Python package for calculating refractive index dispersion of various materials

# ndispers

ndispers is a Python package for calculating refractive index dispersion of various crystals and glasses used in the field of nonlinear/ultrafast optics. It is based on Sellmeier equartions and thermo-optic coefficients (dn/dT) reported in literature.

You can easily compute

• Refractive index
• Group delay
• Group velocity
• Group index
• Group velocity dispersion
• Third-order dispersion
• Walk-off angles
• dn/dT
• d^2n/dT^2

as a function of

1. Wavelength of light
2. Polar (theta) or azimuthal (phi) angles of wavevector with respect to dielectric principal axes of anisotropic crystals
3. Temperature of crystal
4. Polarization of light (ordinary- or extraordinary-ray)

The crystals have nonlinear-optics methods:

• Phase-mismacth, dk
• Phase-matching angles
• Phase-mathcing factor, sinc^2(dk*L/2)
• Effective nonlinear coefficient, deff

In the latest version v0.2.7, these methods are only for sum-frequency mixing, and deff method only for BetaBBO.

## Installation

In terminal,

pip install ndispers


## Simple example

Firstly, make an object of β-BBO crystal.

>>> import ndispers as nd
>>> bbo = nd.media.crystals.BetaBBO_Eimerl1987()


To look into the material information,

>>> bbo.help
β-BBO (β-Ba B_2 O_4) crystal

- Point group : 3m  (C_{3v})
- Crystal system : Trigonal
- Dielectic principal axis, z // c-axis (x, y-axes are arbitrary)
- Negative uniaxial, with optic axis parallel to z-axis
- Tranparency range : 0.19 µm to 2.6 µm

Sellmeier equation
------------------
n(wl) = sqrt(A_i + B_i/(wl**2 - C_i) - D_i * wl**2) + dn/dT * (T - 20)  for i = o, e

Validity range
---------------
0.22 to 1.06 µm

Ref
---
- Eimerl, David, et al. "Optical, mechanical, and thermal properties of barium borate." Journal of applied physics 62.5 (1987): 1968-1983.
- Nikogosyan, D. N. "Beta barium borate (BBO)." Applied Physics A 52.6 (1991): 359-368.

Example
-------
>>> bbo = ndispers.media.crystals.BetaBBO_Eimerl1987()
>>> bbo.n(0.6, 0.5*pi, 25, pol='e') # args: (wl_um, theta_rad, T_degC, pol)


To compute refractive indices,

>>> bbo.n(0.532, 0, 25, pol='o')
array(1.67488405)
>>> bbo.n(0.532, 3.1416/2, 25, pol='e')
array(1.55546588)


where the four arguments are, respectively,

1. wavelength (in micrometer),
3. temperature (in degree Celsius),
4. polarization (pol='o' or 'e', ordinary or extraordinary ray).

Default is pol='o'. Note that pol='e' corresponds to pol='o' in index surface when theta angle is 0 radians. Output values are generically of numpy.ndarray type. You can input an array to each argument, getting an output array of the same shape,

>>> import numpy as np
>>> wl_ar = np.arange(0.2, 1.5, 0.2)
>>> wl_ar
array([0.2, 0.4, 0.6, 0.8, 1. , 1.2, 1.4])
>>> bbo.n(wl_ar, 0, 25, pol='o')
array([1.89625189, 1.692713, 1.66892613, 1.66039556, 1.65560236, 1.65199986, 1.64874414])


See documentation for more features and examples.

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