Counter-propagating spectrally uncorrelated biphotons at 1550  nm generated from periodically poled MTiOXO₄ (M = K, Rb, Cs; X = P, As)

Abstract

We theoretically investigated spectrally uncorrelated biphotons generated in a counter-propagating spontaneous parametric downconversion (CP-SPDC) from periodically poled M T i O X O 4 ( M = K , Rb, Cs; X = P , As) crystals. By numerical calculation, it was found that the five crystals from the KTP family can be used to generate heralded single photons with high spectral purity and wide tunability. Under the type-0 phase-matching condition, the purity at 1550 nm was between 0.91 and 0.92, and the purity can be maintained over 0.90 from 1500 nm to 2000 nm wavelength. Under the type-II phase-matching condition, the purity at 1550 nm was 0.96, 0.97, 0.97, 0.98, and 0.98 for PPKTP, PPRTP, PPKTA, PPRTA, and PPCTA, respectively; furthermore, the purity can be kept over 0.96 for more than 600 nm wavelength range. We also simulated the Hong–Ou–Mandel interference between independent photon sources for PPRTP crystals at 1550 nm, and interference visibility was 92% (97%) under the type-0 (type-II) phase-matching condition. This study may provide spectrally pure narrowband single-photon sources for quantum memories and quantum networks at telecom wavelengths.

Optical Frequency Down-Conversion With Bandwidth Compression Based on Counter-Propagating Phase Matching

“…We can see that in the traditional co-propagating process the coefficients of frequency offsets only depend on the difference of the reciprocal of group velocities, and thus in such process the phase-matching function is usually engineered by selecting working frequencies and structures to control the dispersion and group velocities [34]. While, in the counter-propagating process, the coefficients also depend on the sum of the group velocities, enabling intrinsic features for phase-matching engineering [20][21][22][23][24][25][26].…”

“…On the other hand, counter-propagating quasi-phase-matching (QPM) spontaneous parametric down-conversion (SPDC) process has been extensively studied due to its unique spectral properties [19,20], such as narrow bandwidth [21,22] and frequency uncorrelated [23][24][25][26] photon pairs. In contrast to the traditional co-propagating process, in the counter-propagating process the phase-matching function is greatly affected by the counter propagation of the signal and idler photons, and hence such method can be applied in a large range of nonlinear materials and working wavelengths.…”

Compact generation scheme of path–frequency hyperentangled photons using 2D periodical nonlinear photonic crystal

“…The momentum mismatches can be perfectly compensated through the periodic poling method. [36,37] By periodically modifying the susceptibility of NPC in real space, we can obtain six peak values in its Fourier space (reciprocal space) to perform QPM. The designed distribution of NPC's χ (2) is shown in Fig.…”

Generation of spectrally uncorrelated biphotons via fiber nonlinear quantum interference

“…Therefore, a nonlinear interferometer (NLI) can be used to engineer quantum state. N-stage NLI, consisting of N-stage nonlinear gain medium with one piece dispersion modulation medium between every adjacent two, has applications in dispersion compensation of optical parametric amplifier, [13][14][15][16] precision phase measurement beyond standard quantum limit, [17][18][19] super-resolution spectroscopy and imaging [20,21] and biphoton spectrum shaping. [22] Cui et al [23][24][25] have demonstrated that the spectrally uncorrelated biphotons can be obtained via fiber NLI, therein dispersion-shifted fiber as nonlinear gain medium and single mode fiber as dispersion modulation medium in a small frequency detuning case.…”