Extraordinary enhancement of Second harmonic generation in cavity-resonator integrated grating couplers

Cavity resonator integrated grating filters (CRIGF) [1] are composed with a sub-wavelength coupling grating of a few tens of periods (GC), surrounded with two distributed Bragg reflectors (DBR), etched on a multilayer stack of lossless dielectric materials (see Fig. 1). Illuminated with an incident beam overlying the GC, CRIGF exhibit resonances characterised by a strong electromagnetic field concentrated in the guiding layer beneath the structuration. We are currently exploiting this property to enhance second order nonlinear optical effects, in particular second harmonic generation (SHG) [2]. The main applications targeted in the long term are efficient and compact optical sources in wavelength ranges where technological solutions are rare. For this exploratory work, we are interested in the conversion from $1.55 \mu \mathrm{m}$ to 775nm.