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Thread: Whitelight Diode

  1. #11
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    Oh well.. maybe optical combiners will be improved and new and different wavelengths e.g. 485, 550, 610nm etc dpss will appear on the market making for more flexability in the future. They're always coming up with new stuff.. Maybe even a tunable module ... or a diode pumped compact dye laser or...?

    I found this article in Laser Focus World:
    Ultrafast white-light continua from filaments in water interfere

    Given the proper conditions, a white-light continuum (WLC) can be generated by focusing pico- or femtosecond pulses into condensed matter. One property of a WLC produced in this manner is its coherence: each spectral component has the same coherence as the pump light and thus appears as if it were laser light. Scientists at Heriot-Watt University Edinburgh, Scotland, and Qinetiq (Malvern, England) have made this property plain to see by creating more than one WLC from the same laser and interfering their light to produce fringes.
    Focusing the output of a Ti:sapphire laser (1-mJ, 12-fs pulses) into water using a cylindrical lens produced a stable one-dimensional array of white-light filaments. Reducing the pulse energy to 780 µJ caused all but two filaments to disappear. The two that remained were separated by 184 µm and had 1/e2 diameters of 25.8 and 19.3 µm for 700- and 600-nm wavelengths, respectively. Light from the pair interfered to produce fringes that were stable over greater than a 10-min time interval, easily observed at the 600- and 700-nm wavelengths with bandpass filters. Contact Ajoy Kar at a.k.kar@hw.ac.uk.
    Last edited by steve-o; 02-22-2007 at 05:50. Reason: added article

  2. #12
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    Doped glass fiber, end-pumped with a blue laser diode, makes RGB.

    http://www.sumita-opt.co.jp/en/news.htm

    "World First Dream Light Source

    -Succeeded in white laser oscillation with a single fluoride glass fiber-

    First time in the world, Sumita Optical Glass, Inc. (Address: 4-7-25 Harigaya, Urawa-ku, Saitama, 330-8565 Japan, President: Mr. Masatoshi Sumita, Phone No. 81-48-832-3165) has succeeded in continuous white laser oscillation with a newly developed single fluoride glass fiber by combining the three primary colors, namely 522nm green, 635nm red lasers, oscillated simultaneously by guiding 440nm blue diode laser into a single fluoride glass fiber, and a part of 440nm blue diode laser out put.

    To date, white laser has been created by combining the three primary colors generated separately by guiding IR laser into nonlinear crystal like YAG laser, ti-sapphire laser and etc., or gas laser, however those methods suffer problems like conversion inefficiency which enlarges energy consumption, needs large size laser oscillator and extremely high cost.

    Since white laser of this new development is configured with a single fluoride glass fiber and 440nm blue LD only, it is an outstanding product in terms of conversion efficiency, energy consumption, a compact size laser oscillator, cost performance and etc.

    This uniquely developed fluoride glass fiber used for white laser oscillation is a practicable one. It is made of a series of aluminum fluoride glass doped with praseodymium, which emits green and red fluorescence by absorbing blue diode laser. The distance between resonators at both ends of the fluoride glass fiber is 25cm in this time.

    Some fluoride glass fibers for researches are available in the market, but almost all of them are made of a series of zircon-fluoride glasses, which are unendurable to practical use.

    As the wavelength of green laser obtained with this white laser is of 522nm which is that of pure green, by using this white laser as a light source of display, such a display would have closer colors to natural colors than those of traditional CRT display, plasma display, projectors with ultrahigh pressure mercury lamp, LCD and etc., it becomes possible to create a display with high-luminance, low-power-consumption, compact and low cost performance.
    In anticipation of new appliances development, making use of this new development of white laser in the future, Sumita Optical Glass, Inc. is committed to pursuit improvement of the performance of this fiber in terms of out put and conversion efficiency as well as development of souped-up blue LD to be guided into the fluoride glass fiber.

    Reference (PDF)" at link: http://www.sumita-opt.co.jp/en/other/whitelaser.pdf
    Attached Thumbnails Attached Thumbnails RGB-Fiber-Laser.jpg  

    "We can't solve problems by using the same kind of thinking we used when we created them."
    --Albert Einstein

  3. #13
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    Cool

    That's a DPSS solution. There are already a couple instances of that technology.

    Steve-o was talking about a direct-injection whitelight diode. Whole different animal.

    Basically, in a direct injection diode you've got electrons and holes pairing up within the boundary region of a semi-conductor PN junction. As such, you're dealing with a substrate and a closely matched doping element, so the energy transition involved in electron-hole pair-ups is a well defined quantity.

    Now you somehow need to broaden the possible energy transitions available when electrons and holes pair up in this single substrate material so you can get multiple wavelengths of light. Oh, and they need to have near-equal probability, or else one line will have much higher gain than the others and will compete. (No dielectric optics on a diode, remember!)

    Ok - carbon has lots of energy transitions... So - invent a carbon semiconductor, then build a laser out of it. Riiiiight. And even that is the longest of longshots. The goal is really "out there" in terms of semiconductor physics.

    DPSS whitelight solutions are easier because you're dealing with electrons that are still bound to the atom, and thus can occupy a whole slew of different energy levels. So all you need is a substance with a few different metastable high energy levels (metastable, so you can get a population inversion) and you can then tune the optics of the cavity to selectively favor one, a few, or even several different wavelengths which correspond to the available transitions. The physics behind this is well established. (EG: dye lasers, since the mid-to-late 1960's, though they were first pumped with flashlamps, and later with Argon ion lasers.)

