QUANTUM INTEGRATED PHOTONICS

Team

Group photo

Front row from left to right: Iman Jizan, Chunle Xiong (project leader), Benjamin Eggleton (CUDOS Director), Alvaro Casas Beodya;
Rear row from left to right: Bryn Bell, Jiakun He, Birgit Stiller, Andri Mahendra, Runyu Jiang, Xiang Zhang (Bruce).


What is Quantum Photonics?

Figure 2


Figure 2. Quantum photonics research in CUDOS.

At the University of Sydney, the Quantum Photonics Group is working on the generation of single photons and entangled photons through nonlinear processes from integrated nanostructures, in collaboration with Australia National University, Macquarie University, University of York, and University of Toronto. More particularly, we are aiming to generate telecom-band correlated photon pairs with high brightness through spontaneous four-wave mixing (SFWM) (Fig. 3) in optical nonlinear waveguides. When a pair of photons is generated spontaneously from vacuum noise fluctuations in a nonlinear device, the photons exhibit correlations in energy, time, and sometimes polarization, and are commonly referred to as a ‘quantum-correlated pair’. Such photon pairs can serve either as entangled photons, or as a simple heralded single-photon source where one photon acts as a signal to ‘herald’ the existence of the other.

Figure 3


Figure 3. Concept of SFWM for heralded single photon generation.

We are also pursuing other possible ways to exploit quantum technologies. These include quantum communication networks, where through the use of single photons or entangled photons one can implement an un-hackable quantum internet, as well as enabling technologies such as quantum frequency conversion to allow disparate users to communicate and novel encoding schemes to implement in satellite communications. CUDOS researchers are also inventing new methods of single photon or quantum-enhanced sensing through quantum metrology and are innovating in the areas of quantum information processing and quantum simulation.

Research Highlights

Slow-light enhanced heralded single photon generation


Over the last decade, great research efforts have been put into the miniaturization of SFWM-based heralded single photon sources for scalable photonic quantum technologies. Figure 4 shows the development of such photon sources in terms of device length. The flux of generated photon pairs is related to the effective nonlinear phase shift γPL, where P is the pump power, L the device length, and γ measures the strength of the optical nonlinearity that depends on the material and structure of the device. To reduce the path length of a nonlinear device for photon pair generation at a given power consumption, the key is to enhance the device nonlinearity, either by choosing a highly nonlinear material, or using a special structure, or both.

Figure 4


Figure 4. Miniaturization of heralded single photon sources via SFWM.

A silicon photonic crystal waveguide (PhCW) is made from a highly nonlinear material silicon and has periodically arranged air holes in the cladding, forming a photonic crystal structure [Fig. 5(a)]. With careful engineering, such a structure exhibits a photonic bandgap. At the bandgap edge, the dispersion is huge and the group index ngs can be much greater than the native material refractive index ng0. Therefore the group velocity of light propagating in a silicon PhCW is much smaller than that in a silicon nanowire. This is called the slow-light effect and the slow-down factor is defined as S = ngs/ng0. For efficient SFWM, ngs should be nearly constant across a broad bandwidth [Fig. 5(b)]. This can be achieved through laterally shifting the first row of holes on both sides of the core away from the core by tens of nanometers. The photon-pair generation in a silicon PhCW through SFWM is illustrated in Fig. 5(c). A coherent pulse of light enters the PhCW with group index of 30, where two photons from the pump are converted to signal and idler photons of higher and lower frequencies respectively to form a quantum correlated state. As the effective nonlinear interaction between light and these waveguides is enhanced by two orders of magnitude due to the slow-light propagation, the physical path length of the device is as short as 100 μm, which makes the integration of a large number of such sources for quantum information processing and computation a reality. To show that the photons emitted from a silicon PhCW are in the single photon regime, we measured the second-order correlation function g(2)(0). Figure 5(d) shows the measured g(2)(0) as a function of coupled pump peak power. The lowest g(2)(0) is 0.09, indicating a nearly single photon regime. To further verify that the very low g(2)(0) is actually measured at zero delay and not because the photons are misaligned in time, we measured g(2)(nT) at delays that are integer times of the laser period. The results are shown in Fig. 5(e). It can be seen that g(2)(nT) is close to 1 when n is a non-zero integer.

