It’s an older Efratom rubidium frequency reference. Steve
> On Jun 9, 2018, at 8:34 AM, Dana Whitlow <k8yumdoo...@gmail.com> wrote: > > What is an 'FRK'? > > Thanks, > > Dana > > >> On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts <time-nuts@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.griffi...@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 <mimit...@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 <att...@kinali.ch> >> wrote: >>>> >>>> On Mon, 4 Jun 2018 21:31:56 +0800 >>>> mimitech mimitech <mimit...@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 >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.