An optimized design of a birefringent filter with an off-plane optical axis is presented to enable multi-wavelength operation of diode-pumped Yb-ion solid-state lasers. The simulation results indicate that such birefringent filters can be used for the development of powerful tunable multi-wavelength Yb-ion laser sources. A comparison with performance of a standard birefringent filter that has its optical axis lying in plane of a plate is also given.
A diode-pumped femtosecond Kerr-lens mode-locked Yb:CALGO laser with a low repetition rate of 10.2 MHz was developed. The oscillator produced 650 mW of average output power with pulse duration of 66 fs. This corresponds to the pulse energy of 64 nJ with a peak power of 0.97 MW. No external pulse compression was used. To the best of our knowledge, this is the first Yb:CALGO laser that generated sub-100 fs pulses directly out of the cavity at such a low repetition rate. The ∼98 ns time delay between the pulses can be useful for fluorescence lifetime imaging of biological samples.
Multi-watt dual-wavelength operation of a diode-pumped Yb:CALGO laser was achieved by introducing a thin birefringent filter (BRF) plate into a standard laser cavity. A BRF plate with a thickness of 0.5 mm was capable of generating a dual-wavelength output with a frequency offset of 1.31 THz (equivalent to a wavelength separation of 4.8 nm). The output power of the dual-wavelength laser at 1044.7 nm and 1049.5 nm was 2.6 W. The developed dual-wavelength Yb:CALGO laser with multi-watt output power is an attractive and cost-effective candidate for generation of THz radiation and dual-wavelength mode-locked lasers.
Thermal lensing in diode pumped solid state lasers can seriously affect laser performance and cause beam distortions resulting in degradation of beam quality. Estimating thermal lens is important in designing stable laser cavities with minimum laser mode size fluctuations and high output power. The common techniques used to estimate the thermal lens under lasing condition deploy a probe beam or a wave front sensor. Both these techniques need precise alignment and the laser beam quality factor has to be measured separately for thermal lens calculations. It is well-known that beam quality varies considerably at different pump intensities. We demonstrate a simple technique based on ABCD law for Gaussian beams that is capable of estimating the thermal lens accurately by taking into account the fluctuation of beam quality factor at various pump intensities. The technique is experimentally tested using a diode-pumped Yb:KYW laser at different pump intensities.