An electron beam apparatus is disclosed that includes a plurality of current source elements disposed in at least one field emitter array. Each current source element can be a gated vertical transistor, an ungated vertical transistor, or a current controlled channel that is proximate to an optically-modulated current source. The electron beam apparatus includes a plurality of field emitter tips, each field emitter tip of the plurality of field emitter tips being coupled to a current source element of the plurality of current source elements. The electron beam apparatus is configured to allow selective activation of one or more of the current source elements.