Bernina pump laser

The Bernina pump laser system is based on a 20 mJ Ti:Sapphire system at 100 Hz. The source pulses can be converted to pulses from ultravioiet to THz range, see table below for typical performance parameters.

Ongoing developments on closing the THz range gap between 5 and 15 THz are not available to user experiments yet, interested Scientists are invited to get in touch and communicate concrete need for their experiments. 

THz pulses below the gap (< 5 THz central energy) are passively carrier envelope phase (CEP) stable by their generation, please see section below for typical temporal field shapes and spectral contents for different generation mechanisms.

Mid - infrared pulses in the range 10-18um can be actively CEP stabilized in the range that can be temporally resolved by the FEL pulses.

Bernina optical pump laser
Source typeWavelength rangePulse energy / max. FieldPulse lengthComments
Primary pump source   800 nm20 mJ35 fs
or 100 fs		100 Hz repetition rate (can be reduced by choppers). 2nd and 3rd Harmonic (400 nm and 266 nm), as well as ~10 fs compressed fundamental 800 nm available upon request.
OPA240 – 480 nm     10 – 100 uJ  ≤ 50 fs (fwhm)Pulse energy variation includes typical losses between source and sample.
 
480 – 780 nm150 – 1000 uJ≤ 50 fs (fwhm)
780 – 1160 nm10 – 100 uJ≤ 50 fs (fwhm)
1.16 – 1.58 µm1000 - 2000 uJ≤ 50 fs
1.58 – 2.4 um500 – 1000 uJ≤ 50 fs
NOPA500 – 750 nm10 – 70uJ
 		≤ 25 fs 
OPA DFG4.4 – 20 um  (70 – 15 THz)1 – 20 µJ
 		≤ 300 fs 
CEP stabilized
10 – 18 um  (30 – 17 THz)		1 – 20 µJ≤ 250 fs 
Org. crystals2 – 5 THz single cycle>500 kV/cm—Circularly polarized at specific frequencies
LiNbO₃ based0.5 – 2 THz single cycle>500 kV/cm— 

Optical rectification in organic crystals is intrinsically phase matched, which makes the generating infrared pulses point collinearly to the emitted THz pulse. This facts enables rotation of both linear and circular polarisation around the pointing direction, well suited for studies on oriented samples. 

The typically used setup using the Terahertz chamber (see schematic drawing) can be applied also in air on the surface diffractomter setup. 

Below plots show electro-optic sampling (EOS) measurements of THz waveforms generated by optical rectification in the organic crystals DSTMS, OH1, and PNPA and with different low-pass filters. The crystals were pumped with 1.5 µm, 35 fs pump pulses and characterized using 800 nm, 35 fs probe pulses. The linearly polarized THz radiation was detected with a 100 µm-thick GaP crystal.

THC organic crystal setup
DSTMS EOS trace
oh1_eos
PNPA EOS traces

LiNbO₃ based source

Optical rectification in LiNbO₃ is extrinsically phase matched, which makes the generating infrared pulses point noncollinearly compared to the emitted THz pulse. This limits polarisation control with respect to the intrinsically phase-matched case shown above, the source is typically chosen for its low Frequency spectral content. 

The typically used setup using the Terahertz chamber (see schematic drawing) can be applied also in air on the surface diffractomter setup. 

Below plot shows electro-optic sampling (EOS) measurements of THz waveform generated in a LiNbO₃ (LNO) prism via the tilted-pulse-front excitation technique. The prism was pumped with a 7 mJ, 800 nm laser with 100 fs pulse duration. The THz waveform was characterized using an 800 nm, 100 fs probe. The linearly polarized THz radiation was detected using a 100 µm-thick GaP crystal.

thz_lno_setup
THz LNO EOS