Correlation Properties of an Optical–Terahertz Biphoton Field

An Improvement of the Cherenkov THz Generation Scheme Using Convex Silicon Prism-Lens Adapters

“…TНz    +  depends on the azimuthal angle THz  (measured from the OY axis directed perpendicular to the crystal/prism interface, see Figure 3a) in our case of an eee-type process in LN [35]. The angular distribution of the THz power density at ω THz inside the crystal can be found as To obtain the corresponding angular distribution inside the Si prism, for the THz radiation transmitted through the LN/Si surface, we had to decompose the as-generated THz waves into s-and p-polarized components and then use the Fresnel equations together with Snell's law.…”

“…Here, ∆k || ≡ ∆k || ,n THz is a refractive index for the THz waves in the crystal (its value was taken for our calculations from [33] and the crystal dispersion parameters in the optical range were taken from [34]), µ THz ≡ α THz 2 cos ϑ THz depends on the crystal absorption coefficient for the THz waves α THz (taken for calculations from [18]) and polar angle of the THz wave propagation ϑ THz with respect to the pump beam direction OX (Figure 3a), and the nonlinear coefficient χ (2) ≈ χ 1 + 3 cos 2 ϕ THz depends on the azimuthal angle ϕ THz (measured from the OY axis directed perpendicular to the crystal/prism interface, see Figure 3a) in our case of an eee-type process in LN [35]. The angular distribution of the THz power density at ω THz inside the crystal can be found as S(ϑ THz , ϕ THz , ω THz ) ∝ |A(ϑ THz , ϕ THz , ω THz )| 2 .…”

Prism Couplers with Convex Output Surfaces for Nonlinear Cherenkov Terahertz Generation

“…However, when the azimuthal angle changes significantly, one has to take into account a decrease in the working Z-projection of the corresponding field. Equation ( 3) accounts for a convolution of the crystal secondorder susceptibility tensor χ (2) with the polarization vectors of interacting waves in the form of χ (2) ≈ χ 1 + 3 cos 2 ϕ THz [27]. µ THz accounts for the crystal intensity absorption coefficient α THz at THz frequency: µ THz ≡ α THz 2 cos ϑ THz .…”

Visible–Telecom Photon Pair Source Based on a Photonic-Crystal Fiber under Continuous-Wave Pumping

“…Carrier frequencies of correlated photon pairs can be strongly different, which significantly expands the capabilities of the applications listed above, in particular, in spectroscopy. For this reason, methods for the generation of photon pairs at frequencies in various spectral bands, e.g., in the visible and near infrared bands [9,10], as well as in the optical and terahertz bands [11,12], have been actively developed in recent times. Furthermore, the generation of biphotons with frequencies in the visible and telecommunication spectral bands is one of the important approaches in the creation of quantum entanglement between remote sites of a quantum network and in the implementation of distributed quantum computing [10].…”