Fig. 2

Characterization of laser performance. a Recorded light-current-voltage (LIV) curve of the laser, showing the fiber-coupled output power. The corresponding laser output power on chip is 5 dB higher, determined by the chip-to-fiber coupling efficiency. b Optical spectrum of single-mode lasing. The left inset shows a zoomed-in view of the spectrum. The right inset shows the measured transmission of the grating. c Recorded frequency noise spectra of two laser devices (D1, D2), with the white noise floor highlighted in red shading. NC: photodetector noise cancellation achieved via the cross-correlation technique. Right: zoomed-in spectra with the offset frequency from 1 to 10 MHz. d Recorded time–frequency spectrograms of the beat note between the Pockels laser and a reference diode laser at different modulation frequencies. The lower panels display the corresponding linearity deviation of the laser frequency chirping. The red dashed line in the figures represents the temporal waveform of the driving electrical signal, generated by an arbitrary waveform generator (AWG). For modulation speed ≥1 MHz, broadband electric amplifiers are used to boost the driving signal before it is applied to the laser. Limited amplifier bandwidths lead to certain waveform distortion on the driving electrical signal, particularly at high modulation frequencies. V_p−p shown on the figure indicates the peak-to-peak voltage of the driving electrical signal. Additional details are in Supplementary Information. e Recorded laser-frequency tuning efficiency versus modulation speed (i.e., modulation frequency). The red-shaded region indicates the frequency region where the tuning efficiency degrades. The error bars reflect measurement uncertainty from short-time Fourier transform processing due to instrument limitations. f Comparison of state-of-the-art laser frequency tuning performance. Red dots indicate results from our devices. g Similar to d, at a modulation speed of 100 MHz but with V_p−p of 25 V