Optical constants

Refractive index of KI (Potassium iodide)

Li 1976: n 0.25–50 µm

Data: formula 1
Range: 0.25–50 µm
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.66633
Extinction coefficient k: 0

Permittivity ε₁: 2.77667
Permittivity ε₂: 0

Absorption coefficient α: 0 cm⁻¹
Penetration depth δ = λ/(2πk): — nm

Abbe number V_d: 23.659
Chromatic dispersion dn/dλ: -0.141347 µm⁻¹

Group index n_g: 1.74939
Group velocity dispersion: 294.265 fs²/mm

Dispersion parameter D: -1605.37 ps/(nm·km)
Photon energy: 2.11001 eV

ε = (n + ik)², α = 4πk/λ, n_g = n − λ dn/dλ, GVD = λ³/(2πc²) d²n/dλ², D = −(λ/c) d²n/dλ². Group-velocity dispersion is given for formula data only.

Use it in Lightsmith

Load this data in Python, simulate in one more line

pip install lightsmith

import lightsmith as ls

# KI (Potassium iodide): Li 1976: n 0.25–50 µm
ki = ls.fetch_refractiveindex("main", "KI", "Li", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(ki.range_nm)  # (250, 50000) nm
eps = ki.eps([633])  # complex permittivity

Downloads the original record once (pinned to the imported snapshot) and caches it.

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_176b34402fb6/lightsmith"
ki = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(ki.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (ki/li-1976).

# ... load ki as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=ki)],
    medium_index=1.0,
    wavelengths=ls.WavelengthRange(start_nm=400, stop_nm=1000, num=81),
)
res = ls.solve(sim)  # exact Mie for a sphere
print(res.q_ext)     # extinction efficiency at each wavelength

Same spec runs with DDA, FDTD, BEM or T-matrix: ls.compare(sim, ["mie", "dda"]).

import json, urllib.request
import lightsmith as ls

url = "https://materials.lightsmith.dev/v1/datasets/ds_176b34402fb6/lightsmith?model=drude_lorentz"
ki_dl = ls.DrudeLorentz.model_validate(json.load(urllib.request.urlopen(url)))

A dispersive Drude–Lorentz model for time-domain solvers.

Materials guide Open a sphere of it in Studio Quick start Ask the community

Lightsmith is open source (MIT): Mie, T-matrix, BEM, DDA, FDTD, RCWA, TMM, mode solvers and inverse design behind one spec, on CPU or GPU. GitHub.

Dispersion formula

Sellmeier (formula 1), λ in µm

n^{2} - 1 = 0.47285 + \frac{0.16512 λ^{2}}{λ^{2} - {0.129}^{2}} + \frac{0.41222 λ^{2}}{λ^{2} - {0.175}^{2}} + \frac{0.44163 λ^{2}}{λ^{2} - {0.187}^{2}} + \frac{0.16076 λ^{2}}{λ^{2} - {0.219}^{2}} + \frac{0.33571 λ^{2}}{λ^{2} - {69.44}^{2}} + \frac{1.92474 λ^{2}}{λ^{2} - {98.04}^{2}}

Valid from 0.25 to 50.0 µm.

Coefficients as stored

C_i	Value
C1	0.47285
C2	0.16512
C3	0.129
C4	0.41222
C5	0.175
C6	0.44163
C7	0.187
C8	0.16076
C9	0.219
C10	0.33571
C11	69.44
C12	1.92474
C13	98.04

Comments and conditions

297 K (24 °C).

References

H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data 5, 329-528 (1976) and references therein.
* Sellmeier formula is derived by critical analysis of experimental data from several sources.

doi:10.1063/1.555536 Refractive index of alkali halides and its wavelength and temperature derivatives, Journal of Physical and Chemical Reference Data (1976)

Cite

H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. Journal of Physical and Chemical Reference Data, 5, 329-528 (1976), doi:10.1063/1.555536; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

Computed on 400 wavelengths, the same grid as the API and the library

CSV comma separated TXT tab separated YAML n, k Full database record original YAML All quantities CSV JSON metadata

