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From: sam@colossus.stdavids.picker.com (Sam Goldwasser)
Subject: Re: Broken CD Rom drives
In-Reply-To: wagray@taz.dra.hmg.gb's message of 3 Oct 1994 11:13:35 GMT
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Date: Mon, 3 Oct 1994 13:49:54 GMT
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In article <36op0v$b9e@trog.dra.hmg.gb> wagray@taz.dra.hmg.gb (Walter Gray) writes:

   looked in a CD player, I was under the impression that it used red light,
   because red was the shortest wavelength that a laser-diode could produce.
   Hence, we read articles saying there is a desperate effort being made to
   produce blue lasers, to increase the information density on the disks.

   Can someone (perhaps a manufacturer?) post the final definitive answer?

I am not a manufacturer, but have done some research on the subject.
CD players use IR Laser diodes - most of the emission is at 780 nm (most
common).  There are various other spurious lines at least one of which is
in the red wavelength but it is at a much lower power level.  I would guess
that room temperature continuous output
red laser diodes were either very expensive or simply not available
when the CD technology was developed (1980 or so).  Obviously, shorter
wavelengths would be better as you pointed out.

--- sam
