At one wavelength

Refractive index n: 0.142228
Extinction coefficient k: 3.01987

Permittivity ε₁: -9.09941
Permittivity ε₂: 0.859024

Absorption coefficient α: 645828 cm⁻¹
Penetration depth δ = λ/(2πk): 30.968 nm

Abbe number V_d: —
Chromatic dispersion dn/dλ: -10.511 µm⁻¹

Group index n_g: 6.31849
Group velocity dispersion: — fs²/mm

Dispersion parameter D: — 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

# Au (Gold): Chen et al. 2025: n,k 0.210–0.600 µm
au = ls.fetch_refractiveindex("main", "Au", "Chen", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(au.range_nm)  # (210, 600) nm
eps = au.eps([355])  # 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_2d2b4825287b/lightsmith"
au = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(au.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (au/chen-2025).

# ... load au as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=au)],
    medium_index=1.0,
    wavelengths=ls.WavelengthRange(start_nm=400, stop_nm=600, 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"]).

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.

References

Z. Chen, S. Yang, Z. Xie, J. Hu, X. Zhang, Y. Xia, Y. Shen, H. Su, M. Xie, T. Christensen, Y. Yang. Broadband measurement of Feibelman’s quantum surface response functions. Proc. Natl. Acad. Sci. U.S.A. 122, e2501121122 (2025) (Numerical data kindly provided by Zeling Chen)

doi:10.1073/pnas.2501121122 Broadband measurement of Feibelman’s quantum surface response functions, Proceedings of the National Academy of Sciences (2025)

Cite

Zeling Chen et al.. Broadband measurement of Feibelman’s quantum surface response functions. Proceedings of the National Academy of Sciences, 122, e2501121122 (2025), doi:10.1073/pnas.2501121122; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)

