Surface light source apparatus with dual-side emitting light

A surface light source apparatus with dual-side emitting light, comprising:

• a first conductive transparent substrate and a second conductive transparent substrate, opposite to each other and served as an anode structure;
• a fluorescent structure layer, disposed on the first conductive transparent substrate and the second conductive transparent substrate;
• a spacer, disposed between the first conductive transparent substrate and the second conductive transparent substrate to construct a space;
• a low-pressure gas layer, filling a space and functioning to induce cathode for evenly emitting electrons;
• and
• a filamentary cathode structure, distributed on a plane between the first conductive transparent substrate and the second conductive transparent substrate, wherein the filamentary cathode structure comprises a plurality of filaments in the space aligned in parallel and all at one direction and a portion of the filaments is structurally floating in the space,
• wherein an electron mean free path of the low-pressure gas layer allows at least sufficient electrons to transversely move and directly impact the fluorescent structure layer under an operation voltage.