Figure 5


Figure 5. (a) Diagram of a silicon PhCW. (b) Group index and total transmission of light in a 96 μm long silicon PhCW. The window (between dotted lines) with a flat group index of 30 and slightly increased loss defines the slow-light regime. The pump, signal, and idler bands are represented by green (middle), blue (left), and red (right) lines, respectively. (c) Schematic of SFWM in a silicon slow-light PhCW. (d) The measured g(2)(0) as a function of coupled peak power. (e) g(2)(nT) as a function of discrete delay.

Active multiplexing of heralded single photons from a silicon chip

It is well known that a heralded single photon source based on spontaneous nonlinear wave mixing such as SFWM is a probabilistic photon source. The major challenge of such source is that heralded single photons cannot be produced deterministically. This is because single pairs cannot be produced with high probability, while simultaneously suppressing the probability of yielding two or more pairs. A promising solution is to actively multiplex many non-deterministic photons in different spatial or temporal modes to enhance the probability of single-photon output while maintaining a constant multi-photon noise level. A schematic of the spatial multiplexing is shown in Fig. 6. The compact silicon PhCW we developed makes it possible to multiplex single photons from two such devices on a monolithic chip. This breakthrough, published in Nature Communications, took two PhC waveguides which could generate heralded single photons and multiplexed them together to a single output using a fast, low-loss optical switch. The enhancement to the single photon output probability is 62%.

Figure 6


Figure 6. A spatial multiplexing scheme using many PhCWs to generate single photons deterministically. AWG: arrayed waveguide grating, SSPD: superconducting single photon detector.

As shown in Fig. 6, in the spatial multiplexing scheme, the number of nonlinear devices, optical components and single photon detectors increases rapidly with the number of modes to be multiplexed. Temporal multiplexing, illustrated in Fig. 7(a), can multiplex photons from many temporal modes and thus can reuse the same detectors and photon generation components, and thus is significantly more resource efficient and scalable. Figure 7(b) shows that at the same coincidence to accidental ratio (CAR, i.e, quantum signal to noise ratio) level, the heralded single photon rate from a silicon waveguide is enhanced by 100% by ×4 temporal multiplexing. A four-fold Hong-Ou-Mandel quantum interference using the multiplexed photons shows a 91% visibility [Fig. 7(c)], indicating that the multiplexed photons are highly indistinguishable. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies.

Figure 7


Figure 7. (a) The principle of active temporal multiplexing. A nonlinear device is pumped by pulses separated in time by period T, each generating correlated photon pairs randomly. The two photos from each pair are spatially separated by frequency (color) and the heralding photons (red) are detected, indicating the existence of the heralded photons (blue). Depending on in which time bin a pair is generated, an appropriate delay is applied to the heralded photon so that it always appears in time bin t1 with a nominal period NT (N=4 here). (b) Comparison between sources with and without multiplexing. CAR: coincidence to accidental ratio. (c) Four-fold HOM dip using the multiplexed photons.

Ultra-compact silicon quantum spitter

While correlated photon pairs generated via SFWM are usually at different wavelengths (Fig. 3), they can also be generated at the same wavelength provided that two pump waves at different wavelengths are used [Fig. 8(a)]. However the separation of such wavelength degenerate photon pairs is challenging because simply using a 50:50 beam splitter only has 50% chance to separate the photons. We demonstrate an ultra-compact quantum splitter for such photon pairs based on a monolithic silicon chip. It incorporates a Sagnac loop and a microring resonator with a total footprint of 0.011 mm2, generating and deterministically splitting indistinguishable photon pairs using two-photon interference [Fig. 8(b)]. The ring resonator provides an enhanced photon generation rate, and the Sagnac loop ensures the photons travel through equal path lengths and interfere with the correct phase to enable the reversed HOM effect to take place. Figure 8(c) shows that the quantum splitter has nearly 89% chance to split the photons. Using the photons for a quantum interference experiment, we observed a HOM dip visibility of 94.5% [Fig. 8(d)], indicating that the generated photons are in a suitable state for further integration with other components for quantum applications such as controlled-NOT gates.

