We demonstrate the ultrafast modulation of interband (IB)-resonant light (1.0-1.1 μm) by near-infrared intersubband (ISB)-resonant light (1.55-1.9 μm) in n-doped InGaAs/AlAsSb multiple quantum wells (QWs) using non-degenerate pump-probe spectroscopy. A modulation with an absorption recovery time of 1.0-2.0 ps has been observed in a planer-type modulation device due to ultrafast ISB relaxation of the carriers. The IB carrier relaxation process in the absence of an ISB-resonant light has also been investigated by time-resolved photoluminescence (PL) measurement. The modulation speed is determined by the inter- and intra-subband relaxation of the carriers in the conduction subband. The modulation speed at 1.1 μm due to an ISB-resonant pump light at 1.95 μm has been observed to be 1.4 ps at excitation energy of 500 fJ/μm2.
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