Ti-Doped Sapphire (Al₂O₃) Single Crystals Grown by the Kyropoulos Technique and Optical Characterizations

Abstract

Transparent high optical quality and large Ti-sapphire (Ti 3þ -doped Al 2 O 3 ) single crystals have been grown by the Kyropoulos technique (KT) for optical amplification. The present work shows that by the utilization of KT growth technology and the optimization of the growth conditions it is possible to grow Ti-doped Al 2 O 3 , 100 mm in diameter and 5 kg in weight. We have demonstrated that large Ti(0.25 atom %)-doped Al 2 O 3 crystals show high chemical homogeneities and good optical properties and amplify the energy without any special annealing. Ti-doped sapphire crystals are for high power laser applications and particularly for the shortest pulses ever produced from a laser oscillator.

Scattering defect in large diameter titanium-doped sapphire crystals grown by the Kyropoulos technique

“…Ti-doped sapphire single crystals have been grown by the Kyropoulos [7]. The Ti: sapphire crystals used in this study were both grown along a-axis [112 � 0] and m-axis [1100] in argon atmosphere.…”

“…They are obtained by the growth method called HEM (Heat Exchange Method) [6]. But the other techniques such as Kyropoulos method are promising for obtaining large-diameter sapphire crystals able to meet the specifications [3] [7].…”

Laser Active Materials for High-Intensity Lasers

“…Nowadays, crystals of about 5 cm diameter can be grown by using the standard Czochralski or the vertical-gradient freeze growth technique [2] and can be provided [3], by special order, with FOM = 500 and above for dopant concentrations up to about 0.15wt%Ti (which means an absorption coefficient α 532nm ≈ 2.1 cm −1 ); it remains a challenge however to grow and provide large crystals with dopant concentration exceeding 0.25 wt%Ti while preserving such a FOM and also by avoiding gradients of concentrations. This is the reason why efforts are still being dedicated in this domain around the world by using other techniques such as the HEM [4] or the Kyropoulos technique [5], [6], also to develop crystals for larger scale applications like light emitting diodes in which case the sapphire crystals are used as substrates and titanium doping serves to strengthen and toughen the materials [7]. The present objective is to grow crystals with high and homogeneous dopant concentrations like it is the case of the disc shown in the Fig.…”

Growth and spectroscopic properties of Ti-doped sapphire single-crystal fibers

“…Until now, all the gain media are obtained from bulk Ti:Al 2 O 3 crystals, which can be grown by various methods, such as Czochralski [13], heat exchanger method (HEM) [14], temperature gradient technique (TGT) [15], and Kyropoulos technique (KT) [16]. On the other hand, laser heated pedestal growth (LHPG) and micro-pulling-down (l-PD) techniques are used to grow single crystal fibers [17,18].…”

“…The concentration of the activator ion can be lower because of the long interaction length. Especially for the Ti:Al 2 O 3 crystal, the segregation coefficient is as small as 0.20 because of the ionic radii difference between Ti 3+ (60.5 pm) and substituted Al 3+ (53.3 pm) ions [16].…”