1305 nm MoTe2-on-silicon Laser

Hanlin Fang1,2, Jin Liu2, Hongji Li1,2, Lidan Zhou1, Lin Liu1, Juntao Li1,2*, Xuehua Wang1,2, Thomas F. Krauss3, Yue Wang3

1 State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou, 510275, China 2 School of Physics, Sun Yat-Sen University, Guangzhou, 510275, China 3 Department of Physics, University of York, York, YO10 5DD, UK

*correspondence to: lijt3@mail.sysu.edu.cn

ABSTRACT

The missing piece in the jigsaw of silicon photonics is a light source that can be easily incorporated into the standard silicon fabrication process. Recent advances in the development of atomically thin layers of semiconducting transition metal dichalogenides (TMDs), with direct bandgaps in the near-infrared region, have opened up new possibilities for addressing this need. Here, we report a unique silicon laser source that employs molybdenum ditelluride (MoTe2) as a gain material in a photonic crystal nanocavity resonator, fabricated in silicon-on-insulator. We demonstrate optically pumped MoTe2-on- silicon devices lasing at 1305 nm, i.e. in the centre of the O-band used in optical communications, operating in the continuous-wave (CW) regime, at room temperature and with a threshold power density as low as 1.5 kW/cm2. This 2D-on-silicon geometry offers the promise of an integrated low-cost electrically pumped nanoscale silicon light source, thereby adding an essential building block to the silicon photonics platform.

INTRODUCTION

Due to its excellent integratability and compatibility with CMOS technology, silicon photonics has been widely recognized as the most promising platform a for future broadband, high-speed data transmission infrastructure [1]. Photonics offers substantial reductions in operating energy and improvements in the performance of data communication systems, which for instance explains its wide use in datacentres [2]. While many essential silicon photonics components have already been demonstrated with excellent performance, such as extremely low-loss waveguides [3], ultra-fast modulators [4], and high bandwidth detectors [5], a silicon light source that can be easily incorporated into the standard fabrication process has remained challenging. Silicon itself is a poor light emitter due to its indirect bandgap, so a combination with suitable light emitting materials that can be directly incorporated into the process flow needs to be investigated. Most notably, the hybrid integration of III-V materials with silicon has made significant progress [6,7], but the approach is costly and complex, so there is still an appetite for exploring alternative solutions. The MoTe2-on-silicon laser we present here is such a promising alternative, especially as it operates in the centre of the technologically important 1260 - 1360 nm wavelength range, also known as “O band” in fiber-optic communications.

We identified molybdenum ditellurite (MoTe2) as a suitable gain material for this laser. MoTe2 is one of a family of two-dimensional (2D) materials that were spawned out of the graphene revolution. Many of these 2D materials, especially atomically thin transition metal dichalcogenides (TMDs) such as tungsten diselenide (WSe2), molybdenum disulfide (MoS2) and now MoTe2, exhibit remarkable optoelectronic properties, such as strong exciton binding energy and high carrier mobility [8-12]. 2D materials are a unique group of materials whereby atoms are strongly bonded in the plane but only weakly attached out-of-plane; this weak interaction between layers makes the extraction of single or a few layers of atoms possible, which underpins this burgeoning research area [13]. Excitingly, several TMD-based lasers have been recently demonstrated, including a continuous-wave (CW) WSe2 monolayer laser emitting around 740 nm at 80 K, based on a gallium phosphide photonic crystal (PhC) cavity [14], a microdisk laser including a tungsten disulfide (WS2) monolayer that is sandwiched by a Si3N4 and hydrogen silsesquioxane (HSQ), operating at 612 nm at 10 K [15], and a room temperature four layer MoS2 laser emitting in the wavelength range of 600 to 800 nm, based on a vertically coupled microdisk and microsphere cavity [16]. Whereas these initial demonstrations were focussed on the visible regime, a TMD-based laser operating in the silicon transparency window has now also been demonstrated [17], using a silicon nanobeam cavity and a monolayer of MoTe2 as the gain material. Our work now demonstrates that the operating wavelength can be pushed further into the infrared and into the 1260 nm to 1360 nm communications window (“O band”), which signifies a technological step-change for this type of laser. We also show that a monolayer of MoTe2 is not necessarily required for laser operation, by demonstrating lasing from multilayers, thereby increasing manufacturing tolerances.

RESULTS

…(Full text truncated)…