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Thread: Whitelight Diode

  1. #51
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    Mar 2006
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    I already said I'd gone off-topic.. You wouldn't be trying to steer me even further off, would you? I mentioned which of the two cases I'd choose, answering a direct question. We'd already both gone clear off the topic of pulsing in femtosecond duration for fibres...

    I still like the idea of PWM at fast rates a LOT, it solves the problem of linearity nicely, you can get a perfect fade, I imagine. My first base will be to build a very simple driver that can handle either PWM, or analog proportional, entirely dependent on the signals sent to it.

    Edit: Never mind, I got thread titles confused, the subject of fibres and femtoseconds came up in your other recent thread in this subforum. Anyway, I just took the discussion up as I found it, I don't worry much about topics, they just make a starting point.
    Last edited by The_Doctor; 03-24-2007 at 11:52.

  2. #52
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  3. #53
    Join Date
    Mar 2023
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    Quote Originally Posted by steve-o View Post
    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.

    Among the impressive features of our TDL analyzer are its fast response time, direct absorption technique and sensitive detection (ppm to ppb). Along with its ease of use (i.e. no skilled operator needed), it provides a high selectivity of gases and impurities and requires virtually no recalibration.

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