Optical constants

Refractive index of KH₂PO₄ (Potassium dihydrogen phosphate, KDP)

Zernike et al. 1964: n(o) 0.214–1.53 µm

Data: formula 4
Range: 0.2138–1.529 µm
Temperature: 297.95 K
Optical axis: o
Licence: CC0-1.0

Uniaxial crystal, axes: oe

Axis Log x Log y

Click the plot to set the calculator wavelength.

At one wavelength

Refractive index n: 1.50944
Extinction coefficient k: 0

Permittivity ε₁: 2.2784
Permittivity ε₂: 0

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

Abbe number V_d: 56.299
Chromatic dispersion dn/dλ: -0.0482416 µm⁻¹

Group index n_g: 1.53778
Group velocity dispersion: 60.2865 fs²/mm

Dispersion parameter D: -328.895 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

# KH2PO4 (Potassium dihydrogen phosphate, KDP): Zernike et al. 1964: n(o) 0.214–1.53 µm
kh2po4 = ls.fetch_refractiveindex("main", "KH2PO4", "Zernike-o", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(kh2po4.range_nm)  # (213.8, 1529) nm
eps = kh2po4.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_cd6480e31c92/lightsmith"
kh2po4 = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(kh2po4.source)  # citation and provenance travel with the data

Any dataset here, as the library's Tabulated material (kh2po4/zernike-1964-o).

# ... load kh2po4 as above, then:
sim = ls.Simulation(
    particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=kh2po4)],
    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"]).

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

RefractiveIndex.INFO (formula 4), λ in µm

n^{2} = 2.259276 + \frac{13.00522 λ^{2.0}}{λ^{2} - {400.0}^{1.0}} + \frac{0.01008956 λ^{0.0}}{λ^{2} - {0.0129426}^{1.0}}

Valid from 0.2138 to 1.529 µm.

Coefficients as stored

C_i	Value
C1	2.259276
C2	13.00522
C3	2.0
C4	400.0
C5	1.0
C6	0.01008956
C7	0.0
C8	0.0129426
C9	1.0

Comments and conditions

24.8 °C. Ordinary ray (o).

Conditions

temperature: 297.95 K
direction: o

References

F. Zernike, Jr. Refractive indices of ammonium dihydrogen phosphate and potassium dihydrogen phosphate between 2000 Å and 1.5 µ. J. Opt. Soc. Am. 54, 1215-1219 (1964).

doi:10.1364/josa.54.001215 Refractive Indices of Ammonium Dihydrogen Phosphate and Potassium Dihydrogen Phosphate between 2000 Å and 15 μ, Journal of the Optical Society of America (1964)

Cite

Frits Zernike. Refractive Indices of Ammonium Dihydrogen Phosphate and Potassium Dihydrogen Phosphate between 2000 Å and 15 μ. Journal of the Optical Society of America, 54, 1215 (1964), doi:10.1364/josa.54.001215; 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

