Su8-waveguide based phase corrected fourier transform spectrometer chip with low side ripples

Abstract

Integrated Fourier transform spectrometer (FTS) chip is of great interest recently due to its small size, low cost, and inherent high throughput. Phase and intensity errors caused by fabrication imperfections can give rise to severe side ripples in the retrieving spectrum of an FTS chip. To suppress the side ripples poses a great challenge, especially for the spatial heterodyne spectrometer (SHS) chip constituted by numerous Mach-Zehnder interferemoters (MZI) and having a relatively large size. Pseudoinverse algorithm combined with apodization function is considered to be able to compensate the phase and intensity errors efficiently. However, recent researches show that it still has its limitations, some results illustrate the side ripples of the retrieving spectra can be as large as −6 dB. In this article, we design, fabricate and characterize an Su8-waveguide based SHS chip with 51 MZIs, each MZI is accompanied with a pair of heating electrodes to correct the phase error. Different factors that contribute to the side ripples of the retrieved spectrum are analyzed and simulated. Our experimental result shows that by means of physically heat-tuning the metal electrodes and mathematically compensating the transmissivity fluctuations, the side ripples can be suppressed to be in the range from −19 dB to −15 dB for monochromatic and doublet light in our Su8-waveguide based SHS chip.