We demonstrate an integrated spectrometer-on-a-chip composed of an echelle diffraction grating (EDG) and metal-semiconductor-metal (MSM) waveguide photodetector array based on silicon-on-insulator (SOI). In the passive section, silicon oxynitride (SiON) is chosen as the material for the waveguide core and is deposited after selectively removing the top silicon layer of the SOI wafer. The buried silicon dioxide layer of the SOI wafer functions as the lower cladding for the SiON core waveguide. In the active section, the MSM photodetector array is fabricated on the top silicon layer of the SOI waveguide with a pitch width of 7.5 μm. With the butt-coupling structure, a responsivity of 0.41 A/W is obtained at 850 nm. Based on the CMOS-compatible fabrication process, we have fabricated a 60-channel spectrometer with a chip size of 9 mm × 6 mm operating around 850 nm. The measured channel spacing is 0.494 nm, with an adjacent channel crosstalk around 18 dB. The channel nonuniformity is less than 1.5 dB. The CMOS-compatible spectrometer with integrated silicon photodetector array can provide a low-cost solution for high-resolution on-chip spectral analysis for visible and near-infrared light with the wavelength below 1100 nm.

Lithium niobate’s substantial nonlinear optical and electro-optic coefficients have recently thrust it into the limelight. This study presents a thorough review of bound states in the continuum (BICs) in lithium niobate metasurfaces, also suggesting their potential for sensing applications. We propose an all-dielectric tunable metasurface that offers high Q factor resonances in the terahertz range, triggered by symmetry-protected BICs. With exceptional sensitivity to changes in the refractive index of the surrounding medium, the metasurface can reach a sensitivity as high as 947 GHz/RIU. This paves the way for ultrasensitive tunable terahertz sensors, offering an exciting path for further research.

Plasma-enhanced chemical vapor deposition (PECVD) is commonly used for the deposition of silica waveguide layers. When the gaps between waveguides are small, voids are created during the deposition of the upper cladding. This letter presents a new process for filling the gaps of PECVD silica waveguides using boron-germanium codoped upper-cladding and high-temperature annealing. Using appropriate doping concentrations as determined by processing gas flow rates, the image of completely filled gap was observed by scanning electron microscopy, and the measured transmission loss of an arrayed waveguide grating triplexer is reduced by about 2 dB. By avoiding the use of toxic phosphine, the proposed method has potential advantages compared with the commonly used borophosphosilicate glass process.

The CLP Publishing collects CLP journals and partnered optics and photonics journals, and provides readers an optical publishing platform with global influence. SPIE, OSA, CUP. Chinese Laser Press (CLP), established by Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS) and Chinese Optical Society (COS) in 2009, nowadays publishes eight journals and manages three online platforms.