KH2PO4 (Potassium dihydrogen phosphate, KDP), Zernike et al. 1964: n(o) 0.214–1.53 µm: n and k versus wavelength
λ (µm)	n
0.2138	1.60178
0.214857	1.600465
0.215919	1.59917
0.216986	1.597898
0.218059	1.596646
0.219136	1.595414
0.22022	1.594202
0.221308	1.59301
0.222402	1.591836
0.223501	1.590681
0.224606	1.589545
0.225716	1.588426
0.226832	1.587325
0.227953	1.586241
0.22908	1.585174
0.230212	1.584123
0.23135	1.583088
0.232493	1.582069
0.233643	1.581066
0.234797	1.580077
0.235958	1.579104
0.237124	1.578145
0.238296	1.5772
0.239474	1.57627
0.240658	1.575353
0.241847	1.574449
0.243043	1.573559
0.244244	1.572682
0.245451	1.571817
0.246665	1.570965
0.247884	1.570125
0.249109	1.569298
0.25034	1.568481
0.251578	1.567677
0.252821	1.566884
0.254071	1.566102
0.255327	1.565331
0.256589	1.564571
0.257857	1.563821
0.259132	1.563082
0.260412	1.562352
0.2617	1.561633
0.262993	1.560924
0.264293	1.560224
0.265599	1.559534
0.266912	1.558853
0.268232	1.558182
0.269557	1.557519
0.27089	1.556865
0.272229	1.55622
0.273574	1.555583
0.274927	1.554955
0.276285	1.554335
0.277651	1.553723
0.279023	1.553119
0.280403	1.552523
0.281789	1.551935
0.283181	1.551354
0.284581	1.550781
0.285988	1.550215
0.287401	1.549657
0.288822	1.549105
0.29025	1.548561
0.291684	1.548023
0.293126	1.547492
0.294575	1.546968
0.296031	1.54645
0.297494	1.545939
0.298965	1.545434
0.300442	1.544936
0.301927	1.544443
0.30342	1.543957
0.304919	1.543476
0.306427	1.543002
0.307941	1.542533
0.309463	1.54207
0.310993	1.541612
0.31253	1.54116
0.314075	1.540714
0.315627	1.540272
0.317187	1.539836
0.318755	1.539406
0.320331	1.53898
0.321914	1.538559
0.323505	1.538143
0.325104	1.537732
0.326711	1.537326
0.328326	1.536925
0.329949	1.536528
0.33158	1.536136
0.333219	1.535748
0.334866	1.535365
0.336521	1.534986
0.338184	1.534612
0.339856	1.534242
0.341536	1.533876
0.343224	1.533514
0.34492	1.533156
0.346625	1.532802
0.348339	1.532452
0.35006	1.532106
0.351791	1.531764
0.35353	1.531425
0.355277	1.531091
0.357033	1.53076
0.358798	1.530432
0.360571	1.530109
0.362353	1.529788
0.364145	1.529471
0.365944	1.529158
0.367753	1.528848
0.369571	1.528541
0.371398	1.528238
0.373233	1.527937
0.375078	1.52764
0.376932	1.527346
0.378795	1.527055
0.380668	1.526768
0.382549	1.526483
0.38444	1.526201
0.38634	1.525922
0.38825	1.525646
0.390169	1.525372
0.392098	1.525102
0.394036	1.524834
0.395983	1.524569
0.397941	1.524307
0.399907	1.524047
0.401884	1.52379
0.403871	1.523535
0.405867	1.523283
0.407873	1.523033
0.409889	1.522786
0.411915	1.522541
0.413951	1.522299
0.415997	1.522059
0.418053	1.521821
0.42012	1.521586
0.422196	1.521352
0.424283	1.521121
0.42638	1.520893
0.428488	1.520666
0.430606	1.520441
0.432734	1.520219
0.434873	1.519999
0.437023	1.51978
0.439183	1.519564
0.441353	1.519349
0.443535	1.519137
0.445727	1.518926
0.44793	1.518718
0.450145	1.518511
0.45237	1.518306
0.454606	1.518103
0.456853	1.517901
0.459111	1.517701
0.46138	1.517504
0.46366	1.517307
0.465952	1.517113
0.468255	1.51692
0.47057	1.516728
0.472896	1.516539
0.475233	1.516351
0.477582	1.516164
0.479943	1.515979
0.482315	1.515795
0.484699	1.515613
0.487095	1.515433
0.489503	1.515253
0.491922	1.515076
0.494354	1.514899
0.496797	1.514724
0.499253	1.51455
0.50172	1.514378
0.5042	1.514207
0.506692	1.514037
0.509197	1.513869
0.511714	1.513701
0.514243	1.513535
0.516785	1.513371
0.519339	1.513207
0.521906	1.513044
0.524486	1.512883
0.527078	1.512723
0.529684	1.512563
0.532302	1.512405
0.534933	1.512248
0.537577	1.512092
0.540234	1.511937
0.542904	1.511784
0.545588	1.511631
0.548285	1.511479
0.550995	1.511328
0.553718	1.511178
0.556455	1.511028
0.559206	1.51088
0.56197	1.510733
0.564747	1.510586
0.567539	1.510441
0.570344	1.510296
0.573163	1.510152
0.575996	1.510009
0.578843	1.509866
0.581704	1.509724
0.58458	1.509584
0.587469	1.509443
0.590373	1.509304
0.593291	1.509165
0.596224	1.509027
0.599171	1.50889
0.602132	1.508753
0.605108	1.508617
0.608099	1.508482
0.611105	1.508347
0.614126	1.508212
0.617161	1.508079
0.620212	1.507946
0.623277	1.507813
0.626358	1.507681
0.629454	1.50755
0.632565	1.507419
0.635692	1.507288
0.638834	1.507158
0.641992	1.507029
0.645165	1.5069
0.648354	1.506771
0.651559	1.506643
0.654779	1.506515
0.658016	1.506388
0.661268	1.506261
0.664537	1.506134