Figure 8


Figure 8. (a) Diagram of wavelength degenerate photon pair generation via SFWM. (b) Schematic of the quantum splitter: waveguides A and B, connected to two grating couplers, reach the same side of a multimode interference coupler, whose two output ports are connected, forming a Sagnac loop; a silicon ring resonator is coupled to the Sagnac loop in order to enhance the photon-pair generation rate. (c) Count rate for split and bunched pairs. Top: When two pumps were injected separately into the two ports of the sample, a splitting ratio of 88.9±6.7% after subtracting noise was achieved. Bottom: When two pumps were injected together into one of the ports of the sample, a bunching ratio of 88.2±9.0% after subtracting noise was achieved. (d) HOM experimental results. A visibility of 94.5±3.3% is observed after subtracting accidental coincidences.

Compact and reconfigurable silicon nitride time-bin entanglement circuit

We are not only working on single photon generation on-chip, but also investigating on-chip entanglement generation and analysis. We are particularly interested in time-bin entanglement because it (i) can be extended to higher dimensions for computation, (ii) is insensitive to polarization fluctuation and polarization dispersion, and therefore very promising for long-distance quantum key distribution, and (iii) is naturally compatible with integrated optics: photons can be generated in nonlinear waveguides, and entangled and analyzed using on-chip unbalanced Mach–Zehnder interferometers. We chose silicon nitride circuit made from double-stripe TriPleX waveguide technology with LioniX BV for on-chip time-bin entanglement because it combines the low-loss characteristics of silica and tight integration features of silicon. Figure 9(a) shows a photograph of the Si3N4-based time-bin entanglement chip. The yellow parts are wire bonds for heaters, and the green parts are printed circuit boards for providing voltage to the heaters that control the on-chip phase shifters. On the left-hand side is the pigtailed fiber array. On the 28 mm ×8 mm chip, there are 15 heaters, 3 unbalanced Mach–Zehnder interferometers, and two wavelength division multiplexers. Figure 9(b) shows a picture of the 16-bit digital-to-analog converter made by our student for controlling the heaters. Figure 9(c) shows the measured two-photon interference fringes, which exhibit high visibility without subtracting any noise, indicating the high performance of the entanglement chip. Such a demonstration of on-chip entanglement is a significant step toward the ultimate goal of completely integrating all components to realize chip-scale time-bin qubit transmitters and receivers for quantum key distribution, and integrating many entanglement sources and analysis circuits on a chip for large-scale quantum computation.

Figure 9


Figure 9. On-chip time-bin entanglement. (a) Silicon nitride photonic circuit with wire bonding for time-bin entanglement generation. (b) 16-channel heater control circuits. (c) Measured two-photon interference fringes in two non-orthogonal bases.

Laboratory

The Quantum Photonics Lab at the University of Sydney is fully equipped with mode-locked picosecond fibre lasers with variable repetition rates of 10, 20 and 50 MHz, erbium doped fibre amplifiers, multiple channel external cavity diode lasers, nano-positioning stages, optical spectral analysers, delay generators and time interval analysers. We currently own and operate four ID-Quantique infrared InGaAs/InP single-photon detectors, all of which have the free-running mode and up to 100 MHz triggering mode, the ID210. We also house a state-of-the-art superconducting single photon detector system from Single Quantum which allows us to have low-noise, high-efficiency photon detection. The National Facility for Cryogenic Photonics grant we won will allow us to develop our own in-house detectors and integrate these with our photonic waveguide technology.

Figure 10


Our single photon detectors: (a) the Single Quantum superconducting detector system, and (b) the ID210 detectors.

Grant and Funding News

25th Sep. 2015 Professor Benjamin Eggleton and Dr Chunle Xiong have secured research funds from Huawei Technology to work on Silicon Quantum Photonics.

