Noncollinear Quasi-phase Matching Research Articles

Temperature-insensitive broadband optical parametric chirped pulse amplification based on a tilted noncollinear QPM design.

Ultrafast pulsed laser of high intensity and high repetition rate is the combined requisite for advancing strong-field physics experiments and calls for the development of thermal-stable ultrafast laser systems. Noncollinear phasing matching (PM) is an effective solution of optimizing the properties of optical parametric chirped pulse amplification (OPCPA) to achieve broadband amplification or to be temperature-insensitive. But as a cost, distinct noncollinear geometries have to be respectively satisfied. In this paper, a noncollinear quasi-phase-matching (QPM) scheme of both temperature- and wavelength-insensitive is presented. With the assistance of the design freedom of grating wave vector, the independent noncollinear-angle requirements can be simultaneously realized in a tilted QPM crystal, and the temperature-insensitive broadband amplification is achieved. Full-dimensional spatial-temporal simulations for a typical 1064 nm pumped mid-IR OPCPA at 3.4 µm are presented in detail. Compared with a mono-functional temperature-insensitive or broadband QPM scheme, the presented QPM configuration shows a common characteristic that simultaneously optimizes the thermal stability and the gain spectrum. Broadband parametric amplification of a ∼40 fs (FWHM) pulsed laser is achieved with no signs of gain-narrowing. Both of the beam profiles and the amplified spectra stay constant while the temperature is elevated by ∼100°C. Finally, influence of the QPM grating errors on the gain spectrum is discussed.

Research on Second Harmonic Generation in Two-Dimensional Periodical Nonlinear Photonic Crystals Based on Intelligent Materials

The works are focused on finding out proper shape of reversed domains to obtain effective harmonic generations with high conversion efficiency. The conversion efficiency of second harmonic wave in two-dimensional nonlinear photonic crystals consisting of square lattice and reversed domains of various shapes are studied numerically. The shapes of reversed domains are extended from circle, square to ellipse and rectangle. The conversion efficiency of different order quasi-phase matched process can be maximized by adjusting the orientation of noncircular reversed domains. Moreover, a cross-shaped reversed domain is utilized to improve the conversion efficiency of two-order non-collinear quasiphase matching.

Non-collinear quasi phase matching and annular profiles in difference frequency generation with focused Gaussian beams

We present and experimentally test a simple model for difference frequency generation (DFG) in periodically-poled crystals with gaussian pumping beams. Focusing of input beams originates several non-collinear quasi-phase-matching configurations of the interacting wavevectors, which contribute to the idler output field. In this picture, we accurately describe a number of effects, such as the occurrence of annular idler intensity profiles and the asymmetric trend of DFG power vs temperature. Finally, we quantitatively test the model by means of an indirect measurement of the crystal poling period.

Group-Velocity Matched Femtosecond Parametric Oscillation by Noncollinear Quasi-Phase Matching

A general model of noncollinear femtosecond parametric oscillation in periodically poled gratings is proposed, in which the group velocities of interacting waves are matched, based on a noncollinear quasi-phase matching (QPM) scheme. We demonstrate that group velocity matching and quasi-phase matching can be simultaneously achieved for ultrashort pulses. The corresponding noncollinear angles and grating periods are calculated for periodically poled lithium niobate (PPLN) and periodically poled KTP (PPKTP). With a suitable choice of parameters, the effective interaction length in the crystal can be remarkably increased, and an enhancement of parametric gain by orders of magnitude obtained, thus reducing the operational threshold significantly

Adiabatic compression of quadratic temporal solitons in aperiodic quasi-phase-matching gratings

We numerically show that it is possible to achieve adiabatic compression of femtosecond quadratic solitons in aperiodically poled lithium niobate device. Two-colored solitons of the fundamental wavelength of 1560 nm can be adiabatically shaped by using group-velocity matching schemes available in quasi-phase-matching (QPM) devices. We investigate the performance of the adiabatic compression based on two different group-velocity matching schemes: type-I (e: o + o) collinear QPM geometry and type-0 (e: e + e) non-collinear QPM geometry. Two-colored temporal solitons with pulse duration of 35 fs are generated without visible pedestals from 100-fs fundamental pulse. We also show that walking solitons with shorter pulse durations are adiabatically excited under small group-velocity mismatch condition. The walking solitons experience deceleration or acceleration during compression, depending on the sign of the groupvelocity- mismatch. The demonstrated adiabatic pulse shaping is useful for generation of shorter pulses with clean temporal profiles, efficient femtosecond second harmonic generation and group-velocity control.

Broadband quasi-phase-matched second-harmonic generation of ultrashort optical pulses with spectral angular dispersion

Noncollinear quasi-phase matching, in combination with spectral angular dispersion, can be used to broaden the bandwidth of second-harmonic generation (SHG) beyond the bandwidth for collinear, nondispersed interactions. A general theoretical treatment is presented, in addition to a solution that predicts the generated field for the case of a Gaussian input field; a comparison is made between this technique and others available for broadband SHG. An experiment in periodically poled lithium niobate demonstrates SHG of a 138 fs pulse at 1550 nm in a 1 cm length crystal (with a collinear acceptance bandwidth 13 times narrower than the first-harmonic bandwidth) with minimal spectral narrowing.

High-order quasi-phase matching harmonic generation in two-dimensional nonlinear photonic crystal

The high-order collinear and non-collinear quasi-phase matching harmonic generations were realized in a two-dimensional periodically poled LiNbO3 wit h square lattice by tuning the input wavelength. The output spots lay at different symme tric positions with respect to the input beam of picosecond pulse, and the relat ive intensities of spots at certain wavelengths were measured. The high-order no nlinear harmonic processes were also realized by tuning the input angle. The exp erimental and theoretical results are in good agreement with each other. Our stu dies might be beneficial to the development of optics integration and compact de vices.