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Quantum-Cascade Polychromatic Lasers
eznihm writes: "This article describes a new laser, developed by Lucent and others, that emits a band of light and operates at room temperature. "The result: a beam of high intensity at every wavelength from 6 to 8 micrometers, in the so-called midinfrared range.""
Pardon my ignorance (it's been a very long time since my last physics class) but aren't lasers *SUPPOSED* to be monochromatic? I thought one thing that characterizes a laser is that all the photons are in the same phase. It must be a limitation of my imagination but how can this happen if you have multiple wavelengths?
Can someone who know more tell me what's going on here?
Never attribute to stupidity what can be construed as a monopoly preservation tactic.
Researchers at MIT have already moved on to more advanced technology. With cascading, the laser accelerates the nanodes in the visible spectrum to get its "beam" effect. Obviously, this is a huge drawback because of the excess power consumption wasted on acceleration.
Professor Warton, whom I work for, has implemented a prototype "Quantum Tripoly" laser. "Tri" because it uses three quarks rather than one and "poly" because it's basically 3^3=27 quantum cascade lasers in one. And there's no acceleration downside that I mentioned above, no waste, just laser goodness.
The future isn't cascading, so why is Lucent still working on this dead-end technology?? Anyone with a PhD in physics care to comment??
These aren't exactly new, but this is a new(ish) way of getting larger bandwidths. Before you have been more limited by the physical properties of your material, which meant you had to use interesting carcinogenic dyes, or expensive crystals to get broad stimulated emission cross sections.
I'd publish my course notes on the issue, but I'm not certain my prof would be too happy. I'll check with him when I see him Monday.
-Yarn - Rio Karma: Excellent
Argh. It seems there is one of those unwritten Slashdot rules that dictates any story about lasers must be accompanied by posts about laser weapons... usually in the Death Ray variety. For the most part lasers make poor offensive weapons, at least in the Burning a Hole Through X variety.
(Thank you Alien54 for not suggesting such a thing)
I've posted this before but here it is again:
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It seems inevitable that whenever there is a story regarding lasers we get to see all sorts of silly posts about blasting people with laser.
Even antimissle lasers have a long way to go. Between power requirements, beam handling, divergence, and atmospheric interference, lasers do not make great destructive weapons.
However, they would be damned good for some nasty tricks like blinding the enemy army (or, unfortunately, civilians).
Take this scenario: a bomber/cargo style aircraft has been outfitted with a large infrared laser (similar things have been done). Fly said aircraft over the people you wish to 'zap'. Release some fireworks or other attention getting devices and when the crowd looks up turn on and start scanning the laser.
Since the laser is infrared nobody would know they are being exposed to blinding levels of light, nor would the blink/aversion reaction take place. By the time you noticed anything the permanent damage has been done. Scary huh?
Another scenario under serious consideration by police (at least here in Canada, I've participated in meetings on the subject) is the use of lasers against commercial aircraft. The idea isn't to shoot down the aircraft, but to scan at temporarily blind the pilot during final night approaches. The effect is like someone flashing a camera flash in your face when your in a dark room.
As the few moments prior to landing are the most critical, distracting and flash blinding the pilot could easily lead to the plane crashing.
Worse, new solid state lasers are available in the 3watt (plenty of power to cause permanent blindness) range and can be powered off a car with an inverter. Simply park at the end of a convenient runway at night, plug 'er in and away you go. Ok, so it's not quite that easy, but the concept is...
Doesn't that all just scare you a bit more than some silly death ray?
Note: after saying all that I want to point out that I do not support the insane regulations placed against the use of lasers in the United States by the CDRH. It's totally ridiculous and overzealous.
"They do not preach that their god will rouse them, a little before the Nuts work loose." Kipling, 'The Sons of Martha'
Do they really have a polychromatic laser or is it just a laser that allows the user to choose an arbitrary wavelength in a given range? The article explains how they get spontaneous emission with a wide range of wavelengths, however it does not explain how to build a cavity that keeps a polychromatic wavepacket (wide in the momentum space) in a stationary state.
I had the chance to play with a 200mW Argon laser last year. It can laze at many different wavelengths, but i can set the cavity only to a discrete set of wavelengths. This was crucial for deciding between the 351.1nm and the 351.4nm (iirc) line. *g*
This sig is a true statement, but I cannot prove it.
I'm going out on a ledge, but I'd believe one of the major applications of this is in DWDM down single mode fiber. It simplifies manufacturing costs to have a laser that can output on different wavelengths vs. multiple lasers all specifically designed for a single wavelength. I was reading a telecom book today at Barnes and Noble that pointed to that specifically as one reason for the current high costs of DWDM. Of course I have to take the book for a grain of salt considering it was yellow and black :).