Attila Kinali wrote:
On Mon, 01 Apr 2013 22:32:11 +1300
Bruce Griffiths<[email protected]> wrote:
Attila Kinali wrote:
On Mon, 01 Apr 2013 09:08:51 +1300
Bruce Griffiths<[email protected]> wrote:
Nothing to do with laser line width.
Merely indicating that the photodiode mixer can be used with a suitable
LO to build an optical spectrum analyser front end.
Are you refering to heterodyne spectrum analyser?
Essentially, however if the photdiode has say a 1GHz bandwidth the LO
could be stepped in say 1GHz steps with subsequent circuitry providing
finer resolution.
The difficulty here is to get an LO laser that can be stepped in 1GHz
steps and keep it there, stable. The only way i have seen sofar is
using a mode locked laser and referencing/stabilizing the LO to one
of the comb tooths. Technically seems to be relatively simple,
but unfortunately a mode locked laser is financially out of the reach
of a mere mortal.
Constructing an optoelectronic version of either an LSB or USB converter
may be interesting.
Yes, an optoelectronical I/Q mixer would be very intersting. But also
very difficult and fragile to build, considering that you have to
keep the distances stable down to a couple of 10nm.
Attila Kinali
Back to the original problem:
An AOM could be used to generate a sideband 7GHz above (or below) the
output of 1 laser which could then be mixed with the output of the other
laser using a narrow bandwidth photodiode.
How do ensure a suitably wide mode hop free tuning range for the lasers
to be locked to the first laser?
Bruce
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