## Bright narrowband source of photon pairs at optical telecommunication wavelengths using a type-II periodically poled lithium niobate waveguide

Optics Express, Vol. 15, Issue 20, pp. 12769-12776 (2007)

http://dx.doi.org/10.1364/OE.15.012769

Acrobat PDF (136 KB)

### Abstract

We report on the generation of narrowband photon pairs at telecommunication wavelengths using a periodically poled lithium niobate waveguide that utilizes the nonlinear tensor element *d*_{24} for type-II quasi phase matching. The FWHM bandwidth of the spontaneous parametric downconversion was 1 nm. The brightness of the photon pair source was ∼6×10^{5}/s/GHz when the pump power was 1 mW. The indistinguishability of the signal and idler photons generated by the degenerate spontaneous parametric downconversion process was studied in a Hong-Ou-Mandel type interference experiment.

© 2007 Optical Society of America

## 1. Introduction

1. N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. **74**, 145–195 (2002). [CrossRef]

3. D. Bouwmeester, J. W. Pan, K. Mattele, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum tele-portation,” Nature **390**, 575–579 (1997). [CrossRef]

4. P. G. Kwiat, K. Mattel, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. Shih “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. **75**, 4337–4341 (1995). [CrossRef] [PubMed]

*d*

_{33}for the type-0 quasi-phase matching (QPM) in which copolarized photon pairs are generated. Since the element

*d*

_{33}has the higher nonlinear coefficient than any other elements, the type-0 PPLN waveguide has the highest conversion efficiency[5

5. A. Yoshizawa, R. Kaji, and H. Tsuchida, “Two-photon interference at 1550nm using two periodically poled lithium niobate waveguides,” Jpn. J. Appl. Phys. **42**, 5652–5653 (2003). [CrossRef]

*d*

_{24}for the type-I I QPM. We have demonstrated that the brightness of the photon pair source is higher than that of a conventional type-0 photon pair source (a proton-exchanged PPLN waveguide). Furthermore, the type-II PPLN generates crosspolarized photon pairs that can be efficiently split into two different spatial modes even if the photon pairs are generated by the degenerate SPDC process. This indicates that an optical loss in a transmission fiber can be minimized by setting the wavelengths of both of the signal and idler photons to 1550 nm (C-band). Finally, in order to investigate the indistinguishability of the signal- and idler- photons, we performed a Hong-Ou-Mandel (HOM) type interference experiment [7

7. C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. **59**, 2044–2046 (1987). [CrossRef] [PubMed]

## 2. Narrowband photon pairs

_{3}, frequency ω

_{3}) is coupled into the nonlinear waveguide, then the photon pairs (λ

_{1}, ω

_{1}: idler photon and λ

_{2}, ω

_{2}: signal photon) are generated by the SPDC process. The relation between the three wavelengths is

*n*is the refractive index at

_{k}*λ*, Δ is the phase-mismatch parameter, and ∧ is the QPM grating period. In the case of the type-0 QPM,

_{k}*n*

_{1,2,3}are the ordinary refractive indices of the bulk LiNbO

_{3}crystal[8

8. H. Y. Shen, H. Xu, Z. D. Zeng, W. X. Lin, R. F. Wu, and G. F. Xu, “Measurement of refractive indices and thermal refractive-index coefficients of LiNbO_{3} crystal doped with 5 mol.%MgO,” Appl. Opt. **31**, 6695–6697 (1992). [CrossRef] [PubMed]

*n*

_{1,3}and

*n*

_{2}are the ordinary and extraordinary refractive indices, respectively. The QPM grating period is determined by Δ = 0. The power of the SPDC outputs from the nonlinear waveguide is then given by the expression [9

9. T. Suhara and H. Kintaka, “Quantum theory analysis of twin-photon beams generated by parametric fluorescence,” IEEE Quantum Electron. **41**, 1203–1205 (2005). [CrossRef]

*l*is the interaction length, κ is the nonlinear coupling coefficient, and

*P*

_{3}is the input pump power. In Fig. 1(a), the phase-mismatch-parameter of the type-II and type-0 QPM devices are shown as functions of the emission wavelength. When the degenerate wavelength was 1550 nm, ∧ for the type-0 and type-II QPM were 19 μm and 9 μm, respectively. In the case of the type-0 QPM, Δ gently varies with changing the emission wavelength. On the other hand, in the case of the type-II QPM device, Δ is significantly changed, which is due to the difference of the refractive indices for the signal and idler photons. This suggests that the SPDC bandwidth of the type-II QPM device is much narrower than that of the type-0 QPM device, because the SPDC can occur at a neighborhood of Δ = 0. Figure 1(b) shows the interaction-length dependence of the SPDC bandwidth that is the full width at half maximum (HWHM) of the power spectrum evaluated from Eq. (3). As the interaction length is longer, the SPDC bandwidth becomes narrower. As shown in Fig. 1(b), the 30-mm-long type-II QPM device can realize a SPDC bandwidth of ∼ 1 nm.

