Nanophotonics

Nanophotonics explores how light behaves and can be controlled when structures are scaled to nanometre dimensions, comparable to or smaller than the wavelength of visible, infrared or ultraviolet radiation. At these scales, new optical effects arise from strong light–matter interactions that are not accessible in bulk materials. Metallic nanostructures support plasmonic resonances, concentrating electromagnetic energy into subwavelength “hotspots” for enhanced sensing, nonlinear optics and nanoscale field confinement. Dielectric nanoresonators exploit Mie modes to tailor scattering, local density of states and optical forces without the losses intrinsic to metals. Periodic arrangements of subwavelength elements—photonic crystals and metasurfaces—further control dispersion, reflection and transmission with designer band-gaps or anomalous refraction. Integration of such devices on chip-scale platforms, using low-loss materials like silicon nitride, enables compact waveguides, microresonators, modulators and frequency comb generators. Meanwhile, advances in quantum nanophotonics harness single-photon sources, quantum memories and entangled-photon gates for emerging applications in secure communications, metrology and information processing. Across sensing, communications, energy harvesting and quantum technologies, nanophotonics engineers both the spatial confinement of light and its spectral or temporal properties to achieve performance far beyond conventional optics.

Research from Nature Portfolio

Sub-1 V ⋅ cm electro-optic modulators operating from the visible into the near-infrared have been realised in thin-film lithium niobate, demonstrating voltage-length products below 1 V ⋅ cm, on-chip optical losses under 1 dB cm⁻¹ and electro-optic bandwidths exceeding 35 GHz. Such devices, integrated into Mach–Zehnder interferometers, enable tunable on-chip frequency combs and frequency shifting of pulsed light beyond classical Fourier limits, opening routes to sub-volt control in imaging, optogenetics and quantum photonics.

Wafer-scale fabrication of ultralow-loss silicon nitride photonic circuits has been achieved via a high-yield process yielding dispersion-engineered microresonators with mean quality factors above 30 × 10⁶ (loss ≈ 1 dB m⁻¹). Statistical analysis of tens of thousands of resonances across 4-inch wafers confirms metre-long spiral waveguides with losses as low as 2.4 dB m⁻¹. Self-calibrated Kerr nonlinear measurements further reveal intrinsic absorption-limited quality factors exceeding 2 × 10⁸, providing a platform for metrology-grade frequency combs and integrated parametric amplifiers.

Visible–near-infrared phase and amplitude modulators featuring voltage-length products well below 1 V ⋅ cm and bandwidths above 35 GHz have been demonstrated in thin-film lithium niobate. Mach–Zehnder devices achieved VπL as low as 0.55 V ⋅ cm at 738 nm with on-chip losses ~0.7 dB cm⁻¹. Integrated electro-optic frequency combs spanning the visible region, with over 50 lines and tunable spacing, illustrate the potential for sub-volt, high-speed coherent sources in sensing and communications.

Research from all publishers

A heterogeneous silicon nitride platform incorporating active and passive elements on a single chip has enabled fully integrated rubidium-based atomic sensors operating at 780 nm and up to 110 °C. By co-integrating waveguides, modulators and detectors, this approach realises compact atomic-clock and magnetic-field sensors with sub-pm Hz⁻¹ᐟ² performance in harsh environments.

Nanomechanical photothermal sensing has been used to map the stress-dependent optical extinction of LPCVD silicon nitride. Measurements at 632.8 nm reveal that tensile stress increases the bandgap and decreases optical absorption by two orders of magnitude, correlating with variations in stoichiometry. This technique provides a sensitive, scattering-free probe of loss mechanisms in integrated photonic materials.

The photonic Damascene process has produced thick, high-confinement silicon nitride waveguides (1.35 µm) with optical quality factors above 3.7 × 10⁶, enabling on-chip coherent Kerr soliton frequency comb generation. By using substrate topography for stress control and crack prevention, these microresonators achieve anomalous group-velocity dispersion for ultrabroadband nonlinear photonics in compact footprints.

Nanophotonics publication trend

The graph below shows the total number of articles in nanophotonics across all publications each year (not limited to Nature Index journals).

Technical terms

Photonic Integrated Circuit (PIC): A chip integrating multiple optical functions—guiding, modulation, detection—into a single monolithic device.

Quality Factor (Q): A dimensionless measure of resonance sharpness; higher Q indicates lower loss and longer photon lifetime in a cavity or resonator.

Electro-Optic Modulator: A device that controls the phase or amplitude of light via an applied electric field, typically exploiting the Pockels effect.

Silicon Nitride (Si₃N₄): A low-loss dielectric material with a wide transparency window and high refractive index contrast, compatible with CMOS processes.

Dispersion Engineering: The design of waveguide or resonator geometries to tailor the frequency dependence of phase or group velocity, crucial for slow light and comb generation.

Frequency Comb: A spectrum of equally spaced, phase-coherent laser lines used for precision metrology, timing and communications.

References

1. Sub-1 Volt and high-bandwidth visible to near-infrared electro-optic modulators. Nature Communications (2023).
2. High-yield, wafer-scale fabrication of ultralow-loss, dispersion-engineered silicon nitride photonic circuits. Nature Communications (2021).
3. Photonic integration platform for rubidium sensors and beyond. Optica (2023).
4. Stress-Dependent Optical Extinction in Low-Pressure Chemical Vapor Deposition Silicon Nitride Measured by Nanomechanical Photothermal Sensing. Nano Letters (2024).
5. Photonic Damascene process for integrated high-Q microresonator based nonlinear photonics. Optica (2016).