Random scattering of light in disordered media can be used for highly sensitive speckle-based wavemeters and spectrometers. However, the multiple scattering events that fold long optical paths within a compact space also make such devices exceedingly sensitive to vibrations and small disturbances to the disordered media. Here, we show how scattering can be engineered so that it can be used for a compact computational spectrometer that is largely insensitive to environmental factors. We designed and fabricated a three-dimensional pseudo-random nano-void pattern with 62% scattering efficiency. The controlled amount of multiple scattering ensured a sufficiently long optical path for the target resolution of 100 pm, with optimal long-term stability. The 200-μm-thick scattering silica substrate was integrated in a compact assembly with a low-cost camera sensor. The target resolution was achieved for full spectrum measurements while single wavelengths could be determined with 50 pm resolution. Such tailored scattering systems can improve the trade-off among cost, size, stability, and spectral resolution in computational spectrometers.

We report the use of a terahertz (THz) transparent material, cyclic olefin copolymer (COC or TOPAS), for fabricating a hollow-core antiresonant fiber that provides an electromagnetic wave guidance in the THz regime. A novel fabrication technique to realize a hollow-core antiresonant polymer optical fiber (HC-ARPF) for THz guidance is proposed and demonstrated. The fiber is directly extruded in a single-step procedure using a conventional fused deposition modeling 3D printer. The fiber geometry is defined by a structured nozzle manufactured with a metal 3D printer, which allows tailoring of the nozzle design to the various geometries of microstructured optical fibers. The possibility to use the HC-ARPF made from TOPAS for guiding in the THz region is theoretically and experimentally assessed through the profile of mode simulation and time-frequency diagram (spectrogram) analysis.