8th Nov. 2013 A team of researchers from the Quantum Photonics Group at the University of Sydney, RMIT and the University of Adelaide, have won an Australian Research Council Linkage, Infrastructure, Equipment and Facilities (LIEF) grant to establish a National Facility for Cryogenic Photonics. This will house cryostats at the two nodes of the facility which will develop new materials and devices for quantum technologies.

5th Nov. 2012 Dr Alex Clark has been awarded a prestigious fellowship by the Australian Research Council under the scheme of the Discovery Early Career Researcher Award. He will be working on quantum frequency conversion in integrated devices.

17th Nov. 2011 A Major Equipment Grant has been funded to the team for the purchase of four high-speed and low-noise superconducting single-photon detectors. The establishment of this infrastructure in CUDOS at University of Sydney is unique in Australia and will significantly advance the research for practical quantum communication and computation.

14th Nov. 2011 Dr Chunle Xiong has been awarded a prestigious fellowship by the Australian Research Council under the scheme of Discovery Early Career Researcher Award. He will be working on quantum entanglement using slow-light-enhanced nonlinearity.


Publications

  1. Bryn A. Bell, Chunle Xiong, David Marpaung, Colin J. McKinstrie, and Benjamin J. Eggleton,
    "Uni-directional wavelength conversion in silicon using four-wave mixing driven by cross-polarized pumps,"
    Opt. Lett. 42, 1668-1671 (2017)
  2. Iman Jizan, Bryn Bell, L. G. Helt, Alvaro Casas Bedoya, Chunle Xiong, and Benjamin J. Eggleton,
    "Phase-sensitive tomography of the joint spectral amplitude of photon pair sources,"
    Opt. Lett. 41, 4803-4806 (2016)
  3. Bryn A. Bell, Jiakun He, Chunle Xiong, and Benjamin J. Eggleton,
    "Frequency conversion in silicon in the single photon regime",
    Opt. Express 24, 5235-5242 (2016), doi: 10.1364/OE.24.005235
  4. Xiang Zhang, Yanbing Zhang, Chunle Xiong and Benjamin J Eggleton,
    "Correlated photon pair generation in low-loss double-stripe silicon nitride waveguides",
    Journal of Optics, Volume 18, Number 7, J. Opt. 18 074016
  5. Chunle Xiong, Bryn Bell, Benjamin J. Eggleton,
    "CMOS-compatible photonic devices for single-photon generation",
    Nanophotonics 2016 DOI: 10.1515/nanoph-2016-0022
  6. C. Xiong, X. Zhang, Z. Liu, M. J. Collins, A. Mahendra, L. G. Helt, M. J. Steel, D. -Y. Choi, C. J. Chae, P. H. W. Leong & B. J. Eggleton,
    "Active temporal multiplexing of indistinguishable heralded single photons",
    Nature Communications 7:10853, doi:10.1038/ncomms10853 (2016)
  7. F. Setzpfandt, A. S. Solntsev, J. Titchener, C. W. Wu, C. Xiong, R. Schiek, T. Pertsch, D. N.
    Neshev, and A. A. Sukhorukov,
    “Tunable generation of entangled photons in a nonlinear directional
    coupler”,
    Laser & Photon. Rev., 10: 131–136, doi: 10.1002/lpor.201500216 (2016).
  8. Joel Carpenter, Benjamin J. Eggleton, Jochen Schröder,
    "Observation of Eisenbud–Wigner–Smith states as principal modes in multimode fibre"
