There is a laser used for marine navigation between New London, CT and Orient Point, NY.
A green laser is fed into the eyepiece of a 2" telescope, and the resulting beam of green light is pointed from Avery Point, Groton,CT toward the Orient Point ferry slip.
As long as you keep the green beam centered (from the boat, it would appear to point straight up) over the boat, you are in the navigation channel.
The original plans were for two more lasers (red) to be added to mark the channel boundaries, but I’m not sure if that was ever done.
{{{I know that to see the beam of a laser the photons have to be reflected by something. Are there lasers so powerful that you can see them in nothing but air?}}}—JavaMan99
Come on down to Pine Avenue and Third Street, in Long Beach, CA some evening and wander around the AMC Theater plaza. They have a green LASER (possibly a tuned-dye type) operating from time to time. Even though the beam is diffused, it is visible miles away–if you know what you’re looking for and where to look for it. I have seen the beam, on clear evenings, as far north as Del Amo Blvd.
–Kalél
(The Original EnigmaOne) Common ¢ for all ages.
For those drawing up plans, I got a notice in the mail some time ago about a laser salvage company’s available products. The biggest one was 35 watts and cost about $45,000.00 (used, but rebuildable tube). The actual laser enclosure was only about 6 x 6 x 20 inches, but it also came with six other cabinets, four upright and two horizontal, each measuring about 3 x 3 x 6 feet. - MC
On the tangential topic of using lasers to destroy things: Two years ago, the US tested a ground-based laser on an obsolete sattelite to see it they could fry it. There was a lot of protest about this, because this could escalate things, and what if other countries would start frying our sattelites, etc etc. Also, Hughes didn’t like the idea of their bird being fried, even if it wasn’t doing anythign anymore.They did it anyway.It worked.
At Burning Man they made a tunnel of light from a laser that led to one of there many parties. It was real cool. Also when they pointed the laser over you at about a 10 degree angle, it looked like it bent into a rainbow kind of shape. Optical illusion.
Come to Burning Man this year www.burningman.com it starts Aug 30 though Sept 6th. Worth going to, in North East Nevada Black Rock Playa.
I know someone whose brother lost his sight in an eye from a laser. You would see it. You would also wonder if you should watch that eclipse with the one eye that works.
Actually, it was breaking down and turning into an ionized plasma. I’ve done this with a 40mJ/pulse, DPSS pumped, YAG LASER. The air at the focal point breaks down with a loud ‘pop’ and glows brightly enough to require goggles. With the goggles, you can see a fuzzy area about the size of a Q-tip head. And it smells strongly of ozone.
As to the thread title. Yes, there are certainly lasers powerful enough to be seen in air. Most of the outdoor light shows are relying pretty heavily on smoke/humidity/etc. but they can get by with only about 15W. For those crisp, dry nights, a 40W frequency doubled YAG does nicely.
Undead Dude: I could have the terminology wrong, but I suspect that ‘thermal bloom’ is the term for turning the air into ionized plasma, as Stephen and another mention. If so, I believe the idea in increasing the power of the laser is that the plasma will push itself out of the laser. It will still interfere with the fringe, but the core of the beam will have no interference.
Stephen: are you sure you want to advertise your satellite path prediction software in the same thread that talks about shooting them down with lasers?
This was the first time I had heard that term, but the context made it sound specifically like it was the natural widening if the beam that would occur as a result of diffraction. “Bloom” does seem to be an apt word for it.