KI (Potassium iodide), Li 1976: n 0.25–50 µm: n and k versus wavelength
λ (µm)	n
0.25	2.049339
0.253342	2.022505
0.256728	1.998705
0.26016	1.977386
0.263638	1.958133
0.267162	1.940628
0.270733	1.924619
0.274353	1.909908
0.27802	1.89633
0.281736	1.883753
0.285503	1.872063
0.289319	1.861166
0.293186	1.850982
0.297106	1.841442
0.301077	1.832485
0.305102	1.824059
0.30918	1.816119
0.313313	1.808624
0.317502	1.801539
0.321746	1.794831
0.326047	1.788473
0.330405	1.782438
0.334822	1.776704
0.339298	1.77125
0.343833	1.766056
0.348429	1.761107
0.353087	1.756386
0.357807	1.751879
0.36259	1.747573
0.367437	1.743456
0.372349	1.739517
0.377326	1.735746
0.38237	1.732132
0.387481	1.728668
0.392661	1.725346
0.39791	1.722157
0.403229	1.719096
0.408619	1.716154
0.414081	1.713327
0.419617	1.710609
0.425226	1.707994
0.43091	1.705477
0.43667	1.703054
0.442508	1.70072
0.448423	1.698472
0.454417	1.696304
0.460492	1.694215
0.466647	1.692199
0.472885	1.690255
0.479206	1.688379
0.485612	1.686567
0.492104	1.684818
0.498682	1.683129
0.505348	1.681496
0.512103	1.679919
0.518949	1.678395
0.525886	1.676921
0.532916	1.675495
0.54004	1.674117
0.547259	1.672783
0.554574	1.671492
0.561987	1.670243
0.5695	1.669034
0.577113	1.667863
0.584827	1.66673
0.592645	1.665632
0.600567	1.664568
0.608595	1.663538
0.616731	1.66254
0.624975	1.661572
0.633329	1.660634
0.641795	1.659725
0.650374	1.658844
0.659068	1.657989
0.667878	1.65716
0.676806	1.656356
0.685854	1.655577
0.695022	1.65482
0.704313	1.654086
0.713727	1.653374
0.723268	1.652683
0.732937	1.652012
0.742734	1.651361
0.752663	1.650729
0.762724	1.650115
0.77292	1.649519
0.783252	1.648941
0.793722	1.648379
0.804332	1.647833
0.815084	1.647303
0.82598	1.646789
0.837021	1.646288
0.84821	1.645803
0.859548	1.645331
0.871038	1.644872
0.882682	1.644426
0.894481	1.643993
0.906438	1.643572
0.918555	1.643163
0.930834	1.642765
0.943277	1.642378
0.955886	1.642002
0.968664	1.641637
0.981613	1.641282
0.994735	1.640936
1.00803	1.6406
1.02151	1.640273
1.03516	1.639955
1.049	1.639646
1.06302	1.639346
1.07723	1.639053
1.09163	1.638769
1.10622	1.638492
1.12101	1.638223
1.136	1.637961
1.15118	1.637706
1.16657	1.637457
1.18217	1.637216
1.19797	1.636981
1.21398	1.636752
1.23021	1.636529
1.24665	1.636312
1.26332	1.636101
1.28021	1.635896
1.29732	1.635696
1.31466	1.635501
1.33224	1.635311
1.35004	1.635126
1.36809	1.634946
1.38638	1.634771
1.40491	1.6346
1.42369	1.634433
1.44272	1.634271
1.46201	1.634113
1.48155	1.633959
1.50136	1.633809
1.52143	1.633663
1.54176	1.63352
1.56237	1.633381
1.58326	1.633245
1.60442	1.633113
1.62587	1.632983
1.6476	1.632858
1.66963	1.632735
1.69195	1.632615
1.71456	1.632498
1.73748	1.632383
1.76071	1.632272
1.78425	1.632163
1.8081	1.632057
1.83227	1.631953
1.85676	1.631851
1.88158	1.631752
1.90673	1.631655
1.93222	1.63156
1.95805	1.631467
1.98422	1.631377
2.01075	1.631288
2.03763	1.631201
2.06487	1.631116
2.09247	1.631033
2.12044	1.630951
2.14878	1.630871
2.17751	1.630793
2.20662	1.630716
2.23611	1.630641
2.266	1.630567
2.2963	1.630494
2.32699	1.630423
2.3581	1.630353
2.38962	1.630284
2.42156	1.630216
2.45393	1.63015
2.48674	1.630084
2.51998	1.63002
2.55366	1.629956
2.5878	1.629894
2.62239	1.629832
2.65745	1.629771
2.69297	1.629711
2.72897	1.629652
2.76545	1.629593
2.80242	1.629535
2.83988	1.629478
2.87784	1.629421
2.91631	1.629365
2.95529	1.629309
2.9948	1.629254
3.03483	1.629199
3.0754	1.629145
3.11651	1.629091
3.15817	1.629037
3.20039	1.628983
3.24317	1.62893
3.28652	1.628877
3.33045	1.628824
3.37497	1.628771
3.42009	1.628718
3.46581	1.628665
3.51214	1.628612
3.55909	1.628559
3.60666	1.628506
3.65487	1.628453
3.70373	1.6284
3.75324	1.628347
3.80341	1.628293
3.85426	1.628239
3.90578	1.628185
3.95799	1.62813
4.0109	1.628075
4.06451	1.62802
4.11884	1.627964
4.1739	1.627908
4.2297	1.627851
4.28624	1.627793
4.34354	1.627735
4.4016	1.627676
4.46044	1.627617
4.52006	1.627557
4.58048	1.627496
4.64171	1.627434
4.70376	1.627371
4.76664	1.627307
4.83036	1.627242
4.89493	1.627177
4.96036	1.62711
5.02667	1.627042
5.09386	1.626973
5.16196	1.626902
5.23096	1.626831
5.30088	1.626758
5.37174	1.626684