Data

391 rows as published

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

Au (Gold), Chen et al. 2025: n,k 0.210–0.600 µm: n and k versus wavelength
λ (µm)	n	k
0.21	1.367112	1.452925
0.211	1.364514	1.458807
0.212	1.372025	1.46138
0.213	1.379379	1.459553
0.214	1.386134	1.462659
0.215	1.392143	1.461447
0.216	1.380166	1.471833
0.217	1.381091	1.480652
0.218	1.388826	1.487883
0.219	1.393415	1.482122
0.22	1.39335	1.49273
0.221	1.393087	1.505854
0.222	1.390398	1.510202
0.223	1.390131	1.518864
0.224	1.387286	1.537253
0.225	1.388683	1.547942
0.226	1.395075	1.563094
0.227	1.395623	1.579299
0.228	1.395635	1.585182
0.229	1.391209	1.591168
0.23	1.385358	1.599302
0.231	1.398196	1.603796
0.232	1.396494	1.598107
0.233	1.388041	1.604801
0.234	1.392818	1.613049
0.235	1.40566	1.61519
0.236	1.408854	1.621376
0.237	1.405365	1.629226
0.238	1.409908	1.628317
0.239	1.403182	1.637907
0.24	1.406507	1.644393
0.241	1.406107	1.645774
0.242	1.402621	1.656864
0.243	1.405771	1.662979
0.244	1.408093	1.667339
0.245	1.410908	1.678217
0.246	1.412861	1.687343
0.247	1.416482	1.695761
0.248	1.422868	1.698886
0.249	1.420378	1.702927
0.25	1.415759	1.713777
0.251	1.422886	1.71984
0.252	1.423433	1.72923
0.253	1.4291	1.73928
0.254	1.439467	1.739091
0.255	1.444174	1.745526
0.256	1.447678	1.756165
0.257	1.451919	1.765101
0.258	1.462317	1.772259
0.259	1.469467	1.782325
0.26	1.473032	1.786993
0.261	1.47573	1.798567
0.262	1.484505	1.809435
0.263	1.499444	1.814954
0.264	1.509254	1.818473
0.265	1.518665	1.81982
0.266	1.528561	1.83303
0.267	1.533974	1.835988
0.268	1.539857	1.842531
0.269	1.55088	1.845196
0.27	1.559032	1.84837
0.271	1.562889	1.857946
0.272	1.573257	1.866766
0.273	1.569328	1.86618
0.274	1.571209	1.869123
0.275	1.59687	1.84707
0.276	1.590314	1.87217
0.277	1.6037	1.873528
0.278	1.607148	1.876398
0.279	1.610119	1.890035
0.28	1.630084	1.860755
0.281	1.627408	1.878176
0.282	1.635879	1.895685
0.283	1.642714	1.89597
0.284	1.64515	1.900396
0.285	1.657149	1.91039
0.286	1.653855	1.919184
0.287	1.650762	1.9233
0.288	1.662801	1.906904
0.289	1.641794	1.961766
0.29	1.67243	1.950611
0.291	1.703001	1.918003
0.292	1.658373	1.963106
0.293	1.657864	1.95155
0.294	1.665223	1.96022
0.295	1.683118	1.953736
0.296	1.683267	1.954853
0.297	1.662331	1.977437
0.298	1.667981	1.97393
0.299	1.658975	1.98677
0.3	1.661096	1.993363
0.301	1.666139	1.986765
0.302	1.655643	1.991217
0.303	1.669013	1.984783
0.304	1.675879	1.967959
0.305	1.650953	1.982234
0.306	1.657038	1.984055
0.307	1.670117	1.966955
0.308	1.668954	1.972289
0.309	1.684321	1.937855
0.31	1.667674	1.939479
0.311	1.660446	1.970168
0.312	1.671262	1.957507
0.313	1.679998	1.954124
0.314	1.698256	1.971043
0.315	1.70281	1.956819
0.316	1.716775	1.954545
0.317	1.699332	1.956428
0.318	1.719841	1.961743
0.319	1.723637	1.973683
0.32	1.727041	1.964191
0.321	1.727593	1.944158
0.322	1.726906	1.964177
0.323	1.735575	1.951244
0.324	1.72718	1.998777
0.325	1.717887	1.967012
0.326	1.704759	1.971533
0.327	1.728862	1.972268
0.328	1.749908	1.962793
0.329	1.74144	1.965924
0.33	1.739885	1.939863
0.331	1.733952	1.946452
0.332	1.743054	1.947798
0.333	1.754266	1.936282
0.334	1.743143	1.935006
0.335	1.725914	1.939622
