Two-photon pumped dual-beam lasing: Tristable operation

Using two focused 1064 nm pump beams with an intensity ratio 3:1 and a small crossing angle θ≈3.1∘, two-photon pumped (2PP) tristable lasing behavior has been observed in a dye (AMSPT) solution in dimethyl sulfoxide (DMSO). When each pump beam is incident alone, the measured pump energy threshold for 2PP lasing is ∼3.8mJ. However, when the two pump beams are incident together, the energy of the strong pump beam varies from 4 to 10 mJ and the energy of the weak pump beam varies from 1.3 to 3.3 mJ. We then observe two simultaneous output lasing beams. However, when the strong pump beam is blocked, the weak pump beam is unable to create its own lasing output. This observed dual-beam lasing behavior can be well explained by a physical model of energy transfer between these two pump beams via the reflection of an induced Bragg grating. This observed dual-beam and tristable lasing behavior may be useful for future applications in an optical logical circuit or an optical computing system.