We investigated in-band pumping of Tm,Ho,Lu:CaGdAlO4 (CALGO) using a Raman shifted Er-fiber laser (1678 nm) in the continuous-wave (CW) and mode-locked (ML) regimes. The 6-mm long, antireflection-coated, a-cut CALGO was doped with 4.48at.% Tm (sensitizer), 0.54at.% Ho (emission) and 5.51at.% Lu (compositional disorder). For mode-locking we employed a GaSb SESAM and chirped mirrors (round-trip group-delay dispersion: -1250 fs2). Pumping with 5.5 W (unpolarized), the average output power (0.2% output coupler) was 148 mW at ⁓96 MHz. The spectrum was centered at 2071.5 nm with a FWHM of 21.5 nm (sigma-polarization) and the pulse duration was 218 fs (time-bandwidth product: 0.327).
We demonstrate that thick (3-mm) Periodically-Poled LiNbO3 (PPLN) enables energy scaling of a non-resonant optical parametric oscillator (NRO) operated in the narrowband mode with a Volume Bragg grating (VBG) at the signal wavelength. Utilizing the full available pump power at 1064 nm we obtained maximum average powers of 2.25 and 2.08 W for the signal (1822 nm) and idler (2383 nm) at 10 kHz, at a conversion efficiency of 32.8%, i.e. a two-fold increase in terms of pulse energies. The signal and idler linewidths were ⁓1 nm, the pulse lengths ⁓6 ns and the idler beam propagation factor ⁓5.
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