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Just thought I would show you a video of one of the lasers I get to work with at the Australian National University.
It's a Titanium:Sapphire laser pumping out a thousand 120 femtosecond pulses of 800 nm light a second. Each pulse contains about 500 uJ of energy, giving a peak power of about 5 GW and an average of 500 mW.
The beam size is about 1 cm across when it leaves the laser, and even with that high peak power, you only start to cause some serious damage when you focus it down to a mm or less...and boy does it cause some damage! When you have peak powers like that focused down to such small areas, the intensity goes through the roof and the material, be it paper, plastic, metal or skin, is evaporated instantly. Don't think of it like the industrial laser cutters though, becuase its only 1000 pulses a second and each pulse is 120 femtoseconds long, that average power is quite low and it takes quite a lot of effort to make any serious impact on whatever you are irradiating.
The camera is not the best for showing it to you but its probably better than the human eye. Being 800 nm it's just on the edge of human visability and so while 500 mW in average power, it looks little more than a 5-10mW beam. The dyes in the paper even make it look pink. The camera also isn't the best at showing the result either, but you can see the vapour of the paper floating into the beam as the laser hits it, and you can hear the high pitch whine that the 1000 Hz pulse rate creates. Occasionally it also sounds like it stutters or stops, that occurs when the laser has burnt through the paper, and the laser passes through the hole.
Plastic makes it easier to see the effect. It burnt through a few pens of mine in a few seconds, and on the video you see it burn a swipe card I have. Just little tiny dots burnt into the plastic. Made visible through the use of a scanner that creates a spiral shape. I might post a few closeups of some of the things I have burnt later. For now though, enjoy the amature type video I made
The file is a 13 MB avi and goes for 2:20
I'de make it smaller, but I'de waste too much time trying to set up the right software.
It's a Titanium:Sapphire laser pumping out a thousand 120 femtosecond pulses of 800 nm light a second. Each pulse contains about 500 uJ of energy, giving a peak power of about 5 GW and an average of 500 mW.
The beam size is about 1 cm across when it leaves the laser, and even with that high peak power, you only start to cause some serious damage when you focus it down to a mm or less...and boy does it cause some damage! When you have peak powers like that focused down to such small areas, the intensity goes through the roof and the material, be it paper, plastic, metal or skin, is evaporated instantly. Don't think of it like the industrial laser cutters though, becuase its only 1000 pulses a second and each pulse is 120 femtoseconds long, that average power is quite low and it takes quite a lot of effort to make any serious impact on whatever you are irradiating.
The camera is not the best for showing it to you but its probably better than the human eye. Being 800 nm it's just on the edge of human visability and so while 500 mW in average power, it looks little more than a 5-10mW beam. The dyes in the paper even make it look pink. The camera also isn't the best at showing the result either, but you can see the vapour of the paper floating into the beam as the laser hits it, and you can hear the high pitch whine that the 1000 Hz pulse rate creates. Occasionally it also sounds like it stutters or stops, that occurs when the laser has burnt through the paper, and the laser passes through the hole.
Plastic makes it easier to see the effect. It burnt through a few pens of mine in a few seconds, and on the video you see it burn a swipe card I have. Just little tiny dots burnt into the plastic. Made visible through the use of a scanner that creates a spiral shape. I might post a few closeups of some of the things I have burnt later. For now though, enjoy the amature type video I made
The file is a 13 MB avi and goes for 2:20
I'de make it smaller, but I'de waste too much time trying to set up the right software.
