A simplified design approach for a hard-aperture Kerr-lens mode-locked Ti:sapphire oscillator was proposed. The technique is based on a simple cavity design and the position of the laser crystal with respect to the cavity mode waist which ensures an enhanced Kerr sensitivity of the oscillator. Experimental results were demonstrated and compared to the numerical calculations. Such a technique can be used and for other laser hosts.
Dual-wavelength (DW) operation of Yb:KGW laser was demonstrated by using a 1 mm-thick birefringent filter (BRF). Based on gain balancing around a single transmission peak of the filter, DW pairs with wavelength separation far smaller than the free spectral range of the filter could be generated. A series of DW pairs with wavelength separation of around 0.5 nm (Δν≈0.14 THz) and 4 nm (Δν≈1.1 THz) within the available gain bandwidth were generated. This method can be also applied with the other lasers that have broad gain bandwidth.
High power performance of diode-pumped Yb:YAP lasers with different crystal orientation (cuts) was investigated. The crystal samples exhibited similar pump absorption properties. In continuous-wave (CW) regime, the maximum output power of <7 W could be generated using the b-cut and c-cut Yb:YAP crystals with slope efficiency up to 70%, while the laser with the a-cut crystal was limited to 5.6 W of output power most likely due to the thermal lensing effect. Owing to the high thermal conductivity and broad emission bandwidth of Yb:YAP, this crystal is a suitable laser host for high power laser operation in CW and pulsed regimes.
A continuous-wave dual-wavelength Yb:CALGO laser has been demonstrated using a 12-mm thick off-surface axis birefringent filter. The obtained wavelength spacing could be tuned from a few nm up to tens of nm. In the experiments ~7.5 W of output power was obtained for 25 W of the incident pump power.
A high power conical refraction (CR) laser was demonstrated based on Yb:CALGO laser crystal with a separate intracavity CR element. The CR laser delivered the maximum output power of 6.25 W at 25 W of incident pump power which is the highest output power for the CR lasers to date. The separation of the CR element from the laser gain medium reduced the complexity of laser pumping. The generated CR laser beam exhibited excellent quality with well-resolved concentric rings and the Poggendorff dark ring.
The thermal lensing effect in the Ng-cut Yb:KGW and a-cut Yb:CALGO laser crystals was evaluated and compared using a similar laser cavity and pumping scheme. The Yb:KGW crystal exhibited large anisotropy along the horizontal and vertical axes and the thermal lensing sensitivity factors of Mx=0.52 m-1/W (||Np) and My=0.18 m-1/W (||Nm) were determined. The Yb:CALGO crystal exhibited negligible anisotropy in the thermal lensing power, and thermal lensing sensitivity factors of Mx=0.452 m-1/W (⊥c) and My=0.458 m-1/W (||c) were measured.
We demonstrated continuous-wave dual-wavelength (DW) operation of a Nd:CALGO laser using a single birefringent filter (BRF) plate. Owing to a new mechanism of the BRF loss action, the equal lasing thresholds at two wavelengths could be provided by a single transmission peak of the filter and wavelength separation was not limited to the free-spectral range (FSR) of the filter. A wide range of DW pairs with wavelength separation from sub-nm up to ~4 nm with adjustable spectral intensity ratio was experimentally demonstrated using a single 2 mm-thick BRF plate.
High power performance of a continuous-wave Yb:YAP laser was investigated. The laser generated <7 W of output power with 22 W of pump power and slope efficiency of around 70% while maintaining high beam quality. The thermal lensing effect was observed at high pumping power. The combination of high thermal conductivity and broad gain bandwidth make this laser host a suitable candidate for high power CW and ultrashort pulse generation.
A conical refraction (CR) laser based on a separate gain medium (Nd:YVO4) and an intracavity CR element (KGW) was demonstrated. The decoupling of the gain and CR media enabled the laser to produce a well-behaved CR laser beam with excellent quality, while reducing the complexity of the pumping scheme. The proposed laser setup has the potential for power scaling using the efficient diode pumping approach and the properties of the generated CR beam are independent from the laser gain medium.
A high-power diode-pumped pure Kerr-lens mode-locked Yb:KGW laser was demonstrated. The developed laser delivered 240 fs pulses with 2.3 W of average output power at a repetition rate of 86.8 MHz. Shorter pulses of around 120 fs with 1.2 W of average output power were also generated. The self-starting operation of the oscillator was demonstrated. The limiting factor to the laser operation was the appearance of a strong continuous wave component in the mode-locked laser spectrum.