[time-nuts] Re: Temperature accuracy / repeatability / drift of double ovens

[Magnus Danielson]

The DFB lasers you use for this typically has a thermistor and 
termoelectical cooler to form a control loop with external components, 
just as for any other DWDM DFB laser. Tune the setpoint of this to lock 
the laser to the rubidium. The laser becomes warm, so you stabilize it 
by how much you cool it.

Further, it has a photodiode to set a loop to stabilize the current and 
thus the intensity of the laser, which often is of interest to stabilize 
for clock transitions.

Add modulation to the laser for sidebands if that is relevant.

One DFB datasheet I found had typical 0.06 nm / K in temperature 
sensitivity and typ 0.003 nm / mA in current sensitivity. Thus, it could 
be wise to "leak" the current-steering to the temperature to compensate 
for current effect in feed forward rather than indirect lock.

Look at the available DFB lasermodules, I think it should become fairly 
clear quite quickly as you look at datasheets etc. Exactly which laser 
to use depends on power and bandwidth that fit a particular use, so it 
boils down to what you end up needing it to do.

Cheers,
Magnus

On 2023-03-31 00:16, Gerhard Hoffmann via time-nuts wrote:
> Temperature accuracy / repeatability / drift of double ovens:
>
> What can be reached here, with a tolerable effort?
> Is there anything known about that in the public? mK-numbers?
>
> The application is not a crystal oven this time, but diode lasers
> that interrogate Rb atoms and must be kept in lockstep at a certain
> beat frequency. The frequency tuning is mostly by temperature;
> laser diode current plays a minor role, but probably via changing the
> local temperature in the junction and a little bit later in the cavity.
>
> Are there any GoTo thermistors / circuits for stability?
>
> Cheers, Gerhard
> (stumbling into new territory)
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