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Tunable Multi-Wavelength Combined Linear-Cavity Fiber Laser and its Application in Photonics True-Time-Delay Beamforming
Jianling Yang and Zhaohua Guo

A photonics true-time-delay unit for wideband continuous phased array beamforming using a chirped grating-based time-delay network and a novel multi-wavelength tunable combined linear-cavity fiber laser with equal increasing or decreasing wavelength steps is presented. The lasing wavelengths are determined by discrete fiber Bragg gratings in the laser cavity and can be tuned by compressing or extending the gratings. To ensure that the wavelength tuning with equal wavelength spacing, the discrete gratings are mounted onto an organic plastic plate with angles between adjacent gratings such that the tuning forces applied to the gratings experience equal increments in force. Time delays, with equal increasing or decreasing time delay differences for equally spaced wavelengths are achieved if the modulated lightwaves are reflected at different locations of a linearly chirped grating in the time-delay network. A four-channel chirped-grating-based continuously tunable differential true-time-delay gradient system suitable for continuous beam steering at microwave frequencies up to 10 GHz has been constructed and will be demonstrated.