Current projects
High peak-power MIR CPA laser based on Fe:ZnSe
Carrier–envelope phase (CEP)-stabilized, few-cycle lasers with 1 kHz or higher repetition rates in the near-infrared (NIR) region have reached a mature stage of technological development for attosecond science applications. The endeavor to expand this technology deeper into the infrared spectrum is currently gaining significant momentum. Several key phenomena in strong field physics motivate the push for longer wavelength sources.Chirped pulse amplification based on an Fe:ZnSe gain medium with seeding by an optical parametric amplifier has been demonstrated to produce high-energy pulses in the mid-wave infrared (MWIR) region. We conducted the first demonstration of few-cycle, MWIR pulses originating from a cryogenically cooled Fe:ZnSe CPA directed into a gas-filled HCF and the first published use of oxygen for broadening via HCF of a 4-𝜇m source.
Alphonse Marra et al., Optics Letters Vol. 49, Issue 11, pp. 3170-3173 (2024)
High average-power MIR OPCPA laser
High-peak power, high-average power, few-cycle, and CEP-locked lasers at 3-8 μm are needed to generate high flux attosecond X-rays spanning the entire water window and beyond, which are not commercially available. The limited choices of laser gain media for wavelengths at 3 μm and longer motivated the development of optical parametric chirped pulse amplifiers to cover this spectral region.
Our OPCPA design is based on numerical simulations predicting that an idler spectrum covering 4-12 μm can be achieved when ZGP is pumped at 2 μm and seeded with a broadband 2.4-4 μm signal pulse. The signal pulse for the OPCPA and the 2-μm seed pulse for a Ho:YLF chirped pulse amplifier (CPA) will be generated from two optical parametric amplifiers (OPAs) driven by the same Yb:KGW laser. Spectral phase error in the system can be compensated by an acousto-optic modulator to produce near transform-limited amplified idler pulses, 27 fs (single cycle) after the final OPA stage.
Fangjie Zhou et al., Optics Letters Vol. 47, Issue 23, pp. 6057-6060 (2022)
Attosecond X-ray source and spectroscopy
Single isolated attosecond X-ray pulses are required for pump-probe experiments, rather than attosecond pulse trains. To generate such pulses with sufficient photon flux for applications, we must achieve phase matching of HHG, which can be realized by balancing the plasma induced index of refraction change with that of the unionized neutral portion of the target gas. This occurs at a particular ionization probability of the target atoms interacting with a strong infrared laser pulse. Calculations and numerical simulations predicted that by using a driving laser at 3-8 μm and a helium gas target, X-rays with photon energy as high as 5 keV can be produced.
Jie Li et al., Nature Communications volume 11, Article number: 2748 (2020)
Short-wave infrared Ho:YLF laser
High energy picosecond Ho:YLF lasers are normally based on Chirped Pulse Amplification (CPA). In a 2-µm picosecond CPA laser that generates more than 20 mJ of energy, pulses from preamplifiers are boosted by power amplifiers. The final output energy is determined by the input pulse energy and the gain of the booster. We have developed a two-stage Ho:YLF booster amplifier that utilizes two thermoelectric cooling modules (TECs) to achieve higher energy output by applying the temperature dependence of quasi-three level media. An output energy of 60 mJ was recorded for only 8.5 mJ input when the crystals were cooled to -20°C using TECs. To our knowledge, this is the highest output energy that has ever been produced from a tabletop kHz Ho:YLF amplifier. The corresponding gain and efficiency are 7 and 23.4% which, when combined with the fact that TECs are more compact, easier cooling, unequivocally show that using TECs is a superior way to enhance the performance of Ho:YLF amplifiers.
Optics Continuum Vol. 1, Issue 5, pp. 1060-1066 (2022)
