Fig. 1: Schematic and images of the hybrid, microcomb-based, photonic microwave oscillator chip. | Light: Science & Applications

Fig. 1: Schematic and images of the hybrid, microcomb-based, photonic microwave oscillator chip.

From: A chip-integrated comb-based microwave oscillator

Fig. 1

a Schematic of the chip device. The microelectronic circuit supplies current to the DFB laser and stabilizes its temperature. Via edge-coupling, the CW light from the laser enters the \({{\rm{Si}}}_{3}{{\rm{N}}}_{4}\) microresonator (\({A}^{+}\)). Exploiting the optical back-scattering (\({A}^{-}\)) from the \({{\rm{Si}}}_{3}{{\rm{N}}}_{4}\) microresonator to the laser, laser self-injection locking occurs that significantly narrows the laser linewidth. Simultaneously a circulating platicon/dark pulse stream is formed in the microresonator. The output pulse stream is received by the PD chip that outputs a microwave carrier at the pulse repetition rate. \({S}_{\phi }\), microwave phase noise. \({f}_{{\rm{offset}}}\), Fourier offset frequency. b Photo of the hybrid chip device and individual components. c Zoom-in image showing the DFB laser wire-bonded to the PCB and edge-coupled to the \({{\rm{Si}}}_{3}{{\rm{N}}}_{4}\) microresonator chip. d Zoom-in image showing the PD chip edge-coupled to the \({{\rm{Si}}}_{3}{{\rm{N}}}_{4}\) chip and connected by a ground-signal-ground (GSG) probe for microwave signal output. e False-colored SEM image showing PD’s multilayer structure. InGaAs, indium gallium arsenide. InGaAsP, Indium gallium arsenide phosphide. InP, Indium phosphide. BCB, benzocyclobutene, a kind of resin

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