FOTONİK 2022 - Ulusal Optik, Elektro-Optik ve Fotonik Çalıştayı, Ankara, Turkey, 09 September 2022
When light passes through a
multimode fiber, two-dimensional random intensity patterns are formed due to
the complex interference within the fiber. The extreme sensitivity of the
speckle patterns to the frequency of light paved the way for high-resolution multimode
fiber spectrometers. However, this approach requires expensive infrared
cameras and impedes the integration of spectrometers on-chip. In this study, we
propose a single-pixel multimode fiber spectrometer by exploiting wavefront
shaping. The input light is structured with the help of a spatial light
modulator, and optimal phase masks, focusing light at the distal end of the
fiber, are stored for each wavelength. Variation of the intensity in the
focused region is recorded by scanning all wavelengths under fixed optimal
masks. Based on the intensity measurements, we show that an arbitrary input
spectrum two wavelengths 20 pm apart from each other can be reconstructed
successfully (with a reconstruction error of 3%) in the near-infrared regime,
corresponding to a resolving power of R = 105. We also demonstrate the
reconstruction of broadband continuous spectra for various bandwidths. With the
installation of a single-pixel detector, our method provides low-budget and
compact detection at an increased signal-to-noise ratio.