MoTe₂ Photodetector for Integrated Lithium Niobate Photonics.

Area of Science:

• Photonics and Materials Science
• Integrated Optics
• Optoelectronics

Background:

• Scalable integrated lithium niobate photonics requires efficient on-chip photodetectors for optical-to-electrical signal conversion.
• Two-dimensional materials offer promising high-efficiency detection capabilities for integrated photonic circuits.

Purpose of the Study:

• To demonstrate an efficient on-chip photodetector utilizing few-layer Molybdenum Ditelluride (MoTe2) integrated with a thin-film lithium niobate waveguide.
• To integrate this photodetector with a microresonator for operation in the optical telecommunication band.
• To evaluate the performance characteristics of the integrated photodetector.

Main Methods:

• Fabrication of lithium niobate-on-insulator waveguides and micro-ring resonators using femtosecond laser photolithography-assisted chemical-mechanical etching.
• Integration of few-layer MoTe2 onto the lithium niobate waveguide.
• Characterization of optical absorption, transmission loss, responsivity, dark current, and photo-dark current ratio at 1550 nm.

Main Results:

• The lithium niobate waveguide-integrated MoTe2 exhibited a high absorption coefficient of 72% and a low transmission loss of 0.27 dB µm⁻¹.
• The on-chip photodetector achieved a responsivity of 1 mA W⁻¹ at 20 V bias, with a low dark current of 1.6 nA and a photo-dark current ratio of 10⁸ W⁻¹.
• Photocurrent was approximately 160 times higher compared to free-space irradiation due to effective waveguide coupling.

Conclusions:

• An efficient on-chip photodetector based on MoTe2 integrated with lithium niobate photonics was successfully demonstrated.
• The device exhibits excellent performance metrics, including high responsivity and low dark current.
• Integration with a micro-ring resonator (Q factor of 10⁴) enables wavelength-selective detection, paving the way for applications in on-chip spectrometers and biosensors.