Bloch Surface Based Platform for Optical Integration

A novel dielectric multilayer platform sustaining Bloch surface waves is investigated for integrated photonic chips. These surface waves can be manipulated by two dimensional dielectric optical components patterned on top of the platform. We study the properties of high refractive index materials (TiO2) as active top layer of platform. Concept The Bloch surface waves (BSWs) are surface electromagnetic modes, which can be excited in the photonic band gap of truncated dielectric periodic multilayers. BSWs show the potential of higher propagation length and large resonance strength because of low loss characteristics of dielectric materials. These properties are highly desirable features for 2D optics. Another advantage of using BSWs is the possibility to work with any wavelength by properly choosing the refractive index and thickness of the layers constituting the multilayer. Furthermore, because the maximum intensity associated with the BSW can be tuned on the surface, a strong field intensity, increased by several orders of magnitudes, can be achieved and thereby enhance the light-matter interaction close to the surface. Taking the advantage of field confinement, the platform has an application in the integrated optics domain [1], and sensing [2]. A platform consisting of periodic stacks of alternative SiO2 and Si3N4 layers is designed and fabricated to work around the wavelengths of 1.5 µm. Different optical elements can be fabricated on top of the platform by depositing and patterning an additional thin dielectric material. The presence of the additional layer modifies the local effective refractive index, enabling a direct manipulation of the BSW and introducing a refractive index contrast Δn between the additional layer and the platform. This refractive index contrast Δn, which can be deduced from the dispersion relations, plays a key role in managing the propagation of the BSWs on the platform. In order to excite a BSW, momentum of incoming beam should match with the momentum of the BSW. Therefore, we use Kretschmann configuration for this purpose, which consists of BK7-glass prism. The schematic of the configuration and the platform is presented in Fig. 1. Since the top layer is in the order of several tens of nanometers, a multi-heterodyne scanning near-field optical microscopy (MH-SNOM) that allows a simultaneous measurement of the amplitude and the phase is used for the optical characterization. Fig.1. Kretschmann configuration using BK7-glass prism to excite BSW.