All-optical flip-flop operation of polarization bistable VCSELs with an oxide confinement structure

We introduced an oxidation confinement structure to 980-nm polarization bistable VCSELs. A threshold current as small as 0.22 mA was achieved. The VCSEL exhibited bistability between linear polarizations and operated in the single longitudinal and lowest order transverse modes in both polarization modes. We demonstrated AOFF operation at a bias current of 1.15 mA, which is a record low to the best of our knowledge. Polarization switching was achieved with a high optical gain of 22 dB using a low-power injection light (2.6 μW). Thus, these bistable VCSELs are promising for multi-bit memory operation in which a large number of VCSELs would be used and low power consumption would be needed.