[Laser] Re: How much power

[Chuck Hast]

On 6/7/07, Tim Toast <toasty256 at yahoo.com> wrote:
> Hi all
> Here's some info and application notes/data sheet for the
> MAX9484 a Multimode CD-RW/DVD Laser-Diode Driver. Maybe it
> is typical of 4x DVD-RW drives like the one you described:
> http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4294
> and
> http://www.maxim-ic.com/appnotes.cfm/an_pk/2947
>
> oddly, i didn't see any mention of the diode power level
> that it drives, only the max drive current it provides -
> 350 ma per channel and as high as 400ma total depending on
> the type of dvd disk. The website talks about the
> temperatures the laser produces in the disk as it writes,
> erases, bias etc..
> temperatures:
> Write:500-700°C Erase:200°C Bias 1°C?
> ld currents:
> Write:350-400ma. Read:270ma. Bias:5 - 15 ma.
>
>
> And here's another page with info where someone is
> experimenting with a DVD writer laser diode:
> http://www.felesmagus.com/pages/lasers-howto.html
>
> they claim a 200-225 mw laser output power at 350ma.
> current, and that you can easily feel the heat on your skin
> from an Un-focused 1/8th inch diameter 200mw beam.
>
> i can see now why the disks seem warm when they come out of
> a burner.. They literally "cook" in there 8)
>

Maxim indicates in one of their documents that the write layer has to be
heated to 500-700C in order to obtain the proper melt and re-crystallization.
If that disk is spinning at 8X the base rate that means you have to hit that
layer with a lot of power melt and get off of it. So the power they are talking
about starts to really become understandable. A 16X is even more demanding.


-- 
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."