[Paper Review] 1305 nm MoTe2-on-silicon Laser

Hanlin Fang, Jin Liu+7 more|arXiv (Cornell University)|Oct 4, 2017

Photonic and Optical Devices3 citations

TL;DR

This paper demonstrates an optically pumped, continuous-wave (CW) laser at 1305 nm using molybdenum ditelluride (MoTe2) as a gain material integrated into a silicon photonic crystal nanocavity on a silicon-on-insulator platform. The device achieves a low lasing threshold of 1.5 kW/cm² at room temperature, marking a critical step toward electrically pumped, on-chip 2D semiconductor lasers for silicon photonics in the O-band window.

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.

Motivation & Objective

• To develop a monolithic, on-chip silicon laser source compatible with standard CMOS fabrication processes.
• To address the lack of efficient, integrable light sources in silicon photonics by leveraging atomically thin transition metal dichalcogenides (TMDs).
• To demonstrate lasing at 1305 nm—within the O-band used in optical communications—using MoTe2 as a direct-bandgap gain material.
• To achieve low-threshold, continuous-wave lasing at room temperature in a 2D-on-silicon hybrid platform.
• To establish a foundation for future electrically pumped, nanoscale silicon light sources for integrated photonic circuits.

Proposed method

• The laser structure employs a photonic crystal nanocavity fabricated in a silicon-on-insulator (SOI) wafer to confine light and enhance light-matter interaction.
• Monolayer MoTe2 is mechanically exfoliated and transferred onto the SOI nanocavity to serve as the gain medium.
• Optical pumping at 532 nm is used to excite the MoTe2, inducing population inversion and stimulated emission.
• The device operates in continuous-wave (CW) mode, with lasing confirmed via spectral analysis and threshold power measurements.
• The cavity-Q factor and mode profile are engineered to maximize optical confinement and gain enhancement.
• Lasing wavelength is tuned to 1305 nm, matching the central O-band window for telecommunications.

Experimental results

Research questions

• RQ1 Can MoTe2 be effectively integrated into a silicon photonic nanocavity to achieve room-temperature lasing?
• RQ2 What is the minimum pump power density required to achieve lasing in a 2D-on-silicon platform at 1305 nm?
• RQ3 Can the laser operate in continuous-wave mode under ambient conditions with high efficiency?
• RQ4 How does the performance of MoTe2 compare to other 2D TMDs in terms of lasing threshold and wavelength stability?
• RQ5 Is the 2D-on-silicon geometry viable as a scalable, low-cost platform for on-chip light sources?

Key findings

• The MoTe2-on-silicon laser achieves lasing at 1305 nm, precisely within the O-band used in optical fiber communications.
• The device operates in continuous-wave (CW) mode at room temperature, demonstrating practical viability for real-world applications.
• A low threshold pump power density of 1.5 kW/cm² is achieved, indicating high optical gain and efficient light confinement.
• The laser operates with a high-quality factor (Q) photonic crystal nanocavity, enabling strong mode confinement and enhanced light-matter interaction.
• The integration of monolayer MoTe2 with silicon photonic circuits is experimentally validated, showing promise for on-chip integration.
• The results establish a foundational platform for future electrically pumped, nanoscale silicon light sources based on 2D materials.