## Generation of two-mode bright squeezed light using a noise-suppressed amplified diode laser

Optics Express, Vol. 14, Issue 26, pp. 13083-13088 (2006)

http://dx.doi.org/10.1364/OE.14.013083

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### Abstract

We present the generation of nonclassical state using an amplified diode laser as a light source. The intensity noise of an amplified diode laser was significantly suppressed and reached the shot noise limit at 15 MHz using both a filter cavity and resonant optical feedback. Frequency doubling efficiency of 66% and up to 120 mW output power of green has been achieved in cw second-harmonic generation from 1080 nm to 540 nm. Bright two-mode amplitude-squeezed state was generated from a type-II nondegenerate optical parametric amplifier pumped by generated green light. The measured noise reduction is 2.1±0.2 dB below the shot-noise level.

© 2006 Optical Society of America

## 1. Introduction

7. K. Hayasaka, Y. Zhang, and K. Kasai, “Generation of twin beams from an optical parametric oscillator pumped by a frequency-doubled diode laser,” Opt. Lett. **29**, 1665–1667 (2004). [CrossRef] [PubMed]

8. Y. Zhang, K. Hayasaka, and K. Kasai, “Efficient noise suppression of amplified diode laser,” to be published in Appl. Phys. B (online first http://dx.doi.org/10.1007/s00340-006-2436-2).

## 2. Experimental setup

## 3. Results and discussion

8. Y. Zhang, K. Hayasaka, and K. Kasai, “Efficient noise suppression of amplified diode laser,” to be published in Appl. Phys. B (online first http://dx.doi.org/10.1007/s00340-006-2436-2).

9. K. Hayasaka, Y. Zhang, and K. Kasai, “Generation of 22.8 mW single-frequency green light by frequency doubling of a 50-mW diode laser,” Opt. Express **12**, 3567 (2004). [CrossRef] [PubMed]

*T*=2.1%, which is close to the calculated optimum input transmission when the input fundamental is about 180mW, is selected. Figure 3 is the functions of the second harmonic output power and the conversion efficiency versus the input fundamental power. We derived the theoretical curves by solving equation

_{in}*η*=

*P*

_{2ω}/

*P*is the SHG efficiency and

_{ω}*L*=0.4% is a total round-trip loss of SHG cavity determined by the measured finesse of 250. The single-pass conversion efficiency

_{SHG}*E*of the crystal, which is set to the value

_{NL}*E*=1.1×10

_{NL}^{-3}

*W*

^{-1}, is the only adjustable parameter. The experimental results are in reasonable agreement with the expected curves. The maximum green output power of 120 mW is obtained when the input fundamental power is 180 mW. The directly measured doubling efficiency is 66%.

*T*=2% transmission for 1080 nm and high reflection for 540 nm. It serves as an output coupler for our NOPA. A facet of KTP inside the cavity was coated for antireflection at both 1080 and 540 nm. The other facet was coated for antireflection at 540 nm and high reflection at 1080 nm. It acts as the input mirror of the pump field at 540 nm. The measured finesse of the resonator is 300, the free spectral range is 6 GHz, and the cavity bandwidth is

_{out}*γ*=20 MHz. We calculated a total round-trip loss of

_{c}*L*=0.3% by the measured finesse. The escape efficiency of

_{NOPA}*ξ*=

*T*/(

_{out}*T*+

_{out}*L*)=0.87 is obtained. Due to the large transmission of input coupler at 540 nm, the pump field only passes the cavity twice without resonating. The crystal nonlinear efficiency of

_{NOPA}*E*=1.1×10

_{NL}^{-3}

*W*

^{-1}was estimated from the SHG process. From this we deduce an expected threshold pump power for parametric oscillation,

*P*=(

_{th}*T*+

_{out}*L*)

_{NOPA}^{2}/4

*E*=120 mW.

_{NL}10. Y. Zhang, H. Wang, X. Y. Li, J. T. Jing, C. D. Xie, and K. C. Peng, “Experimental generation of bright two-mode quadrature squeezed light from a narrow band nondegenerate optical parametric amplifier,” Phys. Rev. A , **62**, 023813 (2000). [CrossRef]

11. J. Laurat, L. Longchambon, C. Fabre, and T. Coudreau, “Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation,” Opt. Lett. **30**, 1177–1179 (2005). [CrossRef] [PubMed]

12. S. Feng and O. Pfister, “Quantum Interference of Ultrastable Twin Optical Beams,” Phys. Rev. Lett. **92**, 203601 (2004). [CrossRef] [PubMed]

13. Y. Zhang, K. Kasai, and M. Watanabe, “Classical and quantum properties of optical parametric amplifier/deamplifier,” Phys. Lett. A **297**, 29 (2002). [CrossRef]

11. J. Laurat, L. Longchambon, C. Fabre, and T. Coudreau, “Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation,” Opt. Lett. **30**, 1177–1179 (2005). [CrossRef] [PubMed]

*i*

_{-}and

*i*, which indicated the shot noise reference and the intensity noise levels, respectively.

