Shirin Ghanbari

Femtosecond Kerr-lens mode-locked Alexandrite laser.

Generation of 170 fs pulses at 750 nm from a Ker-lens mode-locked Alexandrite laser is demonstrated. We believe that these are the shortest pulses that have been produced from a mode-locked Alexandrite laser to date.

High power continuous-wave Alexandrite laser with green pump

We report on a continuous-wave (CW) Alexandrite (Cr:BeAl2O4) laser, pumped by a high power green source at 532 nm with a diffraction limited beam. An output power of 2.6 W at 755 nm, a slope efficiency of 26%, and wavelength tunability of 85 nm have been achieved using 11 W of green pump. To the best of our knowledge, this is the highest CW output power of a high brightness laser pumped Alexandrite laser reported to date. The results obtained in this experiment can lead to the development of a high power tunable CW and ultrafast sources of the near-infrared or ultraviolet radiation through frequency conversion.

Thermo-optical properties of Alexandrite laser crystal

Alexandrite is a well-known material for broadly tunable and power-scalable near-IR lasers. We measured the thermal coefficients of the optical path (TCOP) and thermo-optic coefficients (TOCs) of Alexandrite at 632.8 nm for three principal light polarizations, E || a, E || b and E || c. All TOCs are positive and show a notable polarization-anisotropy, dna/dT = 5.5, dnb/dT = 7.0 and dnc/dT = 14.9×10-6 K-1. We also characterized thermal lensing in a continuous-wave Alexandrite laser which used a Brewster-oriented c-cut 0.16 at.% Cr3+ doped BeAl2O4 crystal pumped at 532 nm and emitted at 750.9 nm (E || b). The measured thermal lens was positive and astigmatic. The sensitivity factors of the thermal lens (Mx,y = dDx,y/dPabs) were found to be Mx = 1.74 and My = 2.38 [m-1/W].

InP/InGaP quantum-dot SESAM mode-locked Alexandrite laser

A semiconductor saturable absorber mirror (SESAM) passively mode-locked Alexandrite laser was demonstrated. Using an InP/InGaP quantum-dot saturable absorber mirror, pulse duration of 420 fs at 774 nm was obtained. The laser was pumped at 532 nm and generated 325 mW of average output power in mode-locked regime with a pump power of 7.12 W. To the best of our knowledge, this is the first report of a passively mode-locked Alexandrite laser using SESAM in general and quantum-dot SESAM in particular.

Dual-wavelength operation of a continuous-wave Alexandrite laser

A continuous-wave dual-wavelength operation of an Alexandrite laser was demonstrated. The oscillator produced 870 mW of average output power for 5W of incident pump power. This corresponded to a slope efficiency of 21% and an optical-to-optical efficiency of 17.4%. A single 4-mm-thick intracavity birefringent filter plate placed at Brewster’s angle resulted in dual-wavelength radiation at 744.2 nm and 757.2 nm wavelengths (6.9 THz of frequency difference). To the best of our knowledge, this is the first report of a dual-wavelength operation of an Alexandrite laser.