an electroluminescent material slot waveguide generates light in response to current injection . in one embodiment , the waveguide is formed as part of an optical resonator , such as ring resonator waveguide or distributed bragg reflector with an anode and cathode for electrical stimulation . a compact , electrically - driven resonant cavity light emitting devices for si microphotonics may be formed . several different rare - earth ions , such as erbium , terbium and ytterbium , can be used to dope sio2 in order to emit light at different wavelengths .