Refractive index of GaSe (Gallium selenide)

import lightsmith as ls

# GaSe (Gallium selenide): Chen et al. 2009: n,k(e) 3–1500 µm
gase = ls.fetch_refractiveindex("main", "GaSe", "Chen-nk-e", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(gase.range_nm)  # (2997.9, 1.499e+06) nm
eps = gase.eps([67000])  # complex permittivity

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_35bc8fbc51d3/lightsmith"
gase = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(gase.source)  # citation and provenance travel with the data

# ... load gase as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=gase)],
    medium_index=1.0,
    wavelengths=ls.WavelengthRange(start_nm=2998, stop_nm=1.499e+06, num=81),
)
res = ls.solve(sim)  # exact Mie for a sphere
print(res.q_ext)     # extinction efficiency at each wavelength