Ti-sapphire laser

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Titanium-sapphire, or Ti:sapphire, lasers emit near-infrared light, tunable in the range from 750 to 900 nanometer. These lasers are mainly used in scientific research because of their tunability and the possibility of generating ultra-short pulses.

Titanium-sapphire refers to the lasing medium, a crystal of sapphire (Al₂O₃) that is doped with titanium ions. A Ti:sapphire laser is usually pumped with another laser with a wavelength of 514 to 532 nm, for which argon lasers (514.5 nm) and frequency-doubled Nd:YAG, Nd:YLF, and Nd:YVO lasers (527-532 nm) are used. Ti:sapphire lasers operate most effectively at a wavelength of 800 nm.

Common types of Ti:sapphire lasers include:

Table of contents

1 Mode-locked oscillators
2 Regenerative amplifiers
3 Tunable continuous wave lasers

Mode-locked oscillators

These generate ultrashort pulses with a duration of 10 femtoseconds to a few picoseconds, typically with a repetition-frequency of 70 to 90 MHz. Oscillators are normally pumped with a continuous laser beam from an argon or frequency-doubled Nd:YVO laser. Typically, an oscillator has an average output of 0.5 to 1.5 watt.

Regenerative amplifiers

Also called chirped-pulse amplifiers, these generate ultrashort, ultra-high-intensity pulses with a duration of 20 to 100 femtoseconds and pulse energies up to 5 milli-joule. This corresponds to a peak-intensity of 50 giga-watt, most often at a repetition-frequency of 1000 hertz. Usually, regenerative amplifiers are pumped with a pulsed frequency-doubled Nd:YLF laser at 527 nm and operate at 800 nm.

Regenerative amplifiers operate by amplifying single pulses from an oscillator (see above). Instead of a normal cavity with a partially reflective mirror, they contain high-speed switches that insert a pulse into a cavity and take the pulse out of the cavity exactly at the right moment when it has been amplified to a high intensity. The term 'chirped-pulse' refers to a special construction that is necessary to prevent the pulse from damaging the components in the laser.

The pulses from regenerative amplifiers are most often converted to other wavelengths by means of various nonlinear optics processes.

Tunable continuous wave lasers

These are used as a laser source with a tunable well-defined wavelength.