## 1 Introduction  
Integrated photonics is a branch of optics that is dedicated to the development of miniature devices on a single chip that generate, guide, modulate and detect optical signals. The approaches that utilise surface electromagnetic waves (SEWs) seem to be advantageous compared to the bulky waveguide mode approaches. SEW-supporting optical components are intrinsically planar and thus compatible with well-developed lithographic techniques. Subwavelength confinement of SEW amplifies light-matter interaction, which enhances refractive index sensitivity as well as switching efficiency of SEW-based photonic devices. The most widely-studied type of SEWs are surface plasmon polaritons (SPPs). Unfortunately, SPPs suffer from severe shortcomings that strongly limit the performance of SPP-based devices: sensors and elements of integrated optics. SPPs propagating on a metal surface are strongly attenuated due to Ohmic losses. Plasmonic waveguide performance is always a trade-off between field confinement and propagation distance: for waveguides with high confinement, SPP propagation distances are only dozens of microns (channel plasmon-polaritons), while millimetre range propagation distances lead to a very weak confinement, much larger then the incident wavelength (long-range surface plasmon-polariton waveguides) [1]. Moreover, the SPP dispersion law is strictly defined by the properties of several metals. Bloch surface waves (BSWs) are SEWs confined on an interface between one-dimensional (1D) photonic crystal and dielectric medium [2; 3]. In contrast to SPP, BSW modes are supported by fully dielectric structures, which relieves them from Ohmic losses. The propagation length of BSWs was demonstrated to be in the millimetre range at telecommunication wavelengths [4]. The BSW dispersion law may be arbitrarily tuned by changing parameters and material of one-dimensional photonic crystal [4]. BSWs may be excited in a wide wavelength range from IR to UV [5]. They have received much attention in recent years, mostly because of their potential in sensing. BSW-based gas, protein, antibody, glucose, and protease detectors as well as BSW-induced enhanced Raman scattering have been successfully demonstrated [6; 7; 8; 9; 10; 11; 12; 13]. Different effects in the presence of BSWs have been experimentally observed including the enhancement of fluorescence [14] and magneto-optical effects [15], giant Goos-Hanchen effect [16], and BSW-induced radiation forces [17; 18]. In Reference \"Guided Bloch surface waves on ultrathin polymeric ridges\" [19], it was demonstrated that BSW may be confined and guided in thin polymeric stripes. This pioneering work proved that BSW propagation may be easily managed by simple lithographic nanostructuring of the top layer of the photonic crystal. Since then, a wide spectrum of complex photonic devices has been demonstrated, including lenses [20], a prism [21], square and round gratings [22; 23], a subwavelength focusing device [24], a polarisation-sensitive beam splitter [25], and a disk resonator [26]. However, the basic and the most important element of integrated photonics--waveguide--remains not fully studied. There are a number of works where the BSW propagation in thin dielectric waveguides has been studied [27; 28; 29; 30]. The excitation of BSW was achieved in either Kretschmann configuration, or by tapered fiber. However, these bulky methods of coupling the BSW with incident radiation are not compatible with ready for use devices. Practical applications demand more compact diffraction grating excitation schemes, which can be easily integrated into the photonic chip, optimized, and aligned in the flat optical scheme. Although there are a number of works where diffraction grating was successfully applied to excite the BSW on the surface of the photonic crystal [22; 23], there is no experimental proof of the possibility of the BSW waveguide mode coupling to incident radiation by the diffraction grating excitation method.