    Nature Photonics, doi:10.1038/nphoton.2015.188 (2015)
  9. M. J. Collins, A. S. Clark, C. Xiong, E. Mägi, M. J. Steel and B. J. Eggleton,
    "Random number generation from spontaneous Raman scattering,"
    Appl. Phys. Lett. 107, 141112 (2015)
  10. Jiakun He, Bryn A. Bell, Alvaro Casas-Bedoya, Yanbing Zhang, Alex S. Clark, Chunle Xiong, and Benjamin J. Eggleton
    "Ultracompact quantum splitter of degenerate photon pairs,"
    Optica 2, 779-782 (2015)
  11. Iman Jizan, L. G. Helt, Chunle Xiong, Matthew J. Collins, Duk-Yong Choi, Chang Joon Chae, Marco Liscidini, M. J. Steel, Benjamin J. Eggleton, & Alex S. Clark,
    Bi-photon spectral correlation measurements from a silicon nanowire in the quantum and classical regimes.
    Sci. Rep. 5, 12557; doi: 10.1038/srep12557 (2015).
  12. C. Xiong, X. Zhang, A. Mahendra, J. He, D.-Y. Choi, C. J. Chae, D. Marpaung, A. Leinse, R. G. Heideman, M. Hoekman, C. G. H. Roeloffzen, R. M. Oldenbeuving, P. W. L. van Dijk, C. Taddei, P. H. W. Leong, and B. J. Eggleton ,
    "Compact and reconfigurable silicon nitride time-bin entanglement circuit,"
    Optica 2, 724-727 (2015)
  13. X. Zhang, I. Jizan, J. He, A. Clark, D. Choi, C. Chae, B. Eggleton, and C. Xiong,
    "Enhancing the heralded single-photon rate from a silicon nanowire by time and wavelength division multiplexing pump pulses,"
    Opt. Lett. 40, 2489-2492 (2015)
  14. Chunle Xiong; Collins, M.J.; Steel, M.J.; Krauss, T.F.; Eggleton, B.J.; Clark, A.S.,
    "Photonic Crystal Waveguide Sources of Photons for Quantum Communication Applications,"
    Selected Topics in Quantum Electronics, IEEE Journal of , vol.21, no.3, pp.1,10, May-June 2015 doi: 10.1109/JSTQE.2014.2375154
  15. Simon Lefrancois, Alex S. Clark, and Benjamin J. Eggleton,
    "Optimizing optical Bragg scattering for single-photon frequency onversion,"
    Phys. Rev. A 91, 013837 (2015)
  16. Simon Lefrancois, Chad Husko, Andrea Blanco-Redondo, and Benjamin J. Eggleton,
    "Nonlinear silicon photonics analyzed with the moment method,"
    J. Opt. Soc. Am. B 32, 218-226 (2015)
  17. Alexander S. Solntsev, Frank Setzpfandt, Alex S. Clark, Che Wen Wu, Matthew J. Collins, Chunle Xiong, Andreas Schreiber, Fabian Katzschmann, Falk Eilenberger, Roland Schiek, Wolfgang Sohler, Arnan Mitchell, Christine Silberhorn, Benjamin J. Eggleton, Thomas Pertsch, Andrey A. Sukhorukov, Dragomir N. Neshev, and Yuri S. Kivshar,
    "Generation of Nonclassical Biphoton States through Cascaded Quantum Walks on a Nonlinear Chip,"
    Phys. Rev. X 4, 031007 (2014)
  18. Alexander S. Solntsev, Frank Setzpfandt, Alex S. Clark, Che Wen Wu, Matthew J. Collins, Chunle Xiong, Andreas Schreiber, Fabian Katzschmann, Falk Eilenberger, Roland Schiek, Wolfgang Sohler, Arnan Mitchell, Christine Silberhorn, Benjamin J. Eggleton, Thomas Pertsch, Andrey A. Sukhorukov, Dragomir N. Neshev, and Yuri S. Kivshar,
    "Generation of Nonclassical Biphoton States through Cascaded Quantum Walks on a Nonlinear Chip,"
    Phys. Rev. X 4, 031007 (2014)
  19. I. Jizan, A.S. Clark, L.G. Helt, M.J. Collins, E. Mägi, C. Xiong, M.J. Steel and B.J. Eggleton,
