[time-nuts] ?==?utf-8?q? a newbie question: where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

Henk Peek henkp at nikhef.nl
Thu Jun 7 15:18:59 EDT 2018

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 


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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