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

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Jun 9 07:23:12 EDT 2018


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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