0.667821	1.506008
0.671122	1.505882
0.674439	1.505756
0.677773	1.505631
0.681123	1.505506
0.68449	1.505381
0.687873	1.505256
0.691273	1.505132
0.69469	1.505008
0.698124	1.504884
0.701574	1.504761
0.705042	1.504638
0.708527	1.504514
0.712029	1.504392
0.715549	1.504269
0.719085	1.504146
0.72264	1.504024
0.726212	1.503901
0.729801	1.503779
0.733408	1.503657
0.737034	1.503535
0.740677	1.503413
0.744338	1.503291
0.748017	1.503169
0.751714	1.503047
0.75543	1.502926
0.759164	1.502804
0.762916	1.502682
0.766687	1.50256
0.770477	1.502439
0.774285	1.502317
0.778112	1.502195
0.781958	1.502073
0.785823	1.501951
0.789707	1.501829
0.793611	1.501706
0.797533	1.501584
0.801476	1.501462
0.805437	1.501339
0.809418	1.501216
0.813419	1.501093
0.81744	1.50097
0.82148	1.500847
0.82554	1.500724
0.829621	1.5006
0.833722	1.500476
0.837843	1.500352
0.841984	1.500227
0.846146	1.500103
0.850328	1.499978
0.854531	1.499852
0.858755	1.499727
0.863	1.499601
0.867265	1.499475
0.871552	1.499348
0.87586	1.499221
0.880189	1.499094
0.88454	1.498966
0.888912	1.498838
0.893306	1.49871
0.897721	1.498581
0.902158	1.498452
0.906617	1.498322
0.911099	1.498192
0.915602	1.498061
0.920128	1.49793
0.924676	1.497798
0.929246	1.497666
0.933839	1.497533
0.938455	1.4974
0.943094	1.497266
0.947755	1.497131
0.95244	1.496996
0.957148	1.496861
0.961879	1.496725
0.966633	1.496588
0.971411	1.49645
0.976213	1.496312
0.981038	1.496173
0.985887	1.496034
0.99076	1.495894
0.995657	1.495753
1.00058	1.495611
1.00552	1.495469
1.01049	1.495326
1.01549	1.495182
1.02051	1.495038
1.02555	1.494892
1.03062	1.494746
1.03572	1.494599
1.04084	1.494451
1.04598	1.494302
1.05115	1.494153
1.05635	1.494002
1.06157	1.493851
1.06681	1.493698
1.07209	1.493545
1.07739	1.493391
1.08271	1.493236
1.08806	1.49308
1.09344	1.492922
1.09885	1.492764
1.10428	1.492605
1.10974	1.492445
1.11522	1.492284
1.12073	1.492121
1.12627	1.491958
1.13184	1.491793
1.13743	1.491628
1.14306	1.491461
1.14871	1.491293
1.15438	1.491124
1.16009	1.490953
1.16582	1.490782
1.17159	1.490609
1.17738	1.490435
1.1832	1.49026
1.18905	1.490083
1.19492	1.489905
1.20083	1.489726
1.20676	1.489545
1.21273	1.489363
1.21872	1.48918
1.22475	1.488995
1.2308	1.488809
1.23688	1.488622
1.243	1.488433
1.24914	1.488242
1.25532	1.488051
1.26152	1.487857
1.26776	1.487662
1.27402	1.487466
1.28032	1.487268
1.28665	1.487068
1.29301	1.486867
1.2994	1.486664
1.30582	1.486459
1.31228	1.486253
1.31876	1.486045
1.32528	1.485835
1.33183	1.485624
1.33842	1.485411
1.34503	1.485196
1.35168	1.484979
1.35836	1.48476
1.36507	1.48454
1.37182	1.484318
1.3786	1.484094
1.38542	1.483867
1.39226	1.483639
1.39915	1.483409
1.40606	1.483177
1.41301	1.482943
1.42	1.482707
1.42702	1.482469
1.43407	1.482229
1.44116	1.481987
1.44828	1.481742
1.45544	1.481496
1.46263	1.481247
1.46986	1.480996
1.47713	1.480742
1.48443	1.480487
1.49177	1.480229
1.49914	1.479969
1.50655	1.479706
1.514	1.479442
1.52148	1.479174
1.529	1.478905

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: —

KH₂PO₄ (Potassium dihydrogen phosphate, KDP): all datasets

About KH2PO4 (Potassium dihydrogen phosphate, KDP)

Potassium dihydrogen phosphate, commonly known as KDP (KH₂PO₄), is a widely used nonlinear optical crystal, especially esteemed for its applications in laser technology. It serves as an efficient frequency converter and is often deployed for second and third harmonic generation, as well as for electro-optical modulation. KDP's transparency range is quite broad, extending from the ultraviolet to the infrared spectrum. Another advantage of this material is its relatively low cost and ease of large-scale production, which makes it particularly useful for high-power laser systems. It does, however, have lower damage thresholds compared to some other nonlinear optical materials. KDP is also hygroscopic, requiring careful handling to prevent moisture-related degradation. Overall, KDP remains a cornerstone material in nonlinear optics and laser science.

Monopotassium phosphate - Wikipedia

More about KH2PO4 (Potassium dihydrogen phosphate, KDP) →

Provenance

Version: 1 (snapshot c5c2f18)
Source page: refractiveindex.info
Original file: database/data/main/KH2PO4/nk/Zernike-o.yml
ID: ds_cd6480e31c92
API: /v1/datasets/ds_cd6480e31c92

Plot