Third-order Nonlinear Phenomena Research Articles

Third order nonlinear correlation of the electromagnetic vacuum at near-infrared frequencies

In recent years, electro-optic sampling, which is based on Pockel’s effect between an electromagnetic mode and a copropagating, phase-matched ultrashort probe, has been largely used for the investigation of broadband quantum states of light, especially in the mid-infrared and terahertz frequency range. The use of two mutually delayed femtosecond pulses at near-infrared frequencies allows the measurement of quantum electromagnetic radiation in different space-time points. Their correlation allows therefore direct access to the spectral content of a broadband quantum state at terahertz frequencies after Fourier transformation. In this work, we will prove experimentally and theoretically that when using strongly focused coherent ultrashort probes, the electro-optic sampling technique can be affected by the presence of a third-order nonlinear mixing of the probes’ electric field at near-infrared frequencies. Moreover, we will show that these third-order nonlinear phenomena can also influence correlation measurements of the quantum electromagnetic radiation. We will prove that the four-wave mixing of the coherent probes’ electric field with their own electromagnetic vacuum at near-infrared frequencies results in the generation of a higher-order nonlinear correlation term. The latter will be characterized experimentally, proving its local nature requiring the physical overlap of the two probes. The parameters regime where higher order nonlinear correlation results predominant with respect to electro-optic correlation of terahertz radiation is provided.

Anisotropic Optical Shock Waves in Isotropic Media with Giant Nonlocal Nonlinearity.

Dispersive shock waves in thermal optical media are nonlinear phenomena whose intrinsic irreversibility is described by time asymmetric quantum mechanics. Recent studies demonstrated that the nonlocal wave breaking evolves in an exponentially decaying dynamics ruled by the reversed harmonic oscillator, namely, the simplest irreversible quantum system in the rigged Hilbert spaces. The generalization of this theory to more complex scenarios is still an open question. In this work, we use a thermal third-order medium with an unprecedented giant Kerr coefficient, the m-cresol/nylon mixed solution, to access an extremely nonlinear, highly nonlocal regime and realize anisotropic shock waves with internal gaps. We compare our experimental observations to results obtained under similar conditions but in hemoglobin solutions from human red blood cells, and found that the gap formation strongly depends on the nonlinearity strength. We prove that a superposition of Gamow vectors in an adhoc rigged Hilbert space, that is, a tensorial product between the reversed and the standard harmonic oscillators spaces, describes the beam propagation beyond the shock point. The anisotropy turns out from the interaction of trapping and antitrapping potentials. Our work furnishes the description of novel intriguing shock phenomena mediated by extreme nonlinearities.

Stimulated four-wave mixing in linearly uncoupled resonators.

We experimentally demonstrate stimulated four-wave mixing in two linearly uncoupled integrated $ {{\rm Si}_3}{{\rm N}_4} $Si3N4 micro-resonators. In our structure, the resonance combs of each resonator can be tuned independently, with the energy transfer from one resonator to the other occurring in the presence of a nonlinear interaction. This method allows flexible and efficient on-chip control of the nonlinear interaction, and is readily applicable to other third-order nonlinear phenomena.

Theoretical investigation on nonlinear absorption of multilevel organic molecular system in ns, ps and fs regime

The nonlinear absorption properties of organic materials in nanosecond (ns), picoseond (ps) and femtosecond (fs) regime were theoretically investigated by rate equations based on multilevel organic molecular system, respectively. The simulation results show that the RSA is mainly due to the absorption contribution of the triplet first excited state in the ns regime and that of the singlet first excited state in the ps regime, both of which are a third-order nonlinear phenomena. The RSA in fs regime is mainly due to the excited state absorption (ESA) induced by two-photon absorption (TPA), which is a fifth-order nonlinear phenomenon.

Single 10-fs deep-ultraviolet pulses generated by broadband four-wave mixing and high-order dispersion compensation

Broadband chirped-pulse four-wave mixing and a pulse compressor consisting of a prism pair and a grating pair are used to generate 10.3-fs deep-ultraviolet pulses. A large proportion of the dispersion up to 1000 fs2 is compensated without inducing third-order dispersion, which together with the smooth spectral and temporal profiles of the pulses makes them suitable for ultrafast spectroscopy. Unexpected spectral narrowing is observed when short input pulses were used for four-wave mixing. This narrowing is explained in terms of other third-order nonlinear phenomena, namely self-phase and cross-phase modulations, which occur simultaneously with four-wave mixing.

Stability analysis of semiconductor bistable lasers

In this paper, the rate equations for semiconductor bi-stable lasers are analyzed. Bistability and self-pulsation conditions are deduced, respectively. The former corresponds to a persistently increasing solution for the small-signal equations, while the latter corresponds to an enhanced oscillating solution. Bistability and self-pulsation are both third-order nonlinear phenomena, but the latter takes place only when the gain coefficient possesses a certain nonlinearity.

Nonlinear Guided Wave Applications

Potential device applications of third-order nonlinear phenomena in guided wave structures are discussed. One of the waveguiding media is assumed to exhibit an intensity-dependent refractive index that results in both an intensity-dependent propagation wavevector and field distribution for the guided waves. These two characteristics lead to many interesting all-optical devices whose operating principles and power levels are outlined here. For example, the intensity-dependent field patterns can be used for thresholding and switching operations in a waveguide context. The intensity-dependent wavevector, used in conjuction with a distributed input or output coupler, can lead to devices such as optical limiters and light-controlled spatial scanners. When gratings are used as distributed feedback elements within a nonlinear waveguide, a whole class of novel devices such as bistable switches and optically tunable optical filters should be feasible.

Applications of guided waves to nonlinear optics

Electromagnetic waves guided by single or multiple interfaces offer exciting possibilities for nonlinear optics because of the high power densities that can be achieved with small total powers. Progress in this area with the use of second-order and third-order nonlinearities is reviewed, including the current status of second harmonic generation by correctional and contradictional guided waves. A number of third-order nonlinear phenomena have recently been observed and are described. In particular new nonlinear modes unique to guided waves have been verified to show optical limiter characteristics. Coherent anti-Stokes Raman scattering has been demonstrated experimentally in thin-film waveguides with unparalleled conversion efficiencies.