Bistable ring resonator utilizing saturable photorefractive gain and loss

We demonstrate the bistable behavior of a unidirectional ring resonator that employs photorefractive loss as well as photorefractive gain. The gain and loss are established by two-beam coupling in two separate photorefractive BaTiO(3) crystals. Two-beam coupling loss plays the role of a programmable saturable absorber. Irreversible bistability occurs when the maximum net gain exceeds unity, while reversable bistability is obtained when the maximum net gain is less than one.