diff --git a/pykat/utilities/optics/gaussian_beams.py b/pykat/utilities/optics/gaussian_beams.py
index 82cfda3e06fc421959ef4bec04102cbcf72d5bd7..2708735b99ad3ad779bb79dc778eac4d1b5d2da6 100644
--- a/pykat/utilities/optics/gaussian_beams.py
+++ b/pykat/utilities/optics/gaussian_beams.py
@@ -145,6 +145,10 @@ class gauss_param(object):
     def imag(self): return self.__q.imag
     @imag.setter
     def imag(self, value): self.__q.imag = SIfloat(value)
+
+    # reverse beam direction 
+    def reverse(self):
+        self.__q = -1.0 * self.__q.real + 1j * self.__q.imag
     
 class HG_gauss_beam(object):