Taking silicon photonics modulators to a higher performance level: state-of-the-art and a review of new technologies

Optical links are moving to higher and higher transmission speeds while shrinking to shorter and shorter ranges where optical links are envisaged even at the chip scale.The scaling in data speed and span of the optical links demands modulators to be concurrently performant and cost-effective.Silicon photonics(SiPh),a photonic integrated circuit technology that leverages the fabrication sophistication of complementary metal-oxide-semiconductor technology,is well-positioned to deliver the performance,price,and manufacturing volume for the high-speed modulators of future optical communication links.SiPh has relied on the plasma dispersion effect,either in injection,depletion,or accumulation mode,to demonstrate efficient high-speed modulators.The high-speed plasma dispersion silicon modulators have been commercially deployed and have demonstrated excellent performance.Recent years have seen a paradigm shift where the integration of various electro-refractive and electro-absorptive materials has opened up additional routes toward performant SiPh modulators.These modulators are in the early years of their development.They promise to extend the performance beyond the limits set by the physical properties of silicon.The focus of our study is to provide a comprehensive review of contemporary(i.e.,plasma dispersion modulators)and new modulator implementations that involve the integration of novel materials with SiPh.

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.

High speed phase modulators for silicon photonic integrated circuits:a role for lithium niobate?

Lithium niobate(LN)has been and still is a prominent material for high speed optical modulators.The performance of such LN-modulators—as a stand-alone building block for optical systems—has been unchallenged for many years.But in many ways it has proven to be very hard to integrate lithium niobate modulators with other functions on a single optical chip.As a result,scientific interest in this material has been fading away.

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。