Optical constants

Refractive index of KBr (Potassium bromide)

Li 1976: n 0.20–42 µm

Data: formula 1
Range: 0.2–42 µm
Licence: CC0-1.0

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.55995
Extinction coefficient k: 0

Permittivity ε₁: 2.43343
Permittivity ε₂: 0

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

Abbe number V_d: 33.645
Chromatic dispersion dn/dλ: -0.0842971 µm⁻¹

Group index n_g: 1.60948
Group velocity dispersion: 168.848 fs²/mm

Dispersion parameter D: -921.153 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

# KBr (Potassium bromide): Li 1976: n 0.20–42 µm
kbr = ls.fetch_refractiveindex("main", "KBr", "Li", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(kbr.range_nm)  # (200, 42000) nm
eps = kbr.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_4c1514fa6372/lightsmith"
kbr = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(kbr.source)  # citation and provenance travel with the data

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

# ... load kbr as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=kbr)],
    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_4c1514fa6372/lightsmith?model=drude_lorentz"
kbr_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 = 0.39408 + \frac{0.79221 λ^{2}}{λ^{2} - {0.146}^{2}} + \frac{0.01981 λ^{2}}{λ^{2} - {0.173}^{2}} + \frac{0.15587 λ^{2}}{λ^{2} - {0.187}^{2}} + \frac{0.17673 λ^{2}}{λ^{2} - {60.61}^{2}} + \frac{2.06217 λ^{2}}{λ^{2} - {87.72}^{2}}

Valid from 0.2 to 42.0 µm.

Coefficients as stored

C_i	Value
C1	0.39408
C2	0.79221
C3	0.146
C4	0.01981
C5	0.173
C6	0.15587
C7	0.187
C8	0.17673
C9	60.61
C10	2.06217
C11	87.72

