Difference of carrier dynamics in a semiconductor saturable absorber mirror with and without B+ ion-implantation

Abstract

Three samples whose growth temperatures were 450°C, 500°C, and 560°C for SESAM1, SESAM2, and SESAM3, respectively, were tested by femto-second time-resolved transient absorption spectroscopy. The results indicate that the carrier dynamics of excited state absorption were dominant, and the lifetimes of carriers trapped by defect levels were about tens of pico-seconds. To further study the influence of carrier dynamics and recovery time of samples by ion-implantation, B+ ions of 80 and 130 KeV were implanted into the samples with dose of 1014/cm2. The modified samples showed a dominance of ultra-fast carrier dynamics of ground-state bleaching and direct recombination, which lasted for hundreds of femto-seconds, over excited state absorption. Additionally, carrier fast trapping was observed to be competitive with the excited state absorption process. After ion-implantation, the carrier dynamics of carrier trapping were enhanced, which contributed to forming an ultra-short laser, while the carrier dynamics of absorption of the excited state were suppressed. The conclusion that defect levels were partially eliminated by B+ ion-implantation can be drawn.