Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide

Abstract

We demonstrate photon-pair generation in a reverse proton exchanged waveguide fabricated on a periodically poled magnesium doped stoichiometric lithium tantalate substrate. Detected pairs are generated via a cascaded second order nonlinear process where a pump laser at wavelength of 1.55 µm is first doubled in frequency by second harmonic generation and subsequently downconverted around the same spectral region. Pairs are detected at a rate of 42 per second with a coincidence to accidental ratio of 0.7. This cascaded pair generation process is similar to four-wave-mixing where two pump photons annihilate and create a correlated photon pair.Quantum optics is one of the leading approaches for the implementation of quantum information science protocols [1]. Recently, the demonstration of quantumcomputational gates [2,3] and multimode quantum interference of photons [4] in integrated structures received great interest because it raised the possibility of fabricating future quantum computers on a solid state substrate where photons can be generated, propagate and be manipulated inside optical waveguides. Waveguide based photon-pair sources have also been demonstrated in different materials such as periodically poled lithium niobate [5] (via spontaneous parametric down conversion (SPDC)), in silicon [6] and chalcogenide [7] waveguides (via spontaneous four wave mixing (SFWM)).The full potential of stability and scalability inherent in the integrated photonic approach can be fully exploited only in a single-chip platform which can incorporate both nonclassical sources and reconfigurable quantum gates together. In this context, ferroelectric crystals like lithium niobate (LN) and lithium tantalate (LT) represent two candidates as host materials for parametric downconversion sources and linear-optics quantum gates. Both LN and LT have a high second order nonlinear coefficient and high quality optical waveguides have been fabricated on both materials through reverse proton exchange [8,9]. SPDC in a broad wavelength range can be obtained in periodically poled crystals via the quasiphase-matching technique while fast reconfigurable circuits can be realized by taking advantage of the electrooptic effect of the substrates. * mirko.lobino@bristol.ac.ukHere we demonstrate photon pair generation in a reverse proton exchanged waveguide fabricated on a substrate of periodically poled 1% MgO doped stoichiometric lithium tantalate (PP:MgSLT) [10]. Although PP:MgSLT has a lower nonlinear coefficient than congruent LN it has a much higher optical damage thresh-

Slow light enhanced correlated photon pair generation in photonic-crystal coupled-resonator optical waveguides

“…Integrating quantum photonic devices on a small chip [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] is under intense study with a view to achieving quantum communication and computation technologies, which have the potential to outperform classical information processing [18][19][20][21][22]. For this purpose, it is crucial to develop sources of non-classical states of light such as single photons and correlated photon pairs on an integrated photonic circuit platform [8][9][10][11][12][13][14][15][16][17]. To perform protocols that handle a large number of photonic qubits simultaneously [19][20][21], we require many independent sources each of which must guarantee stable operation in a simple setup preferably at room temperature.…”

Nonlinear Optics for Photonic Quantum Networks

“…QPM in poled waveguides makes phase-matching so flexible that it allows not only SPDC through three-wave mixing [31,67], but also four-wave mixing type SPDC via cascaded second-order nonlinear processes [66,68]. This makes it possible to generate photons in the telecom-band using readily available telecom-band pump lasers.…”

“…Another elegant approach is to use ring resonator structures [64] in which the variation of the orientation of the crystal axes and field polarisation guarantees phase-matching. However, the most common approach is to adopt quasi-phase matching (QPM) [65] in periodically poled second-order nonlinear waveguides such as periodically poled KTP (PPKTP) [59,60], lithium niobate (PPLN) [31,66,67] and lithium tantalate (PPLT) [68].…”

Bragg reflection waveguides as integrated sources of entangled photon pairs

“…Tightly confined waveguide modes are also more suitable for coupling into photonic circuits. Efficient photon pair generation has been achieved in periodically poled LiNbO 3 (PPLN), KTiOPO 4 (PPKTP), and LiTaO 3 (PPLT) waveguides [2][3][4].…”