Broadband noncollinear optical parametric amplification without angularly dispersed idler

Abstract

We report a new scheme for direct generation of broadband angular-dispersion-free mid-IR idler pulses via noncollinear optical parametric amplification when group-velocity matched wavelengths cannot be found and the traditional noncollinear geometry fails to increase the phase-matching bandwidth. The scheme does not require any post-amplification idler angular dispersion compensation. We derive and interpret the condition for broadband amplification and absence of idler angular dispersion. A broadband angular-dispersion-free 2.15 μm idler pulse is generated as an experimental demonstration. We identify the potential of the scheme to generate a broadband 3.5 μm idler, with a bandwidth supporting a sub-two-cycle pulse. Due to the lack of mid-IR laser media, differencefrequency generation or optical parametric amplification (OPA) have been largely employed to down-convert visible or near-IR light sources [7][8][9][10]. It has been shown that mid-IR crystals such as LiIO 3 , KNbO 3 , and MgO:LiNbO 3 have group-velocity matched wavelengths, when pumped at 800 nm, between 950 nm and 1050 nm, and thus allow the direct generation of a broadband mid-IR idler with spectra supporting three-cycle pulses [7]. For wavelengths where signal and idler group velocities (V gs and V gi ) are not matched, a noncollinear geometry can be employed so that V gs V gi cos Ω. This achieves a broad phase-matching bandwidth at the cost of introducing idler angular dispersion [11]. It has been shown that once its angular dispersion is compensated, the idler can also be utilized for experiments [12].However, there is no guarantee that the condition of the traditional noncollinear OPA, i.e., V gs V gi cos Ω , can be satisfied and thus broadband amplification is sometimes prohibited. For example, when pumped at 1 μm, the condition cannot be fulfilled for all signal wavelengths below the degenerate wavelength in mid-IR crystals such as LiIO 3 , KNbO 3 , and MgO:LiNbO 3 . The same is true in lithium triborate (LBO) for signal wavelengths shorter than 720 nm, pumping at 523 nm. On the other hand, pumping at 1 μm or its second harmonic is advantageous for power and energy scalability because it is compatible with high-power ytterbium (Yb) fiber technology and high-energy Yb:YAG laser technology.In this Letter, we present a new scheme for direct generation of broadband, angular-dispersion-free mid-IR idler pulses when signal-idler group velocity matching cannot be achieved and the traditional noncollinear geometry fails to increase the phase-matching bandwidth. The conditions for broadband amplification and absence of idler angular dispersion can be fulfilled simultaneously by introducing not only noncollinear geometry but also signal angular dispersion. A broadband (1.8-2.4 μm), angular-dispersion-free idler pulse, which can be used to seed a 2.15 μm optical parametric chirped pulse amplifier (OPCPA) [6,13], is demonstrated as a proof of principle. Furthermore, we identify the potential of the scheme to generate a broadband 3.5 μm idler from a 1 μm ...

Temperature- and wavelength-insensitive parametric amplification enabled by noncollinear achromatic phase-matching

“…Previously, the seed signal with angular dispersion has been proposed for ultra-broadband parametric amplification24 and pulse durations of 5.8 fs has been experimentally demonstrated25. The needed angular dispersion can be introduced with a grating2425 or grating pair26, etc. The exact amount of angular dispersion can be measured with the aid of spectrally resolved interferometry27 and the re-collimation of the amplified signal can be achieved by angular-dispersion-compensation scheme28.…”

Mid-infrared pulse generation via achromatic quasi-phase-matched OPCPA

“…A related non-collinear phase-matching scheme, based on an angularly chirped input signal wave, was proposed for PPLN in Ref. [25]. Until now, however, such schemes have not been experimentally demonstrated for broadband QPM OPCPA.…”

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

“…As discussed above, the first-order phase-mismatch ∆k 1 is proportional to the group velocity mismatch (GVM) between the signal and idler pulses δ si = 1/v gs − 1/v gi . The idea of removing GVM to realize first-order phase-matching leads to the development of noncollinear OPA (NOPA) schemes [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74]. In NOPA, the pump and seed beams enter the nonlinear crystal with a noncollinear angle α in between.…”