Electro-Optic Crystals

1. BBO (Beta-Ba2BO4)

BBO has much higher damage threshold than KD*P and LiNbO3. More than 80W output power and 50KHz repetition rate was reached by using BBO crystal and Nd:YVO4 crystal as gain media. At 5KHz, it has pulse width as short as 6.4ns,and energy of 5.7mJ or peak power of 900 KW. It has advantages over the commercial A-O Q-switch, including a very short pulse, high beam quality and compact size.

However, BBO has a relative small E-O coefficient, the Half-wave voltage is high (7KV at 1064nm, 3x3x20mm3). Long and thin crystal can reduce the voltage requirement. 25mm long and 1mm thin high optical quality BBO crystal with Z-cut, AR-coated and Gold/Chrome plated on the side faces is now supplied in OptoCity.

2. KTP---KTiOPO4

KTP has promising E-O and dielectric properties comparable to those of LiNbO 3, which makes it extremely useful to various E-O devices. The following table gives the comparison of KTP and those commonly used E-O modulator materials:

Table 1. Electro-Optic Modulator Materials

Combining these properties with high damage threshold, low optical loss at high average power, wide optical bandwidth, thermal and mechanical stability, KTP crystals are expected to replace LiNbO 3 crystals as E-O modulators, especially for mode-locking diode laser pumped Nd:YAG and Nd:YLF lasers as well as Ti:Sapphire and Cr:LiSrAlF6 lasers.

OptoCity provides as large as 7x7x25mm KTP crystal for E-O application at a resonable price. Please Contact Us for more information.

3. LiTaO3

LiTaO3 crystal is also a widely used E-O crystal. Its optical, NLO and E-O poperties are similar to those of LiNbO3 crystal, but with higher damage threshold (> 500 MW/cm2 for ns pulsed). Main properties include:

Transparent Range: 0.4 - 5.0 mm;
E-O Coefficient: r 33 =30.4;
Refractive Indices: n o =2.176, n e =2.180 @ 633 nm.

OptoCity provides LiTaO3 in boubles, wafers or slices.

Capabilities:

Boules:
1) Diameter: 40mm ~ 102mm
2) Length: 50mm ~ 150mm
3) Orientation: X, Z, 36deg.Y, 42deg.Y, 128deg.Y
4) Polish: 0.016 µm
Wafers :
1) Diameter: 40mm ~ 102mm
2) Length: 0.2~1.2mm
3) Orientation: X, Z, 36deg.Y, 42deg.Y, 128deg.Y
Slices :
1) Size: 100x45x1.5mm ~ 120x40x2mm

4. LiNbO3

LiNbO 3 is widely used as electro-optic modulator and Q-switch for Nd:YAG, Nd:YLF and Ti:Sapphire lasers as well as modulator for fiber optics, etc. The transverse modulation is mostly employed for LiNbO3 crystal. If the light propagates in z-axis and electric field applies to x-axis, the refractive retardation will be:

G = pLnr22V/ l d

The electro-optic coefficients of LiNbO 3 are:

r 33 = 32 pm/V, r 31 = 10 pm/V, r 22 = 6.8 pm/V at low frequency

r 33 = 31 pm/V, r 31 = 8.6 pm/V, r 22 = 3.4 pm/V at high electric frequency.

MgO:LiNbO 3 and ZnO: LiNbO 3 crystals have similar electro-optic properties as LiNbO3 but with higher damage threshold. The refractive index of an optical medium is altered by the presence of sound, this is called acousto-optic effect which can be used in many devices include optical modulators, switches, deflectors, filters, frequency shifters and spectrum analyzers. OptoCity provides several kinds of acousto-optic crystals: LiNbO3 SAW wafers, LiTaO 3 SAW wafers, TeO2 and PbMnO4 crystals.

Table 2. Electro-Optic Waveguide Materials