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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 16 — Jul. 30, 2012
  • pp: 18319–18325
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Controllable optical analog to electromagnetically induced transparency in coupled high-Q microtoroid cavities

Can Zheng, Xiaoshun Jiang, Shiyue Hua, Long Chang, Guanyu Li, Huibo Fan, and Min Xiao  »View Author Affiliations


Optics Express, Vol. 20, Issue 16, pp. 18319-18325 (2012)
http://dx.doi.org/10.1364/OE.20.018319


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Abstract

We experimentally demonstrate an all-optical analog to electromagnetically induced transparency (EIT) on chip using coupled high-Q silica microtoroid cavities with Q-factors above 106. The transmission spectrum of the all-optical analog to EIT is precisely controlled by tuning the distance between the two microtoroids, as well as the detunings of the resonance frequencies of the two cavities.

© 2012 OSA

1. Introduction

2. Experiment

Figure 1(a)
Fig. 1 (a) Schematic diagram of the experimental setup for measuring the transmission spectrum of the coupled microtoroid cavities. (b) Top-view optical microscope image of the two coupled microtoroid cavities coupled to a tapered fiber. The diameters of the two microtoroids are 60.4 µm and 67.5 µm, respectively. VOA: variable optical attenuator.
shows a schematic diagram of the experimental setup used to characterize our coupled microcavity system. A narrow linewidth tunable laser (New Focus, model TLB-6328) operated at wavelength of 1550 nm is used to excite the WGMs through a low-loss (<0.5 dB) fiber taper with a diameter of ~1 µm [18

18. M. Cai, O. Painter, and K. J. Vahala, “Observation of critical coupling in a fiber taper to a silica-microsphere whispering-gallery mode system,” Phys. Rev. Lett. 85(1), 74–77 (2000). [CrossRef] [PubMed]

, 19

19. S. M. Spillane, T. J. Kippenberg, O. J. Painter, and K. J. Vahala, “Ideality in a fiber-taper-coupled microresonator system for application to cavity quantum electrodynamics,” Phys. Rev. Lett. 91(4), 043902 (2003). [CrossRef] [PubMed]

]. The transmitted light is measured using a 125-MHz-bandwidth photodetector (New Focus, model 1811) for transmission spectrum measurement. During the experiment, the launched optical power is ensured to be below 1 µW by using a variable optical attenuator to prevent thermal effect, while the cavities are kept in a N2 purged enclosure to avoid contamination.

To precisely control the coupling between the first microtoroid (microtoroid 1 in Fig. 2(a)
Fig. 2 (a) Schematic diagram of the coupled microcavity system. (b) Thermal tuning of the second microtoroid cavity. (c) Typically measured and theoretically calculated all-optical analog to EIT spectrum of the coupled microtoroid cavities.
) to the fiber taper and to the second microtoroid (microtoroid 2 in Fig. 2(a)), we first prepare two microtoroids located at the edge of silicon chips. The fabrication process of the edge-located silica toroids is similar to the one as described in Refs. 20

20. I. S. Grudinin, H. Lee, O. Painter, and K. J. Vahala, “Phonon laser action in a tunable two-level system,” Phys. Rev. Lett. 104(8), 083901 (2010). [CrossRef] [PubMed]

and 21

21. G. Anetsberger, O. Arcizet, Q. P. Unterreithmeier, R. Rivière, A. Schliesser, E. M. Weig, J. P. Kotthaus, and T. J. Kippenberg, “Near-field cavity optomechanics with nanomechanical oscillators,” Nat. Phys. 5(12), 909–914 (2009). [CrossRef]

. Then we place each of the silica microtoroids on a piezoelectric stage to precisely control its position. To change the detuning of the coupled microtoroids, the second microtoroid is mounted on a thermoelectric cooler (TEC) to tune its resonance frequency, while the first one is kept at room temperature. The temperature of the TEC is monitored by a thermistor and actively controlled by a temperature controller with a stability of 0.01 °C. Figure 2(b) presents the dependence (microtoroid 2) of the resonance frequency shift on the increasing temperature with a sensitivity of −3.56 GHz/°C.

