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

Dana Whitlow k8yumdoober at gmail.com
Mon Jun 11 06:52:21 EDT 2018

Mark's description about how (most) green laser pointers work is a bit in
error, and is perhaps
over-simplified- the reality is actually more fascinating yet:

First a diode laser operating at around 808 or 809 nm is used to optically
pump a solid
state laser which generates light at 1064 nm.  This light is then frequency
doubled with an
intra-cavity nonlinear element to produce the final  output at 532 nm.
 For all this to work
the optical elements must be critically aligned, and to me the most amazing
thing about
the low selling price is how this alignment is effected so cheaply.  One of
these units I've
opened up has the doubler crystal held down by a lump of cement on one
side- it looks
for all the world like it must have pushed into alignment and "held" there
while the cement
was cured.  Green pointers made in this way are characterized by quite good
beam quality
and very little wavelength spread from unit to unit. However, they are
generally quite
delicate and ruined by mechanical shock.

Although not commonly known, at least one outfit (Z-Bolt) is now selling
"direct diode"
green pointers, where there is just one laser which emits directly in the
green, at around
515-530 nm.   These are much more robust, operate well over a wider
temperature range,
but have the usual poor beam quality (non-circular beam with some residual
characteristic of diode lasers made with simple collimating optics.  And,
the output
wavelength spread from unit to unit is quite large.


On Mon, Jun 11, 2018 at 2:43 AM, Mark Sims <holrum at hotmail.com> wrote:

> Well, no.  Green laser pointers convert a rather high power 800 nm laser
> to 1600 nm in one crystal then divide it to 533 nm in another one.   The
> physics and manufacturing of them is best described as black magic.  They
> are cheap because China developed the process to grow the crystals in bulk
> and crank out zillions of them for consumer products.
> I suspect that a 1600-ish nm to 800-ish nm converter is not a stock
> consumer-quantity device and will cost a pretty penny or two... like a
> red/IR laser diode can be had for 50 cents and a telecom VCSEL diode can be
> $500.
> ------------------
> > It cannot be too much, given the fact that these are used in
> green laser pointers.
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