Guiju Zhang

This study addresses the critical challenge of detecting ultrafine particles with diameters as small as 0.1 μm in high-sensitivity optical particle counters (OPCs), which is of great importance for semiconductor manufacturing and environmental monitoring. Based on Mie scattering theory, a physical scattering model is established, and a novel orthogonal light-collection system integrating a spherical mirror and a collection lens is optimized. Simulation results indicate that, when targeting the 0.1 μm particle channel using a 405 nm diode laser and a wide collection angular range of 30°–150°, the proposed configuration enhances the scattering-light collection efficiency by at least 17.8% compared with conventional structures. This design markedly improves the acquisition capability for weak scattering signals and provides important theoretical and technical support for the development of high-sensitivity OPCs.

On-chip filters are widely used in integrated optical systems and are indispensable for expanding the communication capacity. A silicon waveguide filter is fabricated into a subwavelength Bragg grating structure using the optical phase-change material Ge2Sb2Se4Te1 (GSST). Three-dimensional finite-difference time-domain method simulations showed that this structure performed multichannel filtering in the communications C-band (1530 to 1565 nm), demonstrating a minimum insertion loss of 0.238 dB and a full width at half-maximum of 3.4 nm with an incident TE0 mode. The number and width of channels can be adjusted using structural parameters. Furthermore, the overlapping frequencies of passbands and stopbands are obtained by the phase transition of GSST. This structure could potentially find use as an optical signal modulation device in on-chip integrated systems.

We propose a six-layer waveguide structure embedded in a single-layer grating based on guided-mode resonance (GMR), which can realize ultra-narrowband filtering with a tunable resonance wavelength. The filtering characteristics were analyzed and calculated by rigorous coupled-wave analysis (RCWA) and COMSOL Multiphysics. The narrowband resonance wavelength and absorption are tuned by changing the geometry and physical parameters of the structure such as the grating period and width, layer thickness, and materials. We designed and calculated the full width at half maximum (FWHM) and resonance absorption spectra in detail under different polarization states of electromagnetic waves. We obtained an absorption FWHM of 8.51e-5 nm for the transverse electric (TE) mode and 0.023 nm for the transverse magnetic (TM) mode, with the absorption coefficients having a value over 99.2%. The GMR filtering structure shows a good sensitivity and figure of merit (FOM) for refractive index sensing. For instance, a very high FOM of 17782.6/RIU for TM incidence is observed. These structures can have possible applications in optical information devices and sensors.