3-1
Chapter 3 Laser Description
General Overview
The Tsunami
®
laser head contains the Ti:sapphire rod and the optics that
form the resonator cavity. Elements include pump beam mirrors, rod focus-
ing mirrors, an output coupler (OC), a high reflector (HR), beam folding
mirrors, dispersion control elements, and tuning elements. A femtosecond
(fs)-configured system uses prisms for dispersion control whereas a Gires-
Tournois Interferometer (GTI), which contains the HR, is the dispersion
control element in a picosecond (ps)-configured system. The fs configura-
tion uses a slit for wavelength selection while the ps configuration uses a
birefringent filter. The laser head also houses the GTI high-voltage circuit
for the ps configuration. For your convenience, the major tuning controls
are located on top of the laser head so the cover does not have to be
removed under normal circumstances.
Connections to the head include power and control from the Model 3955
electronics module, power and control from the optional Model 3930 Lok-
to-Clock
®
electronics module, nitrogen gas from the Model 3910 purge
unit, and cooling water from the chiller.
The Model 3955 electronics module included with the laser contains heater
and rf driver circuits for the mode locker and for the GTI. All indicators and
controls are located on the front panel, and three cables connect it to the
laser head input bezel. These cables include the control cable, the mode
locker
BNC cable and the photodiode BNC cable.
The optional Lok-to-Clock system provides phase-locked loop (PLL) stabi-
lization of output pulses and allows you to precisely synchronize output
pulses to either its internal 80 MHz reference source or to an external one,
such as an rf synthesizer, or to another mode-locked laser. The Model 3930
Lok-to-Clock electronics module contains the PLL circuit and the drive cir-
cuits for the M
1
HR motor drive and M
4
PZT-controlled mirror (Figure 3-3
and Figure 3-4)
. Two cables connect the Model 3930 to the laser head input
bezel: the control cable and the photodiode BNC cable. The Model 3930 is
the same shape and size as the Model 3955 and should be placed under it.
Chapter 8 contains a complete description of the Lok-to-Clock system.
The Model 3910 purge regulator/filter unit connects between an external
nitrogen gas supply and the laser head, and it removes dust and water vapor
from the purge gas to provide clean, dry nitrogen for purging the sealed
laser head. A flow gauge, flow control knob, and the gas in/out connections
are located on the front panel.
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