A wide band antenna, which has a wide frequency band so that it can be used in a wireless local area network and can be manufactured in a small size at a low cost, is provided. The quantum dot optical amplifier and the quantum dot saturable absorber are connected in series with a transmission path of the signal beams, and shape the waveform of the signal beams. Since the first electrodes and the second electrodes are formed in the same plane, brightness uniformity is improved and manufacturing processes are simplified. The first carrier frequency is then combined with a second audio channel’s data forming a composite signal.