Beamsplitter

beamsplitter
bs
Beamsplitter

The beamsplitter component represents a thin dielectric surface with associated properties such as reflectivity, tuning, and radius of curvature. It has four optical ports p1, p2, p3, and p4 which describe the four beams incident on either side of this surface. p1 and p2 are on side 1 and p3 and p4 are on side 2. A 100% transmissive beamsplitter will transmit all of the light incident at p1 to p3.

It also has a mechanical port mech which has nodes for longitudinal, yaw, and pitch motions. These mechanical nodes are purely for exciting small signal oscillations of the mirror. Static offsets in longitudinal displacements are set by the phi parameter (in units of degrees), misalignments in yaw by the xbeta parameter, and pitch the ybeta parameter. Macroscopic angle of incidence of the beamsplitter is set by the alpha parameter. Beamsplitters physically operate the same as mirror components, except for the non-normal angle of incidence option.

Syntax

bs name R=none T=none L=none phi=0 alpha=0 Rc=inf xbeta=0 ybeta=0 plane=0 misaligned=false

Required

name: Name of newly created beamsplitter.

Optional

R: Reflectivity of the beamsplitter.

T: Transmissivity of the beamsplitter.

L: Loss of the beamsplitter.

phi: Microscopic tuning of the beamsplitter (in degrees).

alpha: Angle of incidence (in degrees)

Rc: Radius of curvature (in metres); defaults to numpy.inf to indicate a planar surface.

xbeta, ybeta: Angle of misalignment in the yaw plane (xbeta) and pitch (ybeta), respectively (in radians); defaults to 0.

plane: Plane of incidence, either ‘xz’ or ‘yz’. Defaults to ‘xz’.

misaligned: When True the beamsplitter will be significantly misaligned and assumes any reflected beam is dumped. Transmissions will still occur.

Phase relationship

See Mirror and beamsplitter phase relationships for more details on the phase relationship to ensure energy conservation that is used in |Finesse|.

Ports

The order of the ports is shown below. In a typical Michelson interferometer the order of the ports is: input-reflection-transmission-output.

Parameters

Listed below are the parameters of the beamsplitter component. Certain parameters can be changed during a simulation and some cannot, which is highlighted in the can change during simulation column. These changeable parameters can be used by actions such as xaxis or change. Those that cannot must be changed before a simulation is run.

Name	Description	Units	Data type	Can change during simualation
R	Reflectivity	None	float	✓
T	Transmission	None	float	✓
L	Loss	None	float	✓
phi	Phase	degrees	float	✓
alpha	Angle of incidence (-90 <= alpha <= 90)	degrees	float	✗
Rcx	Radius of curvature (x)	m	float	✓
Rcy	Radius of curvature (y)	m	float	✓
xbeta	Yaw misalignment	radians	float	✓
ybeta	Pitch misalignment	radians	float	✓
plane	Plane of incidence	None	int	✗
misaligned	Misaligns beamsplitter reflection (R=0 when True)	None	bool	✓