Ultrafast Mid-IR Laser Pulses Generation via Chirp Manipulated Optical Parametric Amplification

Infrared spectroscopic monitoring of solid-state processes

We put a spotlight on IR spectroscopic investigations in materials science by providing a critical insight into the state of the art, covering both fundamental aspects, examples of its utilisation, and current challenges and perspectives focusing on the solid state.

Efficient second-harmonic and terahertz generation from single BiB3O6crystal using nanosecond and femtosecond lasers

The paper reports the efficient UV and terahertz generation from a 1.29 mm thick and Type I, θ=28.9^∘ cut BiB₃O₆ (bismuth triborate, BIBO) crystal using femtosecond and nanoseconds laser pulses. We have employed 800 nm wavelength pulses of 50 and 140 fs obtained from a Ti:sapphire laser amplifier and oscillators at 1 kHz and 80 MHz repetition rates, respectively. The conversion efficiency of second-harmonic generation (SHG) was ∼50% while that obtained for terahertz (THz) generations was of the order of 1.85×10^-5%. In addition, LDS-698 dye laser radiation tunable between 650-700 nm was also used as a source for SHG between the 325-350 nm range. The dye laser was pumped by SHG (532 nm) radiation from an electro-optically Q-switched Nd:YAG laser having a pulse repetition rate of 10 Hz and a pulse width of 10 ns. A conversion efficiency of 4.01% was obtained for generation of UV at 343.5 nm. Finally, we have measured the transmission, refractive index, absorbance, and conductivity properties of BIBO crystal in the THz domain. We also ascertained the coherence length, relative permittivity and reflectivity of the crystal.

Efficient Generation of Spectrum-Manipulated Few-Cycle Laser Pulses through Cascaded Dual-Chirped OPA

The cascaded dual-chirped optical parametric amplification (DC-OPA) is presented for efficient generation of few-cycle infrared (IR) laser pulses. The input pulses are strategically chirped to optimize the phase-matching bandwidth in each nonlinear crystal, and four regions of the signal spectrum are amplified in cascaded crystals with different cutting angles, enabling flexible manipulation of the output spectrum. Broadband gain and high conversion efficiency are simultaneously achieved owing to the cascaded-crystal arrangement, the signal pulse duration of 4.2 cycles is obtained with 11.7-mJ pulse energy, corresponding to a conversion efficiency of 39.0%. The proposed scheme offers a robust and simple approach to pushing the phase-matching bandwidth limits introduced by the nonlinear crystal, which manifests great prospect in various researches involving ultrafast optics and strong-field physics.

Few-cycle 1.9-μm pulse generation via collinear spectrum synthesis in multiple-crystal OPA

A multiple-crystal optical parametric amplification (OPA) design is reported for efficiently generating few-cycle 1.9-μm laser pulses. Different spectral regions of the idler pulse are successively amplified in three nonlinear crystals with delicately adjusted phase-matching angles, and a broadband spectrum supporting a three-cycle transform-limited (TL) pulse duration is obtained. Near-TL duration of 21.5 fs is realized by simple compression in a silicon window. Owing to sufficient exploitation of the pump energy in the crystals, total conversion efficiency of 31.3% is achieved with idler pulse energy of 65.8 μJ. The gain bandwidth in multiple-crystal OPA is markedly broadened compared to OPA using a single thick crystal; meanwhile, the high efficiency is preserved. Further energy scaling of the proposed scheme is potentially feasible using dual-chirped OPA geometry.