Fig. 2: Microwave detection via four-spin-wave mixing and frequency combs.
From: Broadband microwave detection using electron spins in a hybrid diamond-magnet sensor chip
a Energy diagram of four-spin-wave mixing. The signal at frequency fs stimulates the conversion of the pump to the idler at fNV. b Normalized NV photoluminescence (PL) versus fs. Without pump (orange data), an ESR dip is only observed when \({{f}_{{{\mbox{s}}}}=f}_{{{\mbox{NV}}}}\). With pump at \({f}_{{{\mbox{p}}}}={f}_{{{\mbox{NV}}}}+\delta f/2\) (blue data), a signal at \({f}_{{{\mbox{s}}}}={f}_{{{\mbox{NV}}}}+\delta f\) becomes detectable. c Tuning the pump (colored arrows) shifts the detectable signal frequency, observed through the shifting ESR dips (matching colors). d Normalized NV PL vs fs and magnetic field in the absence of a pump. Only signals at fNV (dashed black line) can be detected. Dotted black line: Frequency above which three-magnon scattering limits the spin-wave amplitude33. White line: Ferromagnetic resonance (FMR) frequency (Supplementary Note 1). e Applying a pump at \({f}_{{{\mbox{p}}}}=({f}_{{{\mbox{s}}}}+f_{{{\mbox{NV}}}})/2\) opens a detection window from the FMR up to the second node (dashed red line) in the Fourier spectrum of the stripline field (Supplementary Fig. 1). (Dashed) white line: Signal (Pump) drives FMR. Black arrow: Line of reduced contrast caused by scattering into the first perpendicular standing spin-wave mode11. f Spin-wave comb observed in the PL versus fs and fp. Data is normalized (Supplementary Fig. 2). Upper inset: Spectrum (sketch) illustrating the detection of idlers I–III (black: pump, orange: signal, blue: idlers). Lower inset: Linecut along the small black line at the star in the main panel, showing idlers up to the tenth order.
