The orthogonality among optical beams with different orbital angular momentum (OAM) modes presents a new perspective as independent data-carrying channels for multiplexing and demultiplexing. In particular, the theoretically infinite topological charge of OAM beam promises the unbounded capacity in communication systems. As a key part for the advancement of OAM technologies, OAM source has attracted considerable interest and experienced a rapid development. Nevertheless, conventional approaches to create OAM modes mainly rely on the use of bulky optical devices and external laser source, preventing their implementation into a miniaturized system. As a contrast, on-chip generation of OAM beams with a built-in source stands out with several advantages, including small footprint, compactness, portability, and high-power efficiency. In this work, a versatile approach to directly produce OAM modes with on-demand characteristics on a chip is demonstrated. Featuring the judicious combination of the emerging dielectric metasurface with the standard vertical cavity surface-emitting laser (VCSEL) platform, the approach represents a feasible solution to the wide implementation of wafer-level OAM emitters for optoelectronic integrations. Prototype laser chips for the generation of both individual OAM beam and OAM array with novel functionalites, such as controllable directionality and spatially varying topological charge and distribution, are systematically presented.