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GTR-KTP - Gray-Track Resistance KTP


GTR-KTP - Gray-Track Resistance KTP
  • GTR-KTP - Gray-Track Resistance KTP

  • CASTECH's GRT-KTP, as an excellent NLO crystal, has lower absorption and higher damage threshold than the conventional KTP, which we can conclude it possesses a higher gray track resistance.
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KTP is an excellent nonlinear crystal, but its gray tracking phenomena limits its use in high repetition rate and high power laser systems. CASTECH's GTR-KTP crystal has higher gray tracking resistance than the regular flux grown KTP crystal. Through Photo-thermal Common-path Interferometer, the occurrence of gray tracking can be measured by an increase of bulk absorption through a strong CW 532 nm green laser within several minutes.


1. Bulk absorption measurements before gray tracking testing:



It appears that the absorption of CASTECH's GTR-KTP at 1064 nm is only 1/10 of conventional KTP.


2. Gray Tracking Testing:

When a green laser beam (400 mW, beam diameter 0.07 mm, power density 10 KW/cm2) goes through the crystal, it causes an increase in the IR absorption of the crystal. This phenomenon is correlated with “gray tracking effect”. The following graphs show the absorption level changes over time at 1064 nm for CASTECH's GTR-KTP and the conventional KTP separately.



3. Bulk absorption measurements at 1064 nm after gray tracking testing



4. Bulk absorption measurements at 532 nm after gray tracking testing



5. Damage threshold testing:

After testing a group of GTR-KTP and the conventional KTP crystals (polished only) with laser condition of 10 ns, 1 Hz, we found that CASTECH's GTR-KTP has laser damage threshold around 1.8 GW/cm2 at 1064 nm, which is much higher than the conventional KTP (450 MW/cm2 in the same condition).


6. Transmission curves in visible and UV region:



Apparently CASTECH's GTR-KTP has lower absorption than the conventional KTP in the range of 350-550 nm. We can conclude that CASTECH's GTR-KTP is expected to have a higher gray tracking resistance than the regular flux grown KTP crystals.


CASTECH offers GTR-KTP with

  •   Strict quality control
  •   Large crystal size up to 7 × 7 × 20 mm3
  •   Quick delivery (3 weeks for polished only, 4 weeks for coated)
  •   Unbeatable price and quantity discount
  •   Technical support
  •   AR, HR-coating, mounting and re-working service


       GTR-KTP's Parameters

Table 1. Specifications

  Dimension Tolerance

  (W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.5/-0.1 mm)  (L2.5 mm)

  (W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.1/-0.1 mm)  (L2.5 mm)

  Clear Aperture    Central 90% of the diameter
  Internal Quality   No visible scattering paths or centers when inspected by a 50 mW green laser
  Flatness   ≦ λ/8 @633 nm
  Transmitted Wavefront Distortion   ≦ λ/8 @633 nm
  Surface Quality (Scratch/Dig)   10/5 (Polished) to MIL-PRF-13830B
  20/10 (AR-coated) to MIL-PRF-13830B
  40/20 (HR-coated) to MIL-PRF-13830B
  Parallelism   20 arc sec
  Perpendicularity   ≦ 15 arc min
  Angle Tolerance   ≦ 0.25 °
  Chamfer   ≦ 0.2 mm × 45 °
  Chip   ≦ 0.1 mm





CASTECH provides the following AR-coatings:

  •   Dual Band AR-coating (DBAR) of GTR-KTP for SHG of 1064 nm
  •   low reflectance (R<0.2% @1064 nm and R<0.5% @532 nm)
  •   High damage threshold (˃1 GW/cm2 @1064 nm, ˃300 MW/cm2 @532 nm, at 10 ns, 10 Hz), long durability
  •   High reflectivity coating: HR1064 nm & HT 532 nm, R˃99.8% @1064 nm, T˃95% @532 nm
  •   Broad Band AR-coating (BBAR) of GTR-KTP for OPO applications
  •   Other coatings are available upon request
  • NLO Crystals_Gray-track Resistance KTP(KTiOP04 , GTR-KTP).pdf

    2020-11-19 10:55:52
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