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ACTA PHOTONICA SINICA

Preparation of Multi-channel Photon Pairs in a Periodically Poled Potassium Titanyl Phosphate Waveguide

Guo Guang-Can

Published Jan 1, 2009• 0 citations
OpenAlex

Abstract

A scheme to generate multi-channel photon pairs is presented,based on a periodically poled(PP) Potassium Titanyl Phosphate(KTP) waveguide via spontaneous parametric downconversion(SPDC).Type-II and type-I phase matching cases with a pulsed and a cw pump laser are discussed respectively.It is analytically shown that several photon pairs could be generated in a single type-II PPKTP waveguide,and the wavelengths of all photon pairs are in the telecom band.In type-I case,several photon pairs can be prepared,but one photon of each pair is not in telecom band.And,a multi-channel photon pairs source could be realized.

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Optics Express•Sep 24, 2020•12 citations
A scheme to generate multi-channel photon pairs is presented,based on a periodically poled(PP) Potassium Titanyl Phosphate(KTP) waveguide via spontaneous parametric downconversion(SPDC).Type-II and type-I phase matching cases with a pulsed and a cw pump laser are discussed respectively.It is analytically shown that several photon pairs could be generated in a single type-II PPKTP waveguide,and the wavelengths of all photon pairs are in the telecom band.In type-I case,several photon pairs can be prepared,but one photon of each pair is not in telecom band.And,a multi-channel photon pairs source could be realized.
We report on the generation of indistinguishable photon pairs at telecom wavelengths based on a type-II parametric down conversion process in a periodically poled potassium titanyl phosphate (PPKTP) crystal. The phase matching, pump laser characteristics and coupling geometry are optimised to obtain spectrally uncorrelated photons with high coupling efficiencies. Four photons are generated by a counter-propagating pump in the same crystal and anlysed via two photon interference experiments between photons from each pair source as well as joint spectral and g((2)) measurements. We obtain a spectral purity of 0.91 and coupling efficiencies around 90% for all four photons without any filtering. These pure indistinguishable photon sources at telecom wavelengths are perfectly adapted for quantum network demonstrations and other multi-photon protocols.
We report on the generation of indistinguishable photon pairs at telecom wavelengths based on a type-II parametric down conversion process in a periodically poled potassium titanyl phosphate (PPKTP) crystal. The phase matching, pump laser characteristics and coupling geometry are optimised to obtain spectrally uncorrelated photons with high coupling efficiencies. Four photons are generated by a counter-propagating pump in the same crystal and anlysed via two photon interference experiments between photons from each pair source as well as joint spectral and g((2)) measurements. We obtain a spectral purity of 0.91 and coupling efficiencies around 90% for all four photons without any filtering. These pure indistinguishable photon sources at telecom wavelengths are perfectly adapted for quantum network demonstrations and other multi-photon protocols.
In this paper, we propose a single integrated waveguide device to generate two different polarization-entangled Bell states involving nondegenerate photon pairs (with the signal photons being emitted in the telecom CCC band) by utilizing type-0, type-I, and type-II quasi-phase-matching (QPM). In this context, we have studied ppKTP (periodically-poled potassium titanyl phosphate) in detail. To obtain polarization entanglement of the emitted photons, we have used two different situations, two cascaded QPM gratings (of the same length) to obtain $|{\ensuremath{\psi}}^{+}\ensuremath{\rangle}$, and two separate QPM gratings (of different lengths) to obtain $|{\ensuremath{\phi}}^{+}\ensuremath{\rangle}$. In such a scenario, maximal entanglement can be quantified in terms of overlap bandwidths of the two phase-matched processes.
The properties of the backward-wave spontaneous parametric down-conversion (SPDC) in a periodically poled potassium titanyl phosphate (KTP) waveguide are studied in the context of creating narrowband heralded sources of single-photon states. The effective index of refraction and spatial profile of different waveguide modes, efficiency of different SPDC processes and purity of heralded photons are calculated numerically for a given waveguide. Compared to the usual co-propagating SPDC, spectral narrowing of the backward-wave SPDC was observed as should be expected. Generation biphoton states in backward-wave regime is experimentally observed in two-photon detection scheme.
We report on the generation of an indistinguishable heralded single-photon state, using highly nondegenerate spontaneous parametric downconversion (SPDC). Spectrally factorable photon pairs can be generated by incorporating a broadband pump pulse and a group-velocity matching (GVM) condition in a periodically-poled potassium titanyl phosphate (PPKTP) crystal. The heralding photon is in the near IR, close to the peak detection efficiency of off-the-shelf Si single-photon detectors; meanwhile, the heralded photon is in the telecom L-band where fiber losses are at a minimum. We observe spectral factorability of the SPDC source and consequently high purity (90%) of the produced heralded single photons by several different techniques. Because this source can also realize a high heralding efficiency (> 90%), it would be suitable for time-multiplexing techniques, enabling a pseudo-deterministic single-photon source, a critical resource for optical quantum information and communication technology.
Photon pair sources in the visible to NIR wavelength region play a key role in quantum optics. The wavelength range around 800 nm provides an opportunity for using low cost detectors, which makes it highly interesting for practical, large scale quantum applications. Here, we report on the realization of single mode Rubidium (Rb) exchanged waveguides in periodically poled (PP) Potassium Titanyl Phosphate (Rb:KTiOPO4 or Rb:KTP) for frequency-non-degenerate type II parametric down-conversion pumped at 400 nm and generating pairs of photons at around 800 nm. The source exhibits a nonlinear conversion efficiency of 2.0%/(Wcm2), estimated from SHG measurements. Characterisation of the generated two-photon state confirms nonclassical photon-number correlations, characterized by g(1,1). The high nonlinear conversion efficiency and low temperature sensitivity make this source a promising candidate for operations in both classical and quantum integrated network applications.