Author(s): Zhang, LD (Zhang, Linde); Zhang, JY (Zhang, Jingyuan); Wang, X (Wang, Xiang); Tao, M (Tao, Meng); Dai, GT (Dai, Gangtao); Wu, J (Wu, Jing); Miao, ZW (Miao, Zhangwang); Han, SF (Han, Shifei); Yu, HJ (Yu, Haijuan); Lin, XC (Lin, Xuechun)

Source: LIGHT-SCIENCE & APPLICATIONS Volume: 11 Issue: 1 Article Number: 181 DOI: 10.1038/s41377-022-00848-y Published: JUN 14 2022

Abstract: We discover that the spatially coherent radiation within a certain frequency range can be obtained without a common nonlinear optical process. Conventionally, the emission spectra were obtained by de-exciting excited centers from real excited energy levels to the ground state. Our findings are achieved by deploying a high-entropy glass system (HEGS) doped with neodymium ions. The HEGS exhibits a much broader infrared absorption than common glass systems, which can be attributed to be high-frequency optical branch phonons or allowable multi-phonon processes caused by phonon broadening in the system. A broadened phonon-assisted wideband radiation (BPAWR) is induced if the pump laser is absorbed by the system. The subsequent low-threshold self-absorption coherence modulation (SACM) can be controlled by changing excitation wavelengths, sample size, and doping concentrations. The SACM can be red-shifted through the emission of phonons of the excited species and be blue-shifted by absorbing phonons before they are de-excited. There is a time delay up to 1.66 ns between the pump pulse and the BPAWR when measured after traveling through a 35 mm long sample, which is much longer than the Raman process. The BPAWR-SACM can amplify the centered non-absorption band with a gain up to 26.02 dB. These results reveal that the shift of the novel radiation is determined by the frequency of the non-absorption band near the absorption region, and therefore the emission shifts can be modulated by changing the absorption spectrum. When used in fiber lasers, the BPAWR-SACM process may help to achieve tunability.

Accession Number: WOS:000811201400002

PubMed ID: 35701403

ISSN: 2047-7538

Full Text: https://www.nature.com/articles/s41377-022-00848-y