Fig. 1. Calibration system and orientation of each device (angle with x-axis)

Fig. 2. Images of Bessel functions of order 0 to 2

Fig. 3. Calibration curve of fourth- and second-order ratio method, fundamental frequency component extreme value method and frequency-free response calibration method

Fig. 4. Simulation curves. (a) Simulation curve when A_m is set to π rad; (b) simulation curves when A_m is set to 3.106 rad; (c) simulation curve when A_m is set to 3.178 rad

Fig. 5. Waveforms under different control voltages. (a) Flat-top waveform generated when the control voltage is 2.53 V (corresponding to A_m= π rad); (b) the upper circle and lower sharp waveform generated when the control voltage is 2.5 V (corresponding to A_m=3.106 rad); (c) the concave and downward tip waveform generated when the control voltage is 2.56 V (corresponding to A_m=3.178 rad)

Fig. 6. Calibration curves. (a) Original calibration curve with calibration deviation per point; (b) A_m calibration deviation curve caused by light intensity fluctuations