A strong light-matter interaction between the optical field and the material medium is essential for a diverse field of applications, ranging from integrated photonics, optical sensing, quantum optics, and nonlinear optics etc. Two-dimensional Photonic Crystals (PhC) offer such strong interaction due to their ability to confine light in a tiny space or to control the speed of light. It has been well established now that by using the slow light property of PhC waveguides, light can be propagated through them at a fraction of the speed of light in vacuum. This ability of PhC waveguides has been exploited for many linear or nonlinear applications, such as electro-optic modulation and optical switching, optical delay line, signal regeneration through four wave mixing and Raman amplification etc. Silicon-on-insulator (SOI) has always been the most preferred material for such demonstrations with PhC structures for telecomm wavelengths, primarily because of two reasons: first, Si-air or Si-SiO2 material combination offers a high index contrast material platform to realize PhC structures with large photonic band gap (PBG) and secondly, the fabrication process for Si is well established. However, strong nonlinear absorption, i.e. Two Photon Absorption (TPA) in Si adversely effects the performance of nonlinear Si photonic devices. Recently, Silicon Nitride (Si3N4) is being exploited as an alternative material platform for nonlinear photonic applications. Si3N4 platform offers several advantages, such as optical nonlinearity without any TPA for telecom wavelengths, large transmission window from visible wavelengths all the way to mid infrared wavelengths.
In this work, we demonstrate, to our knowledge for the first time, PhC waveguides in in a silicon rich silicon nitride membrane. Showing a demonstrated group index up to 110 and and losses as low as 4.6 dB/cm.
The SIN platform development was initiated within the EPSRC first grant EP/K02423X/1 HERMES: High dEnsity Silicon GeRManium intEgrated photonicS. The platform is currently developped further through collaboration under the EPSRC : A Platform Grant EP/N013247/1: Electronic-Photonic Convergence, EP/L021129/1 CORNERSTONE: Capability for OptoelectRoNics, mEtamateRialS, nanoTechnOlogy aNd sEnsing and European project H2020 COSMICC,