[time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

Dana Whitlow k8yumdoober at gmail.com
Fri Jun 15 04:47:17 EDT 2018


I don't know of any particular reason why a DVD-player laser should be
faster,
since neither CD nor DVD players need to deliberately modulate the lasers
anyway.  At least, that's the first blush answer.

However, these diode lasers are generally noisy, apparently due to the
inevitable presence of optical reflections back into the diodes.  I once
read that deliberately FM'ing the laser by applying a high frequency RF
tone along with the DC bias current could be helpful in mitigating the
problem.  But this was in connection with the *analog* Laser Disk video
recording format.  I don't know if the laser noise was ever much of a
problem
with reading the digital formats of CDs and DVDs.  If not, then surely the
makers of diodes for these mass market applications would not be investing
effort in making the lasers fast.

On additional factor is that CD players and DVD players use different light
wavelengths: ~780 nm for CDs, ~650 nm for DVDs.  It might be that the
difference in semiconductor composition between the two types makes
a significant difference in the response speed.  However, I doubt that this
would would be relevant for present purposes, unless Rb also has some
*useful* transitions in the 650 nm regime.

Dana


On Thu, Jun 14, 2018 at 11:25 PM, Hal Murray <hmurray at megapathdsl.net>
wrote:

>
> k8yumdoober at gmail.com said:
> > I've been told that CD player type diodes can be successfully modulated
> up to
> > about 600 MHz, but that going much further is either difficult or perhaps
> > impossible.
>
> Are DVD lasers faster?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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