KTP is the most commonly used material for frequency doubling of Nd:YAG lasers and other Nd-doped lasers, particularly at the
low or medium power density. The following Table lists the major NLO properties of KTP for frequency-doubling of Nd:YAG laser.
PM angle
q=90o, f=23.5o,
where q & f are polar angles referring to Z and X.
Effective SHG coefficient
deff » 8.3xd36(KDP)
Angular acceptance
20 mrad-cm
Temperature acceptance
25oC-cm
Spectral acceptance
5.6 Å-cm.
Walk-off angle
4.5mrad (0.26o)
Optical damage threshold
> 450MW/cm2, (@ 1.06mm, 10ns, 10Hz)
Today, extra- and intra-cavity frequency doubled Nd:lasers using KTP have become a preferred green laser source for many R&D,
medical, industrial and commercial applications. By using extracavity KTP SHG, over 80% conversion efficiency and 700mJ green
laser were obtained with a 900 mJ injection-seeded Q-switched Nd:YAG laser.
Applied to diode-pumped Nd:laser, KTP is a basic NLO crystal for the construction of compact visible solid state laser systems. Recent advances in intracavity-doubled Nd:YVO4 and Nd:YAG lasers have increased the demand for compact green lasers used in display, construction, optical disk and laser printer. Over 200 mw TEM00 green outputs are available from LD pumped Nd:YVO4 and Nd:YAG lasers and 3 W TEM00, mode-locked green laser was generated by intracavity SHG in a 5.3 W mode-locked diode-laser pumped Nd:YAG laser. Moreover, 2.5mW green light was obtained from 50mW LD pumped and intracavity doubled Nd:YVO4 mini-lasers with a 9mm long cavity.
Type II SHG in XY Plane
KTP is also a powerful crystal for SHG and SFG of laser with wavelength from about 1mm to 3.4 mm. The SHG phase-matching angle and effective SHG coefficients (deff) of KTP in XY plane (0.9 mm to 1.08 mm) and XZ plane (1.1 mm to 3.3 mm) are showed as the figtures. Although KTP cut in YZ plane can be phase-matched for SHG of 1 mm to 3.45 mm, it is seldom used in practices because of the low deff.
Type II SHG in XZ Plane
Applications for OPG , OPA and OPO
As an efficient OPO crystal pumped by the fundamental and second harmonics of a Nd:YAG or Nd:YLF laser, KTP plays an important role in parametric sources for tunable output from visible (0.6mm) to mid-IR (4.5mm). The phase-matching angles and effective NLO coefficient for OPO/OPA pumped at 532 nm and 1064 nm in XZ plane are showed as following figures. NCPM KTP OPO pumped by 1064nm, the signal output is around eye safe wavelength, find applications in eye-safe devices. The OPO/OPA in XY and YZ is seldom employed because of their low effective nonlinear coefficients and other limitation. For more information about the design of KTP-OPO, please contact KASTON.
OPO Pumped at 532 nm
OPO Pumped at 1064 nm
KTP's OPO results in stable, continuous outputs of femtosecond pulse of 108 Hz repetition rate and miliwatt average power levels in both signal and idler outputs. KTP's OPO pumped by a 1064nm Nd:laser has generated above 66% conversion efficiency for degenerate conversion from 1064 to 2120 nm.
The recently developed new application is the non-critical phase-matched (NCPM) KTP OPO/OPA pumped by the tunable lasers such as Ti:Sapphire, Alexandrite and Cr:LiSrAlF6 (see right figure). The NCPM KTP OPO keeps the KTP crystal fixed in X-axis and tunes the pumping wavelength. If a tunable Ti:Sapphire laser is used as a pumping source (0.7 mm to 1 mm), the output can cover the wavelength range from 1.04mm to 1.45 mm (signal) and from 2.15 mm to 3.2 mm (idler). Due to the favorable NLO properties of NCPM KTP, as high as 45% conversion efficiency was obtained with narrow output bandwidth and good beam quality.
Type II NCPM OPO
Quasi-Phase-Matched Waveguide
Recently, type II SHG conversion efficiency of 20%/W/cm2 was achieved by quasi-phase-matched waveguide doubler, in which the phase mismatch from one section is balanced against a phase mismatch of the opposite sign from a second section. Furthermore, segmented KTP waveguide have been applied to type I quasi-phase-matchable SHG of 0.76-0.96mm for tunable Ti:Sapphire laser and directly doubled diode laser for 0.43-0.40mm output. Conversion efficiency in excess of 100%/W/cm2 has been obtained.
Now, KASTON can provide as large as 30x30x1 mm KTP with -Z or both faces polished for waveguide applications. Other size is also available upon request.
Oven for heating KTP crystal:
Increasing the temperature of KTP crystal can enhance the damage threshold of KTP crystal. Therefore, for high power or high power density SHG of Nd laser, heating KTP to a certain temperature(e.g., 80oC)is recommended. KASTON provides precision oven with temperature controller for heating KTP. A full assembly including KTP crystal, oven and temperature controller is also available. Please click here for more information about oven and temperature controller.
KASTON's warranty on KTP specifications:
Transmitting wavefront distortion
less than l/4 @ 633nm
Dimension tolerance
( W¡À0.1mm )x( H¡À0.1mm )x( L+0.2/-0.1mm )
Clear aperture
> 90% central area
Flatness
l/8 @ 633nm
Surface quality
10/5 Scratch / Dig
Parallelism
better than 20 arc sec.
Perpendicularity
5 arc min.
Angle tolerance
Dq <¡À0.5o, Df<¡À0.5o
AR coating
dual wave band AR coating at 1064/532 nm for both faces
Residual reflectivity
< 0.2% at 1064 nm and < 0.5% at 532 nm per surface
Quality Warranty period
one year under proper use
Note:
1.
KASTON has large quantities of standard size KTP crystals in-stock. The next-day delivery is available for the in-stock crystals. The standard size crystals include 2x2x5mm, 3x3x5mm and 5x5x5mm etc. with dual-band AR-coating for frequency-doubling 1064 nm.
2.
KASTON provides free crystal samples for long term technical and business cooperation as well as the developments of KTP's new applications. Qualified end-users can also obtain free samples upon request.
3.
AR-coatings and High Reflection coatings ( HR-caotings ) at other wavelengths are available upon request.
4.
Technical information and specific designs for KTP crystals are provides by our sales engineers and the scientists in our R&D center.
