Lazing With A 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.

34 thoughts on “Lazing With A Ruby

  1. Rod. It is a rod.


    edit v.

    1. prepare (written material) for publication by correcting, condensing, or otherwise modifying it.

    I suppose a ruby laser would seem incredibly complex when the simple process for preparing a couple paragraphs in the production of profit is just too unmanageable.

      1. *You’re







        I think it is the whole ‘expecting to be competent at communicating in order to have a job or post-secondary education’ thing that brings people to the chuckle-fuck fold.

    1. As strider_mt2k and… that other guy have pointed out, it’s supposedly a reference to the movie “The 5th Element”.

      I don’t quite fully understand the need for said reference myself (maybe I could understand if Ben had used said reference), as I feel it somewhat needlessly subtracts & distracts from the post topic content, but it’s not my site, and Brian can write what he wants.

      I’ve said it before, and I’ll say it again. If the content of the HaD summary really does p*ss everyone off so much, then just scan the key words and click on through if it sounds interesting! It’s become my method, so much so that I hadn’t even noticed the “rhod” until it was s̶o̶ ̶p̶o̶l̶i̶t̶e̶l̶y̶ pointed out.

      In fact, it appears a good deal of the people who visit this site now do so just to poke holes in the write-ups.

      You’re not paying for it, so give it a rest. It’s getting kind of old.

  2. It would be very nice of you to send him (or, indeed, me) an erbium or neodymium rod, however I am not sure why you would do so. These are metallic elements; thus opaque. Not exactly useful for lasing.

        1. Yep. erbium and neo-doped yittrium aluminum garnet. The YAG is colorless; the doping adds the color and does all the lazing stuff.

          It’s the same way with rubies; Aluminum Oxide doesn’t laze. Add some chromium and it becomes a ruby and shoots lazers.

  3. I gave up on the video. If you want to hold people’s attention with a science video, show the thing working at the start. That’ll hook those who care into watching the explanation.

    It’s a frikkin laser, I want to see it working. (Shark head mounting optional.)

  4. Why a flash lamp and not laser diodes for the pump light? For historical accuracy? Rod lasers can be pumped much more efficiently by diodes. A flash lamp’s pump efficiency is about 7% at best. Diode pump efficiency can be 30%+.

    1. Laser diodes need to have a wavelength matching the absorption spectrum of the rod being pumped, which can be a PITA and expensive to find (and sufficiently good alignment could be a bit fussy as well). Flash tubes are much easier to make work – even if you have to use xenon tubes instead of krypton, you can still make it work. Just less efficiently than the “optimal” coupling solution.

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