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20-07-2007, 08:03 PM
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amateur
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Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 7,078
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Quote:
Originally Posted by wasyoungonce
Does that make any sense? Anyone here knowledgeable on atomic models? Ionisation energy of elements?
All very intriguing  ! |
I think not. IR laser cuts aluminium also, but it needs to have higher power output, to cope with high thermal conductivity of aluminium. And it is pure thermal effect, no need for intricacies of quantum mechanics here, apart from absorbing the energy of the beam... Things like that (destruction of chemical bonds due to strong EM fields produced by laser pulse) are happening at very high power and short pulses, lasers like that are being under development these days. I have read somewhere that they achieved ultra-short pulses, duration of couple of femto seconds, and peak powers achieved were >MW or higher.
Laser steel cutting with relatively low powers are possible by the help of violent oxidation that releases a lot of additional heat.
BTW, aluminium is also very hard to weld for the same reason, apart from oxidation at the surface (so there is a need for neutral atmosphere or anything that prevents oxygen to come in contact with aluminium surface)
Last edited by bojan; 20-07-2007 at 08:13 PM.
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20-07-2007, 08:56 PM
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Certified Village Idiot
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Join Date: Jul 2006
Location: Mexico city (Melb), Australia
Posts: 2,357
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I was looking at the thermal conductivity of Aluminium but discarded it because it was mentioned that it wouldn't cut thin sheet, still it must have heated it.
Still, thermal conductivity is a product of the elements strong ionic bond. IR Laser is already probably producing greater energy more than likely due to the nature of the crystals used and crystal pump (flash tube energy). A flash tube producing light, Ep=hf. Decrease wave length of light (UV light) thus Increase the photon energy to do work upon Laser crystal....
Also high powered Lasers reflect the wave back and forth in the crystal rod creating a nice standing wave harmonic and this is output by a Q switch as a pulsed wave.
Thanks.
Last edited by wasyoungonce; 24-07-2007 at 03:53 PM.
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21-07-2007, 02:35 AM
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Certified Village Idiot
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Join Date: Jul 2006
Location: Mexico city (Melb), Australia
Posts: 2,357
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Back on subject. This wiki link describes Laser and aviation dangers and shows simulated vision strikes with various powered Lasers.
http://en.wikipedia.org/wiki/Lasers_and_aviation_safety
It's probably a bit over the top but may help in visualising (pardon the pun) the dangers.
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11-08-2007, 03:52 PM
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Registered User
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Join Date: Nov 2004
Posts: 20
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Dave put me onto this thread and it's pretty mind blowing. The MPAS uses a green laser for public viewing nights but I feel thats not going to happen anymore. I intend to contact the AFP member mentioned and find out what we need to do. 
I'm also in the CFA, and thought of using a 5mW green laser to detect faint smoke in confined spaces... smoldering light fittings, that sort of thing, so I got one off ebay for about $30. It didn't arrive: it was returned as unclaimed. I asked them to repost it so it'll be interesting to see if/when I get it.
I agree with almost everyone else it's a bit 
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11-08-2007, 04:59 PM
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Certified Village Idiot
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Join Date: Jul 2006
Location: Mexico city (Melb), Australia
Posts: 2,357
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It is quite apparent that the Laws are lagging new technology. Quite obviously Lasers have many modern uses that are quite legitimate.
It's just the odd few idiots that spoil it all for the sensible users:
http://www.news.com.au/story/0,23599...-29277,00.html
I was also watching the footy highlights on TV last week..some Westcoast game where some idiot fan (read drunken yob) stripped to his Jocks and was waving his top over his head.
If you looked closely you can see his body being spotted buy a HeNe Laser.
So you have to ask what idiot brings a Laser to a footy game?....to spot opposition players eyes?
What we need is bigger penalty's to mis-use not totalitarian bans.
edit:
Have to Laugh, maybe the Military should be banned for mis-use as well!:
http://www.abc.net.au/news/stories/2...07/1998980.htm
That was with a very high powered NdYag IR Laser no less!
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11-08-2007, 07:20 PM
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Registered User
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Join Date: May 2006
Location: Karratha, Western Australia
Posts: 119
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For those of us in WA the legal limit is <5mw then you have to apply for registrations,licences,safety licence and so on and so on and so on
$138 per year just for the registration, OMG!
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11-08-2007, 07:24 PM
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Registered User
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Join Date: Oct 2005
Location: Tassie
Posts: 1,104
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I think players were being 'laser-ed' in last nights AFL game
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12-08-2007, 01:18 PM
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Certified Village Idiot
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Join Date: Jul 2006
Location: Mexico city (Melb), Australia
Posts: 2,357
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Yep they were, confirmed in the Press today! It was a green Laser.
As you can see...idiots and things like this don't mix.
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22-08-2007, 07:58 AM
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I have a To-Do List?
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Join Date: Jun 2007
Location: Melbourne, Australia
Posts: 152
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Quote:
Originally Posted by ballaratdragons
They are legal in Victoria (no permit required either) for Astronomy use only, and must be held in a Laser pointer bracket attached to a telescope.
That is the only condition an exemption is made.
So, if you wack it in a bracket (Bintel sell them) and attach it to your scope, you are filling the requirements.
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I have no doubt about this but where is this written on an official document somewhere. Dept. of Justice or similar government office.
I want to be able to quote it when someone comes knocking on my door.
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26-08-2007, 11:01 PM
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Registered User
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Join Date: Jan 2005
Location: Newcastle, NSW, Australia
Posts: 4,116
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Did you know you can make a 200+ mW red laser strong enough to light a match, by taking the laser diode from a DVD RW unit and putting it into a low power laser pointer, replacing its existing low power diode
http://www.instructables.com/id/EWM4YR2F4WY1LQ2/
I had a dead DVd RW here (Liteon) I got the diode/heatsink assembly out, connected it to 2 Ni Mh AA cells and wow this deep red diffuse light lit up the ground (I had it facing down). It was many, many times brighter then my 0.8 mW red laser pointer. Ive no doubt if that diode was installed into a laser pointer it would show a very visible red beam and go for many km. Sadly, on trying to remove the diode from the heatsink I damaged it, it no longer lases, rather just emits a small amount of red light like a normal diode.
To make a really exotic (and dangerous ) pointer get one of these
http://www.photonic-products.com/pro...violetblue.htm
a blue-violet laserdiode
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29-08-2007, 09:26 PM
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Registered User
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Join Date: Jan 2005
Location: Newcastle, NSW, Australia
Posts: 4,116
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30-08-2007, 01:55 PM
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amateur
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Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 7,078
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Visibility of the red laser beam is very, very low, compared to green.. Red light simply does not scatter in the atmosphere sufficiently, plus our eyes are not sensitive to red light.
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03-09-2007, 03:59 PM
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sword collector
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Join Date: Oct 2006
Location: Mount Evelyn
Posts: 2,925
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08-09-2007, 10:50 PM
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I have a To-Do List?
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Join Date: Jun 2007
Location: Melbourne, Australia
Posts: 152
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Quote:
Originally Posted by mill
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Not anymore! It has been removed.
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11-09-2007, 10:13 AM
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SDM Convert
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Join Date: Jun 2007
Location: Brisbane
Posts: 582
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26-04-2014, 10:33 AM
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Registered User
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Join Date: Oct 2013
Location: Wonthaggi Vic
Posts: 625
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No they are not up to 1mW search the Victorian Police web site for laser pointers. This is what is on the site @ 26_04_14:-
Laser pointer
A hand-held, battery-operated article designed or adapted to emit a laser beam with an accessible emission limit of greater than 1 mW.
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