CSIR-developed laser technology to make almost any laser operate in a ‘high-brightness’ mode will result in more efficient lasers for long-range communication systems, and in the military for target designation. The technology may also be used to make lasers smaller and less expensive, by exploiting the extra efficiency to make the support systems work a little less.
With lasers one generally has to choose between having lots of energy, and having a ‘nice’ laser beam. A quality that incorporates both these parameters is the so-called ‘brightness’ of a laser: high brightness means good laser beam quality and high energy. This is difficult to achieve because good beams tend to come at the expense of energy, while high-energy beams are highly distorted and difficult to use in practical applications. So is it possible to have the best of both worlds? This question was posed to the CSIR by a South African company intent on making industrial lasers to compete in the international market.
The CSIR has for several years invested in developing core expertise in shaping light with diffractive optical elements; optics that have feature sizes down to the micrometre scale, and sometimes to the nanometre scale. The idea is that, given a laser beam of a particular intensity profile (ie, how the energy carried by the laser is distributed in space), it is possible to reshape the profile of this laser beam by redistributing the energy.
If this is done correctly, then in principle any laser beam shape can be achieved. The group worked on achieving this same result, but inside a laser, so that the diffractive optical elements are the mirrors of the laser. The idea was that if the mirrors were correctly calculated, and then fabricated, the laser itself would select the best beam for maximum brightness. The shape of the laser beam bouncing around inside the laser was chosen to extract as much energy as possible from the laser, but in a ‘good’ shape. The idea worked, and the result was a 25 times improvement in the performance of the laser – just with the help of carefully designed micro-structured mirrors.
The research has been taken up by the local photonics industry with a signed licence agreement that sees the technology a permanent part of the product line of export-orientated lasers. With a 25 times improvement in performance with only a change of one mirror in the design, the company can now offer a vastly improved product at very little additional cost.
For more information contact CSIR, +27 (0)12 841 3417.
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