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

KBr (Potassium bromide), Li 1976: n 0.20–42 µm: n and k versus wavelength
λ (µm)	n
0.2	2.099534
0.202698	2.039658
0.205433	1.993052
0.208205	1.955244
0.211014	1.923641
0.21386	1.896625
0.216746	1.873127
0.21967	1.852409
0.222634	1.833938
0.225637	1.817322
0.228681	1.802262
0.231767	1.788526
0.234894	1.77593
0.238063	1.764325
0.241274	1.753589
0.24453	1.743622
0.247829	1.73434
0.251172	1.725671
0.254561	1.717554
0.257995	1.709938
0.261476	1.702775
0.265004	1.696027
0.268579	1.689659
0.272203	1.683639
0.275875	1.67794
0.279597	1.672539
0.283369	1.667412
0.287192	1.662541
0.291067	1.657908
0.294994	1.653496
0.298974	1.649291
0.303007	1.64528
0.307095	1.64145
0.311238	1.637791
0.315438	1.634292
0.319693	1.630944
0.324006	1.627738
0.328378	1.624666
0.332808	1.621721
0.337298	1.618896
0.341849	1.616185
0.346461	1.613582
0.351135	1.61108
0.355872	1.608676
0.360674	1.606364
0.36554	1.60414
0.370471	1.601999
0.375469	1.599938
0.380535	1.597953
0.385669	1.59604
0.390872	1.594197
0.396146	1.592419
0.40149	1.590705
0.406907	1.589051
0.412397	1.587454
0.417961	1.585914
0.4236	1.584426
0.429315	1.582989
0.435107	1.5816
0.440977	1.580258
0.446926	1.578962
0.452956	1.577708
0.459067	1.576496
0.465261	1.575323
0.471538	1.574189
0.477899	1.573091
0.484347	1.572029
0.490881	1.571001
0.497504	1.570006
0.504216	1.569042
0.511019	1.568109
0.517913	1.567204
0.524901	1.566329
0.531982	1.56548
0.53916	1.564658
0.546434	1.563861
0.553806	1.563089
0.561277	1.56234
0.56885	1.561614
0.576525	1.56091
0.584303	1.560227
0.592186	1.559565
0.600175	1.558922
0.608272	1.558299
0.616479	1.557695
0.624796	1.557108
0.633226	1.556538
0.641769	1.555986
0.650427	1.55545
0.659202	1.554929
0.668096	1.554423
0.67711	1.553933
0.686245	1.553456
0.695503	1.552993
0.704887	1.552544
0.714397	1.552108
0.724035	1.551684
0.733803	1.551272
0.743703	1.550872
0.753737	1.550483
0.763906	1.550106
0.774212	1.549739
0.784657	1.549382
0.795244	1.549035
0.805973	1.548699
0.816846	1.548371
0.827867	1.548053
0.839036	1.547744
0.850356	1.547443
0.861828	1.547151
0.873456	1.546866
0.88524	1.54659
0.897183	1.546321
0.909287	1.54606
0.921555	1.545806
0.933988	1.545558
0.946589	1.545318
0.95936	1.545084
0.972303	1.544856
0.985421	1.544635
0.998716	1.544419
1.01219	1.54421
1.02585	1.544005
1.03969	1.543807
1.05371	1.543614
1.06793	1.543426
1.08234	1.543243
1.09694	1.543064
1.11174	1.542891
1.12674	1.542722
1.14194	1.542557
1.15735	1.542397
1.17296	1.542241
1.18878	1.542089
1.20482	1.541941
1.22108	1.541797
1.23755	1.541656
1.25425	1.541519
1.27117	1.541386
1.28832	1.541256
1.3057	1.541129
1.32332	1.541006
1.34117	1.540885
1.35926	1.540768
1.3776	1.540653
1.39619	1.540542
1.41503	1.540433
1.43412	1.540326
1.45346	1.540222
1.47307	1.540121
1.49295	1.540022
1.51309	1.539926
1.5335	1.539832
1.55419	1.539739
1.57516	1.539649
1.59641	1.539562
1.61795	1.539476
1.63978	1.539392
1.6619	1.53931
1.68432	1.539229
1.70705	1.539151
1.73008	1.539074
1.75342	1.538999
1.77708	1.538925
1.80105	1.538853
1.82535	1.538782
1.84998	1.538713
1.87494	1.538645
1.90023	1.538578
1.92587	1.538513
1.95185	1.538448
1.97818	1.538385
2.00487	1.538323
2.03192	1.538262
2.05934	1.538203
2.08712	1.538144
2.11528	1.538086
2.14382	1.538029
2.17274	1.537973
2.20205	1.537917
2.23176	1.537863
2.26187	1.537809
2.29239	1.537755
2.32331	1.537703
2.35466	1.537651
2.38643	1.537599
2.41862	1.537549
2.45125	1.537498
2.48433	1.537448
2.51784	1.537399
2.55181	1.53735
2.58624	1.537301
2.62113	1.537253
2.6565	1.537204
2.69234	1.537157
2.72866	1.537109
2.76547	1.537061
2.80278	1.537014
2.8406	1.536967
2.87892	1.53692
2.91776	1.536872
2.95713	1.536825
2.99702	1.536778
3.03746	1.536731
3.07844	1.536683
3.11997	1.536636
3.16206	1.536588
3.20472	1.53654
3.24796	1.536492
3.29178	1.536444
3.33619	1.536395
3.3812	1.536346
3.42682	1.536297
3.47305	1.536247
3.51991	1.536197
3.56739	1.536146
3.61552	1.536095
3.6643	1.536043
3.71374	1.53599
3.76384	1.535937
3.81462	1.535884
3.86609	1.535829
3.91825	1.535774
3.97111	1.535718
4.02469	1.535661
4.07899	1.535603
4.13402	1.535545
4.18979	1.535485
