Photonic orbital angular momentum (OAM) carried by phase-structured vortex light is an important and promising resource for the ever-increasing demand towards high-capacity data information due to its intrinsic unlimited dimensionality. However, on-demand generation of arbitrary OAM spectra such as an OAM comb like a frequency comb is still a challenge; especially, the on-demand OAM comb and arbitrary multiple OAM modes have not yet been realized at the source. Recently, the team led by Prof. Hui-Tian Wang and Prof. Xi-Lin Wang from the School of Physics at Nanjing University successfully challenged this issue. They reported a flexibly and dynamically switchable on-demand digital OAM comb laser for the first time, by controlling the phase degree of freedom itself rather than any proxy. They proposed a versatile at-source design strategy that a nested ring cavity configuration is composed of a degenerate cavity embedded into a stable ring cavity and a pair of conjugate multi-spiral-phase digital holograms. This cavity design strategy successfully not only avoids the random competition among different OAM modes, but also resolves the control issues related to the number and chirality of OAM modes. Our strategy has also universality as it has the ability of encoding OAM spectra with arbitrary distribution. They further demonstrated the cavity-enhanced second harmonic generation of multiple OAM modes. This at-source spatial structure laser control strategy not only facilitates the development of new laser technologies and promotes the broader application of structured light but also provides new opportunities for manipulating cavity-enhanced structured light interactions with matter. Their findings were published 10 July 2024, in the journal Optica, entitled “On-demand orbital angular momentum comb from a digital laser” (Optica 11, 951-961 (2024), https://doi.org/10.1364/OPTICA.529425).