A Sensitive Biosensor Based on Optical Bistability in a Semiconductor Quantum Dot-Dna Nanohybrid

We propose a scheme of a sensitive biosensor based on optical bistability (OB) in a biological semiconductor quantum dot (SQD)-DNA coupled nanohybrid. By plotting bistability phase diagrams within the system's parameter space, we show that the bistable effect can be switched on or off by only tuning the pumping intensity or the detuning of the pump field from the exciton resonance. Simultaneously, we reveal that the bistability only exists in the strong SQD-DNA coupling regime. Specifically, we derive the matching relation between the excitation conditions and the coupling strength when the bistability just appears. Moreover, we demonstrate that the OB is highly sensitive to the SQD-DNA coupling strength which is strongly correlated to the length of DNA molecules and DNA concentration. This investigation may be useful for opening a new way to build optical switches and providing a novel and convenient platform to detect DNA molecules.