As I understand it, one of the major reasons why a Blu-Ray can store so much more data than a CD or DVD of the same size is that the player uses a laser with a shorter wavelength, allowing it to read smaller regions of the disc. I’m not sure I would’ve come up with that, but in retrospect it seems somewhat obvious. Why didn’t CD and DVD players use shorter wavelength lasers?
20-25 years ago, solid-state blue lasers or LEDs suitable for use in home electronics were some combination of non-existent or wildly expensive.
Yes, the shorter blue-range wavelengths allow you to carve (and read) smaller pits, thus leading to greater data density.
A very interesting story about the struggle to develop a diode-based blue laser:
http://archive.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm
They were made of unobtainium, which has become more available in recent years.
I should’ve figured something like that. As time goes by and laser technology improves, should we expect to see even shorter wavelengths being used?
Remember, they started inventing CDs in the late 1970s. The first mass-market CDs were released in 1982. At the time, the only solid-state lasers that could be made cheaply were infra-red, so that was the limiting factor.
Later, they invented cheap solid-state red lasers (Cool, let’s put movies on them!) Then even later they invented cheap solid-state blue lasers (Cool, let’s put HD movies on them, but have a stupid format war first because we’re idiots!)
Why yes you should – the logical next step has been taken:
Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone.
Only for killer movies where the hero also dies.
Yeah, the gamma ray and x-ray laser apps. I’ve seen discussed are generally so energetic that they are being discussed for weapons. Energy increases linearly with frequency.
Like some sort of 1920’s-style Death Ray?
Probably, but at some point it becomes impractical. Even if we knew how to make an x-ray or gamma ray laser, using them in consumer electronics would be problematic. Obviously, there’s a much bigger containment issue since x-rays and gamma rays are much worse for you than visible or UV light.
Secondly, as the frequency of light increases, the amount of energy in a single quantum increases. As a consequence, the photoelectric effect comes into play. Basically, if you slam an x-ray or gamma ray at a chunk of metal, it emits an electron. CDs and DVDs contain a metallic reflective layer, which is not going to react well to being struck with high energy photons. Have you ever seen a CD in a microwave? It would be kind of like that everywhere that the laser hit it.
And you thought a scratch messed up a movie now…
Time again to post one of my favorite projects.
A real attention getter at the corporate meetings when you need to make a point.
Just wanted to say thanks for that link. Fascinating stuff. I’d heard of Shuji Nakamura before while reading about blue LEDs, but I didn’t know his story.
Awesome , now thats the killer app.
Declan
What’s that saying about not looking into the laser with your remaining eye?
That thing is scary, and isn’t a toy.
I note to my dismay that Metacafe has started superimposing ads across the bottom of their videos while they are playing. Ick.