Superficial waveguide splitters fabricated by femtosecond laser writing of LiTaO 3 crystal

Abstract

We report on Y-branch superficial depressed-cladding waveguides fabricated by femtosecond laser writing of MgO∶LiTaO 3 crystal. The cladding waveguides with a rectangular cross-section are single mode for both transverse electric and transverse magnetic polarization, and show good transmission properties at a telecommunication wavelength of 1.55 μm. Divergence angles as large as 2.6 deg are successfully achieved in the splitters with nearly equalized splitting ratios (1:1). The fabricated shallow structures are excellent photonic elements for optoelectronic applications.

Femtosecond-laser-written superficial cladding waveguides in Nd:CaF 2 crystal

“…Furthermore, for many optoelectronic applications, such as large area mode amplifiers, lasers, sensors and electro-optic modulators, the waveguides or photonic circuits are required to be near the surface of the host material. In consequence, the superficial cladding waveguides, with the excellent wave-guiding characteristics, are fabricated by femtosecond laser writing, which indicates the potential applications of the superficial cladding structures [23].…”

Cladding waveguide splitters fabricated by femtosecond laser inscription in Ti:Sapphire crystal

“…It can be seen that, the splitters produced in our work are of comparable performance. In addition, unlike the previously demonstrated superficial splitters in Nd: YAG [17] and LiTaO 3 [29] crystals, in which a square input is split into two rectangular outputs, the output facets of the splitters in this work are square. This ensures the symmetry of the output modal profiles, therefore a high coupling efficiency with other optical devices or circuits can be achieved, making them advantageous in integrated photonics.…”

“…With an architecture that consists of a quasi-continuous barrier (low-index damage tracks) and an intact core region, depressed cladding waveguides show excellent features such as arbitrary geometry and dimensions, well-preserved guiding core, strong light confinement, low propagation loss and, more attractively, two-dimensional (2D) guidance without strong polarization dependence, making this approach advantageous for construction of functional photonic devices. Based on the cladding geometry, superficial splitters with rectangular cross-sections has been fabricated in Nd:YAG [17] and LiTaO 3 crystals [29]. These structures possess good properties for both passive and active applications.…”

Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal

“…Fabrication of such elements with Type-II and Type-III waveguides faces substantial challenges: the design of the interaction region, waveguide cladding alignment, finding the preferential shape of the waveguide cladding, etc. The 2D 1×2 Y-splitters with square shape depressed cladding waveguides were realized in LiTaO 3 [54], in Nd:YAG [55,56] and in sapphire [57]. The circularly shaped depressed cladding waveguides in Nd:YAG [58] and LiNbO 3 [59] were adopted to inscribing 2D 1×2 Y-splitter and 3D 1×2 Y-splitter respectively.…”