0.336	1.729949	1.941454
0.337	1.737543	1.950494
0.338	1.795074	1.88314
0.339	1.733111	1.965444
0.34	1.710431	1.965858
0.341	1.774777	1.882031
0.342	1.699085	1.967191
0.343	1.721758	1.912063
0.344	1.741204	1.856895
0.345	1.729599	1.897032
0.346	1.715317	1.889292
0.347	1.712423	1.913841
0.348	1.710631	1.912217
0.349	1.699055	1.891975
0.35	1.70862	1.88773
0.351	1.703155	1.866835
0.352	1.688169	1.888256
0.353	1.671802	1.909747
0.354	1.682215	1.880302
0.355	1.664453	1.870037
0.356	1.649893	1.920604
0.357	1.652544	1.884549
0.358	1.635831	1.91853
0.359	1.629262	1.93643
0.36	1.626199	1.905701
0.361	1.621759	1.906305
0.362	1.607649	1.911066
0.363	1.617554	1.91141
0.364	1.593151	1.914982
0.365	1.563041	1.925248
0.366	1.579472	1.916189
0.367	1.578829	1.919114
0.368	1.580896	1.925
0.369	1.553934	1.928706
0.37	1.562264	1.917243
0.371	1.518987	1.957315
0.372	1.527049	1.93832
0.373	1.564	1.914542
0.374	1.505785	1.949788
0.375	1.547413	1.93987
0.376	1.52852	1.930936
0.377	1.519903	1.939346
0.378	1.542641	1.935217
0.379	1.524207	1.953577
0.38	1.522485	1.953461
0.381	1.492528	1.972401
0.382	1.498394	1.952701
0.383	1.514888	1.925497
0.384	1.520638	1.956345
0.385	1.526472	1.983456
0.386	1.517357	1.962572
0.387	1.500963	1.965799
0.388	1.549	1.952198
0.389	1.502474	1.982782
0.39	1.51494	1.983553
0.391	1.546379	1.95714
0.392	1.524007	1.97215
0.393	1.511446	1.980449
0.394	1.522059	1.978612
0.395	1.5351	1.982865
0.396	1.53753	1.978262
0.397	1.51202	1.971768
0.398	1.513434	1.981896
0.399	1.524238	1.982273
0.4	1.536707	1.980726
0.401	1.546037	1.972885
0.402	1.536113	1.998781
0.403	1.513538	1.973063
0.404	1.559149	1.958855
0.405	1.555926	1.96669
0.406	1.494778	1.98081
0.407	1.535301	1.977791
0.408	1.533732	1.965501
0.409	1.522427	1.978472
0.41	1.517017	1.989812
0.411	1.522251	1.984052
0.412	1.525241	1.966621
0.413	1.520296	1.963616
0.414	1.533869	1.969162
0.415	1.520885	1.979331
0.416	1.503729	1.964886
0.417	1.525453	1.964392
0.418	1.529215	1.968672
0.419	1.521503	1.954923
0.42	1.518955	1.969168
0.421	1.519799	1.984596
0.422	1.522599	1.98458
0.423	1.511682	2.000481
0.424	1.522856	1.985799
0.425	1.530004	1.955877
0.426	1.523352	1.964896
0.427	1.523422	1.966172
0.428	1.513687	1.977208
0.429	1.498567	1.987863
0.43	1.501425	1.972396
0.431	1.491314	1.968828
0.432	1.489206	1.9635
0.433	1.489632	1.978617
0.434	1.479708	1.987537
0.435	1.483994	1.965987
0.436	1.509576	1.970367
0.437	1.48569	1.983349
0.438	1.469436	1.969238
0.439	1.456921	1.967861
0.44	1.454283	1.973089
0.441	1.451788	1.972317
0.442	1.456248	1.963304
0.443	1.4514	1.957982
0.444	1.431631	1.962301
0.445	1.441385	1.959955
0.446	1.420656	1.94937
0.447	1.426154	1.942075
0.448	1.433911	1.9488
0.449	1.418843	1.947305
0.45	1.414531	1.939655
0.451	1.422495	1.936092
0.452	1.410597	1.923568
0.453	1.387854	1.932477
0.454	1.393643	1.934227
0.455	1.388504	1.922621
0.456	1.370645	1.924857
0.457	1.372256	1.914892
0.458	1.382257	1.913333
0.459	1.371471	1.913829
0.46	1.351194	1.906056
0.461	1.348216	1.902248
0.462	1.353535	1.904713
0.463	1.345613	1.898617
0.464	1.33679	1.895565
0.465	1.328071	1.903639
0.466	1.310949	1.91158
0.467	1.305404	1.899094
0.468	1.306642	1.890578
0.469	1.2951	1.884494
