Low-loss LiNbO(3) tapered-ridge waveguides made by optical-grade dicing.

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.

Fast-beam self-trapping in LiNbO(3) films by pyroelectric effect.

We report light-beam self-trapping triggered by the pyroelectric effect in an isolated ferroelectric thin film. Experiments are performed in an 8-µm-thick congruent undoped LiNbO(3) film bonded onto a silicon wafer. Response time two orders of magnitude faster than in bulk LiNbO(3) is reported. The original underlying physics specific of this arrangement is discussed.

Acoustic resonator based on periodically poled lithium niobate ridge.

The constant improvement of industrial needs to face modern telecommunication challenges leads to the development of novel transducer principles as alternatives to SAW and BAW solutions. The main technological limits of SAW (short-circuit between electrodes) and BAW (precise thickness control) solutions can be overcome by a new kind of transducer based on periodically poled ferroelectric substrate. The approach proposed in this paper exploits a ridge structure combined with a periodically poled transducer (PPT), allowing for the excitation of highly coupled modes unlike previously published results on planar PPTs. High-aspect-ratio ridges showing micrometer dimensions are achieved by dicing PPT plates with a diamond-tipped saw. An adapted metallization is achieved to excite acoustic modes exhibiting electromechanical coupling in excess of 15% with phase velocities up to 10 000 m·s(-1). Theoretical predictions show that these figures may reach values up to 20% and 18 000 m·s(-1), respectively, using an appropriate design.