Low-loss LiNbO_3 tapered-ridge waveguides made by optical-grade dicing

Abstract

We report on low-loss vertical tapers for efficient coupling between confined LiNbO₃ optical ridge waveguides and Single Mode Fibers. 3D-Pseudo-Spectral-Time-Domain calculations and Optical-Coherence-Tomography-based methods are advantageously used for the numerical and experimental study of the tapers. The tapered-section is done simultaneously with the ridge waveguide by means of a circular precision dicing saw, so that the fabrication procedure is achieved in only two steps. The total insertion losses through a 1.6 cm long ridge waveguide are measured to be improved by 3 dB in presence of the taper. These tapered-ridge waveguides open the way to the low-cost production of low-loss phase modulators or resonators.

Lithium Niobate Optical Waveguides and Microwaveguides

“…They are made simply by progressively decreasing the ridge depth, which can be done by lifting the blade before the end of the ridge. In this case, the total insertion losses are measured to be lower than 3 dB for a 2-cm-long ridge, and only the fundamental mode is allowed to propagate in the ridge [40].…”

Glass integrated optic waveguides combining optical grade dicing and ion-exchanged planar waveguide

“…Rotation speed and translation speed of the blade are respectively 10000 rpm and 0.2 mm/s which are the couple values used for lithium niobate substrate. 12 This allows both the dicing and the polishing of the vertical surfaces. The feed rate, the distance travelled by the blade in one revolution, is 1.2 µm / rev.…”

“…It has been already used on Niobate Lithium substrate with encouraging results. [12][13][14] Other goups apply this technology to obtain waveguides in nonlinear material. 15,16…”

3D pseudospectral time domain for modeling second-harmonic generation in periodically poled lithium niobate ridge-type waveguides

“…Limitations of Fast Fourier Transform (FFT), due to the periodic boundary conditions, are avoided by using absorbing boundary conditions formulated for Perfect Matched Layer (PML) in nonconductive media [11][12][13]. As a consequence, this numerical method can be used to study various problems on larger scales, more efficiently and with a better accuracy than Finite-Difference TimeDomain (FDTD) methods [11,[14][15][16][17][18]. In particular, because accurate modelling of nonlinear optical processes with the FDTD method requires extremely fine sampling to minimize numerical dispersion errors, PSTD schemes offer significant improvements in computational efficiency and accuracy [19,20].…”