Switching between the mode-locking and Q-switching modes in two-section QW lasers upon a change in the absorber properties due to the Stark effect

Abstract

The passive Q-switching and mode-locking modes are implemented in two-section lasers with three quantum wells. It is demonstrated that raising the reverse bias on the absorbing section changes its spectral and dynamic properties and, accordingly, leads to a change from the Q-switching mode to mode-locking. The pulse-repetition frequency in the mode-locking mode is 75 GHz, with the product of the pulse duration by the spectrum bandwidth being 0.49, which is close to the theoretical limit. It is shown that, in structures with three quantum wells, strong absorption at the lasing wavelength gives rise to a photocurrent across a section of the saturable absorber, which is sufficient for compensation of the applied bias.

Three-Level Optical Stark Effect of Excitons in GaAs Cylindrical Quantum Wires

“…In low-dimensional semiconductor systems, scientists have observed the excitonic optical Stark effect when irradiat-ing a strong pump laser pulse in [30,31]. This effect resulted from the interaction between exciton states, displayed through splitting and shifting the absorption spectrum of the exciton [32][33][34][35]. Based on these properties, the researchers proposed a number of prospective applications of the excitonic optical Stark effect, such as making optical switching devices [33,34], optical modulators [35], mesoporous hybrid multifunctional system [36], or optically controlled field-effect transistors [37].…”

“…This effect resulted from the interaction between exciton states, displayed through splitting and shifting the absorption spectrum of the exciton [32][33][34][35]. Based on these properties, the researchers proposed a number of prospective applications of the excitonic optical Stark effect, such as making optical switching devices [33,34], optical modulators [35], mesoporous hybrid multifunctional system [36], or optically controlled field-effect transistors [37]. So far, the excitonic optical Stark effect has been primarily studied on quantum wells and quantum dots [30,31].…”