Lasers for Fun and Profit

Stuart of Wapping writes "This is a very interesting site, links to pages describing real-life, tried-and-tested Star-Trek/James Bond gadgets... The Laser Medical Pen, or Medpen, developed in-house by the Laser Division of the Air Force Research Laboratory's Directed Energy Directorate, is a second-generation device that provides a physician or paramedic with a unique, compact, portable, and battery-operated laser capability. The laser can cut like a scalpel as well as coagulate bleeding."

High Power Microwaves?

[MiTEG]

What intrigued me was the information about high power microwaves [af.mil]. It says

"High Power Microwave produces burnout and disruption in electronics while not affecting humans."

Yes, I realize that anything within a range of the spectrum around 2.4Ghz is considered microwave (cell phone, cordless phones, 802.11, etc.) but isn't the only reason they don't hurt people because they are relatively low power? I imagine if you pump enough power into one of those things it could start to make you boil.

Anyway, I'd hate to be one of the test subjects used in determining whether or not this actually does cause damage.

Re:Interesting...

[ThePyromaniak]

Thats soooo true but those corny 60's SCI-FI movies said that we would have flying cars and such by the year 2000...here it is 2002 and we havent even developed a decent personal interplanetary travel capsule....maybe science fiction writers overestimated us

Suitcase laser

[hedley]

I used to work at a laser lab and we had a suitcase laser. Looked like a photographers case, brushed aluminum, plug it in, and out from the corner came a beam of Alexandrite produced photons (Alexandrite is a vibronic and can be tuned to lase at many different frequencies). This suitcase was shopped around the military quite a bit, that same lab used to buy meat from the grocery store and cut it with the lasers to test surgical properties. Most dangerous place I ever worked, coding with green goggles on, possible instant blindness, 20kv shocks whilst standing in water from leaking cooling pumps! I even got my belt burned like a high school ticker tape experiment, an ND (neutral density) filter exploded because the energy from the beam was so powerful, my boss knocked the hamamatsu(sp?) energy meter out of the way, and I was behind it at belt level, two burns close together in the leather belt and one further away as I tried to escape :)

Hedley

I've got one

[Mister Transistor]

Everyone should have a Death Ray.

Especially a battery operated, portable Death Ray!

I just picked up a 3 Watt laser diode at a Hamfest recently. It's whats at the core of the med-pack and portable med-pens displayed. This thing is really fucking cool. It will make paper and wire insulation, plastic, etc. burst into flame from about 1/4 inch away.

The diode is made by Spectra Diode Labs (SDL) and channels 3 Watts of optical energy at 808 nanometers into a fiber optic. I have that clamped into a standard mechanical pencil to hold the fiber and allow it to be directed with some control.

The spot that appears is very scary because it appears weak red, about 5 mW of visible light energy is present but 98 % of the optical power is invisible in the infrared spectrum.

I haven't tried any home laser surgery yet, but it makes a dandy wire stripper or marking scribe. I also use it to open sealed ni-cad battery packs and change cells for walkie-talkies, etc.

Yep, Everyone should have a Death Ray!

COIL lasers are bad.

[Anonymous Coward]

They give off nasty gasses when they operate, HELLO EPA and if one of those planes that carries them crashes there is a 2 mile radius kill zone from the chemicals. Yea, it doesn't tell you that on the website.

The laser pen is cool though.

Re:Not exactly.

[Medevo]

the reason they can heat up water is due to the frequency itself, and it's ability to cause water molecules to move around in the field. It's not, as some say, because it's the resonant frequency of a water molecule.


Wouldnt this mean that we could also make a large microwave, and use it as some sort of weapon (not realy).

Also do the home microwaves use a very specific frequency?, or else photoelectric effect could short circit the hearts electric timing system.

Medevo

Re:I've got one

[peatbakke]

Sounds like you've got an Nd:LSB laser. If you want to see something cool, track down a suitably sized potassium titanyl phosphate (KPT) crystal. It doubles the frequency, turning that faint red to a brilliant green. I'm not sure what the efficiency loss is, but it's a neat trick.

