Spatial nonlinear optics anisotropy and directional growth of TbCOB crystal by micro-pulling-down for SHG application

•The largest deff of TbCOB crystal was 1.39 pm/V.•TbCOB crystal was grown along the optimum SHG direction using the μ-PD method.•A high efficiency SHG can be realized through the μ-PD grown TbCOB crystal.•The directional growth for NLO crystal devices by using μ-PD was feasible.

Towards the spatial optimum phase matching (PM) crystal device through a novel way, the micro-pulling-down (μ-PD) technique was used for crystal growth along second-order harmonic generation (SHG) direction for the first time to the best of our knowledge. In this paper, the spatial distribution of |deff| for a potential nonlinear optical (NLO) crystal TbCa4O(BO3)3 (TbCOB) at 1064 nm was calculated and analyzed firstly, and the PM angle (113°, 46°) was found to possess the largest deff value (type-I) being on the order of 1.39 pm/V. Along the optimum SHG direction, a rod-shape TbCOB crystal with 3 mm in diameter was successfully grown by using the μ-PD method. After simple cutting and polishing of the ends for μ-PD grown crystal, a high SHG efficiency (single-pass light reached up to 57%) was realized through a Nd:YAG pico-second laser at 1064 nm, which was comparable to that of crystal samples from Czochralski (Cz) growth. TbCOB crystals also exhibit a high laser damage threshold of >15 GW/cm2.