[Ben Krasnow] and His 8 kJ Ruby Laser

 

We were again pleased to find another person who attended Maker Faire just to show off the awesome and not to hawk some goods. In our mind [Ben Krasnow] represents the highest echelon of hardware hacking (apparently Google[x] agrees because they just snatched him up) . But [Ben] always makes a point to explain how he does what he does so that others may learn and someday achieve a similar type of greatness. This time around it’s a functional ruby laser which is backed by a capacitor bank that stores a whopping 8 kilojoules of energy. This is what allows the laser to cut through steel plate. He sure has come a long way since he first showed off the project in January.

Unfortunately we didn’t get to [Ben's] booth until late on Sunday. His previous demonstrations burned through some seals and left him with a non-functional laser. But he’s a trustworthy guy so we believe him and look forward to him posting a video about the laser and hopefully about the failure. He also mentions that he may make an attempt at lunar laser ranging with this device; bouncing the laser off of reflectors on the moon and measuring the delay. This can then be used to calculate the distance to the moon.

By the way, it was super difficult not to crack a joke when he says the words “Ruby Rod“.

Lazing With A Ruby

ruby

[Ben Krasnow], builder of amazingly complex and technical devices, is finally starting work on his ruby laser. He’s been collecting parts for this project for the past few years, but only recently has he started recreating the first visible light laser.

While the design and manufacture of the first ruby laser was astonishingly complex, the basic idea behind it is pretty simple. [Ben]‘s laser uses a synthetic ruby rhod with the ends ground optically flat. This rod is placed inside a flash tube. When the flash tube lights up, the rod absorbs the light and re-emits it as a coherent beam for several milliseconds. This beam bounces between two mirrors – one fully reflective and another partially reflective – and emits a constant stream of coherent photons. It’s tremendously more complex than simply connecting a laser diode to a power source, but replicating a build that graced the covers of Time and Newsweek only fifty years ago is pretty impressive

Right now, [Ben] has most of the mechanical and optical parts of his ruby laser on his workbench. The next step is constructing a huge capacitor bank to charge the flash tube every millisecond or so. What [Ben] will end up using his laser for remains up in the air, but if we come across some erbium or neodymium rods we’ll be sure to send them his way.

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