South African Research Team Creates World's First Digital Laser 81
smi.james.th writes in with news about new laser technology developed in South Africa. "The Council for Scientific and Industrial Research (CSIR) announced in Pretoria on Tuesday that it had developed the world's first digital laser. 'I am always very cautious about using the term "breakthrough",' noted Science and Technology Minister Derek Hanekom. 'We scrutinized this very carefully before we said that this is really new! South African scientists are once again making noteworthy contributions to the world.'... A normal laser contains two mirrors, opposed to each other and at opposite ends of the instrument. One is highly reflective and the other is a curved, partially reflective mirror. In the digital laser, the curved mirror is replaced by a liquid crystal display (LCD) system. The LCD is connected to a computer and monitor."
Important part the summary neglected (Score:5, Informative)
Researchers use the computer to specify the laser beam shape they require and to programme it into the LCD. By this means, one laser can swiftly produce many different beam shapes. Previously, changing the shape of a laser beam required physically replacing the curved mirror in the laser. As the mirror has to be carefully aligned, this is a time consuming process.
Re:Important part the summary neglected (Score:4, Informative)
I fail to see how that's digital, but it's a cool advancement none the less. The beam itself is still just a laser beam.
Summary seems to be somewhat misleading. (Score:5, Informative)
My impression is that, because the mirror is "replaced" with the LCD, the LCD is inside the cavity, with each pixel modulating either the Q or the polarization of a particular chunk of the cross-section of the cavity. This amounts to adjusting the gain of the various modes of the cavity and thus switching which one(s) oscillate and consume the energy from the amplifier in the cavity.
Though the modes that are selected would not be mapped one-to-one onto the pixels, , you can control a lot of modes with the ciquid crystal display - probably all of them available, or up to the number of pixels in the liquid crystal device.
You can also switch them as fast as the liquid crystal switches. With modern drivers (which remember the previous state of the liquid crystal in each pixel and temporarily overdrive those that must change more in order to switch them rapidly, rather than just letting them settle passively into the new state) you can switch it at 60 Hz or better.
You might use holographic techniques to change the angle of the beam, or emit a number of beams of various intensities in various directions. Result: Scanning and image formation without moving parts (other than the molecules in the display).
I think the computation to turn it into a (one-color) projector would be pretty much a straight 2-D FFT times a nonliinear tweak to deal with energy-stealing among modes.
I'd like to see versions of this with array-of-Kerr-cells in place of the liquid crystal device (for more rapid modulation, at the cost of high voltage drivers), or digital light processors for the mirrors (though the latter are more on/off than continuously adjustable so they might be more limited on what beams they can form).
Re:Important part the summary neglected (Score:4, Informative)
Exactly, I believe the TI DLP system has been in use for this for quite a while. Last time I went looking they had DLP chip in the lab that was able to handle almost 15 watts of laser power without a problem. http://focus.ti.com/pdfs/dlpdmd/Using_Lasers_with_DLP(r)_Technology.pdf [ti.com] for one of their earlier papers on this.