Announcement

Collapse
No announcement yet.

Blacker than black

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Blacker than black



    Pitch Black The New Black

    Scientists at the University of Rochester have found a way to change the properties of almost any metal to render it, literally, pitch black. Pitch black metals could increase the efficiency of a multitude of devices such as fuel cells, solar cells, imaging devices, and undoubtedly, fashion items.

    The master of darkness behind the discovery, the University of Rochester's Chunlei Guo, said the discovery was made by accident. "We wanted to see what would happen to a metal's properties under different laser conditions and we stumbled on this way to completely alter the reflective properties of metals."

    Creating pitch black metals involves exposing them to an ultra-intense femtosecond duration laser pulse (a femtosecond is to a second what a second is to 32,000,000 years). In a few quadrillionths of a second, Guo's laser unleashes as much power as that generated by the entire North America power grid onto a spot the size of a needle point.

    The intense blast alters the surface of the metal, forming nano-sized pits, globules, and strands, which dramatically increase surface area and radiation capture. Guo and his fellow researchers have tested the absorption capabilities for the black metal and confirmed that it can absorb virtually all the light that falls on it.

    Pitch black metals should allow far more data to be captured in light detecting devices, making them much more sensitive and efficient. The process could also have applications in replacing black paint, or creating fashion items. Guo reports that the new process has worked on every metal he has tried, and because it's a property of the metal itself, there are no concerns about the black wearing off. As well as the light absorbing properties of pitch black metal, the dramatic increase in the metal's surface area could open up new catalysis techniques.
    >
    Dr. Mordrid
    ----------------------------
    An elephant is a mouse built to government specifications.

    I carry a gun because I can't throw a rock 1,250 fps

  • #2
    Yay! Fäshn!
    There's an Opera in my macbook.

    Comment


    • #3
      What is the mechanism that allows a laser to pulse at only such a precisely minute fraction of a second?

      Comment


      • #4
        It's done by a process called mode locking. Locking can be either active or passive. In active an external signal is used to induce a modulation in the lasers cavity. Most often used for picosecond pulses. In passive the cavity has elements designed to self modulate the beam. Most femtosecond lasers use this technique.

        In practice it comes down to something like this (VERY basic);



        the gain medium compensates for losses and the saturable absorber mirror (SA) enforces pulse generation. Each time the circulating pulse hits the output coupler mirror (OC), a pulse is emitted.

        SA's (often lead sulfide or gallium arsenide) have a degree of lossiness except at high intensities.

        OC's return the vast majority of the beam to the laser cavity and transmit the rest for use.

        The gain medium is a lasing material; a crystal, gas mixture, glass doped with ions or dye, or semiconductor.

        How it actually looks:



        SESAM (semiconductor saturable absorber mirror) is the SA
        Last edited by Dr Mordrid; 24 November 2006, 03:35.
        Dr. Mordrid
        ----------------------------
        An elephant is a mouse built to government specifications.

        I carry a gun because I can't throw a rock 1,250 fps

        Comment


        • #5
          Keeping those things tuned and stable is a true art. I've built 'ovens' for the crystals that needed (and provided) better than 1mK stability, and peizo controllers for accurately switching the position of the optics in a DIAL system (Differential Absorption LiDAR).
          Keeping your output aligned through the rest of your system really does require a brain that can think in 3 dimesions and 8 steps ahead!
          FT.

          Comment


          • #6
            interesting. but fashion? come on:
            unleashes as much power as that generated by the entire North America power grid
            doesn't seem to be an accurate way of measuring power, but I guess it's possible to translate that into "a huge f.. lot", resulting in needle-point of pitch black. wonder how that translates into jewelry which larger sizes. or even solar panels, when you are talking squaremeters. they are even now just energy efficient (production vs. life time payback).

            mfg
            wulfman
            "Perhaps they communicate by changing colour? Like those sea creatures .."
            "Lobsters?"
            "Really? I didn't know they did that."
            "Oh yes, red means help!"

            Comment


            • #7
              Its a lot of Joules in a very short space of time, so high power numbers come easily.
              Depending on the power supply and a number of other things, it'll likely fire at many times per second, so scanning across a surface in a reasonable time is likely feasible.
              FT.

              Comment


              • #8
                Don't get the impression they are just workbench toys; femtosecond lasers are commercial. Here in the US the IntraLase Pulsion FS is the best example of a femtosecond medical device and it's been around for several years.

                It's used to perform LASIK surgery without the need for a bladed microkeratome cutter. Makes for a much more precise cutting of the flap.

                Last edited by Dr Mordrid; 24 November 2006, 10:52.
                Dr. Mordrid
                ----------------------------
                An elephant is a mouse built to government specifications.

                I carry a gun because I can't throw a rock 1,250 fps

                Comment

                Working...
                X