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.