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Some time ago, (September 2003 if memory serves) I posted a topic entitled "Aquarium Laser Lighting" in which I hypothesised that if certain technical problems could be overcome, then LED laser diodes arranged in arrays may provide an energy-efficient high-intensity lighting system for the future. Well, the December 2003 issue of Practical Fishkeeping contains an article (pages 24-26) by Mike Paletta (I spelt his name correctly this time!), in which he 'gets out the crystal ball' and looks at future development in marine aquaria. Where, of course, lighting systems play a very important part, especially in those systems containing corals with symbiotic zooxanthellae. I wrote my topic starter post with the idea that a laser LED lighting system would be useful in any aquarium, providing complete control over the spectrum, and delivering light with very little heat output, because the conversion of electrical energy to light in a laser diode is an extremely efficient process. Mike Paletta, after discussing the development of T5 tubes, metal halide and an experimental system involving sulphur irradiation with microwaves (see the magazine for more details!), moves on to the subject of LED lighting. He says:

There is another method of lighting which is still a few years away, but when available will probably make all the others obsolete. It will use light emitting diodes (LEDs) to generate the light and promises a source that produces virtually no heat, will never need to be replaced and can be placed wherever the light is desired.

Unfortunately, LED technology as present does not produce light with enough intensity or a high enough colour temperature to be useful to illuminate a reef tank. Also, these lights are on the expensive side at the moment.

However, over the next five years these technical shortcomings should be overcome and this method for lighting reef aquariua should become widespread and very useful within the hobby.

So, remember everyone, you read it here in FishProfiles first! I thought that it was a workable idea if enough R&D money was spent upon it, and it seems that there are, to my surprise and delight, companies doing just that in order to produce what promises to be THE lighting solution for the future. Nice to know that others share my lateral thinking, including those with the backing capital to act upon it

Initially, I foresaw the major problems with the system as being [1] generating a wide spectral spread, and [2] delivering the light over a wide area at a workable intensity (problem [2] I initially considered to be solvable once the spectral spread issue of problem [1] was resolved). LEDs, particularly the laser diodes I envisaged being used (because these offered the best potential for light intensity) have very narrow spectral outputs. Indeed, in the case of a laser diode, a single wavelength is produced. To produce a lighting system that covered the daylight spectrum, one would need thousands of different laser diodes, all producing a different part of the spectrum, and some of these might need exotic materials such as lanthanide elements to work. The blue end of the spectrum is particularly problematic at the moment, although Sony recently announced that they had produced a high-capacity DVD read-write drive that used a blue laser diode to increase the packing density of the data on the disc (which is partly a function of the wavelength used: blue light has a shorter wavelength than red, and so can be focused onto smaller regions of the disc while maintaining accuracy).

One BIG advantage that a laser LED offers is penetrating power. Laser light is coherent (all the light waves are aligned with each other, instead of randomly distributed as with a normal light source), is usually a tight-beam source, and a low-wattage laser has very efficient penetrating power. A 1 milliwatt laser (that's a thousandth of a watt!) is actually powerful enough to damage the human retina if one is foolish enough to stare into the beam. I've seen 1-milliwatt lasers generate beams that could produce a dot on the side of a building from three miles away. Even if one assumes that water, being a good deal denser than air, attenuates the beam via volumetric absorption at a much faster rate, a 1-milliwatt laser beam will still produce a considerable degree of illumination at the bottom of a 2-metre deep aquarium (and most of us have systems a LOT shallower than this!).

However, the single wavelength problem only becomes a problem when you want lots of wavelengths. The laser beam produced from a laser diode relies upon the quantum tunnelling effect, and ultimately, upon the Einstein photoelectric equation relating energy to wavelength. Manipulating this in a solid state environment at the moment relies upon exotic semiconductor mixes involving gallium, yttrium and a brace of other rarely seen and rarely encountered chemical elements. But, one of the more interesting research ideas related to this field involves investigating the effect of 'caging' metal and semiconductor atoms inside molecular 'cages' made from Buckminsterfullerene molecules. If this line of research proves fruitful, we could have broad-spectrum laser lighting systems, that don't need hideoulsy expensive lanthanides or weird composites (most aquarists would probably not want to delve too deeply into the radiation physics of yttrium-gallium-cobalt arsenide polysilicates ). And, for those who haven't encountered them before, Buckminsterfullerene molecules are, wait for it, molecular 'footballs' composed of 60 carbon atoms each. Millions of them are generated in candle flames every second as part of the soot yield of incomplete combustion. They are, literally, as common as dirt. If these can be harnessed, and moreover, used to 'fine tune' the spectral output of a semiconductor, giving us complete spectral control without the need for exotic materials, then they could form the basis of the first laser diode lighting system for an aquarium.

Such a system would be revolutionary. It would be a flat panel instead of a tube, rather like an LCD computer monitor. It would probably be no more than 15 millimetres thick. And a third of the weight of a fluorescent tube. It would generate a complete spectrum, possibly under the control of a microprocessor, so that the aquarist could select the desired colour temperature of the output using a small keypad. More sophisticated variants might even allow the shape of the spectral distribution curve to be editable via one's PC or Mac, accentuating the wavelengths that are important for higher plants in freshwater aquaria, or zooxanthellae in reef aquaria. Imagine popping something like a Sony camera memory stick in your PC, editing a spectral distribution, then popping the memory stick in your aquarium lighting system and instantly having the desired spectrum ... I thought that would make you likc your lips! Indeed, once the technological hurdles were overcome, the options available would be literally limitless. How about a lighting system that you could submerge? Small waterproof discs that could be used to 'spotlight' particularly light-demanding corals, and which, if necessary, could be mounted underwater, fixed beneath some piece of rock, illuminating the coral directly. Not to mention the creative possibilities offered by the chance to 'spotlight' other areas, and replicate such effects as shafts of sunlight dancing between bogwood roots in a big catfish aquarium ... imagine being able to 'light sculpt' your aquarium to replicate effects normally only seen by those lucky enough to snorkel dive in South American rivers, or scuba dive off the Maldives ...

Combine this with technology that aims to produce LED arrays on flexible textile-type fabrics, and you could have a light source that could be shaped to fit any convenient receptacle. Some researchers are already working to this end, with one of their goals being to produce T-shirts that display moving imagery on one's chest - the ultimate in nightclub one-upmanship - but this could be applied more practically to the aquarium too. With a combination of very high energy efficiency (and virtually no wastage through heat), very light weight, malleable mechanical flexibility, and directly controllable spectral output, such a system would make T5s or metal halides look like the products of the Stone Age. And, it would last for years, decades even, as semiconductors don't wear out. Imagine a light source that would produce a consistent output, year in, year out, and possibly outlast not only you, but your grandchildren too ... I think reef keepers would be willing to pay quite a bit for a light source like that! Imagine a light source whose lifetime was measured not in thousands, but millions of hours ... to put it in perspective, a 1 million hour lifetime is around 114 years!

So, it looks as if my original piece of lateral thinking wasn't so wide of the mark after all. Watch this space - you saw it here first - so if anyone out there builds one of these things, I hereby exercise my intellectual property rights and demand a percentage of the royalties




Panda Catfish fan and keeper/breeder since Christmas 2002

Wow, AMAZING article. *thinks how incredibly expensive it would be*

Closest thing I've seen to that is http://www.aquaticplantcentral.com/forum/viewtopic.php?t=1068