[17p-A404-1~14] 3.16 Optics and Photonics English Session

▲ [17p-A404-14] Bragg Grating Coupled High Q-Factor Ring Resonator using Liquid Source CVD Deposited Si₃N₄ Film at 150°C

〇(D)Xiaoyang Cheng¹, Shiyoshi Yokoyama¹ (1.Kyushu Univ.)

Keywords:Ring Resonator, Silicon Nitride, LSCVD

The micro-ring resonator is the promising optical device for a variety of applications due to its compact size design, wavelength selectivity, and flexible structure. Based on the intra-cavity effective refractive index change or resonance shift, the micro-ring resonators work as a crucial component in optical sensors, de-multiplex system, optical modulator and so on. In this work, authors report for the first time on CMOS-compatible integrated micro-ring resonators with Bragg gratings coupled at both bus ends using a high quality Si₃N₄ film deposited by the liquid source CVD (LSCVD) method at ultra-low temperature of 150 ºC. Generally, the Si₃N₄ films deposited by either LPCVD or PECVD have demonstrated high tensile stress which prevents a thicker film deposition greater than 250 nm-thick with low loss state. Considering above, LSCVD is developed to fabricate the high quality Si₃N₄ films of several micrometers thickness without the limitation of cracking using the liquid SiN-X source at only 150 ºC, which guaranteed Kerr-based nonlinearity while featured high thermal compatibility with existing silicon photonics and front-end electronic devices especially those involving flexible/organic substrate. Furthermore, LSCVD deposition without needing SiH₄ and NH₃ chemistry also avoided the dangling Si-H and N-H bonds, which usually occur to PECVD and LPCVD and required extra 1200 ºC post-annealing to deal with such intrinsic absorption loss in C-band. We demonstrated high Q-factor ring resonators in this Si₃N₄ films, showing Q-value of over 1.5 × 10⁵ with 100-μm radius. A 3-dB bandwidth of around 70 nm for grating coupler was also achieved with 1550 nm central wavelength, while the coupling efficiency from fiber to grating is around 3 dB. In this case, the measured spectral bandwidth can cover most of operating frequency of C-band and L-band. The LSCVD deposited Si₃N₄ is therefore a promising CMOS-compatible integration platform for nonlinear functional devices and circuits at telecommunication wavelengths.