4.24632	1.535424
4.30361	1.535363
4.36167	1.5353
4.42051	1.535236
4.48015	1.535171
4.5406	1.535105
4.60186	1.535037
4.66394	1.534968
4.72687	1.534898
4.79064	1.534826
4.85527	1.534753
4.92078	1.534678
4.98716	1.534601
5.05445	1.534523
5.12264	1.534443
5.19175	1.534362
5.2618	1.534278
5.33279	1.534193
5.40473	1.534106
5.47765	1.534017
5.55155	1.533925
5.62645	1.533832
5.70236	1.533736
5.77929	1.533638
5.85726	1.533538
5.93629	1.533435
6.01638	1.533329
6.09755	1.533221
6.17981	1.533111
6.26319	1.532997
6.34769	1.532881
6.43333	1.532762
6.52012	1.53264
6.60809	1.532514
6.69724	1.532386
6.78759	1.532254
6.87917	1.532119
6.97198	1.53198
7.06604	1.531838
7.16137	1.531691
7.25799	1.531542
7.35591	1.531388
7.45515	1.53123
7.55573	1.531068
7.65767	1.530901
7.76099	1.53073
7.86569	1.530555
7.97181	1.530375
8.07936	1.53019
8.18837	1.53
8.29884	1.529805
8.4108	1.529604
8.52428	1.529399
8.63928	1.529187
8.75584	1.52897
8.87397	1.528747
8.99369	1.528518
9.11503	1.528283
9.238	1.528041
9.36264	1.527792
9.48895	1.527537
9.61697	1.527274
9.74672	1.527004
9.87822	1.526727
10.0115	1.526442
10.1466	1.526149
10.2835	1.525848
10.4222	1.525539
10.5628	1.525221
10.7053	1.524894
10.8497	1.524558
10.9961	1.524212
11.1445	1.523857
11.2948	1.523491
11.4472	1.523116
11.6017	1.522729
11.7582	1.522332
11.9168	1.521924
12.0776	1.521503
12.2405	1.521071
12.4057	1.520626
12.573	1.520169
12.7427	1.519699
12.9146	1.519215
13.0888	1.518717
13.2654	1.518205
13.4444	1.517678
13.6258	1.517135
13.8096	1.516577
13.9959	1.516003
14.1847	1.515412
14.3761	1.514803
14.5701	1.514177
14.7666	1.513533
14.9659	1.512869
15.1678	1.512186
15.3724	1.511483
15.5798	1.510759
15.79	1.510013
16.003	1.509245
16.2189	1.508454
16.4378	1.507639
16.6595	1.5068
16.8843	1.505936
17.1121	1.505045
17.3429	1.504128
17.5769	1.503182
17.8141	1.502208
18.0544	1.501203
18.298	1.500168
18.5448	1.499101
18.795	1.498001
19.0486	1.496867
19.3056	1.495697
19.5661	1.49449
19.83	1.493246
20.0976	1.491962
20.3687	1.490638
20.6435	1.489271
20.922	1.487861
21.2043	1.486405
21.4904	1.484902
21.7803	1.48335
22.0742	1.481748
22.372	1.480093
22.6738	1.478383
22.9797	1.476617
23.2898	1.474791
23.604	1.472905
23.9224	1.470954
24.2452	1.468937
24.5723	1.466852
24.9038	1.464694
25.2398	1.462461
25.5803	1.460151
25.9254	1.457759
26.2752	1.455282
26.6297	1.452717
26.989	1.45006
27.3531	1.447305
27.7221	1.44445
28.0961	1.441489
28.4752	1.438418
28.8593	1.435231
29.2487	1.431923
29.6433	1.428487
30.0432	1.424919
30.4486	1.42121
30.8594	1.417353
31.2757	1.413342
31.6977	1.409168
32.1253	1.404821
32.5587	1.400294
32.998	1.395575
33.4432	1.390653
33.8944	1.385517
34.3517	1.380155
34.8151	1.374552
35.2848	1.368693
35.7609	1.362562
36.2433	1.356141
36.7323	1.349412
37.2279	1.342352
37.7301	1.334938
38.2392	1.327145
38.7551	1.318944
39.2779	1.310303
39.8079	1.301188
40.3449	1.291559
40.8892	1.281371
41.4409	1.270576
42	1.259116

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: —

KBr (Potassium bromide): all datasets

Li 1976: n 0.20–42 µm n 0.2–42 µm default

About KBr (Potassium bromide)

Potassium bromide (KBr) is a salt commonly used in the form of a transparent crystal for a variety of optical applications. Its wide transmission range, extending from the ultraviolet into the far-infrared spectrum, makes it a popular choice for infrared spectroscopy. KBr is also used as a substrate material for specialized optical coatings. It is hygroscopic, meaning it readily absorbs moisture from the air, so care must be taken in its handling and storage to maintain its optical properties. It is not advisable for applications where it would be exposed to high moisture or extreme environmental conditions. Despite its hygroscopic nature, KBr is highly valued for its excellent transmission characteristics and is a staple in various optical and spectroscopic setups.

Potassium bromide - Wikipedia

More about KBr (Potassium bromide) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/KBr/nk/Li.yml
ID: ds_4c1514fa6372
API: /v1/datasets/ds_4c1514fa6372

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