Embodiments of the disclosure provide an emitter array for an optical sensing system. The emitter array may include a waveguide including a plurality of waveguide branches. The emitter array may also include a plurality of grating switches positioned along each of the plurality of waveguide branches and configured to selectively turn on or off the corresponding waveguide branch for transmitting light. In certain aspects, a grating switch may include an upper grating structure configured to couple to a waveguide branch when the grating switch is activated to allow the light to emit from the waveguide branch.