Spitfire

Operation

Basic Performance Optimization

In addition to optimizing the optical length of the compressor as described in the previous section, the parameters that should be optimized are:

• stability of the seed pulses

• seed beam alignment into the regenerative amplifier

• beam uniformity

• build-up reduction time (optimizing the regenerative amplifier)

These parameters should not need to be checked or optimized on a daily basis; nevertheless they are fundamental to proper operation of the system and so are considered routine.

For convenience, Figure 6-2 shows the components used to align the seed beam into the Spitfire regenerative amplifier. The details of the optical design of the Spitfire models are described in Chapter 7.

Stability of the Seed Pulses

The mode-locked output of the seed laser must be optimized to ensure good stability of the amplifier. Refer to the seed laser user’s manual. In particular, it is important that the duration of the seed pulse be not too long because the stretcher may not sufficiently reduce the peak power to avoid damage to the Spitfire optics. Use a scanning autocorrelator to monitor the seed pulse duration.

Seed Beam Alignment into the Regenerative Amplifier

Seed Pulses

SM

2

M

2

A

2

F

I

A

1

M

3

SM

1

Stretcher

Grating

STRETCHER

SM

3

VRR

PS

1

Compressor

Grating

COMPRESSOR

M

4

M

1

CM

3

CM

2

λ

/4 waveplate

Input

Pockels Cell

Figure 6-2: Optical Path for Seed Beam Alignment

A

3

A

4

Rod

Output

Pockels Cell

CM

4

CM

1

REGENERATIVE AMPLIFIER

6-3