Ultrawide-bandwidth on-chip spectrometer design using band-pass filters

Ultra-efficient diamond plasmonic band-stop filter with enhanced effect

In this paper, a band-stop filter based on a surface plasmon polariton metal-insulator-metal is designed and studied. The relationship between wavelength and filter transmittance is simulated using the finite difference time domain method and coupled mode theory. Compared with a single-diamond resonator, the minimum transmittances of the double-diamond resonator and double-rectangular resonator at a fixed wavelength are increased by 11.33% and 14.25%, respectively, achieving an enhancement effect. The research results also show that the sensitivity of the filter can reach 860 nm/RIU. The structure has good application prospects in optical integration, optical communication, and optical information processing.

Planar Waveguide-Based Fiber Spectrum Analyzer Mountable to Commercial Camera

We present the design of a planar spectrometer that separates the wavelength channels from an input fiber and focuses the spectral lines onto a camera without any free-space optical elements. The geometric arrangements of the waveguides to achieve different spectroscopic parameters are explained in detail, allowing adjustable focal lengths, high spectral resolution, and broad free spectral range. The optical chip is fabricated on a low-cost polymer platform as proof of concept. The optical spectrum of a multiwavelength laser is measured by the proposed device, and the result is in good agreement with a commercial optical spectrum analyzer. The large focal depth of the chip allows an optical assembly of much relaxed alignment accuracy. We demonstrate a tube design to encapsulate the chip fixed with the input fiber. The assembly is then mounted to a commercial camera with standard C-mount threading as a convenient fiber spectrum analyzer without customized detectors and circuits. Our design may provide a low-cost and versatile solution for the development of compact spectroscopic equipment.

3D integrated wavelength demultiplexer based on a square-core fiber and dual-layer arrayed waveguide gratings

We present a 3D integrated wavelength demultiplexer using a square-core fiber (SCF) and matched dual-layer arrayed waveguide gratings (AWGs). The SCF works as a 3D fiber multimode interference device, which splits the input light into symmetric four spots. The spots are then coupled to a pitch-matched 4-waveguide network, each connecting an AWG. Interface waveguides are designed to improve the coupling efficiency between the SCF and the dual-layer chip. The four AWGs are designed with different central wavelengths and a large free spectral range (FSR) of 120 nm. To reach a small and uniform insertion loss among different channels, only the central channels of each AWG are used for demultiplexing. The device is fabricated on a polymer platform. The upper and lower layers of the chip are fabricated using the same photolithography mask but rotated 180° so that 4 different AWG designs can be mapped to a single chip. The measured transmission spectra of the four AWGs cover a bandwidth of 112 nm. The insertion loss variation is smaller than 1.4 dB. The designed device can find applications in fiber optic sensing, communication, and astronomy.