    "High-resolution measurement of spectral quantum correlations in the telecommunication band,"
    Optics Communications, Volume 327, 15 September 2014, Pages 45-48, ISSN 0030-4018
  20. Jiakun He, Alex S. Clark, Matthew J. Collins, Juntao Li, Thomas F. Krauss, Benjamin J. Eggleton, and Chunle Xiong,
    "Degenerate photon-pair generation in an ultracompact silicon photonic crystal waveguide,"
    Opt. Lett. 39, 3575-3578 (2014)
  21. Meany, T., Ngah, L. A., Collins, M. J., Clark, A. S., Williams, R. J., Eggleton, B. J., Steel, M. J., Withford, M. J., Alibart, O. and Tanzilli, S.,
    "Hybrid photonic circuit for multiplexed heralded single photons,"
    Laser & Photon. Rev.. doi: 10.1002/lpor.201400027 (2014)
  22. C. Xiong, T. D. Vo, M. J. Collins, J. Li, T. F. Krauss, M. J. Steel, A. S. Clark, and B. J. Eggleton,
    "Bidirectional multiplexing of heralded single photons from a silicon chip,"
    Opt. Lett. 38, 5176-5179 (2013)
  23. M.J. Collins, C. Xiong, I.H. Rey, T.D. Vo, J. He, S. Shahnia, C. Reardon, T.F. Krauss, M.J. Steel, A.S. Clark, and B.J. Eggleton
    "Integrated spatial multiplexing of heralded single-photon sources"
    Nature Communications 4, 2582; doi:10.1038/ncomms3582 (2013)
  24. B. Bell, S. Kannan, A. R. McMillan, A. S. Clark, W. J. Wadsworth and J. G. Rarity,
    “Multi-Color Quantum Metrology with Entangled Photons,”
    Phys. Rev. Lett. 111, 093603 (2013)
  25. Joel Carpenter, Chunle Xiong, Matthew J. Collins, Juntao Li, Thomas F. Krauss, Benjamin J. Eggleton, Alex S. Clark, and Jochen Schröder,
    "Mode multiplexed single-photon and classical channels in a few-mode fiber,"
    Opt. Express 21, 28794-28800 (2013)
  26. A. R. McMillan, L. Labonté, A. S. Clark, B. Bell, O. Alibart, A. Martin, W. J. Wadsworth, S. Tanzilli and J. G. Rarity,
    “Two-photon interference between disparate sources for quantum networking,”
    Sci. Rep. 3, 2032 (2013)
  27. Chad A. Husko, Alex S. Clark, Matthew J. Collins, Alfredo De Rossi, Sylvain Combrié, Gaëlle Lehoucq, Isabella H. Rey, Thomas F. Krauss, Chunle Xiong & Benjamin J. Eggleton,
    "Multi-photon absorption limits to heralded single photon sources"
    Sci. Rep. 3, 3087, DOI:10.1038/srep03087 (2013)
  28. B. Bell, M. S. Tame, A. S. Clark, R. W. Nock, W. J. Wadsworth and J. G. Rarity,
    “Experimental characterization of universal one-way quantum computing,”
    New J. Phys. 15, 053030 (2013)
  29. A. C. Judge, M. J. Steel, J. E. Sipe, and C. M. de Sterke,
    "Canonical quantization of macroscopic electrodynamics in a linear, inhomogeneous magnetoelectric medium,"
    Physical Review A 87, 033824 (2013)
  30. Alex S. Clark, Shayan Shahnia, Matthew J. Collins, Chunle Xiong, and Benjamin J. Eggleton,
    "High-efficiency frequency conversion in the single-photon regime,"
    Opt. Lett. 38, 947-949 (2013)
  31. Alex S. Clark, Chad Husko, Matthew J. Collins, Gaelle Lehoucq, Stéphane Xavier, Alfredo De Rossi, Sylvain Combrié, Chunle Xiong, and Benjamin J. Eggleton,
    "Heralded single-photon source in a III–V photonic crystal,"
    Opt. Lett. 38, 649-651 (2013)
