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Diffstat (limited to 'abcd2self_repeating_q.m')
| -rw-r--r-- | abcd2self_repeating_q.m | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/abcd2self_repeating_q.m b/abcd2self_repeating_q.m new file mode 100644 index 0000000..cd60aaf --- /dev/null +++ b/abcd2self_repeating_q.m @@ -0,0 +1,19 @@ +function [q] = abcd2self_repeating_q( abcd_cavity ) +% this find q such that q = (A*q+B)/(C*q+D) +% i.e q after abcd is exactly the same +% very handy for cavity mode calculations + +% spelling out abcd coefficients +[A, B, C, D] = abcd2ABCD( abcd_cavity ); + +if ~isCavityStable(abcd_cavity) + display('ABCD is unstable !'); + display('We should stop now. There is no stable self-repeating mode with such ABCD'); + error('Not possible to calculate a self-repeating mode with the unstable ABCD'); +end + +% q is the solution of quadratic equation, we chose one with positive waist size +q = ( -(D-A) - sqrt( (D-A)^2 + 4*C*B ) ) / (2*C); + +end + |