Ultra-Thin MoSe₂ Grating Traps Infrared Light | Phys.org

Scientists at the University of Warsaw’s Faculty of Physics, in collaboration with Łódź University of Technology, Warsaw University of Technology, and the Polish Academy of Sciences, have demonstrated a method of trapping infrared light within a layer of material just 40 nanometers thick, a development announced today, March 19, 2026.

The breakthrough centers on the apply of molybdenum diselenide (MoSe₂), a layered van der Waals semiconductor, engineered into a subwavelength grating. This grating structure, according to researchers, confines infrared light at a scale significantly smaller than the wavelength of the light itself. The refractive index of MoSe₂—approximately 4.5—is substantially higher than that of materials traditionally used in photonics, enabling this enhanced light manipulation.

The research addresses a key challenge in photonics: the difficulty of miniaturizing photonic devices. Conventional photonic components require dimensions comparable to the wavelength of light, limiting the density of integrated photonic circuits. Subwavelength gratings offer a potential solution by controlling light at scales below its wavelength, acting similarly to prisms to diffract and manipulate light.

Researchers have integrated a MoSe₂/WS₂ heterojunction photodiode with a silicon nitride waveguide, achieving high responsivity—around 1 Ampere per Watt—at a wavelength of 780 nanometers. This configuration also suppresses dark current to approximately 50 picoamperes, a significant reduction compared to devices using only MoSe₂. The power spectral density of the dark current was measured as low as 1 x 10⁻¹² Amperes per square root of Hertz, resulting in a noise equivalent power of approximately 1 x 10⁻¹² Watts per square root of Hertz.

The integrated photodetector has been used to characterize the transfer function of a microring resonator on the same chip, demonstrating its utility in advanced optical systems. The ability to integrate such photodetectors with high performance in the near-infrared regime is expected to be critical for future developments in optical communications, quantum photonics, and biochemical sensing, according to a study published in Light Science & Applications.

Detection of near-infrared light is also considered promising for integrated quantum photonic devices, particularly in relation to color centers in silicon carbide, diamond, and hexagonal boron nitride, which emit photons in the visible and near-infrared spectrum. Efforts are underway to integrate these potential qubits with nanoscale devices.