## 3. Experimental setup

11. N. Namekata, Y. Makino, and S. Inoue, “Single-photon detector for long-distance fiber-optic quantum key distribution,” Opt. Lett. **27**, 954–956 (2002). [CrossRef]

^{-5}and 4.8 10

^{-5}, respectively.

## 4. SPDC bandwidth

## 5. Photon counting results

12. S. Mori, J. SÖderholm, N. Namekata, and S. Inoue, “On the distribution of 1550-nm photon pairs efficiently generated using a periodically poled lithium niobate waveguide,” Opt. Com. **264**, 156–162 (2006). [CrossRef]

^{4}s

^{-1}and coincidence-count rate of 6.3×10

^{3}s

^{-1}when the type-II QPM device was pumped with an average power of 25 mW (coupled into the waveguide). Corrected for the detection efficiencies of SPDs and the optical losses, the generation rate of the crosspolarized photon pairs was 2.3×109 s

^{-1}. Table 1 shows the comparison of the performances of the photon pair sources. Here, note that the generation rate and the brightness are normalized to a coupled pump power of 1 mW. The brightness of the type-II photon pair source was ∼6×10

^{5}/s/GHz, which was higher than that of the type-0 photon pair source. The type-II SPDC does not cause a large spectral broadening such as the type-0 SPDC. This is the reason why the type-II photon pair source has the higher brightness, even though the nonlinear tensor element

*d*

_{24}is smaller than

*d*

_{33}.

## 6. HOM-type interference experiment

7. C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. **59**, 2044–2046 (1987). [CrossRef] [PubMed]

*N*is given by the expression [7

_{c}7. C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. **59**, 2044–2046 (1987). [CrossRef] [PubMed]

*V*is a visibility,

_{Hom}*C*is a normalization constant. In the present experiment, the refractive indices for the TM mode (signal photon) and the TE mode (idler photon) are not the same. Therefore, the optical distances (in the waveguide) experienced by the signal photon is different from that experienced by the idler photon. In addition, the difference between the optical distances is not constant but depends upon a position at which a photon pair is generated in the waveguide. As a result, there exists an uncertainty in the optical path-length difference between the two arms (for the signal and idler photons) of the HOM interferometer. The uncertainty degrades the visibility of the quantum interference. Taking into account the difference between the refractive indices for the TE and TM modes, Eq. (4) can be rewritten as the simple expression:

## 7. Conclusions

^{9}s

^{-1}which was corrected for the detection efficiencies of the SPDs and the optical losses. The brightness was∼6×10

^{5}/s/GHz when the pump power was 1 mW. Although the nonlinear coefficient

*d*

_{24}is smaller than

*d*

_{33}, the brightness of the type-II photon pair source was higher than that of the conventional type-0 photon pair source.

^{7}s

^{-1}.

14. C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue “Highly efficient single-photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNb3 waveguide,” Opt. Lett. **30**, 1725, (2005) [CrossRef] [PubMed]

15. R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, “Quantum key distribution at 1550 nm with twin superconducting single-photon detector,”Appl. Phys. Lett. **89**, 241129.1–241129.3 (2006) [CrossRef]

## Acknowledgments

## References and links

1. | N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. |

2. | J. W. Pan, D. Bouwmeester, H. Weinfurter, and A. Zeilinger, “Experimental nonlocality proof of quantum tele-portation and entanglement swapping,” Phys. Rev. Lett. |

3. | D. Bouwmeester, J. W. Pan, K. Mattele, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum tele-portation,” Nature |

4. | P. G. Kwiat, K. Mattel, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. Shih “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. |

5. | A. Yoshizawa, R. Kaji, and H. Tsuchida, “Two-photon interference at 1550nm using two periodically poled lithium niobate waveguides,” Jpn. J. Appl. Phys. |

6. | H.de Riedmatten, I. Marcikic, W. Tittel, H. Zbinden, and N. Gisin, “Quantum interference with photon pairs created in spatially separated source,” Phys. Rev. A. |

7. | C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. |

8. | H. Y. Shen, H. Xu, Z. D. Zeng, W. X. Lin, R. F. Wu, and G. F. Xu, “Measurement of refractive indices and thermal refractive-index coefficients of LiNbO |

9. | T. Suhara and H. Kintaka, “Quantum theory analysis of twin-photon beams generated by parametric fluorescence,” IEEE Quantum Electron. |

10. | M. Motoya, S. Kurimura, S. Inoue, Y. Usui, and H. Nakajima, “Type II quasi-phase matching in waveguide parametric down converter for quantum information technologies,” |

11. | N. Namekata, Y. Makino, and S. Inoue, “Single-photon detector for long-distance fiber-optic quantum key distribution,” Opt. Lett. |

