Bloch surface waves (BSWs) are electromagnetic surface waves which can be excited at the interface between periodic dielectric multilayer and a surrounding medium. In comparison with surface plasmon polaritons these surface states perform high quality factor due to low loss characteristics of dielectric materials and can be exited both by TE and TM polarized light. A platform consisting of periodic stacks of alternative SiO2 and Si3N4 layers is designed and fabricated to work at the wavelength of 1.55 µm. The platform has an application in sensing and in integrated optics domain. A standard way of BSW excitation is coupling via Kretschmann configuration, but in this work we investigate a grating coupling of BSWs. Grating parameters are analytically and numerically optimized by RCWA and FDTD methods in order to obtain the best coupling conditions. The light is launched orthogonally to the surface of the photonic crystal and the grating. Due to a special grating configuration we demonstrate directionality of the BSW propagation depending on polarization of the incident light. The structure was experimentally realized on the surface of the photonic crystal by FIB milling. Experimental results are in a good agreement with a theory. The investigated configuration can be successfully used as a BSW launcher in on-chip all-optical integrated systems and work as a surface wave switch or modulator.
We present easy-to-implement technologies to produce LiNbO3 PhCs in confined optical waveguides. Ti-indiffusion or
Annealed Proton Exchange (APE) are combined with optical grade dicing to fabricate ridge waveguides with
propagation losses that can be lower than 0.2 dB/cm. Firstly we show how a PhC inscribed in a confined ridge
waveguide can be exploited as a temperature sensor with an unexpectedly high 8 nm/°C temperature sensitivity. LiNbO3
PhCs with high aspect ratio are also demonstrated. The performance is achieved by properly tilting the ridge before
patterning its walls by Focused Ion Beam (FIB). A eight micrometer long 1D-PhC on a Ti:LiNbO3 ridge waveguide has
been fabricated and its reflectivity has been evaluated using an optical coherence tomography (OCT) system: it is
measured to be 53 % for the TM wave and 47 % for the TE wave. The period can be optimized in order to increase the
reflection of the 1D-PhC up to 80 %. These developments open the way to the dense integration of compact dynamic
devices such as modulators, spectral filters or electric field sensors.
We report on photonic crystal electro-optic devices formed in engineered thin film lithium niobate (TFLN™) substrates.
Photonic crystal devices previously formed in bulk diffused lithium niobate waveguides have been limited in performance by the depth and aspect ratio of the photonic crystal features. We have overcome this limitation by implementing enhanced etching processes in combination with bulk thin film layer transfer techniques. Photonic crystal
lattices have been formed that consist of hexagonal or square arrays of holes. Various device configurations have been
explored, including Fabry Perot resonators with integrated photonic crystal mirrors and coupled resonator structures. Both theoretical and experimental efforts have shown that device optical performance hinges on the fidelity and sidewall profiles of the etched photonic crystal lattice features. With this technology, very compact photonic crystal sensors on the order of 10 μm x 10 μm in size have been fabricated that have comparable performance to a conventional 2 cm long bulk substrate device. The photonic crystal device technology will have broad application as a compact and minimally invasive probe for sensing any of a multitude of physical parameters, including electrical, radiation, thermal and chemical.
We report two novel kinds of LiNbO3 electro-optic modulators. The first one is oriented toward long haul high bit rate telecommunication systems. An original single-ended structure with a poled section and phase reversal electrodes is proposed to prevent the intensity modulation from chirp, without sacrifice on the driving voltage. We also show that improvements can be performed with the use of several poled sections. To remain attracting, LiNbO3 modulators should also exhibit a lower size. The second configuration described here is a new generation of LiNbO3 modulators based on photonic crystals, with a micrometric active length. We theoretically show that the optimal photonic structures for an efficient electro-optical tuning are based on a triangular array of holes integrated on a X-cut substrate. The first optical characterizations confirm the theoretical predictions, and exhibit a -12dB extinction ratio in the transmission response.