RTP Crystal

RbTiOPO₄(RTP) crystal is currently the most commonly used type of practical electro-optic crystals with high frequency repetition, high power and narrow pulse width laser Q switching. RTP electro-optical devices are not only used in laser micromachining and laser ranging, but also in major scientific exploration projects because of their excellent comprehensive performance.

RbTiOPO₄(RTP)—a crystal with large electro-optical coefficient, high photoresist damage threshold and stable physical and chemical properties

The growth temperature ranges from 950 °C to 800 °C and the growth period is usually between 45 and 60 days.As RTP is transparent from 0.4 to 3.5 μm, it can be used in multiple types of laser such as Er:YAG laser at 2.94 μm with fairly good efficiency. Bulk absorption measurements at 1.064 μm range from 50 to 150 ppm using Photothermal Common Path Interferometer.

Parameter

Physical and Chemical Properties

Chemical formula	RbTiOPO₄
Crystal structure	Orthorhombic
Point group	mm²
Lattice parameters, Å	a 12.96
	b 10.56
	c 6.49
Density, g.cm^-3	3.6
Resistivity (20°C, 20% Humidity), Ohm.cm	10¹²
Aperture, mm²	from 2×2 to 9×9
Length, mm	up to 10
Dimension tolerance	±0.1 mm
Flatness	<l/8 @633 nm
Surface quality	Scratch/Dig 10/5
Parallelism	better than 30 arc sec
Perpendicularity	better than 30 arc min
Angle tolerance	△q < 0.5°, △f < 0.5°
Coating	AR coatings
Clear aperture	>90% central area
Transmitting wavefront distortion	less than l/8 @ 633 nm Dimension
Melting Point	~ 1000 °C
Ferroeletric transition temperature	~810 °C
Mohs Hardness	~5
Thermal Expansion Coefficients, /°C	a₁=1.01×10^-5, a₂=1.37×10^-5, a₃=-4.17×10^-6
Hygroscopic Susceptibility	No
Ionic conductivity (room temperature, 10 kHz)	10^-8 S/cm

Electro Optical Properties

Average refractive index	1.8
Transparency range, μm	0.35 → 4.5
Residual Absorption (PCI) at 1064 nm	<250 ppm/cm
Electro-optical constants (@ 633 nm, 1 kHz), pm. V^-1	r₁₃	10.9
	r₂₃	15
	r₃₃	33
Dielectric constant	ε_eff=13

Standard Specifications of Laser Grade RTP Crystals

High damage threshold	>15 J/cm² at 10 Hz,10 ns at 1064 nm performed on coated crystals of 10 mm long
Low operating voltage	1300 V for Y-cut and 1600 V for X-cut at 1064 nm applied to a crystal pair of 4×4 mm^² for the aperture and 2×10 mm for the length
Low bulk absorption	<250 ppm/cm at 1064 nm

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