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

mimitech mimitech mimitech at gmail.com
Sat Jun 9 03:01:54 EDT 2018


Thanks, Henk.

This is a very interesting paper. The 1560nm VCSEL is indeed very easy to
source thanks to widely application in Telecom, but the frequency double
and stabilization scheme in the paper is very complex. the purpose of this
paper to use 1560nm is because of its higher spectral purity than
customized and small-scale manufactured 780/795nm VCSEL, to achieve better
atomic clock performance (short-term stability).

If I could find some simple frequency multiplier schemes, it is worth
considering using a 1560 nm VCSEL. Anyway, I need to do further research on
it. Thanks.

mimitech.

On Thu, 07 Jun 2018 21:18:59 +0200, "Henk Peek" <henkp at nikhef.nl> wrote:
>
> Rb vapor-cell clock demonstration with a frequency-doubled telecom laser
>
> Applied Optics Vol. 57, Issue 16, pp. 4707-4713 (2018) •
https://doi.org/10.1364/AO.57.004707
>
> Abstract
>
> We employ a recently developed laser system, based on a low-noise telecom
laser emitting around 1.56 μm, to evaluate its impact on the performance of
an Rb vapor-cell clock in a continuous-wave double-resonance scheme. The
achieved short-term clock instability below 2.5·10−13·𝜏−1/2 demonstrates,
for the first time, the suitability of a frequency-doubled telecom laser
for this specific application. We measure and study quantitatively the
impact of laser amplitude and frequency noises and of the ac Stark shift,
which limit the clock frequency stability on short timescales. We also
report on the detailed noise budgets and demonstrate experimentally that,
under certain conditions, the short-term stability of the clock operated
with the low-noise telecom laser is improved by a factor of three compared
to clock operation using the direct 780-nm laser.
>
> © 2018 Optical Society of America under the terms of the OSA Open Access
Publishing Agreement
>
> Henk Peek
>
> On Tuesday, June 5, 2018 11:11 CEST, Attila Kinali <attila at kinali.ch>
wrote:
>
> > On Mon, 4 Jun 2018 21:31:56 +0800
> > mimitech mimitech <mimitech at gmail.com> wrote:
> >
> > > I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
> > > as my next hobby project. The main purpose is to learn the principles
> > > behind CPT rubidium clock, and hopefully got similar or better
performance
> > > than commercial miniature rubidium clock such as FE-5680A.
> >
> > Building a CPT clock is slightly more involved than you might think
> > at first. The laser diode is only one part of it. You will most likely
> > be able to improve on the short-term stability of the FE-5680 (which
> > is rather poor). But I doubt you will be able to improve much on
> > the long term stability, which is where things actually become
interesting,
> > if you use a naive approach.
> >
> > Nevertheless, I have not seen many 794/795nm diodes around. The only
> > one that I have the datasheet of is the one from Vixar.
> > You might want want to consider going for the D2 line instead of the
> > D1 line, as 780nm diodes are more commonly available than 795nm. You
will
> > also need to buy several of those and select the ones that come closest
> > to the wavelength at the desired opearating conditions (usuall spread
> > is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
> > temperature and current (rule of thumb is that you get about 10GHz
> > per °C and mA). If you need more tuning range, you will need to add an
> > external cavity (can give you up to 5nm range), which then needs to be
> > tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
> >
> > Alternatively, you can get two S1-0780-XXX from Sacher Laser
> > (cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
PLL).
> > If you have enough money to spend, I'd go for two Cateye diode laser
CEL's
> > from Moglabs (cost AFAIK 5000€ each)
> >
> > No matter what you choose, you will need some wavelength stabilization
> > scheme. You can either do that with the vapor cell itself or use
> > an additional cell and do a DVALL or a saturated absorption locking.
> > Note that this addtional cell will need to be without buffer gas.
> > An external cell will offer better stability and thus lower noise,
> > which directly translates into higher stability.
> >
> > As polarisation scheme, I suggest using σ+/σ- as it seems to be more
> > robust than the lin/lin schemes.
> >
> >                       Attila Kinali
> > --
> > It is upon moral qualities that a society is ultimately founded. All
> > the prosperity and technological sophistication in the world is of no
> > use without that foundation.
> >                  -- Miss Matheson, The Diamond Age, Neil Stephenson
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