Re: Which OPTICs design program is best ?

Hi James,
Thanks for the detailed response!
Generally, I use a similar technique (with different grating periods)
to model an acousto-optic pulse shaper. The benefit of using a
ray-tracing package here is in modeling the temporal dispersion of an
ultrashort pulse (distance traveled along the propagation path vs.
wavelength).
Wolfgang

Jamie wrote:
Generally, one can separate the temporal (and more exact physical
optics) model from the design of systems using AOM. Remember that the
optical system is, for all intents and purposes, static to the signal
injected into the sonic field. Further, the work of the optical
designer, ultimately, is the design of real optics that give a linear
transfer function by balancing all (or as many as possible) of the
higher order geometrical terms (aberrations).

Typically I will model the AOM as an immersed grating but I will "zoom"
the grating frequency over its corresponding RF bandwidth using
multiple configurations. One may even weight these configs with the
AOM's RF spectral efficiency as measured or specified by the
design/vendor and even include spurious orders. In this model, all of
the spatial frequencies that support diffraction are included in the
model and their resulting (diffracted) optical response in optical
plane wave spectrums are accounted as well.

The optical system is then optimized for the application based on these
interactions. This allows the optical design to accommodate all signals
that may be used in the device based on its linear system response.
Arbitrary signals cases can be assessed on the basis of superposition.

If you are concerned about non-linear effects such as intermodulation
products, non-linear interaction (ie approaching 100% diffraction
efficiency) or non-linear propagation in the sonic field, then these
types of analyses are best left to Matlab or Mathcad.

James Carter
http://www.jacarter3.com
http://www.opticalconsulting.com


I should add that I'm trying to deflect at multiple angles
simultaneously (by mixing multiple (RF) drive frequencies), so my
deflector would have to be modeled by a grating with multiple periods.
I'm a bit new to optical design programs, but I'm assuming that this is
possible to do.

Wolfgang, that's interesting. I'm not immediately sure that the optical
design programs would give the right answer in this case. (You would simply
stack gratings.) I think that in reality you will get not only the directly
diffracted beams, but also multiply diffracted beams. Usually, in the
optical design programs, you tell it which diffracted order you want.
Thinking out loud, it probably will work, but you'd have to use multiple
configurations to track all of the beams you may be interested in.

.

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