Three-dimensional femtosecond laser fabrication of waveguide beam splitters in LiNbO_3 crystal

Three-dimensional femtosecond laser micromachining of dielectric crystals for photonic waveguiding applications

“…The few-layer laser tracks serve as lowindex claddings with generally hexagonal layout, which confine the enclosed track-free region to be the waveguiding Ili' , core. Figure 3 illustrates the prototypes and simulated modal distributions of 4-, 3-, 2-, and 1-layer photonic-lattice-like cladding structures, respectively [19]. As one can see, the light field can be confined in the center of the structures, i.e., the region without laser-written tracks, and the confinement becomes better as the number of layers of the Type II modification related tracks increases.…”

“…Another advantage of the introduction of axial-defect-lines is that the area of the guiding core region may be also changed to allow smooth and effective confinement of light beams. In order to implement beam steering, connections in a reasonable manner of a few cladding photonic structures are achievable for 3D devices [19]. Figure 4 shows the design of a 3-element waveguide structure for the evolution from a single Gaussian input beam to a ring-shaped output beam.…”

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

“…Type-I waveguides suit best for implementation of complex integrated photonic devices: two-dimensional (2D) 1×2 beam splitter in LiNbO 3 [51] and three-dimensional (3D) 1×4 beam splitters in BGO [52] and in LiNbO 3 [53] were demonstrated. 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.…”

Monolithic integration of a lithium niobate microresonator with a free-standing waveguide using femtosecond laser assisted ion beam writing

“…The combination of two approaches allows a high fabrication efficiency mainly determined by the femtosecond laser direct writing and a high fabrication resolution completely determined by the FIB writing. At last, the femtosecond laser has been widely used in fabricating photonic structures in various crystals thanks to the unique 3D fabrication capability in transparent materials1011121314. The high-precision 3D microfabrication is realized by irradiating inside transparent materials with tightly focused femtosecond laser pulses of which the ultrashort pulse duration and ultrahigh peak intensity together can lead to efficient confinement of the nonlinear interactions within the focal volume.…”