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

Dana Whitlow k8yumdoober at gmail.com
Sat Jun 9 09:34:54 EDT 2018


What is an 'FRK'?

Thanks,

Dana


On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts <time-nuts at febo.com> wrote:

> Having followed the conversation and having looked at the p[possibility
> using a FRK with laser diode, it is low on our list because of all the
> ongoing projects but please if you want to spend time and money use any
> thing but a FE5680. I was one of the first using it and noticed and posted
> a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
> attached. Do not have info as to who posted it.
> Using a FRK is the easiest way to do so if interested contact me off list,
> based on our tests is a close second to the HP 5065A.
> Bert Kehren
>
> In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
> bruce.griffiths at xtra.co.nz writes:
>
>
>  Theres also
>
> http://www.photonics.philips.com/application-areas/sensing/components
>
> and
>
> https://www.sacher-laser.com/home/industriallasers/point_
> and_line_laser_module/industrial_laser_modules/micron_laser.html
> Bruce
> > On 09 June 2018 at 20:54 mimitech mimitech <mimitech at gmail.com> wrote:
> >
> >
> > Thanks Attila for your suggestion.
> >
> > I prefer the 780/795nm VCSEL scheme for its simplicity. After some
> > searching, looks like the 780nm VCSELs are also not easy to source,
> > although other types of 780nm LD are common.
> >
> > I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
> > mode VCSEL from a local distributor, price is about $500/pcs. I'm not
> sure
> > whether this model could work in CPT rubidium clock.
> >
> > A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
> > VCSEL, with unit price $800, which was proved to work as this paper
> > "A compact atomic magnetometer for cubesats",
> > https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
> 0017N_11402.pdf
> > ,
> >
> > this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
> > Trapping (CPT) in Rubidium"
> > http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
> Thesis_with_papers_V7.pdf
> >
> > and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
> > series. The cheapest model is SA.31m priced about $1100 at Digikey /
> > Mouser.
> >
> > Another paper "VCSEL Laser System for Atomic Clocks"
> > http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
> > several VCSEL from different vendors and found the ULM 794.7 nm single
> mode
> > VCSEL can work.
> >
> > Thanks.
> >
> > mimitech.
> >
> >
> > On Tue, 5 Jun 2018 11:11:59 +0200, 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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