KTP is a positive biaxial crystal, with the principal axes X, Y, and Z (n_z>n_y>n_x) parallel to the crystallographic axes a, b, and c, respectively. 

 Applications

Applications for SHG and SFG of Nd:lasers

KTP is used commonly as one of the doublers of Nd:YAG lasers and other Nd-doped lasers. The following Table lists its major NLO properties for frequency-doubling of Nd:YAG laser.

With KTP, extra- and intra-cavity frequency doubled Nd:laser has become a preferred green laser source for 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.

KTP is also a powerful crystal for SHG and SFG of laser with wavelength from about 1μm to 3.4μm. The SHG phase-matching angle and effective SHG coefficients (deff) of KTP in XY plane (0.9μm to 1.08μm) and XZ plane (1.1 μm to 3.3 μm) are showed as the figtures. Although KTP cut in YZ plane can be phase-matched for SHG of 1μm to 3.45μm, it is seldom used in practices because of the low deff.

Type ll SHG in XY Plane	Type ll SHG in XZ Plane	OPO Pumped at 1064 nm

  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 (0.6μm) to mid-IR (4.5μm). 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. 

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 (0.7μm to 1 μm), the output can cover the wavelength range from 1.04μm to 1.45μm (signal) and from 2.15μm to 3.2μm (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.

Quasi-Phase-Matched Waveguide

Recently, type II SHG conversion efficiency of 20% 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 waveguides have been applied to type I quasi-phase-matchable SHG of 0.76-0.96μm for tunable Ti:Sapphire laser and directly doubled diode laser for 0.43-0.40μm output. Conversion efficiency in excess of 70% has been obtained.

NCPM KTP for OPO

Efficiency of KTP elements in OPO 1064 - 1570 nm

The recently developed new application is the non-critical phase-matched (NCPM) KTP OPO/OPA application. The NCPM KTP OPO keeps the KTP crystal fixed in X-axis and tunes the pumping wavelength. If 1064nm pumping source, the output will be at 1.57μm (signal) and 3.3μm (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.

 DPM Crystal for Green Laser Pointer

  Nd:YVO4+KTP for Green Laser Pointer

The most outstanding advantage of DPSS laser is its compact package, especially for Green Laser Pointer. CORSTEC supply which combine Nd:YVO4 crystal with KTP crystal, resulting in efficient, ultra-compact, diode pumped laser devices emitting the green laser. It greatly reduces your material cost and enhances assembling efficiency.

Diode pumped Nd:YVO4+KTP green laser pointer

Nd:YVO4 (mm3)	KTP (mm3)	Pump Power	Output
2x2x1	2x2x3	150mW	>1mW
3x3x1	3x3x5	500mW	>20mW

Coating: S1: R>99.8% @1064 nm, R<5% @808 nm;S2: R>99.8% @1064 nm, R<5% @532 nm

Standard Products

Part No.	Nd:YVO4	KTP
PDM01	2x2x1	2x2x3mm
PDM02	2x2x1	2x2x5mm
PDM03	3x3x1	3x3x5mm

Wavefront distortion	less than λ/8 @ 633nm
Dimension tolerance	(W ± 0.1mm) x (H ± 0.1mm) x (L + 0.2mm/-0.1mm)
Clear aperture	> 90% central area
Flatness	λ/8 @ 633nm
Scratch/Dig	10/5 to MIL-O-13830A
Parallelism	better than 20 arc seconds
Perpendicularity	5 arc minutes
Angle tolerance	Δθ <± 0.3°, Δφ< ±0.3°

Warranty