-fdtd/-ports

A "port" is a part of the border of the computational volume, that shall be treated as an infinitely long waveguide. In this section you specify the location of ports. You also specify the number of modes whose time amplitudes shall be written to file.

 ##############################################################################
 # Flags: nomenu, noprompt, nomessage,                                        #
 ##############################################################################
 # section: -ports                                                            #
 ##############################################################################
 # name  = noname-001                                                         #
 # plane = xlow                                                               #
 # modes = 1                                                                  #
 #(pxlow=      -1.0e+30    , pxhigh=       1.0e+30    ) Ignored for plane=xlow
 # pylow=      -1.0e+30    , pyhigh=       1.0e+30                            #
 # pzlow=      -1.0e+30    , pzhigh=       1.0e+30                            #
 # epsmaximum=        2.0                                                     #
 # muemaximum=        1.0                                                     #
 # npml      = 20                       -- no of PML-planes                   #
 # dampn     =       50.0e-3            -- damping factor in last plane       #
 ##############################################################################
 # doit, list, ?, return, help                                                #
 ##############################################################################

• name = ANY-STRING-WHICH-COULD-SERVE-AS-FILENAME:
  Specifies the name of the port.
  This name is used eg. to identify the port later on. If you enter the name of an already defined port, you can edit the parameters for this already defined port.
  The length of the name has to be less or equal 64 characters.
• plane= [xlow|xhigh|ylow|yhigh|zlow|zhigh]:
  Specifies at which of the six bounding planes of the computational volume the port is located on.
• modes= NMODES:
  Number of orthogonal modes whose amplitudes shall be monitored. This number can be zero. The absorbing boundary conditions work independently of the orthogonal modes, so there is no need to specify a large number here.
• pxlow, pxhigh, pylow, pyhigh, pzlow, pzhigh:
  Specifies the rectangle where the port is in. These parameters are needed if there is more than one port at one of the possible planes [x|y|z][low|high].
  If the port is at xlow or at xhigh, the values for pxlow and pxhigh are ignored. If the port is at ylow or at yhigh, the values for pylow and pyhigh are ignored. If the port is at zlow or at zhigh, the values for pzlow and pzhigh are ignored.
• epsmaximum, muemaximum:
  Values of the "densiest" materials at the port. These values are needed to compute the patterns of the port-modes.
• npml:
  The number of "Perfectly Matched Layers" to use as absorbing boundary conditions.
  15 is a good value.
  If a relativistic charge enters or exits the computational volume through the port, you should choose a value of 40 or more.
• dampn:
  The damping factor of the outermost "Perfectly Matched Layer".
• doit:
  Stores the current data and enables the editing of the parameters of a port that is not yet defined (a new port).
• list:
  Lists the names of the already defined ports.

Example The following specifies that we want to have attached four ports: Two are at the lower x-boundary, the names are xlow1, xlow2. Two ports are at the upper x-boundary of the computational volume, the names are xhigh1, xhigh2. The ports at the same boundary are distinguished by their pzlow, pzhigh parameters.

-fdtd
  -ports
     name= xlow1,  plane= xlow , pzlow= 0,  modes= 10, doit
     name= xhigh1, plane= xhigh, pzlow= 0,  modes= 2, doit
     name= xlow2,  plane= xlow , pzhigh= 0, modes= 2, doit
     name= xhigh2, plane= xhigh, pzhigh= 0, modes= 2, doit