pyABCDobj

• rev 2 2014-03-10
• a object oriented framework to calculate the propagation of gaussian beams
• provides 2 Classes:
  • GaussianBeam - to calculate the beam parameters
  • LensSystem - to calculate the propagation using the ABCD formalism

class GaussianBeam

• initialization

  beam = GaussianBeam( wavelength, mode, arg )

  • wavelength is the wavelength in nm
  • mode is either 'q' or 'rw', which means you can define your beam by the complex beam parameters or a pair of radius of curvature and waist (both given in meters)
  • examples:
    • b1 = GaussianBeam( 633e-9, 'q', 0 + .45j )
    • b2 = GaussianBeam( 1064-9, 'rw', [30, 2e-3])

• from the input parameters, the following physical values are calculated automatically:

  • GaussianBeam.q - the complex parameter q
  • GaussianBeam.r - the radius of curvature (phase)
  • GaussianBeam.w - the beam waist
  • GaussianBeam.divergence - the divergence in the far field

• furthermore, the beam wavelength is stored GaussianBeam.wavelength

• for convenience, all parameters can be printed out by GaussianBeam.print_params()

---

class LensSystem

public methods

• __init__(wavelength)

  • initializes an empty lens system (wavelength in nm)

• add_beam(mode, params):

  • adds a gaussian bean at z=0
  • mode is either 'rw' or 'q'

• add_element( Type, zpos, params ):

  • adds an element to the system.
  • Type can be
    • 'lens' (params = [focal length])
    • 'curvedmirror' (params = [Radius of curvature])
  • zpos is the z position of the element
  • params is a list of params (e.g. [f] for a simple lens)

• calc_beam(zend,points):

  • calculates the beam up to zend with points as the number or points
  • returns : [ w,r,d,z,q ], where
    • w is the list of waists(z)
    • r is the list of beam curvatures
    • d is the list of divergences
    • z is the list of z values
    • q is the list of q values

• calc_propmatrix_until_z(z_end)

  • calculates the propagation matrix up to z

• clone()

  • returns a copy of the lens system (without beams)

• print_positions():

  • print positions of elements

private methods

• __get_list_order get the order of the elements in the lens system

• __matrix_lens( f ) returns the ABCD matrix of a lens with focal length f

• __matrix_free_space( L, n) returns the ABCD matrix of a free space propagation (length L, refractive index n)

• __matrix_curved_mirror(self, R) returns the ABCD matrix of a curved mirror with radius R

• __matrix_multiplication( A, B ) perform matrix multiplication of A and B