Optical Front-End fibered laser source for ns Pulse Shaping: the latest improvements

High intensities lasers have proven to be useful tools in a wide range of disciplines and studies: warm dense matter, plasma physics, acceleration of ions and electrons, imaging, and more recently industrial laser applications such as material hardening by laser-induced shock wave (peening).

The ModBox-Front-End with ns Pulse Shaping capability is an ideal choice as a master for either the high energetic laser (> 1 kJ, 1 MJ projects) (figure 1) or the solid state pump laser (figure 2)

Figure 1: ModBox-Front-end used as master

Figure 2: ModBox-Front-end seeding a free-space diode pump amplifier, optionally coupled with a ns-OPCPA set-up

Continuous improvements are made on the ModBox-Front-End to generate higher pulse energies > 10 mJ and > 100 mJ with high stability, repeatability and reliability for continuous use in an industrial environment. Also, the ModBox-Front-End features improved optical pulse contrast to minimize noise and a high PER and to avoid FM/AM conversion.

The recent improvements are shown  below. The improvements are based on proprietary and carefully selected new high grade LiNbO₃ modulators and combined with industrial integration expertise gathered from various iXblue divisions.

Sub-ns optical Pulse Shaping

The ModBox-Front-End is a temporally shaped laser integrating a LiNbO₃ modulator driven by a programmable Arbitrary Waveform Generator (AWG). Pulse shaping resolution is 125 ps on pulse durations up to 100 ns with a vertical resolution of 12 bits. The pulse contrast provided can be as high as 60 dB.

Low and extremely low jitter optical pulses

The ModBox-Front-End uses fast microwave electronic to generate low jitter pulses:

• Low jitter: < 7 ps RMS
• Extremely low: < 7 ps peak-peak

Outstanding Pulse amplitude peak to peak stability

This screen shot shows the sum / accumulation of 60 000 superimposed Clean Optical Pulses. One can see the persistence of the low ripple, low jitter and peak pulse power. This measurement proves the high stability and reliability of the optical pulses generated by the laser ModBox-Front-End.

Low ripple: 1 % RMS

The Electrical Arbitrary Waveform Generator is combined with a wide bandwidth and linearized RF amplifier. The RF optimization allows to guarantee a ripple in the square pulse plateau of < 1 % RMS.

Improved power and energy performance

The ModBox-Front-End embeds extremely low loss LiNbO₃ modulators and a high gain optical fiber amplifier. iXblue features ModBox-Front-Ends with the following energy levels:

•  Up to 1 nJ / 1 ns with 35 dB contrast optical pulses (w/o optical pulsed amplifier)
•  300 pJ / 1 ns with 60 dB contrast optical pulses (w/o optical pulsed amplifier)
•  10 mJ and 100 mJ / 1 ns with 60 dB contrast optical pulses

High optical Stability: flat optical output power and energy behavior

A high quality fibered optical amplifier is embedded into an industrial grade ModBox-Front-End. The output optical power variation is guaranteed to be < 1 % RMS.