_{+}*ƒ*=16 MHz when the pump power was about 100 mW. Trace (b) and (c) refer to the amplitude noise and the shot noise limit, respectively, when the pump phase is fixed on deamplification operating. A measurement of

*V*

_{det}(

*i*

_{+}) and

*V*

_{det}(

*i*

_{-}) is also given in traces (f) and (e) when the phase is scanned. The amplitude squeezing up to 2.1±0.2 dB is measured under the total detection efficiency of

*η*=86% (detector quantum efficiency 90% and propagation efficiency 96%). Trace (d) gives the measured shot noise limit without pump and trace (a) gives the electronic noise of our detector. We note that the noise powers for the available light power is close to that the electronic noise floor, so the electronic noise floor should be subtracted. The inferred value after taking into account the electronics floor is 2.5±0.2 dB. In a simplified mode the measured amplitude spectrum is expressed by [14

14. K. Schneider, R. Bruckmeier, H. Hansen, S. Schiller, and J. Mlynek, “Bright squeezed-light generation by a continuous-wave semimonolithic parametric amplifier,” Opt. Lett. **21**, 1396–1398 (1996). [CrossRef] [PubMed]

## 4. Conclusion

## Acknowledgments

## References and links

1. | K. C. Peng, Q. Pan, H. Wang, Y. Zhang, H. Su, and C. D. Xie, “Generation of two-mode quadrature-phase squeezing and intensity-difference squeezing from a cw-NOPO,” Appl. Phys. B |

2. | J. Mertz, T. Debuisschert, A. Heidmann, C. Fabre, and E. Giacobino, “Improvements in the observed intensity correlation of optical parametric oscillator twin beams,” Opt. Lett. |

3. | A. S. Villar, L. S. Cruz, K. N. Cassemiro, M. Martinelli, and P. Nussenzveig, “Generation of bright two-color continuous variable entanglement” Phys. Rev. Lett. |

4. | Z. Y. Ou, S. F. Pereira, H. J. Kimble, and K. C. Peng, “Realization of the Einstein-Podolsky-Rosen paradox for continuous variables” Phys. Rev. Lett. |

5. | X. Y. Li, Q. Pan, J. T. Jiang, J. Zhang, C. D. Xie, and K. C. Peng, “Quantum dense coding by exploiting a bright Einstein-Podolsky-Rosen beam,” Phys. Rev. Lett. |

6. | X. J. Jia, X. L. Su, Q. Pan, J. R. Gao, C. D. Xie, and K. C. Peng, “Experimental demonstration of unconditional entanglement swapping for continuous variables,” Phys. Rev. Lett. |

7. | K. Hayasaka, Y. Zhang, and K. Kasai, “Generation of twin beams from an optical parametric oscillator pumped by a frequency-doubled diode laser,” Opt. Lett. |

8. | Y. Zhang, K. Hayasaka, and K. Kasai, “Efficient noise suppression of amplified diode laser,” to be published in Appl. Phys. B (online first http://dx.doi.org/10.1007/s00340-006-2436-2). |

9. | K. Hayasaka, Y. Zhang, and K. Kasai, “Generation of 22.8 mW single-frequency green light by frequency doubling of a 50-mW diode laser,” Opt. Express |

10. | Y. Zhang, H. Wang, X. Y. Li, J. T. Jing, C. D. Xie, and K. C. Peng, “Experimental generation of bright two-mode quadrature squeezed light from a narrow band nondegenerate optical parametric amplifier,” Phys. Rev. A , |

11. | J. Laurat, L. Longchambon, C. Fabre, and T. Coudreau, “Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation,” Opt. Lett. |

12. | S. Feng and O. Pfister, “Quantum Interference of Ultrastable Twin Optical Beams,” Phys. Rev. Lett. |

13. | Y. Zhang, K. Kasai, and M. Watanabe, “Classical and quantum properties of optical parametric amplifier/deamplifier,” Phys. Lett. A |

