The study asks whether amorphous silicon can supply both intrinsic near-infrared photoluminescence and a compact resonant cavity for integrated photonics. Solution-synthesized silicon microspheres exhibit room-temperature whispering-gallery-mode emission between 800 and 1100 nm, with a maximum measured quality factor of 522. Experiments demonstrate temperature-, environment-, and optical-power-dependent tuning and light routing into an IP-Dip waveguide and flared coupler fabricated by two-photon polymerization. Electromagnetic simulations identify modes and analyze coupling and upward extracti

Make light. Keep it circulating. Send it somewhere useful.

A tiny sphere of amorphous silicon is both a light source and its own optical cavity. A printed polymer waveguide gives that light a path off the sphere.

Based on Zhou et al. · npj Nanophotonics

Emit

Amorphous silicon supplies the near-infrared light.

Confine

A smooth spherical boundary selects resonant wavelengths.

Route

A two-photon-printed guide carries light to a remote output.

A little optical world.

Break the symmetry, turn up the heat, or bring a waveguide into contact.

1000 nm regime: isolated pairs of narrow resonances.

Does the shape matter?

The same silicon can emit with or without an intact cavity. Try breaking the sphere.

Around 1000 nm, TE and TM mode pairs are well separated. The reported free spectral range is about 0.11 eV.

Light repeatedly reflects along the high-index sphere’s boundary. Wavelengths that reinforce themselves around the rim form whispering-gallery modes .

Shape. Size presets represent reported regimes, not individual measured spectra. Breaking the sphere removes the resonant peaks while broad silicon photoluminescence remains.

Tune. λ(T) = 918 + 0.05(T − 293) nm is an illustrative single-resonance model using the measured thermal slope. The moving light shows intensity changes qualitatively.

Route. The loaded-Q and loss readouts interpolate approximate Supplementary Fig. 8 simulation trends. Qint ≈ 945; loss fraction = 1 − Qloaded/945. Gap dependence uses a smooth exponential teaching model. This fraction describes additional waveguide-induced loss; guided-power extraction was not measured by this quantity. The output glow is qualitative. Indices above 1.52 explore hypothetical guide materials.

The material is the cavity.

Silicon is excellent at guiding light. Making it emit useful light is harder. Here, structural disorder in amorphous silicon provides light-emitting states—and the sphere’s shape turns broad emission into distinct resonances.

There is no separate emitter to position inside a cavity. A single particle does both jobs at room temperature.

Near-infrared resonances emerge under visible-light excitation.

A 945.26 nm resonance with a 1.81 nm linewidth in a 1360 nm sphere.

Solution-grown light sources can pair with freely shaped printed routing. The demonstrated single-sphere device points toward compact sensing and reconfigurable photonic systems.

Multi-sphere placement and lasing are future directions discussed in the paper.

Grow the sphere. Print the path.

The silicon sphere is chemically grown. The waveguide and output coupler are printed.

Chemically grow silicon

Decompose trisilane in supercritical n-hexane to form amorphous microspheres.

Write a 3D light path

A focused femtosecond laser prints the waveguide, flared coupler and support in IP-Dip resin.

Let a sphere make contact

Drop-cast spheres onto silica. Capillary forces during solvent evaporation bring a sphere to the guide.

Excite here. Detect there.

A 532 nm laser pumps the sphere. Near-infrared photoluminescence appears at the remote output.

A bend and a flare

The coupler redirects light out of the substrate plane and expands the optical mode. For the simulated coupler at 900 nm, upward extraction is 69.41% and fundamental-mode reflection is 0.05% .

These values describe the output coupler alone. Supplementary Fig. 6, reproduced and resized from Zhou et al. (2026), CC BY 4.0.

Fabrication used a 780 nm femtosecond laser (approximately 98 fs, 80 MHz). The paper reports approximate lateral and axial focal dimensions of 0.37 µm and 0.92 µm.

What the researchers saw.

Same material. Different geometry.

The intact sphere has sharp peaks over a broad emission envelope. After mechanical fracture, the fragments retain broad photoluminescence but lose the sharp resonances. The comparison ties spectral selection to the spherical cavity.

Panel e compares an intact 1413 nm sphere with fractured fragments; the fragments’ curve is multiplied by 4. The full figure also shows the optical setup, microscopy and composition.

A light source with a path forward.

The work brings intrinsic emission, resonant control and printed routing into one compact platform. Explore the relationships here—then see the experiments and simulations in the paper.

Research, made explorable.

Photoluminescent amorphous silicon microspheres with intrinsic whispering-gallery-mode coupling and waveguide integration

Hong-Wei Zhou, Taizhi Jiang, Brian A. Korgel, Yuebing Zheng & Linhan Lin. npj Nanophotonics 3, 41 (2026) · Published 17 September 2026.

DOI: 10.1038/s44310-026-00149-x · Supplementary material

Article and source figures © The Author(s) 2026, licensed under Creative Commons Attribution 4.0 International. Source figures are reproduced and resized without cropping. The workbench and its light paths are conceptual teaching visualizations.