Search

It is recognized that unknown emissivity and ill-posed radiation equations present significant challenges to light-field multi-wavelength pyrometry. Furthermore, emissivity range and choice of initial value also have a significant impact upon the measurement results. This paper demonstrates that a novel chameleon swarm algorithm approach could be used to ascertain temperature information from light-field multi-wavelength data at a higher accuracy level without prior emissivity knowledge. The performance of chameleon swarm algorithm was experimentally tested and compared with the traditional internal penalty function and generalized inverse matrix-exterior penalty function algorithms. Comparisons of calculation error, time, and emissivity values for each channel show that the chameleon swarm algorithm is superior in terms of both measurement accuracy and computational efficiency.

We found that temperature-dependent infrared spectroscopy measurements (i.e., reflectance or transmittance) using a Fourier-transform spectrometer can have substantial errors, especially for elevated sample temperatures and collection using an objective lens. These errors can arise as a result of partial detector saturation due to thermal emission from the measured sample reaching the detector, resulting in nonphysical apparent reduction of reflectance or transmittance with increasing sample temperature. Here, we demonstrate that these temperature-dependent errors can be corrected by implementing several levels of optical attenuation that enable convergence testing of the measured reflectance or transmittance as the thermal-emission signal is reduced, or by applying correction factors that can be inferred by looking at the spectral regions where the sample is not expected to have a substantial temperature dependence.

Mode-division multiplexing can scale the capacity of optical communications and optical interconnects. We demonstrate an ultra-compact and fabrication-error tolerant silicon three-mode multiplexer by shallowly etching rectangular trenches on a multi-mode interferometer. Depending on the selected input port, the TE0 mode is converted to the eigenmodes of the bus waveguide. These modes are coupled to each other owing to the refractive-index perturbation induced by the shallow trenches and finally converted to a selected spatial mode at the output. A three-mode multiplexing device is experimentally demonstrated with a footprint of 2.00 × 17.05 µm2. The bandwidths for the three channels are >70 nm with crosstalk values below –10 dB.