequency band.

  • by Animats ( 122034 ) on Sunday August 08, 2010 @05:24PM (#33183210) Homepage

    Tired Magazine blows it again.

    The article from Tired [] is bogus. The "remote generation of terahertz radiation" is described in this paper. [] They generate terahertz radiation at the target by hitting it with a big enough pulse to heat it up into a plasma. This is a classic spectroscopy technique; hit something with a big laser pulse and look at the spectra coming back.

    Nobody is going to look into pockets that way, unless they burn through first. It may be useful for analyzing toxic and hazardous materials from a distance. A possible application is something that first responders point at a spill from a distance, and it comes back with an analysis. Assuming the energy transfer can be made small enough so as not to ignite anything.

  • Re:wet suit. (Score:3, Informative)

    by JSBiff ( 87824 ) on Sunday August 08, 2010 @09:35PM (#33184926) Journal

    "Time to buy . . . a full metal jacket."

    Yeah, I bet having Ammo in your pockets or bags will really expedite your trip.

  • Re:Plus flying cars? (Score:3, Informative)

    by Foobar_ ( 120869 ) on Monday August 09, 2010 @07:18PM (#33197840)

    If it's a laser pointer made with a red (670, 650, 635 nm), blue (445 nm), or violet (405 nm) laser diode, there's absolutely no infrared emitted.

    If it's a properly made diode-pumped solid-state laser pointer (532 nm green, 473 nm blue, 404 nm frequency doubled violet) there's an infrared filter in the optical train which removes the large amounts of invisible pump light and leaves only the visible green.

    If it's a crap green laser pointer (e.g. the "high power" green pointers sold on eBay and the like) then there is a real possibility the manufacturer omitted the IR filter to increase profits and/or the balloon-popping potential of the pointer. Check with a laser power meter and an IR-passing filter to verify the lack of IR output.

    If no such tools are available, use a camera sensitive to infrared, block the visible beam with a filter, and check that no IR is coming out. IR-passing, visible-blocking filters around the house include the tinted plastic windows on remote controls and the front panels of remote-controlled devices, exposed color photo film negatives, and the disks of coated Mylar film inside floppy disks. Those last two should never be used as filters to observe the Sun due to the fact they totally pass IR and you can cook your retina in seconds without realizing anything bad is happening.

    Infrared leaks may not be collimated like the green beam and will be visible (on camera) as a beam, cone, or ugly spray of light coming out of the filtered device. []

    There are reflected light hazards to worry about with all lasers. For example, shining the laser onto a smooth or polished floor in the direction of your pet will result in some light making a dot on the floor and most of the light bouncing off into your pet's eyes. If you can see the laser's reflection light up your pet's face, you may be causing eye damage.

    If it's a high-power laser pointer (output over 5 mW) you are being carelessly negligent in its operation if you're waving it around in any situation where people or animals can get hit in the eye with its beam. Safe eye exposure is probably much less for cats and dogs due to the presence of a tapetum lucidum which concentrates light hitting their retina, their much larger pupils which take in much more light, and active suppression of the blink/turn reflex due to the fact they're chasing that dot and don't want to look away from their quarry.

"The eleventh commandment was `Thou Shalt Compute' or `Thou Shalt Not Compute' -- I forget which." -- Epigrams in Programming, ACM SIGPLAN Sept. 1982