Broadband laser

(nur in englisch verfügbar)

Diode pumped broadband Ti:sapphire laser

Fig. 1 Schematic setup of the Ti:sapphire laser

For pumping the Ti:sapphire laser a diode pumped passivly Q - switched Nd:YAG laser with an efficient internal frequency doubling was used. The diodes were drived with a maximum duty cycle of 2 % and a maximum pulse duration of 500 µs. A high conversion efficiency was realized by a passiv Q - switch operating with a resonator internal saturable absorber (Cr:YAG crystal). A l/4 - plate inside the folded resonator minimizes the so called "green problem".

The pump laser provides within 500 µs up to 7 single pulses. By absorbing the largest part of the pump energy the Ti:sapphire laser also emits up to 7 single pulses with a burst energy of more than 11 mJ. This results in an average output power of 275 mW (repetition rate = 25 Hz) and it hence sufficient for a field of measurement up to 15 cm × 15 cm. The dimensions of the described broadband laser light source are 50 cm × 20 cm × 10 cm (L × W × H). Likewise the coherence radar system allowed the measurement of the correlation function and therewith the coherence length. Therefore the beam propagation must be exactly parallel and in addition one interferometer mirror has to be tilt. Now it is possible to extract the correlogram by evaluating the cross section perpendicular to the interference pattern. The scaling of the x - axis is determined by the periods of the modulations.

Fig. 2 Correlogram of the Ti:sapphire laser

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