Fig. 1. OAM mode spectra (p=0) for three objects of different rotational symmetries: (a) three-leaf clover, (b) hexagonal snowflake, and (c) cartoon pattern.

Fig. 2. Experimental setup for upconversion detection of rotational Doppler effect. Insets are the typical holograms displayed in Regions I and II of SLM, respectively.

Fig. 3. Experimental results for a rotating clover. (a) and (b) OAM-dependent photon counts (N) of SHG light, where Ω=1 deg/s and 2 deg/s, respectively. (c) and (d) The corresponding power spectra of rotational Doppler signals after FFT, in which the beat frequencies are marked as well.

Fig. 4. Experimental results for a rotating snowflake and a cartoon pattern, respectively. (a) and (b) OAM-dependent photon counts (N) of SHG light, where Ω=4 deg/s for both cases. (c) and (d) The corresponding power spectra of rotational Doppler signals, in which the beat frequencies are marked as well.