EXTREMAG
The Exeter Time-Resolved Magnetism Facility
EXTREMAG
The Exeter Time-Resolved Magnetism Facility
The EXTREMAG facility has three Class IV femtosecond laser systems.
The Fidelity (right), Monaco (center), and Opera (left). In the foreground is the external signal compressor.
The Fidelity is a high-power, modelocked fiber laser with a 10 W output of 140 fs pulses with 1040 nm wavelength and 80 MHz repetition rate. Part of the beam (~10%) is used for time-resolved scanning Kerr microscopy at either 1040 nm, or at 520 nm using external second harmonic generation. The remaining beam (90%) can be used for THz spectroscopy and imaging (under development).
The Monaco is an ultrafast diode-pumped fiber laser with up to 40 W output of pulses of tuneable duration (280 fs to 10 ps) and repetition rate (single shot to 50 MHz) with 1035 nm wavelength. The tuneability of the Monaco output pulse duration, repetition rate, and power has been used for all-optical switching experiments.
At repetition rates up to 1 MHz and pulse duration of 280 fs the Monaco is used to pump the Opera-F OPA to generate a combined signal and idler output up to 4 W, also at 1 MHz. The Monaco second harmonic is used to pump a white light continuum seed, while a non-collinear first stage and collinear second stage provide large bandwidth and tunability. The signal wavelength is tuneable from 650 nm to 900 nm, while the idler is correspondingly tuneable from 2600 nm to 1200 nm. An external prism (internal bulk) compressor is used to reduce the signal (idler) pulse duration down to 25 fs (40 fs) for ultrafast all-optical pump-probe measurements.
Inside the Opera-F OPA cavity. The Monaco 2nd harmonic (green) is used to pump a white light continuum seed, while non-collinear and collinear 1st and 2nd stages provide large bandwidth and tunability of the signal and idler output.
The lasers are installed on a fully enclosed optical table in a dedicated laser room that is interlocked and separated from the EXTREMAG user areas. The laser room is not accessible for visiting users. The laser room optics are configured so that all beams (Fidelity, Monaco, and Opera-F signal and idler) are available in both user areas of EXTREMAG: the so-called free space lab B2, and the microscopy lab B3.
Users can access the laser beam for their experiment by manual remote control of a laser shutter in the path of the beam as it passes from the laser room. Only the laser beam required for the user experiment will be available via the shutters and all other beams to the user area will be blocked within the laser enclosure by the SEO. The wavelength of the Opera-F signal and idler beams is computer controlled and may be remotely adjusted by users from the user areas following the necessary training, e.g. considering possible changes to laser alignment and protective eyewear requirements.
Beam paths will be enclosed where possible and all necessary laser safety infrastructure installed. Laser protective eyewear for the particular wavelength(s) in use will be provided. Before users begin their experiments, a local induction and safety briefing related to the local laser rules and the facility safe operating procedures relevant to the experiment will be provided by the SEO. The SEO will also provide the training required for users to perform measurements and change samples where possible. All user time will be supported by the SEO. Frequently visiting users will be able to work more independently of the SEO as their knowledge of the experiment and measurements develops. However, loan working is not permitted by visiting users, and so it is advisable for pairs of users to visit to avoid loan working when the SEO is not available.
User access to the different beams will be via remote control to the appropriate laser shutter