The linear and nonlinear optical properties of B a G a 4 S 7 , B a G a 4 S e 7 , B a G a 2 G e S 6 , and B a G a 2 G e S e 6 are reviewed, highlighting their potential for frequency downconversion of powerful laser sources from the near- to the mid-IR. Examples of successful applications are summarized and briefly discussed.

We report on sub-50 fs pulse generation from a passively mode-locked (ML) Tm,Ho-codoped crystalline laser operating in a 2 µm spectral region. A T m , H o : C a ( G d , L u ) A l O 4 laser delivers pulses as short as 46 fs at 2033 nm with an average power of 121 mW at a pulse repetition rate of ∼ 78 M H z employing a semiconductor saturable absorber mirror as a saturable absorber. To the best of our knowledge, this result represents the shortest pulses ever generated from a Tm- and/or Ho-based solid-state laser. Polarization switching in the anisotropic gain material is observed in the ML regime without any polarization selection elements which is essential for the shortest pulses.

We report on the first sub-100 fs mode-locked laser operation of a Tm3+-doped disordered calcium lithium tantalum gallium garnet (Tm:CLTGG) crystal. Soliton mode-locking was initiated and stabilized by a transmission-type single-walled carbon nanotube saturable absorber. Pulses as short as 69 fs were achieved at a central wavelength of 2010.4 nm with an average power of 28 mW at a pulse repetition rate of ∼87.7 MHz. In the sub-100 fs regime, the maximum average output power amounted to 103 mW.

We report on sub-30 fs pulse generation from a semiconductor saturable absorber mirror mode-locked Yb:YAP laser. Pumping by a spatially single-mode Yb fiber laser at 979 nm, soliton pulses as short as 29 fs were generated at 1091 nm with an average output power of 156 mW and a pulse repetition rate of 85.1 MHz. The maximum output power of the mode-locked Yb:YAP laser amounted to 320 mW for slightly longer pulses (32 fs) at an incident pump power of 1.52 W, corresponding to a peak power of 103 kW and an optical efficiency of 20.5%. To the best of our knowledge, this result represents the shortest pulses ever achieved from any solid-state Yb laser mode-locked by a slow, i.e., physical saturable absorber.

We report on a detailed investigation of continuous-wave and SESAM mode-locked (ML) laser operation of an Yb:SrLaAlO4 laser. Pumped with a high-brightness fiber laser at 976 nm, the ML Yb:SrLaAlO4 laser delivered soliton pulses as short as 38 fs at 1071 nm with an average output power of 86 mW and a pulse repetition rate of ∼59 MHz. The maximum average output power reached 1.05 W at 1054 nm for longer pulses (94 fs), corresponding to a peak power of 146 kW and an optical efficiency of 38.6%. To the best of our knowledge, this is the first demonstration of SESAM ML operation of the Yb:SrLaAlO4 laser.