1 kHz LASER SOURCE

The source is a laser system from Coherent Inc. It consists of a Ti:SA oscillator (Mira 900) and a Ti:SA amplifier (Legend), in which the crystal is kept at 0°C.

1kHz

Laboratory sketch: 1 = Mira 900, 2 = Legend, 3 = fiber compressor, 4 = TOPAS, 5 = HHG, 6 = TeraHertz, 7 = Supercontinuum pump-probe

1. OSCILLATOR The output consists of pulses with the following specifications: λ = 800 nm (tunable in the range 780-840 nm) bandwidth = 40 nm average power = 400 mW τ = 50 fs Repetition rate = 76 MHz 2. AMPLIFIER The pulses have the following characteristics: λ = 800 nm bandwidth = 26 nm average power = 2.5 W τ = 50 fs Repetition rate = 1 kHz (tunable down to the single shot) 3. HOLLOW FIBER COMPRESSOR (HFC) The 50 fs pulses can be compressed down to 10 fs by means of a glass capillary, filled with Ne. The pulse energy is thus reduced to <1 mJ. 4. OPTICAL PARAMETRIC AMPLIFIER It is possible to tune the laser output in the infrared by means of a TOPAS: λ tuning range: 1150-2600 nm Average Pulse Energy: 250 μJ τ < 50 fs

5. HIGH ORDER HARMONICS (HHG) It is possible to vary the laser output in the EUV (Extreme UltraViolet) by means of an HHG apparatus, developed in collaboration with the LUXOR Laboratory of Padova. Tuning range: 20-80 nm Max photons/sec in the generation chamber: 109 τ < 50 fs 6. TERAHERTZ SPECTROSCOPY 7. SUPERCONTINUUM PUMP-PROBE SET UP This setup allows time-resolved measurement of transmissivity (T) and reflectivity (R) of a solid or liquid sample after excitation with a femtosecond pump pulse. The supercontinuum white-light is used as the probe pulse which allows coverage of very large spectral range (320–950 nm) in a single laser shot. In this way time and frequency resolution of 50 fs and 2 nm, respectively, is simultaneously obtained. Since the setup employs a shot-to-shot acquisition strategy, it reaches high sensitivity of 10-4 (ΔT/T or ΔR/R). In addition, by using the TOPAS, the pump pulse can be tuned from 550–750 nm and from 1100–1500 nm. Finally, by using the pulses from the hollow fiber compressor (HFC), the time resolution of the set-up can be improved to 10 fs which allows to measure the time evolution of the coherent phonons or vibrational coherences in the sample in the far infrared spectral range (40–410 meV, 300-3300 cm-1).

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