5.44355	1.626608
5.51632	1.626531
5.59006	1.626452
5.66478	1.626372
5.74051	1.62629
5.81724	1.626206
5.89501	1.626121
5.97381	1.626033
6.05366	1.625944
6.13459	1.625853
6.21659	1.62576
6.29969	1.625665
6.3839	1.625567
6.46924	1.625468
6.55572	1.625366
6.64335	1.625261
6.73216	1.625154
6.82215	1.625045
6.91334	1.624933
7.00576	1.624818
7.09941	1.624701
7.19431	1.62458
7.29048	1.624457
7.38794	1.624331
7.48669	1.624201
7.58677	1.624068
7.68819	1.623932
7.79096	1.623793
7.89511	1.62365
8.00065	1.623503
8.10759	1.623352
8.21597	1.623198
8.3258	1.62304
8.4371	1.622877
8.54988	1.62271
8.66417	1.622539
8.77999	1.622364
8.89736	1.622184
9.01629	1.621999
9.13682	1.621809
9.25895	1.621614
9.38272	1.621414
9.50815	1.621208
9.63525	1.620997
9.76405	1.620781
9.89457	1.620558
10.0268	1.62033
10.1609	1.620095
10.2967	1.619855
10.4343	1.619607
10.5738	1.619353
10.7152	1.619092
10.8584	1.618823
11.0036	1.618548
11.1506	1.618264
11.2997	1.617973
11.4507	1.617674
11.6038	1.617367
11.7589	1.617051
11.9161	1.616727
12.0754	1.616393
12.2368	1.61605
12.4004	1.615698
12.5662	1.615336
12.7341	1.614963
12.9044	1.61458
13.0769	1.614187
13.2517	1.613782
13.4288	1.613366
13.6083	1.612938
13.7902	1.612498
13.9746	1.612045
14.1614	1.61158
14.3507	1.611101
14.5425	1.610609
14.7369	1.610102
14.9339	1.609581
15.1335	1.609045
15.3358	1.608494
15.5408	1.607927
15.7486	1.607343
15.9591	1.606742
16.1724	1.606124
16.3886	1.605488
16.6077	1.604833
16.8297	1.604159
17.0547	1.603465
17.2827	1.602751
17.5137	1.602016
17.7478	1.601258
17.985	1.600479
18.2255	1.599676
18.4691	1.598849
18.716	1.597997
18.9662	1.59712
19.2197	1.596216
19.4766	1.595285
19.737	1.594325
20.0008	1.593337
20.2682	1.592318
20.5391	1.591268
20.8137	1.590185
21.0919	1.589069
21.3738	1.587918
21.6596	1.586731
21.9491	1.585507
22.2425	1.584245
22.5398	1.582943
22.8411	1.581599
23.1465	1.580213
23.4559	1.578782
23.7694	1.577305
24.0872	1.57578
24.4091	1.574206
24.7354	1.57258
25.0661	1.5709
25.4012	1.569165
25.7407	1.567372
26.0848	1.565519
26.4335	1.563604
26.7868	1.561624
27.1449	1.559576
27.5078	1.557458
27.8755	1.555266
28.2481	1.552998
28.6257	1.55065
29.0084	1.548219
29.3961	1.545701
29.7891	1.543093
30.1873	1.54039
30.5908	1.537588
30.9998	1.534683
31.4141	1.531669
31.8341	1.528542
32.2596	1.525295
32.6909	1.521924
33.1278	1.518422
33.5707	1.514783
34.0194	1.510999
34.4742	1.507063
34.935	1.502967
35.402	1.498702
35.8753	1.494259
36.3548	1.489628
36.8408	1.484798
37.3333	1.479758
37.8323	1.474496
38.3381	1.468997
38.8505	1.463246
39.3699	1.457229
39.8962	1.450928
40.4295	1.444323
40.9699	1.437393
41.5176	1.430117
42.0726	1.422468
42.635	1.41442
43.2049	1.405941
43.7825	1.396997
44.3677	1.387551
44.9608	1.37756
45.5618	1.366975
46.1709	1.355744
46.7881	1.343805
47.4135	1.331088
48.0473	1.317514
48.6896	1.30299
49.3404	1.287409
50	1.270646

Optical transmission calculator

Free-standing sample in vacuum, normal incidence

Transmittance T: —
Reflectance R: —

Fresnel reflection calculator

R_p: —
R_s: —
R = (R_p+R_s)/2: —
Phase φ_p: —
Phase φ_s: —
Brewster angle θ_B: —
Critical angle θ_C: —

KI (Potassium iodide): all datasets

Li 1976: n 0.25–50 µm n 0.25–50 µm default

About KI (Potassium iodide)

Potassium iodide (KI) is a salt that is often used in the field of optics as an infrared-transparent material, particularly in the mid-IR range. With good transmission properties and low-cost production, it finds applications in windows and prisms for spectroscopic applications. KI is highly soluble in water and hygroscopic, making it sensitive to moisture and requiring stringent storage conditions. One notable drawback of KI is its relatively low mechanical strength, making it less ideal for applications requiring high durability. Nevertheless, its broad transmission range and high refractive index make it valuable for specific optical needs.

Potassium iodide - Wikipedia

More about KI (Potassium iodide) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/KI/nk/Li.yml
ID: ds_176b34402fb6
API: /v1/datasets/ds_176b34402fb6

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