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Timestamp: 2019-04-24 18:56:36+00:00

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A novel dual channel Tm:YLF laser system was developed where two degenerate laser cavities were coupled by spectrally beam combining their emission and by implementing a common output coupler. Under continuous wave running conditions, each channel’s slope efficiency was greater than 45% and the maximum combined output power was 11 W. Passive Q-switching was achieved using an 80%, Cr:ZnSe saturable absorber. The output pulses had a maximum energy of 5.8 mJ and duration of 90 ns (~65 kW of peak power) at 5.7 W of absorbed pump power. Each channel showed less than 1 nm of spectral width with central wavelengths around 1880 nm and 1908 nm correspondingly. The system had adjustable spectral difference between the channels ranging from 5 to 20 nm which corresponds to 0.4 – 1.7 THz if the system is used for nonlinear difference frequency generation.
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Fig. 1 Schematic of a tunable dual channel Tm:YLF laser providing spectral beam combining with reflecting volume Bragg gratings.
Fig. 2 Output power versus absorbed pump power per channel for individual and simultaneous CW operation with a 30% transmission coupler.
Fig. 3 Reflectance spectra at normal incidence for each volume reflecting Bragg grating with a thickness of 5 mm. Efficiency of each grating is >99% with bandwidth (FWHM) of 1.6 nm.
Fig. 4 Emission spectra for a single channel Tm:YLF cavity with VBG2 as depicted in Fig. 1 (red) and with a broadband dielectric mirror instead of the VBG2(black).
Fig. 5 Emission spectra taken with a high resolution spectrometer for channel with VBG1 (left) and VBG2 (right).
Fig. 7 Emission spectra for different incident angles at VBGs. Black lines – channel separation 5 nm (0.4 THZ), red lines – channel separation 20 nm (1.7 THz).
Fig. 8 Average output power versus absorbed pump power for CW and PQS operation with a 30% transmission coupler.
Fig. 9 Pulse parameters dependence on absorbed pump power for the passively Q switched dual channel system.
Fig. 10 Temporal pulse train and pulse profile (insertion) for the passively Q switched dual channel system, measuring ~90 ns FWHM pulse duration.

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