Fig. 2: Characterization of the on-chip spectrometer.
From: Compact and high-resolution spectrometer via Brillouin integrated circuits
a–b Experimental setup for characterizing the spectrometer. The phononic mode in the waveguide is driven by a vector network analyzer (VNA) through an interdigital transducer (IDT, c). The optical input signal is reflected through the Brillouin process when the phase-matching condition is fulfilled. The reflected light is measured by the VNA through a heterodyne detection or directly detected by the photodiode (PD) under high signal-to-noise ratio conditions. The Brillouin interaction region is around 1 mm. EDFA erbium-doped fiber amplifier, PC polarization controller. d and g Displacement and electrical field distributions at the waveguide cross-section for the quasi-Rayleigh phononic mode and the fundamental transverse electric photonic mode, respectively. All these simulations were performed using the finite element method (COMSOL Multiphysics). c, e Scanning electron microscope pictures of the IDT and phononic-photonic mode multiplexing device. f S11 parameter of IDT which exhibits a resonance frequency of 8.5 GHz. h Measured reflected optical signal against the input RF frequency, with the input optical wavelength fixed at 1576 nm.
