A modulator for an optical transceiver is disclosed. The modulator has two quarter-wave stack mirrors composed of alternating dielectric layers with an optically absorbing layer sandwiched in between to form the vertical resonant cavity. The optically absorbing layer is made of semiconductor nanocrystals embedded in a dialectic material. The device is configured to operate near the saturation point of the absorption layer. By adjusting the biasing voltage across the absorption layer, the saturation threshold of the semiconductor nanocrystals is altered, resulting in the overall reflectivity of the resonant cavity to vary. The modulator is configured to be fabricated as the extension of the backend process of Si CMOS.