User`s manual

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1. INTRODUCTION
This manual describes installation and operation of Wedge 50
titanium : sapphire (Ti : sapphire) amplifier system. The system
is based on a femtosecond confocal multipass amplifier
configuration and consists of parts, shown in the Figure 1:
1. Pulse stretcher
2. Multipass Ti : sapphire amplifier
3. Pulse compressor
4. Pulse picker and Pockels cell driver
5. Synchronization electronics
The seed pulses used in the system originate from a mode-
locked Ti: sapphire seed oscillator, model Trestles 50 is
recommended. Before amplification, femtosecond pulses are
stretched in time to avoid effects of peak power damage in high
energy ultrafast amplifiers. Femtosecond pulses with pulse
duration 100 fs are stretched to several tens of picoseconds
before pulse selection and amplification.
To decrease pulse repetition rate, a Pockels cell is placed
between crossed polarizers. This pulse picker system permits
transmission of a single pulse during a <6-ns window that is
synchronized with a laser through the countdown and
synchronization unit. The countdown electronics receives 80 –
90 MHz signal from the output pulses of the Ti : sapphire
oscillator and divides this rate to 1000 Hz according to the pulse
repetition rate of Nd:YAG laser pumping the multipass
amplifier.
After the Pockels cell, the pulse is injected into a two-mirror
confocal multipass amplifier (MPA) that is effective device for
amplification of femtosecond pulses in a Ti: sapphire crystal.
After six, eight, or ten passes the seed pulse is amplified by a
factor up to 10
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and leaves the amplifier through the aperture in
the output mirror. The pump radiation is focused by the lens
through the aperture in the input mirror.