Magnus Danielson wrote:
On 01/14/2011 07:24 PM, Bruce Griffiths wrote:
ehydra wrote:
Hi!
By modulating the laser diode current you can modulate the diode
temperature. And that changes the wavelength.
- Henry
At 3.4GHz??
Modulation at 3.4 GHz required by an Rb standard so that the frequency
difference between the 2 first order sidebands is 6.8GHz.
Actually all you need to do is phase modulate the output.
What they actually do is set the DC current for wavelength and AC
modulate at 3.4 GHz for locking frequency. It's obvious if just
looking into one of the papers I linked earlier.
If you look at the Symmetricom paper for the SA.3X they also describe
the overall algorithms of locking in the wavelength etc.
Will have to read up on it.
Cheers,
Magnus
The modulation mechanism has to be other than thermal expansion to
achieve the required bandwidth.
Modulating the current density will also modulate the refractive index
of the laser crystal.
To achieve the required modulation bandwidth one has to use something
like a VCSEL.
With other lasers such as an ECDL which dont have a sufficiently large
modulation bandwidth an external electrooptic phase modulator is required.
Bruce
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