The generation of photon pairs inside metallo-dielectric layered media by spontaneous parametric down conversion is highly efficient. A theoretical model of spontaneous parametric down conversion based on vectorial quantum-mechanial approach is used to obtain spatial, frequency and temporal photon-pair characteristics. As an example, a structure consisting of eleven alternating Galium-Nitride and silver layers is analyzed. Strong constructive interference of the sub-frequency fields results in narrow spatial and frequency distributions of photon-pairs emitted at high generation rates. Photon pairs are mainly created in Galium-Nitride layers, the silver layers serve as a linear reflector.
We present experimental characterization of periodically-poled KTP waveguide studying the process of second harmonic generation. Spatial and spectral properties of three types of the nonlinear processes (Type 0, I, and II) have been observed simultaneously utilizing the first, second, and third harmonics of the spatial nonlinear modulation. Experimental results have been interpreted using a model based on scalar finite elements method, which has been adopted in order to calculate spatial mode profiles, propagation constants, and frequencies of the interacting fields. Correlations between spatial and spectral properties of the fundamental and second- harmonic fields have been revealed. Individual nonlinear processes can be switched on and off combining spatial and spectral filtering. Also the influence of waveguide parameters to the second-harmonic spectra has been addressed.
On the interface between two isotropic linear media the re°ection and transmission of separate monochro- matic waves occur in a normal incidence, which are described by Fresnel's formulas. On the interface between two nonlinear media, namely one of the media may be linear in a limit, the re°ection and the transmission are complicated by a wave mixing of di®erent frequencies. A maximum generality of improved Fresnel formulas is impossible. By using the rotating-wave approximation and the parametric approximation, a model of the parametric down-conversion has been derived in the nonlinear and quantum optics. We present a classical ex- pression of the e®ect of the wave mixing on the interface and treat even the possibility of quantum input{output relations.
Stochastic quasi-phase-matching of the process of spontaneous parametric down-conversion is analyzed. It is
shown that spectral, temporal and spatial properties of photon pairs generated in randomly poled crystals are
similar to those generated in chirped periodically-poled crystals. Especially, randomly poled crystals are capable
to emit photon pairs with ultra-broad spectra.
In this paper, we present Bragg reflection waveguides as a novel universal platform for reaching the phasematching
of spontaneous parametric downconversion process in semiconductor materials. We have designed two
different waveguide structures. The first one is based on AlGaN and it is able to produce spectrally uncorrelated
photon pairs. The second one is based on AlGaAs and it allows us to generate entangled photon pairs with
ultra-broad spectra. Spontaneous-parametric-downconversion and second-harmonic-generation experiments are
presented.
We describe properties of entangled photon pairs generated by spontaneous parametric down-conversion in
periodically poled nonlinear crystals. These materials can serve as a useful bright source of photon pairs which
properties can be tailored on demand. Especially photon pairs with broad spectra and sharp temporal features
can be observed. Both uniform and chirped poling are considered. Spectral properties of the generated photons,
photon fluxes, coincidence-count patterns in a Hong-Ou-Mandel interferometer, entropy of entanglement, as well
as transverse profiles of intensities of the generated photon fields are discussed. Also the correlation area of two
photons comprising a photon pair has been studied as it depends on parameters of periodical poling. Attention
is also paid to structures with randomly distributed boundaries.
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