Theoretical calculation of GaGeTe and its application for ultrafast photonics

GaGeTe represents a characteristic example of topological semimetals, exhibiting exceptional mechanical, physical, and chemical characteristics. The material's reduced structural symmetry renders it highly responsive to external parameters, thereby providing considerable flexibility for property modulation and the development of functional nanodevices. In the present study, first-principles theoretical calculations were conducted to investigate the mechanical, electronic, and optical characteristics of GaGeTe, providing fundamental insights into its intrinsic properties while supporting potential optoelectronic applications. Furthermore, GaGeTe-based saturable absorbers were prepared and incorporated into Er-doped fiber laser cavities, resulting in the achievement of Q-switched and harmonic mode-locked operations. For the Q-switched operation, the minimum pulse duration reached 532.15 ns with signal-to-noise ratio of 80 dB. The GaGeTe-based fundamental mode-locked fiber laser shows decent output performance (pulse width, signal-noise ratio and repetition rate are 463.37 fs, 63.2 dB, and 45.99 MHz). Additionally, it enables stable harmonic mode-locking with maximum repetition rate of 367.99 MHz. The observed performance of GaGeTe-based fiber lasers surpasses that reported in previous studies. These results indicate that GaGeTe materials hold significant promise for nonlinear optical applications and expand the available options for two-dimensional material development.