Re:I've got one

[Mister Transistor]

Actually it's a single diode putting out 3W at 808 nm. They currently sell for around $400.00 (US).

I've got it mounted to the outside of a dual D-Cell battery holder clip (from Radio Shack, of all places!) with a small power switch and a current limiting resistor in series.

These are used as printer's plate thermal developing units in larger arrays.

These are also used as pumps for DPSS (Diode Pumped Solid State) lasers. I've got a nice chunk of KTP used to double 1064nm down to 532 (green), but I need to find a large piece of Nd:YVO (Vanadate) which transforms the 808 up to 1064nm.
This is how most of the green laser pointers work, they have a diode similar but smaller, putting out about 100-500mW at 808 nm and using similar crystals to transform the frequency to 532 nm.

Re:High Power Microwaves?

[DarkMan]

I think that the reason that it's misunderstood is because there's that half degree of true it.

There _is_ a resonance, and thus at frequencies near that, water absorbs stronger than other materials. If memory serves me correctly, the resonance is at around 1.4 GHz (although my mental arithmatic might be out) for the H-O-H bend. At the 2.4 GHz then, it's not having much of an effect, compared to a resonant system. But there is an increase in it's absorbtion cross section, due to that.

Were it not for the resonance, then it wouldn't be principly water that did the absorbing, and the penetration depth in a microwave would be much greater.

IIRC the 2.4 GHz was picked because the ways to generate microwaves are pretty efficent at that frequency, and the energy dispertion inside water is 3Db per inch or so.

Re:I've got one

[peatbakke]

hah. well, that's what I get for reading your post too quickly. i've been using 808nm diodes to pump Nd:LSB, and for some reason I assumed you were pumping Nd:LSB/YVO. duh, me.

See if you can get your hands on Nd:LSB. It's a bit more expensive than YVO, but it's got a *much* higher saturation intensity, and more efficient absorption of 808nm as well ... not that you really have to worry about that sort of thing when you're playing around with a 3W laser. Most of the applications I've seen with LSB are for compact, low powered situations ...

Actually...

[Anonymous Coward]

A lot of things that the general public first saw in sci-fi stories were already being discussed in the scientific community. The science fiction writers were often in contact with scientists (as friends, sometimes coworkers and in other relationships), and were inspired by what the scientists were already discussing.

Re:I've got one

[Anonymous Coward]

3W is classed as a high-power laser. It's perfectly sufficient to cause a lot of damage. Don't get confused by thinking of a standard 40W lamp, which takes 40W of electrical power and dissipates, partly as light over a wide range of wavelengths, and as heat. A 3W laser will produce 3W of coherent, monochromatic light in a low-divergence cone. Note that it probably requires substancially more than 3W of electrical power.

Not Especially Useful in the Field

[vaguelyamused]

While the concept sounds cool this isn't really useful in the field for emergency care. Disposable electrical cauteries that do exactly the same thing have been around for years. Very rarely does someone die from external bleeding that could be cauterized. Those types of wounds can usually be controlled easily with direct pressure, pressure points, etc. What kills people is pulmonary injuries, internal bleeding and/or neurological injuries. If you get shot or stabbed, closing the entrance/exit wounds with cauterization does very little for you. All the serious damage is on the inside and the only answer is being taken to the O.R. This is particually true of gun shot wounds as the shockwave around the bullet cavitates the tissue around its path through the body doing massive damage, of course relative to the size and more so velocity KE=1/2 m * v^2.

Re:I've got one

[Mister Transistor]

Actually, I was amazed that the thing barely gets hot at all. It consumes a full 5A at 3V, so it is taking in 15W and putting 3 of that out in light, so it's actually only dissipating about 12W or so of heat.

The diode package is a small 1/2" dia. gold can embedded in a slab of beryllium copper(?). I have the thing screwed directly into the positive
battery terminal on the battery clip holder.

During operation, I tend to use short bursts, and after about 10-15 minutes of blowing things up it just starts getting warm. Continuously, it would probably heat to dangerous temps within 1-2 minutes. A simple CPU cooling fan/heatsink combo would be more than adequate for continuous operation, which the diode _was_ designed for.