Re: TEM spot sizes

On 5/15/07 7:11 AM, in article 1179239434.431873@xxxxxxxxxxxxxxxx, "SeekUp"
<seek.up.girl@xxxxxxxxx> wrote:

In a number of papers the spot sizes of TEM modes are given:

<quote>

If the spot size of TEM00 mode, w0, is known, the spot sizes of higher-order
modes in rectangular

co-ordinates can be given as

w m / w 0 = (2m + 1)^0.5

and

w n / w0 = (2n + 1)^0.5

where m and n are the null numbers of x and y axles of modes.

<unquote>

Would someone please explain how these relationships are derived, or point
me to a reference that explains it.



Thank you






These mode shapes in rectangular coordinates are products of hermite
functions. The lowest order of these, corresponding to the TEM00 mode is a
two dimensional guassian function. Go to whatever reference you have
covering hermite functions and substitute the higher order hermite functions
for the guassian. Then you can calculate the sizes for the higher order
modes based upon whatever definition is given for size.

Bill
-- Fermez le Bush--about two years to go.


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