# PLaSK User Manual

#### Page Contents

- FreeCarrierCyl

# FreeCarrierCyl

<gain solver="FreeCarrierCyl">

  Corresponding Python class: `gain.freecarrier.FreeCarrierCyl`.

  Quantum-well gain using free-carrier approximation for cylindrical geometry.

  This solver does not use any mesh by default and the the full gain calculation is performed in each requested point. However, if there is a mesh specified then the gain is computed only in the mesh points and interpolated in-between.

  Attributes:

    - name (`required`) – Solver name.

  Contents:
    <geometry>

      Geometry for use by this solver.

      Attributes:

        - ref (`required`) – Name of a Cylindrical geometry defined in the `<geometry>` section.

    <mesh>

      Optional Ordered, Regular mesh used by this solver.

      Attributes:

        - ref (`required`) – Name of a Ordered, Regular mesh defined in the `<grids>` section.

    <config>

      Some important gain parameters.

      Attributes:

        - lifetime – Average carriers lifetime. This parameter is used for gain spectrum broadening. (float (ps), default 0.1 ps)

        - matrix-elem – Value of the squared matrix element in gain computations. If it is not set it is estimated automatically. (float (eV×m0))

        - strained – Boolean attribute indicating if the solver should consider strain in the active region. If set to yes then the substrate material must be either explicitly specified of there must a layer with the role “substrate“ in the geometry. The strain is computed by comparing the atomic lattice constants of the substrate and the quantum wells. (bool, default is `no`)

        - substrate – Name of the substrate material. This attribute is used only if the strained attribute is set to yes. If this attribute is not set then the substrate material must be specified by a layer with the role “substrate“. (material)

        - T0 – Reference temperature. This is the temperature used for initial computation of the energy levels. (float (K), default 300 K)