Potassium Dideuterium Phosphate and its Isomorphs - KDP, KD*P (DKDP) Crystals

Applications:

  • Laser frequency conversion – harmonic generation for high pulse energy, low repetition (<100 Hz) rate lasers;
  • Electro-optical modulation;
  • Q-switching crystal for Pockels cells;
  • Electro-Optical/Q-switching application:

EKSMA OPTICS offers:

  • highly deuterated D>96%  electro-optic (e/o) crystal - DKDP  for Q-switching application;
  • Standard dimensions of electro-optic (e/o) DKDP crystals for Q-switching are cylinders dia 9 x 20 mm and dia 12 x 24 mm however manufacturing of custom size and rectangular shape crystals is available;
  • Gold evaporated or silver paste electrodes are available; Dielectric thin film AR coatings for specified laser wavelengths are available;
  • Typical quarter wave voltage 3.4 kV at 1064 nm; Typical contrast ratio between crossed polarizers better than 1:2000;
  • Damage threshold of AR coated DKDP surface >5 J/cm2 at 1064 nm, 10 ns pulses.

Frequency conversion applications:

  • DKDP crystals are used for second harmonic generation of high pulse energy low repetition rate (<100Hz) Q-switched and mode-locked Nd:YAG lasers. Cut angle of crystal for operation at room temperature is 36.6 deg for Type 1 phase matching and 53.7 deg for Type 2 phase matching.
  • DKDP crystals are used for third harmonic generation of high pulse energy Q-switched and mode-locked Nd:YAG lasers via sum frequency generation. Cut angle of crystal for operation at room temperature is 59.3 deg for Type 2 phase matching.
  • Type 1 DKDP crystals with non-critical cut angle theta=90 deg are used for fourth harmonic generation (532nm → 266nm) of high pulse energy Q-switched and mode-locked Nd:YAG lasers. Crystal must be heated at ~50 deg C temperature to match NCPM conditions.
  • Type 1 KDP crystal with close to non-critical cut angle theta=76.5 deg is used for fourth harmonic generation (532nm → 266nm) of high pulse energy Q-switched and mode-locked Nd:YAG lasers. KDP crystal has lower absorption at UV wavelengths comparing to DKDP.
  • KDP thin crystals are used for second harmonic generation of Ti:Sapphire laser radiation or pulse duration measurement in single shot autocorrelators. KDP possesses ~2.4 times larger spectral acceptance and correspondingly smaller group velocity mismatch comparing to BBO crystal for SHG of 800 nm, what sometime is very critical parameter for femtosecond wide spectrum pulses. 
  • KDP crystals can be supplied by EKSMA OPTICS of aperture up to dia 80 mm. Actually KDP remains the only solution for harmonic generation of very high intensity femtosecond Ti:Sapphire lasers featuring sub-tera Watt or tera Watt peak power pulses in large >30 mm diameter beams.  
Delivery

Estimated delivery time: from 4 - 5 days

Size, mm
θ
φ
Coating
Application
Code Size, mm θ φ Coating Application Price Delivery Add to cart
DKDP-401 15x15x13 36.5 45 AR/AR@1064+532 nm SHG@1064 nm, Type 1 595 $ Request To cart
DKDP-402 15x15x13 53.5 0 AR/AR@1064+532 nm SHG@1064 nm, Type 2 595 $ 4 - 5 days To cart
DKDP-403 12x12x20 59.3 0 AR/AR@1064+532/355 nm THG@1064 nm, Type 2 585 $ 4 - 5 days To cart
DKDP-404 12x12x20 53.5 0 AR/AR@1064/1064+532 nm SHG@1064 nm, Type 2 585 $ 4 - 5 days To cart
DKDP-405 15x15x20 53.5 0 AR/AR@1064/1064+532 nm SHG@1064 nm, Type 2 700 $ 4 - 5 days To cart
DKDP-406 15x15x20 59.3 0 AR/AR@1064+532/355 nm THG@1064 nm, Type 2 700 $ 4 - 5 days To cart
DKDP-409 dia 9x20 - - uncoated* Electro-Optical/Q-switching Request Request To cart
DKDP-412 dia 12x24 - - uncoated* Electro-Optical/Q-switching Request Request To cart

KDP Crystals

Code Size, mm θ φ Coating Application Price Delivery Add to cart
KDP-401 12x12x5 76.5 45 AR/AR@532/266 nm SHG@532 nm, Type 1 500 $ Request To cart
KDP-402 15x15x7 76.5 45 AR/AR@532/266 nm SHG@532 nm, Type 1 575 $ 4 - 5 days To cart
Delicious
Flatness λ/6 @ 633 nm
Parallelism < 20 arcsec
Perpendicularity < 5 arcmin
Angle tolerance < 30 arcmin
Aperture tolerance ± 0.1 mm
Surface quality 20/10 scratch & dig per MIL-O-13830A
Clear aperture 90% of full aperture

Physical and Optical Properties

Crystals KDP Crystal
DKDP Crystal
Chemical formula KH2PO4 KD2PO4
Symmetry 42 m 42 m
Hygroscopicity high high
Density, g/cm3 2.332 2.355
Thermal conductivity, W/cm×K k11= 1.9×10-2 k11= 1.9×10-2
k33= 2.1×10-2
Thermal expansion coefficients, K-1 a11= 2.5×10-5
a33= 4.4×10-5
a11= 1.9×10-5
a33= 4.4×10-5
Transmission range, μm 0.18–1.5 0.2–2.0
Residual absorption, cm-1 (at 1.06 μm) 0.04 0.005
Measured refractive index (at 1.06 μm) no = 1.4938
ne = 1.4599
no = 1.4931
ne = 1.4582
Sellmeier coeff., λ – wavelength in μm   n2=A+Bλ2/(λ2-C)+D/(λ2-E)
A no
   ne          
2.259276
2.132668
2.2409
2.1260
B no
    ne
13.00522
3.2279924
2.2470
0.7844
C no
    ne
400
400
126.9205
123.4032
D  no
     ne
0.01008956
0.008637494
0.0097
0.0086
E  no
     ne
0.012942625
0.012281043
0.0156
0.0120
Nonlinear coeff. d36, pm/V (at 1.06 μm) 0.43 0.40
Effective nonlinear coefficient
     Type 1  
     Type 2
 
dooe=d36xsinθxsin2φ
deoe=d36xsin2θxcos2φ

Phase matching angle and bandwidths for SHG of 1064 nm


KDP
DKDP
Type of phase matching Type 1
ooe
Type 2
eoe
Type 1
ooe
Type 2
eoe
Cut angle θ, deg 41.2 59.1 36.6 53.7
Acceptances for crystal of 1 cm length (FWHM):
Δθ (angular), mrad 1.1 2.2 1.2 2.3
ΔΤ thermal, K 10 11.8 32.5 29.4
Δλ spectral, nm 21 4.5  6.6 4.2
Walk off, mrad 28 25 25 25
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