System for the Generation of Tunable Ultrafast Optical Pulses (Phase I)

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Ultrafast laser pulses featuring broad wavelength tunability can bring a decisive advantage in numerousscientific and industrial applications. However, nowadays the most commonly implemented technologies togenerate such pulses, e.g., optical parametric amplification, necessitate multiple optical nonlinear processes forfrequency conversion and amplification, essentially requiring bulky and expensive apparatus while still notautomatically guaranteeing a gap-free tunability. Also, the time duration of the output pulses remains at thelevel of the initial pump laser, so that further complexity needs to be added to achieve shorter durations. In thiscontext, we have developed a simple and cost-effective system to generate wavelength-tunable optical pulses,with the additional benefit of a pulse duration shorter than the one of the amplified laser employed as a pump.Our strategy is based on nonlinear spectral broadening (arising from self-phase modulation or stimulatedRaman scattering) in a gas-filled hollow-core fiber (HCF), followed by a subsequent optical filtering stage.Once the outermost spectral lobe (which can be tuned by varying the gas pressure) is selected from thebroadened output spectrum by optical filtering, quasi-transform-limited pulses are directly obtained withenergy conversion efficiencies of about 10-15% (comparable with commercial optical parametric amplifiers)and pulse durations 3-4 times shorter than the one of the pump laser. According to a recent market assessmentreport, several companies and researchers have already shown a significant interest in such newly-developedtunable system. This NSERC I2I Phase I project has now the potential to greatly increase the commercial meritof our technology, by targeting the following 3 objectives: (i) devising a more compact system featuring ashorter HCF (< 2 m) than the one previously utilized (~ 6 m), a solution clearly more favorable for realisticimplementations; (ii) developing a practical tunable spectral filtering apparatus based on a folded 4-f layout;and (iii) demonstrating a straightforward application identified in the market study: a convenient terahertzspectroscopy setup employing an organic crystal directly pumped by the filtered pulses.