All-optical modulation for semiconductor lasers by using three energy levels in n-doped quantum wells

An all-optical modulation method for semiconductor lasers using three energy levels in n-doped quantum wells is demonstrated. The modulation principle is based on the third-order interaction between interband-and intersubband-resonant light in the quantum-well structure. The modulation is demonstrated by a real-time single-shot experiment using a semiconductor laser for the interband-resonant light and a CO ₂ laser for the intersubband-resonant light. The dependences of the modulation depth on the intersubband-resonant light polarization and on the interband-resonant light wavelength indicate that the modulation is achieved by this principle. It is pointed out that the thermal effect appears when the power of the intersubband-resonant light becomes strong