An oscillation threshold of 780mW has been demonstrated in a singly-resonant, continuous-wave optical parametric oscillator (CW SRO) using a fiber-amplified, distributed feedback (DFB) fiber laser as pump source. A linewidth of 1MHz was measured, and the idler frequency was fine-tuned by up to 130GHz by tuning the pump laser. To our knowledge, this is the first example of a single frequency CW SRO pumped by an all-fiber pump source, a reduction in threshold by a factor of three over previous 1- microm-pumped CW SROs, and a reduction by two orders of magnitude in the linewidth of CW SROs pumped by fiber pump sources.
We have confirmed that single-frequency oscillation of a continuous-wave singly resonant optical parametric oscillator is limited to operation below a critical value of the pumping ratio, as predicted by early theoretical treatments. We also report different regimes of spectral broadening as well as stimulated Raman conversion of the signal wave above this critical pump level. We show that spectral broadening may be eliminated by implementing output coupling of the signal wave and demonstrate 8.6 W of total signal and idler output with single-frequency spectra at both wavelengths for 14.5 W of pump power.
Highly focused stimulation-tripolar electrical and infrared neural stimulation-has potential for increased performance in noise compared with monopolar stimulation, but much work remains to bear this potential out and to take full advantage of each modality's strengths.
We have demonstrated spectral beam combining of two high power fiber lasers and obtained more than 40 W output power from the system. The system consists of two 30 W fiber lasers, a diffraction grating and a resonator. Both fiber lasers have broadband fiber Bragg gratings on the rear sides and share the diffraction grating and output coupler on the output sides. The wavelengths of the fiber lasers are determined by the optical dispersion provided by the grating and the collimating lens, as well as the fiber spacing. A model that analyzes dependence of laser line-width on beam quality of an SBC system is given in this paper. We also model a novel configuration that can significantly improve beam quality. The experimental results have shown that control of fiber laser line-width is the key to achieving high power SBC lasers. In addition, a new approach using three gratings is proposed and has been proven by the experiment. The new approach consists of three gratings, in which one grating is used in the SBC cavity to lock wavelengths while the other two combine the collimated beams without beam quality reduction. This approach has successfully improved beam quality M 2 from 11 to 2.0.
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