Fabrication of lithium niobate fork grating by laser-writing-induced selective chemical etching

Tianxin Wang,Xiaopeng Hu,Min Xiao,Yong Zhang,Lei Yang,Xiaoyi Xu,Xiaomei Lu,Xueli Hu,Shuo Yan

doi:10.1515/nanoph-2021-0446

Abstract

Abstract We propose and experimentally demonstrate a laser-writing-induced selective chemical etching (LWISCE) technique for effective micro-fabrication of lithium niobate (LN) crystal. Laser writing of LN crystal produces negative domains and domain walls. Also, it causes local lattice defects, in which the etching rates are significantly increased in comparison to the original LN crystal. In experiment, we use the LWISCE technique to fabricate various fork gratings in an X-cut LN crystal for the generation of vortex beams. In comparison to etching an untreated X-cut LN crystal, the etching rates of the laser-writing-induced boundaries and the central laser-irradiated areas are enhanced by a factor of 26 and 16, respectively. The width and depth of fork grating structure can be precisely controlled by laser writing parameters. Our method provides an efficient mask-free micro-fabrication technique for LN crystal, which can be readily applied to other ferroelectric crystals such as lithium tantalate, potassium titanyl phosphate and barium calcium titanate.

Highlights

Lithium niobate (LN) has become an important material for photonic integrated circuits because of its excellent piezoelectric, acoustic-optic, electro-optic, and nonlinear optical characteristics
We propose and experimentally demonstrate a laser-writing-induced selective chemical etching (LWISCE) technique for effective micro-fabrication of lithium niobate (LN) crystal
The effect of laser poling is first examined by using a piezo-response force microscopy (PFM)

Summary

Introduction

Lithium niobate (LN) has become an important material for photonic integrated circuits because of its excellent piezoelectric, acoustic-optic, electro-optic, and nonlinear optical characteristics. By using micro-fabrication methods, one can fabricate waveguides [1,2,3,4,5], micro-disks [2, 5, 6], and photonic crystals on an LN surface, which compose various functional devices such as electro-optic modulators [7,8,9], optical filters [10, 11], optical couplers [12, 13], and optical frequency converters [14, 15]. The designed structures can be obtained through wet etching [22, 23], dry etching [1, 24], and chemomechanically polling [4, 5]

Methods

Results

Conclusion