  32. J. He, C. Xiong, A. S. Clark, M. J. Collins, X. Gai, D.-Y. Choi, S. J. Madden, B. Luther-Davies, and B. J. Eggleton,
    "Effect of low-Raman window position on correlated photon-pair generation in a chalcogenide Ge11.5As24Se64.5 nanowire,"
    J. Appl. Phys. 112, 123101:1-5 (2012), DOI: 10.1063/1.4769740
  33. M. J. Collins, A. C. Judge, A. S. Clark, S. Shahnia, E. C. Mägi, M. J. Steel, C. Xiong, and B. J. Eggleton,
    "Broadband photon-counting Raman spectroscopy in short optical waveguides,"
    Appl. Phys. Lett. 101, 211110 (2012)
  34. C. Xiong, Christelle Monat, Matthew J. Collins, Laurent Tranchant, David Petiteau, Alex S. Clark, Christian Grillet, Graham D. Marshall, M. J. Steel, Juntao Li, Liam O'Faolain, Thomas F. Krauss, and Benjamin J. Eggleton,
    "Characteristics of correlated photon pairs generated in ultra-compact silicon slow-light photonic crystal waveguides,"
    IEEE J. Sel. Top. Quant. Electron. 18, 1676–1683 (2012). DOI: 10.1109/JSTQE.2012.2188995
  35. Matthew J. Collins, Alex S. Clark, Jiakun He, Duk-Yong Choi, Robert J. Williams, Alexander C. Judge, Steve J. Madden, Michael J. Withford, M. J. Steel, Barry Luther-Davies, Chunle Xiong, and Benjamin J. Eggleton,
    "Low Raman-noise correlated photon-pair generation in a dispersion-engineered chalcogenide As2S3 planar waveguide,"
    Opt. Lett. 37, 3393-3395 (2012)
  36. Alex S. Clark, Matthew J. Collins, Alexander C. Judge, Eric C. Mägi, Chunle Xiong, and Benjamin J. Eggleton,
    "Raman scattering effects on correlated photon-pair generation in chalcogenide,"
    Opt. Express 20, 16807-16814 (2012)
  37. X. Gai, R. P. Wang, C. Xiong, M. J. Steel, B. J. Eggleton, and B. Luther-Davies, "Near-zero anomalous dispersion Ge11.5As24Se64.5 glass nanowires for correlated photon pair generation: design and analysis," Opt. Express 20, 776-786 (2012)
  38. M. Lobino, G. D. Marshall, C. Xiong, A. S. Clark, D. Bonneau, C. M. Natarajan, M. G. Tanner, R. H. Hadfield, S. N. Dorenbos, T. Zijlstra, V. Zwiller, M. Marangoni, R. Ramponi, M. G. Thompson, B. J. Eggleton, and J. L. O'Brien,
    "Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide,"
    Appl. Phys. Lett., 99, 081110 (2011)
  39. C. Xiong, Christelle Monat, Alex S. Clark, Christian Grillet, Graham D. Marshall, M. J. Steel, Juntao Li, Liam O’Faolain, Thomas F. Krauss, John G. Rarity, and Benjamin J. Eggleton,
    "Slow-light enhanced correlated photon pair generation in a silicon photonic crystal waveguide,"
    Optics Letters, Vol. 36, Issue 17, pp. 3413-3415 (2011)
  40. C. Xiong, G. D. Marshall, A. Peruzzo, M. Lobino, A. S. Clark, D.-Y. Choi, S. J. Madden, C. M. Natarajan, M. G. Tanner, R. H. Hadfield, S. N. Dorenbos, T. Zijlstra, V. Zwiller, M. G. Thompson, J. G. Rarity, M. J. Steel, B. Luther-Davies, B. J. Eggleton, and J. L. O’Brien,
    "Generation of correlated photon pairs in a chalcogenide As2S3 waveguide,"
    Appl. Phys. Lett. 98, 051101 (2011)
  41. C. Xiong, L. G. Helt, A. C. Judge, G. D. Marshall, M. J. Steel, J. E. Sipe, and B. J. Eggleton
    "Quantum-correlated photon pair generation in chalcogenide As2S3 waveguides,"
    Opt. Express 18, 16206-16216 (2010)