image: a, The direction-dependent optical properties of Ta2PdS6. Theoretical simulations of the polarized optical absorption of Ta2PdS6. Ta2PdS6 exhibits significant polarized absorption properties under optical excitation at 1.56 μm (corresponding to a photon energy of about 0.8 eV). b, The polarization-dependent transmission at various incidence powers. The anisotropic transmittance of Ta2PdS6 was experimentally measured under laser excitation at a wavelength of 1.56 μm. The results show that the light absorption intensity is related to the polarization state, and the polarization contrast increases with the increase in pump power. c, Ta2PdS6 nonlinear transmission versus energy intensity at various tilt angles. d, The nonsaturable loss of Ta2PdS6 for various tilt angles. With the polarization control angle from 0° to 180°, the parameters of Ta2PdS6 saturation intensity and modulation depth formed regular oscillations. Among them, the non-saturable loss shows a significant variation, with the maximum saturable absorption loss of about 65.8% at a tilt angle of 0° and the minimum saturable loss of about 56.3% at a tilt angle of 180°. The polarization-dependent variation of the non-saturable loss in quasi-one-dimensional Ta2PdS6 provides a new degree of freedom for the state regulation of ultrafast systems.
Credit: by Zixin Yang, Qiang Yu, Jian Wu, Haiqin Deng, Yan Zhang, Wenchao Wang, Tianhao Xian, Luyi Huang, Junrong Zhang, Shuai Yuan, Jinyong Leng, Li Zhan, Zongfu Jiang, Junyong Wang, Kai Zhang, and Pu Zhou
Tunable ultrafast lasers with adjustable parameters, such as wavelength, intensity, pulse width, and laser states, are desirable as next-generation intelligent light sources. Due to complex nonlinear effects within the ultrafast system, it is challenging for laser state active controlling (LSAC) in ultrafast fiber lasers, especially for passive mode-locking, in a convenient and controllable manner. Anisotropic low-dimensional materials with reduced in-plane symmetry exhibit polarization-dependent properties, providing additional degrees of freedom in compact tunable photonic devices.
In a new paper published in Light Science & Application, a team of scientists led by Professor Pu Zhou from the College of Advanced Interdisciplinary Studies, National University of Defense Technology, China, Professor Kai Zhang from Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, China, and co-workers have achieved the LSAC between conventional soliton (CS) and noise-like pulse (NLP) by polarization control based on a quasi-one-dimensional layered material switcher. The polarization-sensitive nonlinear optical response facilitates the Ta2PdS6-based mode-lock laser to sustain two laser states, i.e., CS and NLP. The laser state was switchable in the single fiber laser with a mechanism revealed by numerical simulation. Digital coding was further demonstrated in this platform by employing the laser as a codable light source.
Polarization control is a practical approach to adjusting the intracavity parameters and controlling the operating laser states. These scientists summarize the main findings from the tunable ultrafast laser: “(1) the anisotropic quasi-one-dimensional layered material Ta2PdS6 was utilized as a saturable absorber to modulate the nonlinear parameters effectively in an ultrafast system by polarization-dependent absorption; (2) the polarization-sensitive nonlinear optical response facilitates the Ta2PdS6-based mode-lock laser to sustain two distinct types of laser states, i.e., CS and NLP; (3) the laser state was switchable in the single fiber laser with a mechanism revealed by numerical simulation; and (4) digital coding was further demonstrated in this platform by employing the laser as a codable light source.”
"The controlled and stable switching of distinct pulsed laser modes in a single ultrafast fiber laser system represents significant advances in compact ultrafast photonics, which offers prospects of applications such as communications coding and optical switching.", the scientists forecast.
Journal
Light Science & Applications