12. | S. Mori, J. SÖderholm, N. Namekata, and S. Inoue, “On the distribution of 1550-nm photon pairs efficiently generated using a periodically poled lithium niobate waveguide,” Opt. Com. |

13. | H.de Riedmatten, V. Scarani, I. Marcikic, A. Acín, W. Tittel,, H. Zbinden, and N. Gisin, “Two independent photon pairs versus four-photon entangled states in parametric down conversion,” J. Mod. Opt. |

14. | C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue “Highly efficient single-photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNb3 waveguide,” Opt. Lett. |

15. | R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, “Quantum key distribution at 1550 nm with twin superconducting single-photon detector,”Appl. Phys. Lett. |

**OCIS Codes**

(190.4410) Nonlinear optics : Nonlinear optics, parametric processes

(270.0270) Quantum optics : Quantum optics

**ToC Category:**

Nonlinear Optics

**History**

Original Manuscript: July 25, 2007

Revised Manuscript: September 14, 2007

Manuscript Accepted: September 14, 2007

Published: September 21, 2007

**Citation**

Go Fujii, Naoto Namekata, Masayuki Motoya, Sunao Kurimura, and Shuichiro Inoue, "Bright narrowband source of photon pairs at optical telecommunication wavelengths using a type-II periodically poled lithium niobate waveguide," Opt. Express **15**, 12769-12776 (2007)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-20-12769

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### References

- N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, "Quantum cryptography," Rev. Mod. Phys. 74, 145-195 (2002). [CrossRef]
- J. W. Pan, D. Bouwmeester, H. Weinfurter, and A. Zeilinger, "Experimental nonlocality proof of quantum teleportation and entanglement swapping," Phys. Rev. Lett. 88, 017903.1-017903.4 (1998).
- D. Bouwmeester, J. W. Pan, K. Mattele, M. Eibl, H. Weinfurter, and A. Zeilinger, "Experimental quantum teleportation," Nature 390, 575-579 (1997). [CrossRef]
- P. G. Kwiat, K. Mattel, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. Shih, "New high-intensity source of polarization-entangled photon pairs," Phys. Rev. Lett. 75, 4337-4341 (1995). [CrossRef] [PubMed]
- A. Yoshizawa, R. Kaji and H. Tsuchida, "Two-photon interference at 1550nm using two periodically poled lithium niobate waveguides," Jpn. J. Appl. Phys. 42, 5652-5653 (2003). [CrossRef]
- H. de Riedmatten, I. Marcikic. W. Tittel, H. Zbinden and N. Gisin, "Quantum interference with photon pairs created in spatially separated source," Phys. Rev. A. 67, 022301.1-022301.5 (2003). [CrossRef]
- C. K. Hong, Z. Y. Ou and L. Mandel, "Measurement of subpicosecond time intervals between two photons by interference," Phys. Rev. Lett. 59, 2044-2046 (1987). [CrossRef] [PubMed]
- H. Y. Shen, H. Xu, Z. D. Zeng, W. X. Lin, R. F. Wu, and G. F. Xu, "Measurement of refractive indices and thermal refractive-index coefficients of LiNbO3 crystal doped with 5 mol.%MgO," Appl. Opt. 31, 6695-6697 (1992). [CrossRef] [PubMed]
- T. Suhara and H. Kintaka, "Quantum theory analysis of twin-photon beams generated by parametric fluorescence," IEEE Quantum Electron. 41, 1203-1205 (2005). [CrossRef]
- M. Motoya, S. Kurimura, S. Inoue, Y. Usui and H. Nakajima, "Type II quasi-phase matching in waveguide parametric down converter for quantum information technologies," Conference on Lasers and ElectroOptics, Long Beach, USA (2006), CMB5.
- N. Namekata, Y. Makino and S. Inoue, "Single-photon detector for long-distance fiber-optic quantum key distribution," Opt. Lett. 27, 954-956 (2002). [CrossRef]
- S. Mori, J. Soderholm, N. Namekata and S. Inoue, "On the distribution of 1550-nm photon pairs efficiently generated using a periodically poled lithium niobate waveguide," Opt. Com. 264, 156-162 (2006). [CrossRef]
- H. de Riedmatten, V. Scarani, I. Marcikic, A. Acin, W. Tittel, H. Zbinden and N. Gisin, "Two independent photon pairs versus four-photon entangled states in parametric down conversion," J. Mod. Opt. 51, 1637-1649 (2004).
- C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue "Highly efficient singlephoton detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNb3 waveguide," Opt. Lett. 30, 1725, (2005) [CrossRef] [PubMed]
- R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, "Quantum key distribution at 1550 nm with twin superconducting single-photon detector,"Appl. Phys. Lett. 89, 241129.1-241129.3 (2006) [CrossRef]

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