0.47	1.296003	1.874108
0.471	1.276857	1.866006
0.472	1.271419	1.870505
0.473	1.259808	1.872061
0.474	1.25118	1.868743
0.475	1.235785	1.872382
0.476	1.232429	1.873234
0.477	1.212361	1.865436
0.478	1.190011	1.861587
0.479	1.187347	1.856785
0.48	1.166899	1.857621
0.481	1.160663	1.856422
0.482	1.141524	1.856856
0.483	1.131284	1.859216
0.484	1.10139	1.858736
0.485	1.08026	1.863979
0.486	1.078619	1.86118
0.487	1.05291	1.884603
0.488	1.038428	1.881877
0.489	1.02766	1.835363
0.49	1.004041	1.860142
0.491	0.988525	1.874919
0.492	0.967551	1.871867
0.493	0.951157	1.873351
0.494	0.926173	1.869956
0.495	0.905022	1.877778
0.496	0.887432	1.883514
0.497	0.867498	1.890237
0.498	0.840344	1.89695
0.499	0.815063	1.905257
0.5	0.800133	1.918239
0.501	0.776558	1.927548
0.502	0.757693	1.932924
0.503	0.73486	1.94105
0.504	0.716178	1.945941
0.505	0.704604	1.956632
0.506	0.694258	1.971615
0.507	0.674173	1.982285
0.508	0.656376	1.993841
0.509	0.651703	2.009845
0.51	0.641713	2.023755
0.511	0.62426	2.040945
0.512	0.60596	2.048621
0.513	0.595986	2.057477
0.514	0.584861	2.079073
0.515	0.574611	2.087266
0.516	0.564166	2.11449
0.517	0.556036	2.131982
0.518	0.548462	2.136691
0.519	0.542357	2.15542
0.52	0.529535	2.168157
0.521	0.519958	2.186135
0.522	0.515606	2.199553
0.523	0.507399	2.217379
0.524	0.501121	2.235009
0.525	0.491843	2.244555
0.526	0.485201	2.265478
0.527	0.47794	2.279041
0.528	0.478103	2.294509
0.529	0.470893	2.312222
0.53	0.461867	2.334006
0.531	0.470988	2.364397
0.532	0.460657	2.374575
0.533	0.446648	2.392567
0.534	0.444937	2.422941
0.535	0.436831	2.433318
0.536	0.431715	2.453456
0.537	0.427565	2.472678
0.538	0.42994	2.483544
0.539	0.428064	2.505164
0.54	0.41095	2.517595
0.541	0.405998	2.532973
0.542	0.397605	2.54367
0.543	0.395139	2.561499
0.544	0.388715	2.577771
0.545	0.386811	2.593686
0.546	0.379481	2.610084
0.547	0.369619	2.623452
0.548	0.354669	2.628127
0.549	0.355874	2.644963
0.55	0.355427	2.664421
0.551	0.348109	2.675228
0.552	0.346136	2.69686
0.553	0.335241	2.696108
0.554	0.336747	2.72203
0.555	0.336394	2.743046
0.556	0.325055	2.750535
0.557	0.311579	2.762722
0.558	0.304419	2.768689
0.559	0.298565	2.788549
0.56	0.294205	2.801612
0.561	0.285051	2.815175
0.562	0.284579	2.833612
0.563	0.271062	2.82257
0.564	0.263405	2.838818
0.565	0.262081	2.858953
0.566	0.26131	2.861961
0.567	0.259868	2.876276
0.568	0.2483	2.877804
0.569	0.235896	2.865905
0.57	0.235341	2.876576
0.571	0.221938	2.878785
0.572	0.216571	2.878787
0.573	0.214663	2.896019
0.574	0.209049	2.907246
0.575	0.203091	2.910951
0.576	0.192928	2.914569
0.577	0.195663	2.921369
0.578	0.186449	2.930512
0.579	0.1826	2.945969
0.58	0.175958	2.951806
0.581	0.177474	2.94025
0.582	0.182247	2.95734
0.583	0.165868	2.984605
0.584	0.15377	2.99477
0.585	0.156117	2.999387
0.586	0.149822	3.013794
0.587	0.148535	3.019085
0.588	0.138024	3.020399
0.589	0.128782	3.045793
0.59	0.124775	3.058071
0.591	0.128519	3.071412
0.592	0.126213	3.079995
0.593	0.127671	3.073548
0.594	0.121663	3.08727
0.595	0.11149	3.07138
0.596	0.106001	3.099089
0.597	0.093656	3.133691
0.598	0.093516	3.137468
0.599	0.090323	3.133125
0.6	0.087845	3.131318

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: —

Plot