Titanium Sapphire Pumping

Lasers based on TiS active medium have been the workhorse for tunable narrow-linewidth and ultrafast applications since the early 1990s. The most efficient way to excite this active medium is by using a powerful green laser beam matching the spatial profile of the TiS laser mode. CW or mode-locked TiS lasers are pumped by a CW green laser while amplifiers running at 1-10 kHz are efficiently pumped by Q-switched green lasers operating at the same repetition rate of the amplifier and producing pulses compatible with the fluorescence lifetime of TiS (i.e. 100-200 ns).​

CW green pump lasers are based on Nd:YVO or – uniquely at Coherent – on optically pumped semiconductor lasers (OPSLs) while Q-switched pump lasers are based on YAG or YLF hosts producing 532 nm and 527 nm respectively.

​TiS crystals are end-pumped to provide maximum mode matching and efficiency, using dichroic mirrors that couple the green pump beam while reflecting the TiS intracavity beam. All Coherent TiS oscillators and amplifiers are pumped by Coherent green lasers.

​The Coherent Verdi family of Nd:YVO and OPSL lasers provide up to 18 watts of power at 532 nm to pump CW tunable or mode-locked TiS oscillators. Verdi lasers offer superlative noise performance and diffraction-limited mode quality, together with invariant beam parameters as the output power is varied. Coherent Verdi enables high green-to-TiS conversion efficiency, stable CW and mode-locked operation of the TiS laser, and accurate CEP stabilization of oscillators like Coherent Vitara CEP. They are also at the heart of over 3,000 installed Chameleon femtosecond lasers.

TiS 1-10 kHz ultrafast and ns gain-switched amplifiers are pumped with Q-switched lasers. These pump lasers exhibit a higher M squared value because they are transversally pumped – required to achieve tens of mJ pulse energies. The high M squared is not an issue to efficient pumping as far as the laser mode is homogeneous and uniform. These pump lasers should have the highest possible pulse-to-pulse stability because this reflects on the final stability of the amplifier output, although some level of gain saturation in the amplifier alleviate the stability requirement. High pointing stability of the pump beam, over time and with environmental changes, is also important to guarantee stable output from the amplifier.​

Coherent pump lasers are used not only in all Coherent products based on TiS but also to pump home-built devices and for industrial applications like annealing. HALT/HAAS testing and verification insure industrial grade reliability.​