One of our main R&D programs concerns the development of intense Titanium-Sapphire lasers at high power, medium and high frequency (1 to 10 kHz) and stabilized in CEP (Carrier Envelope Phase).
Together with Amplitude Technologies in the joint R&D laboratory “IMPULSE”, we have studied and developed new amplification architectures corresponding to the medium-term needs identified for ATTOLAB’s FAB1/10 laser. Our work has focused on a 10kHz regenerative cavity whose original feature is to include two crystals. By distributing the thermal effects between the two crystals, we manage to maintain the quality of the spatial profile even when high pumping energies are used. This cavity has enabled us to triple the power delivered for equivalent beam quality.
Spatial profile at different pumping powers for 1- and 2-crystal cavities
After re-amplification in a double-pass amplifier with two crystals, the power reaches 10W (1 mJ/pulse).
The improved spatial quality of the beam also favors the operation of the AOPDF filter (Mazzler) inserted in the cavity to attenuate spectral narrowing by the gain, enabling us to produce 17fs pulses (110 nm spectrum in 1/e2).
We were also able to tune the wavelength from 760 to 850 nm with a spectral width of 35 nm (FWHM) and a resolution of 1 nm at the output of the regenerative cavity. Pulse duration is then around 40fs.
Finally, the CEP was stabilized with a residual noise of 200 mrad over several hours (170 mrad over 1 minute) using an original fully analog stabilization loop (see below).
This amplifier is installed on the ATTOLab FAB1/10 laser, where it injects the power amplifiers. Pulses of 17.5fs with a power of 0.9TW (16mJ) and a CEP noise of 350mrad were obtained on the 1kHz channel.
References:
- Golinelli et al, OPTICS LETTERS 42 (12), 2326 (2017)
- Feng et al, OPTICS EXPRESS 21, (21) 25248-25256 (2013)