# PLaSK User Manual

#### Page Contents

- `plask.phys`
  - Constants
  - Functions
  - Descriptions
    - Function Details
      - `eV2nm()`
      - `nm2eV()`
      - `wl()`

# `plask.phys`

Basic physical constants and utility functions.

## Constants

`qe` | Elementary charge (C)
`me` | Electron mass (kg)
`c` | Speed of light (m/s)
`mu0` | Vacuum permeability (V·s/(A·m))
`eps0` | Vacuum permittivity (pF/µm)
`eta0` | Free space impedance (Ω)
`Z0` | Free space impedance (Ω)
`h.J` | Planck constant (J·s)
`h.eV` | Planck constant (eV·s)
`SB` | Stefan-Boltzmann constant (W/(m2·K4))
`kB.J` | Boltzmann constant (J/K)
`kB.eV` | Boltzmann constant (eV/K)

## Functions

`eV2nm`(eV) | Compute wavelength for specified photon energy.
`nm2eV`(nm) | Compute photon energy for specified wavelength.
`wl`(mat, lam[, T]) | Compute real length of optical wavelength in specified material.

## Descriptions

### Function Details

plask.phys.eV2nm(eV)

  Compute wavelength for specified photon energy.

  Parameters:

    eV (float) – Photon energy (eV).

  Returns:

    Wavelength (nm).

  Return type:

    float

plask.phys.nm2eV(nm)

  Compute photon energy for specified wavelength.

  Parameters:

    nm (float) – Wavelength (eV).

  Returns:

    Photon energy (nm).

  Return type:

    float

plask.phys.wl(mat, lam, T=300.0)

  Compute real length of optical wavelength in specified material.

  This is utility function that computes the physical length of a single wavelength in specified material. Its main purpose is easier design of DBR stacks.

  If you are using it with custom materials, make sure that it does provide `nr()` method.

  Parameters:

    - mat (material.Material or str) – Material to compute physical wavelength in.

    - lam (float) – Free-space wavelength to scale for material mat (nm).

    - T (float) – Temperature at which material refractive index is retrieved.

  Returns:

    Real length of the one wavelength in the material (µm).

  Return type:

    float