(self)
return self.w_0*sqrt(1 + (self.z/self.z_r)**2)
The beam radius at `1/e^2` intensity.

        See Also
        ========

        w_0 : the minimal radius of beam

        Examples
        ========

        >>> from sympy.physics.gaussopt import BeamParameter
        >>> p = BeamParameter(530e-9, 1, w=1e-3)
        >>> p.w
        0.001*sqrt(0.2809/pi**2 + 1)
The beam radius at `1/e^2` intensity.
The beam radius at 1 / e^2 intensity .
def w(self):
        """
        The beam radius at `1/e^2` intensity.

        See Also
        ========

        w_0 : the minimal radius of beam

        Examples
        ========

        >>> from sympy.physics.gaussopt import BeamParameter
        >>> p = BeamParameter(530e-9, 1, w=1e-3)
        >>> p.w
        0.001*sqrt(0.2809/pi**2 + 1)
        """
        return self.w_0*sqrt(1 + (self.z/self.z_r)**2)
def w ( self ) : return self . w_0 * sqrt ( 1 + ( self . z / self . z_r ) ** 2 )