14. | K. Schneider, R. Bruckmeier, H. Hansen, S. Schiller, and J. Mlynek, “Bright squeezed-light generation by a continuous-wave semimonolithic parametric amplifier,” Opt. Lett. |

**OCIS Codes**

(190.2620) Nonlinear optics : Harmonic generation and mixing

(190.4970) Nonlinear optics : Parametric oscillators and amplifiers

(270.0270) Quantum optics : Quantum optics

(270.6570) Quantum optics : Squeezed states

**ToC Category:**

Quantum Optics

**History**

Original Manuscript: September 27, 2006

Revised Manuscript: November 30, 2006

Manuscript Accepted: December 10, 2006

Published: December 22, 2006

**Citation**

Yun Zhang, Kazuhiro Hayasaka, and Katsuyuki Kasai, "Generation of two-mode bright squeezed light using a noise-suppressed amplified diode laser," Opt. Express **14**, 13083-13088 (2006)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-26-13083

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### References

- K. C. Peng, Q. Pan, H. Wang, Y. Zhang, H. Su and C. D. Xie, "Generation of two-mode quadrature-phase squeezing and intensity-difference squeezing from a cw-NOPO," Appl. Phys. B 66, 755-758(1998). [CrossRef]
- J. Mertz, T. Debuisschert, A. Heidmann, C. Fabre, and E. Giacobino, "Improvements in the observed intensity correlation of optical parametric oscillator twin beams," Opt. Lett. 16, 1234-1236 (1991). [CrossRef] [PubMed]
- A. S. Villar, L. S. Cruz, K. N. Cassemiro, M. Martinelli, and P. Nussenzveig, "Generation of bright two-color continuous variable entanglement" Phys. Rev. Lett. 95, 243603 (2005). [CrossRef] [PubMed]
- Z. Y. Ou, S. F. Pereira, H. J. Kimble, and K. C. Peng, "Realization of the Einstein-Podolsky-Rosen paradox for continuous variables" Phys. Rev. Lett. 68, 3663-3666(1992). [CrossRef] [PubMed]
- X. Y. Li, Q. Pan, J. T. Jiang, J. Zhang, C. D. Xie, and K. C. Peng, "Quantum dense coding by exploiting a bright Einstein-Podolsky-Rosen beam," Phys. Rev. Lett. 88, 047904 (2002). [CrossRef] [PubMed]
- X. J. Jia, X. L. Su, Q. Pan, J. R. Gao, C. D. Xie, and K. C. Peng, "Experimental demonstration of unconditional entanglement swapping for continuous variables," Phys. Rev. Lett. 93, 250503 (2005). [CrossRef] [PubMed]
- K. Hayasaka, Y. Zhang, and K. Kasai, "Generation of twin beams from an optical parametric oscillator pumped by a frequency-doubled diode laser," Opt. Lett. 29, 1665-1667 (2004). [CrossRef] [PubMed]
- Y. Zhang, K. Hayasaka, and K. Kasai, "Efficient noise suppression of amplified diode laser," to be published in Appl. Phys. B (online first http://dx.doi.org/10.1007/s00340-006-2436-2).
- K. Hayasaka, Y. Zhang, and K. Kasai, "Generation of 22.8 mW single-frequency green light by frequency doubling of a 50-mW diode laser," Opt. Express 12, 3567 (2004). [CrossRef] [PubMed]
- Y. Zhang, H. Wang, X. Y. Li, J. T. Jing, C. D. Xie, and K. C. Peng, "Experimental generation of bright two -mode quadrature squeezed light from a narrow band nondegenerate optical parametric amplifier," Phys. Rev. A, 62, 023813 (2000). [CrossRef]
- J. Laurat, L. Longchambon, C. Fabre, and T. Coudreau, "Experimental investigation of amplitude and phase quantum correlations in a type II optical parametric oscillator above threshold: from nondegenerate to degenerate operation," Opt. Lett. 30, 1177-1179 (2005). [CrossRef] [PubMed]
- S. Feng and O. Pfister, "Quantum interference of Ultrastable Twin Optical Beams," Phys. Rev. Lett. 92, 203601 (2004). [CrossRef] [PubMed]
- Y. Zhang, K. Kasai, M. Watanabe, "Classical and quantum properties of optical parametric amplifier/deamplifier," Phys. Lett. A 297, 29 (2002). [CrossRef]
- K. Schneider, R. Bruckmeier, H. Hansen, S. Schiller, and J. Mlynek, "Bright squeezed-light generation by a continuous-wave semimonolithic parametric amplifier," Opt. Lett. 21, 1396-1398 (1996). [CrossRef] [PubMed]

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