Optimizing the spectro-temporal properties of photon pairs from Bragg-reflection waveguides

Abstract

Bragg-reflection waveguides (BRWs) fabricated from AlGaAs provide an interesting non-linear optical platform for photon-pair generation via parametric down-conversion (PDC). In contrast to many conventional PDC sources, BRWs are made of high refractive index materials and their characteristics are very sensitive to the underlying layer structure. First, we show that the design parameters like the phasematching wavelength and the group refractive indices of the interacting modes can be reliably controlled even in the presence of fabrication tolerances. We then investigate, how these characteristics can be taken advantage of when designing quantum photonic applications with BRWs. We especially concentrate on achieving a small differential group delay between the generated photons of a pair and then explore the performance of our design when realizing a Hong-Ou-Mandel interference experiment or generating spectrally multi-band polarization entangled states. Our results show that the versatility provided by engineering the dispersion in BRWs is important for employing them in different quantum optics tasks. arXiv:1809.03167v2 [quant-ph]

Broadband Biphoton Generation and Polarization Splitting in a Monolithic AlGaAs Chip

“…We notice that a maximal visibility of the HOM dip requires that the splitting ratio curves for the TE and TM modes are superposed and symmetric with respect to the frequency degeneracy for the down-conversion process; a possible way to improve the performances of the present device is to adjust the waveguide width of the generation region to shift the frequency degeneracy of the generated state at the optimal wavelength. Further progress on the device performances is possible following two main directions: on one hand, the design of the epitaxial structure could be optimized in order to reduce the modal birefringence thus increasing the HOM visibility . On the other hand, the design of the polarization splitting region could be refined by using adiabatic couplers which, in LN waveguides without an on-chip photon pair source, have been shown to exhibit a flat spectral profile with splitting ratios above 98% over a spectral range of more than 100 nm .…”

“…Further progress on the device performances is possible following two main directions: on one hand, the design of the epitaxial structure could be optimized in order to reduce the modal birefringence thus increasing the HOM visibility. 38 On the other hand, the design of the polarization splitting region could be refined by using adiabatic couplers which, in LN waveguides without an on-chip photon pair source, have been shown to exhibit a flat spectral profile with splitting ratios above 98% over a spectral range of more than 100 nm. 19 Another interesting approach could be the use of inverse design 39 to improve the figure-of-merit for the directional coupler, as done for example in ref 40. In any case, the device presented in this work can already be used as a source of broadband frequency anticorrelated photon pairs separated in two different spatial modes, directly employable for information processing protocols based on high-dimensional quantum states.…”

Understanding photoluminescence in semiconductor Bragg-reflection waveguides

“…The BRW sample under investigation depicted in figure 1 is a state-of-the-art, low-loss, matching-layer enhanced design optimized for simple fabrication, while simultaneously allowing a bright type-II PDC process [21,41]. Our experimental setup is shown in figure 2.…”

Engineering two-photon wavefunction and exchange statistics in a semiconductor chip

“…This provides a strong incentive for the development of efficient and scalable methods for the generation and the manipulation of frequency-encoded quantum states [16][17][18]. Nonlinear parametric processes such as spontaneous parametric down-conversion (SPDC) and four-wave mixing (SFWM) offer a high versatility for the generation of frequency-entangled photon pairs [19,20]. However, energy conservation naturally leads to the emission of frequency-anticorrelated states, whereas other types of correlations are needed for certain applications: for instance non-correlated states are required for heralded single photon sources [21,22] and correlated states are useful resources for clock synchronization [23] or dispersion cancellation in long-distance communication [24].…”

“…Such shaping can be performed by postmanipulation using time lenses [25], spatial light modulators (SLM) [26,27] or programmable phase filters [14], but this is done at the expense of a reduced brightness of the source and an increased complexity of the experimental setup. Direct production of on-demand frequencystates at the generation stage is therefore preferable [19]. Using parametric processes in solid-state systems, this has been recently realized by engineering the spectral [15,28] and spatial [29] properties of the pump beam, by temperature tuning [30] or by tailoring the material nonlinearity in domain-engineered crystals [31].…”