Silicon and silicon nitride photonic circuits for spectroscopic sensing on-a-chip [Invited]

There is a rapidly growing demand to use silicon and silicon nitride（Si3N4） integrated photonics for sensing applications, ranging from refractive index to spectroscopic sensing. By making use of advanced CMOS technology,complex miniaturized circuits can be easily realized on a large scale and at a low cost covering visible to mid-IR wavelengths. In this paper we present our recent work on the development of silicon and Si3N4-based photonic integrated circuits for various spectroscopic sensing applications. We report our findings on waveguide-based absorption, and Raman and surface enhanced Raman spectroscopy. Finally we report on-chip spectrometers and on-chip broadband light sources covering very near-IR to mid-IR wavelengths to realize fully integrated spectroscopic systems on a chip.

Widely tunable 2.3μm III-V-on-silicon Vernier lasers for broadband spectroscopic sensing

Heterogeneously integrating III-V materials on silicon photonic integrated circuits has emerged as a promising approach to make advanced laser sources for optical communication and sensing applications. Tunable semiconductor lasers operating in the 2–2.5 μm range are of great interest for industrial and medical applications since many gases(e.g., CO_2, CO, CH_4) and biomolecules(such as blood glucose) have strong absorption features in this wavelength region. The development of integrated tunable laser sources in this wavelength range enables low-cost and miniature spectroscopic sensors. Here we report heterogeneously integrated widely tunable III-V-on-silicon Vernier lasers using two silicon microring resonators as the wavelength tuning components. The laser has a wavelength tuning range of more than 40 nm near 2.35 μm. By combining two lasers with different distributed Bragg reflectors, a tuning range of more than 70 nm is achieved. Over the whole tuning range, the side-mode suppression ratio is higher than 35 dB. As a proof-of-principle, this III-V-on-silicon Vernier laser is used to measure the absorption lines of CO. The measurement results match very well with the high-resolution transmission molecular absorption(HITRAN) database and indicate that this laser is suitable for broadband spectroscopy.

Monolithic GaAs/Si V-groove depletion-type optical phase shifters integrated in a 300 mm Si photonics platform

We demonstrate monolithically integrated n-GaAs/p-Si depletion-type optical phase shifters fabricated on a 300 mm wafer-scale Si photonics platform.We measured the phase shifter performance using Mach–Zehnder modulators with the GaAs/Si optical phase shifters in both arms.A modulation efficiency of V_(π)L as low as 0.3 V·cm has been achieved,which is much lower compared to a carrier-depletion type Si optical phase shifter with pn junction.While propagation loss is relatively high at.5 d B∕mm,the modulator length can be reduced by the factor of.2 for the same optical modulation amplitude of a Si reference Mach–Zehnder modulator,owing to the high modulation efficiency of the shifters.

Capacitive actuation and switching of add–drop graphene-silicon micro-ring filters

We propose and experimentally demonstrate capacitive actuation of a graphene–silicon micro-ring add/drop filter. The mechanism is based on a silicon–SiO_2–graphene capacitor on top of the ring waveguide. We show the capacitive actuation of the add/drop functionality by a voltage-driven change of the graphene optical absorption. The proposed capacitive solution overcomes the need for continuous heating to keep tuned the filter's in/out resonance and therefore eliminates "in operation" energy consumption.

将激光集成到硅上的4种方法

在日常生活中,将一系列光电子功能集合在一块芯片上的光子集成电路越来越常见,它们被用于连接数据中心服务器机架的高速光收发器(包括用于提供本刊网站的光收发器)、保持自动驾驶汽车正常行驶的激光雷达、发现大气中化学物质的光谱仪,以及许多其他应用。所有这些系统都变得越来越便宜,并且在某些情况下,使用硅制造技术生产大部分集成电路也是经济可行的。