# Why don't CD players use blue lasers? **URL:** \ **Category:** Factual Questions\ **Created:** [July 21, 2008, 7:18pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290 "2008-07-21T19:18:10Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 21, 2008, 7:18pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/1 "2008-07-21T19:18:10Z")
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? ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [July 21, 2008, 7:24pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/2 "2008-07-21T19:24:12Z")
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. ---
**Author:** ![Huerta88](https://avatars.discourse-cdn.com/v4/letter/h/82dd89/32.png) [@Huerta88](https://boards.straightdope.com/u/Huerta88)\ **Post date:** [July 21, 2008, 7:29pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/3 "2008-07-21T19:29:02Z")
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](http://archive.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm) ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [July 21, 2008, 7:53pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/4 "2008-07-21T19:53:29Z")
They were made of unobtainium, which has become more available in recent years. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 21, 2008, 8:05pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/5 "2008-07-21T20:05:11Z")
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? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [July 21, 2008, 8:06pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/6 "2008-07-21T20:06:11Z")
[QUOTE=ultrafilter] 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? [/QUOTE] 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!) ---
**Author:** ![Huerta88](https://avatars.discourse-cdn.com/v4/letter/h/82dd89/32.png) [@Huerta88](https://boards.straightdope.com/u/Huerta88)\ **Post date:** [July 21, 2008, 8:21pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/7 "2008-07-21T20:21:12Z")
[QUOTE=ultrafilter] 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? [/QUOTE] Why yes you should – the logical next step has been taken: [http://www.theinquirer.net/en/inquirer/news/2004/11/08/pioneer-ultraviolet-laser-promises-500gb-disks](http://www.theinquirer.net/en/inquirer/news/2004/11/08/pioneer-ultraviolet-laser-promises-500gb-disks) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [July 21, 2008, 8:31pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/8 "2008-07-21T20:31:49Z")
Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [July 21, 2008, 8:46pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/9 "2008-07-21T20:46:13Z")
[QUOTE=Q.E.D.] Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone. [/QUOTE] Only for killer movies where the hero also dies. ---
**Author:** ![Huerta88](https://avatars.discourse-cdn.com/v4/letter/h/82dd89/32.png) [@Huerta88](https://boards.straightdope.com/u/Huerta88)\ **Post date:** [July 21, 2008, 8:51pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/10 "2008-07-21T20:51:07Z")
[QUOTE=Duckster] Only for killer movies where the hero also dies. [/QUOTE] 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. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [July 21, 2008, 8:55pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/11 "2008-07-21T20:55:39Z")
Like some sort of 1920’s-style Death Ray? ---
**Author:** ![Stathol](https://avatars.discourse-cdn.com/v4/letter/s/71e660/32.png) [@Stathol](https://boards.straightdope.com/u/Stathol)\ **Post date:** [July 21, 2008, 8:57pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/12 "2008-07-21T20:57:46Z")
[QUOTE=ultrafilter] As time goes by and laser technology improves, should we expect to see even shorter wavelengths being used? [/QUOTE] 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. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [July 21, 2008, 9:33pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/13 "2008-07-21T21:33:30Z")
[QUOTE=Q.E.D.] Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone. [/QUOTE] And you thought a scratch messed up a movie now… ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [July 21, 2008, 9:52pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/14 "2008-07-21T21:52:14Z")
Time again to post one of my favorite [projects](http://www.metacafe.com/watch/756433/laser_flashlight_hack/). A real attention getter at the corporate meetings when you need to make a point. ---
**Author:** ![neutron\_star](https://avatars.discourse-cdn.com/v4/letter/n/51bf81/32.png) [@neutron\_star](https://boards.straightdope.com/u/neutron_star)\ **Post date:** [July 21, 2008, 10:12pm UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/15 "2008-07-21T22:12:06Z")
[QUOTE=Huerta88] 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](http://archive.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm) [/QUOTE] 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. ---
**Author:** ![Declan](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Declan](https://boards.straightdope.com/u/Declan)\ **Post date:** [July 22, 2008, 6:23am UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/16 "2008-07-22T06:23:59Z")
[QUOTE=Projammer] Time again to post one of my favorite [projects](http://www.metacafe.com/watch/756433/laser_flashlight_hack/). A real attention getter at the corporate meetings when you need to make a point. [/QUOTE] Awesome , now thats the killer app. Declan ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [July 22, 2008, 8:00am UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/17 "2008-07-22T08:00:51Z")
[QUOTE=Projammer] Time again to post one of my favorite [projects](http://www.metacafe.com/watch/756433/laser_flashlight_hack/). A real attention getter at the corporate meetings when you need to make a point. [/QUOTE] What’s that saying about not looking into the laser with your remaining eye? That thing is scary, and isn’t a toy. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [July 22, 2008, 9:31am UTC](https://boards.straightdope.com/t/why-dont-cd-players-use-blue-lasers/457290/18 "2008-07-22T09:31:41Z")
[QUOTE=Projammer] Time again to post one of my favorite [projects](http://www.metacafe.com/watch/756433/laser_flashlight_hack/). A real attention getter at the corporate meetings when you need to make a point. [/QUOTE] I note to my dismay that Metacafe has started superimposing ads across the bottom of their videos while they are playing. Ick.