Group velocity mismatch-absent nonlinear frequency conversions for mid-infrared femtosecond pulses generation

Abstract

A novel group velocity mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the group velocities of the pump and the signal waves, while the phase velocities were quasi phase matched. The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium. Desired group-velocity dispersion would be obtained via appropriately temperature regulation. To demonstrate its potential applications in ultrafast mid-infrared pulses generation, aiming at a typical mid-infrared wavelength of ~3.2 μm, design examples of two basic nonlinear frequency conversion procedures are studied for both the narrow-band seeding mid-IR optical parametric amplification (OPA) and the synchronously pumped femtosecond optical parametric oscillation (SPOPO). Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth. The proposed GVM- absent phase matching design may provide a promising route to efficient and broadband sub-100 fs mid-infrared ultrafast pulses generation without group-velocity walk-off.

Efficient idler broadening via oppositely dual-chirped difference frequency generation

“…Normally, to make use of the largest nonlinear coefficient of d 33 , a Type-0 QPM condition (ee-e) should be satisfied. However, the inactive Type-I (oo-e) or Type-II (eo-o) QPM conditions may also have an advantage in certain broadband nonlinear processes [34,35] . Compared to other material counterparts, the Type-II PPLN not only exhibits a stable group-velocity relationship across an extremely broad spectral range (1000-1600 nm), but σ also stays within relatively ideal boundary values (−1.5 < σ < −0.5).…”

Efficient cascaded wavelength conversion under two-peak modulated Stark-chirped rapid adiabatic passage via grating structures

“…Wavelength conversion, via three-wave mixing (TWM) processes in quadratic nonlinear optical crystals, is widely used to generate laser wavelengths that are not available by direct laser action [1][2][3]. During a TWM process, the efficiency mainly depends on the fulfillment of the phasematching condition.…”

Super-tunable, broadband up-conversion of a high-power CW laser in an engineered nonlinear crystal

“…There are many works on second harmonic generation (SHG) and sum frequency generation (SFG) using QPM in uniform gratings in the form of periodically poled crystals 15 , 18 – 23 . However, uniform gratings limit the BW of up-conversion process (and consequently the tunability) as it is inversely proportional to the length of a grating 24 . Since the up-conversion efficiency (assuming an undepleted pump) is increased by the length squared, using a long grating leads to a reduction in the up-converted BW of a few-nm-wide pump and consequently results in a waste of power whilst a short grating up-converts the whole BW with a very low efficiency.…”