    Adam

  4. #14
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    Yes Adam,
    I was also trying to get ideas of un-complicating a laser projector. This seems verrrrry interesting. Looks like they're using 1 blue laser and a fiber as a optical resonator cavity..pretty cool.
    http://www.sumita-opt.co.jp/en/other.htm is the vid that explains the principle (same web-site)
    I'd like to experiment with this setup and try to build a projector using this concept. Imagine just buying 1 laser instead of 3!
    Thanks Ragnarok.

    Adam--what are the other instances of this technology are there out there that you mentioned?

    Steve

  5. #15
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    According to this chart:

    http://www.sumita-opt.co.jp/en/other/whitelaser.pdf (bottom-right)

    there are ALOT of different lines in the output, not just 3. There's one peak at right about 600nm. Awesome!

    Lessee, to make the Dream light laser, all we need is 25cm of the
    Praseodymium doped fluoride glass fiber , a 440nm diode laser and 2 mirrors.
    I'm assuming one is the HR and the other is the OC. Now all we need is the specs for the mirrors and the laser, and a sample of the fiber, and a little info on how to hook it all together.

    Not too difficult of a challenge, eh?

    Ideas anyone?

  6. #16
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    The Jenoptic unit is a multi-line DPSS solution, and then there's the pumped-fiber laser you linked to. (It may be that they're both using the same technology, though I think the Jenoptic unit is pumped with near IR rather than 440 nm blue...) Remember that the filber is actually a lasing meduim in that unit, just like the ND/VO4 crystal in a green DPSS laser. I've read about something similar to the fiber unit before, but I can't find the link...

    Dye lasers are another example of a multi-wavelength laser that can be diode-pumped, though because the lasing medium is a fluid they're not considered solid state. The common factor in all of these lasers is that they all rely on a coherent light source for pumping.

    The idea of a direct injection whitelight diode is what I was panning in my original post. (IE - no pump diode. Just a diode that makes coherent whitelight when you feed it some electricity...) This will be a much harder nut to crack.

    Cool write up on that fiber laser btw...

    Adam

  7. #17
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    Thanks Adam
    Oh, so the Jenoptic laser uses a similar lasing medium? I wonder why more people aren't jumping on this white-lite bandwagon?
    Yeah a direct-injection diode would be cool but tough. DPSS would probably be ok if possible several lines lasing in the same medium..

    Here's some more info on the "Dream-Laser" (good name?)

    In the latest white light source, red and green lights are generated by using fiber optics doped with a wavelength converting material to absorb blue light originally emitted from the semiconductor laser diode. The resultant red and green lights are mixed with the original blue light to generate white light. An aluminum fluoride glass doped with praseodymium (Pr) as a wavelength converting material is used to obtain a core material of the fiber optics. Laser oscillation of green and red lights is enabled by using dichroic mirrors provided at both ends of the fiber optics as a resonator. The wavelengths of blue, green and red lights are 440-450 nm, 522±2nm and 635±2nm, respectively. The fiber optics used as the white light source are currently being shipped as samples. The sample price of a 10 cm product is about ¥10,000.

    ...now let me find my yen to usd converter...

    Oh, and congrats on your 1000th post Adam!
    Last edited by steve-o; 02-23-2007 at 10:39.

  8. #18
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    82 bucks sounds reasonable. I might get me one. Now if I just knew how to put this resonator cavity together..
    I wonder if Spec or Marconi would be interested in this project.
    Hey Y'all--- ?

  9. #19
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    Smile

    Quote Originally Posted by steve-o View Post
    I wonder why more people aren't jumping on this white-lite bandwagon?
    Well, to the best of my knowledge, it's because they're so friggin' expensive. The Jenoptic units cost as much as a starter home. Seriously! So it's cheaper to just combine 3 separate lasers or use a mixed-gas ion laser.
    DPSS would probably be ok if possible several lines lasing in the same medium..
    Oh yeah - it's not only possible, it's here. It's just too expensive, and there isn't any large market force driving the price down. (How many laser show companies are there, anyway?) But if you've got Bill Gates' money, you can get it. (Yadda once posted something to the effect that if he ever won the lottery he'd buy a dozen of the Jenoptic units!)

    As for that Dream Laser - hmmm... If the fiber is so cheap, I'm wondering why we don't have whitelight pointers by now. There's got to be more to it. Either the optical cavity is impossible to align, or the fiber is only good for a few microwatts of power, or the whole thing doesn't scale well... Gotta be something. (But I agree that it would be cool to play with a sample for under $100. Remember that the pump diode alone would cost an order of magnitude more though.)

    Adam

  10. #20
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    Interesting the "whitelight continua" came up We actually have a sample unit in-shop of the "tapered optical fiber" for evaluation that we received early last year. They're actually making them commercially now and the prices, while not good yet are sure to come down. The problem for amateurs is that it requires a very high quality and very fast pump source which are not currently inexpensive. The interesting thing is that it truly is a true continuous spectrum of light!!! The bulk of the actual power output is in the IR range, but there is more than enough in the visible spectrum to be VERY intersesting... There are definitely some problems with it in it's current form, but nothing that prevents it from improving in the future. We are currently working with some companies to develop a color selection system for this laser, but nothing which is laser show specific. There are photos of the very first unit created in operation in my gallery.

    http://photonlexicon.com/gallery/album27

    The way the JenLas unit works is completely different. The JenLas has 3 conventional diode pumped solid state lasers with automatic self alignment. The "interesting" thing about the JenLas (formerly the Schneider Showlaser) is that it uses a diode-pumped nonlinear crystal to generate the red... which is (perhaps surprisingly) the "hard" color to get lots of power from. These are my favorite whitelights to use btw! If this next year goes as projected, we're looking to add one to our arsenal.

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