A hands-free loudspeaker system which is capable of achieving high-quality voice amplification without requiring a human speaker to move to a microphone or a microphone to be moved to a human speaker. A polarization state acquiring part in a control part acquires a polarization state at each wavelength in the measurement wavelength band of the reflected light. In addition to the resonant cavity structure, the light-emitting structure also includes a contact layer, an n-type metal electrode and a p-type metal electrode.