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GHz high repetition rate compact sources with femtosecond pulse durations and stable performance can enable a wide range of applications. In this paper, several high repetition rate ultrafast thulium fiber lasers with repetition rates varying between 532 MHz to 1.25 GHz are demonstrated with femtosecond pulse durations down to 426 fs. An approach of maintaining comparable pulse energies while scaling the repetition rates allows high-quality femtosecond mode-locking performance with low noise performance in thulium soliton lasers for the first time.

Fabrication and experimental characterization of a broadband quarter-wave plate, which is based on two-dimensional and binary silicon high-contrast gratings, are reported. The quarter-wave plate feature is achieved by the utilization of a regime, in which the proposed grating structure exhibits nearly total and approximately equal transmission of transverse electric and transverse magnetic waves with a phase difference of approximately pi/2. The numerical and experimental results suggest a percent bandwidth of 42% and 33%, respectively, if the operation regime is defined as the range for which the conversion efficiency is higher than 0.9. A compact circular polarizer can be implemented by combining the grating with a linear polarizer. (C) 2012 Optical Society of America