That 405nm wavelength is also particularly important in respect to the disc format it is used for. As many of you will doubtless be aware, data is stored on CDs, DVDs, HD DVDs and Blu-rays, in loose terms, as a series of ones and zeros printed onto the disc's surface as pits. Actually it is the transitions, or lack thereof, from a pit to a "land" (no pit) and vice versa that represents a 'bit' of data but that's not particularly important.
What is important is that the wavelength of light used dictates how small these individual bits of data can be, and what data density is possible on a disc. Thus a CD using a 780nm red laser can pack in 700MB, a DVD with a 650nm laser crams about 4.4GB on a single layer while both HD DVD and Blu-ray discs are read with 405nm lasers, offering about 15GB and 25GB per layer respectively. The difference in capacity between Blu-ray and HD DVD is related to the disc itself. In simple terms, HD DVD manufacture is based in that of DVD, so it wasn't possible to pack data as densely as Blu-ray, which used an entirely new manufacturing process and is thus arguably the more technologically advanced format. Seeing as the format war is fought and won by Blu-ray now, it's a bit of a moot argument anyway - what's important is that without the use of a 405nm blue laser, there would be no HD discs as we know them.
Interestingly, although Sony decided to dub its format Blu-ray, colour wise the diode actually produces a beam closer to the violet end of the electromagnetic spectrum. In fact, the Sonar II, and by association Blu-ray, laser beam is very close to being too short for the human eye to even see. Admittedly, when shone onto a white surface, the dot of the laser is blue, but on any other surface it is decidedly purple, as is the beam when visible in the air. I guess Violet-ray didn't have the ring to it that Sony was looking for.
To really get the best 'wow' factor out of the Sonar II you need to use it in a dark room, or at night. As luck would have it I was able to take the laser out into the countryside a fair distance from the nearest town, on a fairly humid night with some pretty low-laying cloud. The end result of this was a complete lack of ambient lighting and lots of moisture in the air, meaning that the laser's beam was clearly visible all the way to the cloud base, upon which a large purple circle was visible.
The only way I can describe the effect is "bloody fantastic" and it is to my great shame that my camera was unable to get any decent photographs. Frankly, it would almost be worth investing in an SLR and decent tripod just for taking photos of the Sonar II.
Yes, the Sonar II is ludicrously expensive, but it also has an undeniable air of coolness and exclusivity that you won't find anywhere else. What else can I say, it's a Blu-ray laser pointer for goodness sake!
Arguably useless, but undeniably awesome; if you can afford to spend £1,000 plus VAT, plus shipping from the US on a gadget that's bound to impress your mates, the Sonar II Blu-ray laser pointer is the one to get. (We can probably expect Roman Abramovich to be ordering one for each of the Chelsea squad then - ed.)