Reverse saturable absorption in Er+3 doped systems

This work reports on reverse saturable absorption (RSA) from Er3+ doped systems. RSA is characterized by a decrease in the transmitted intensity as the incident intensity increases. This effect is interesting due to its potential application in optical devices such as optical inverters, optical limiters and switches. Particularly, Er doped systems pumped at wavelengths around 830 nm may exhibit RSA. In this case, the RSA process is achieved because the resonant excited-state (4I13/2–4S3/2) absorption cross section is larger than the quasiresonant ground state (4I15/2–4I9/2) absorption cross section. We have simulated the transmitted intensity of Er doped samples as a function of laser intensity, laser wavelength and Er concentration. Our results indicate that Er concentration plays an important role in the process. RSA is intensified as cross relaxation between Er ions increases. Moreover, the effect of optical limiting is observed and is dependent on the cross relaxation among Er ions.