Figure 1(b) shows the selected two microtoroids used in the experiment with diameters of 60.4 µm and 67.5 µm, respectively. Although they have a large difference in size, the two cavities have their resonant modes close to each other. The initial resonant wavelengths of the two cavities are 1548.1 nm and 1547.7 nm and their intrinsic Q factors are 1.1 × 106 and 4.7 × 106, respectively.

To investigate the controllability of the EIT spectrum, we first tune the transmission of the coupled microcavity system via changing the coupling between the two cavities. As shown in Fig. 3(a)
Fig. 3 Measured and theoretically calculated transmission spectra of the coupled microtoroid system for various coupling rates of the two coupled WGMs when the first toroid is undercoupled (a) and overcoupled (b). The top curves are the transmission spectra of the first microtoroid coupled to a tapered fiber waveguide in the absence of the second microtoroid. The loaded Q factor of the first microtoroid is 0.94 × 106 for (a) and 0.33 × 106 for (b). The temperature of the second toroid is 64.11 °C for (a) and 65.17 °C for (b), respectively. The coupling between the two coupled WGMs is controlled by changing the distance between the two cavities.
, when the distance between the cavities is decreased, the transmission spectrum is changed from Fano resonance to analog to EIT and then Fano resonance again. The top curve in Fig. 3(a) is the transmission spectrum of the first microtoroid in the absence of the second microtoroid. The loaded Q-factor is 0.94 × 106, indicating that the first microtoroid is undercoupled. The temperature of the second microtoroid is 64.11 °C, corresponding to a frequency detuning of −0.44 GHz. We then make the second microtoroid couple to the first one and tune the distance between them. During the process, the calculated coupling rate is increased from 0.485 GHz to 1.18 GHz when the distance is decreased from 1.21 µm to 0.96 µm. It is worth to mention that the detuning is also changed due to the temperature increase of the first toroid when the second microtoroid is moved towards it. In contrast to the directly coupled microsphere cavities [8

8. A. Naweed, G. Farca, S. I. Shopova, and A. T. Rosenberger, “Induced transparency and absorption in coupled whispering-gallery microresonators,” Phys. Rev. A 71(4), 043804 (2005). [CrossRef]

] where the EIT-like effect is only observed when the first cavity is undercoupled. For the smaller mode volume and hence larger evanescent field around the microtoroid cavities, the all-optical analog to EIT is also observed when the first toroid is overcoupled in our system due to the strong coupling between the two microtoroids. As shown in Fig. 3(b), the loaded Q-factor of the first toroid is 0.33 × 106 (overcoupled) and the temperature of the second microtoroid is 65.17 °C. By changing the distance between the coupled microtoroids, the transmission spectrum of this coupled system can also be controlled.

We then fix the coupling (distance) between the two microtoroid cavities and measure the dependence of the transmission spectrum on the detuning of the cavity mode by changing the temperature of the second microtoroid. Figure 4
Fig. 4 Measured and theoretically calculated transmission spectra of the coupled microtoroid system for various frequency detunings of the coupled WGMs. The top curve is the transmission spectrum of the first microtoroid coupled to the tapered fiber waveguide in the absence of the second microtoroid. The tuning is controlled by change the temperature of the second microtoroid.
shows a series of transmission spectra of the coupled microtoroid system by increasing the temperature of the second microtoroid from 64.74 °C to 64.94 °C. The calculated tuning rate of the frequency detuning between the two microtoroids on the temperature is around −3.49 GHz/°C, in good agreement with the measured results (Fig. 2(b)). During this process, the coupling between the two coupled WGMs is also increased due to the thermal expansion of the TEC and the heated silicon chip.

3. Conclusion

We have experimentally demonstrated an all-optical analog to EIT on chip based on two directly coupled silica microtoroid cavities at the wavelength of ~1550 nm. By optimizing the frequency detuning and the coupling between the coupled microtoroid cavities, we have obtained a narrow (200 MHz) spectral width of the transparency window with a maximum transparency near 90%. All-optical analog to EIT is observed when the first cavity is either undercoupled or overcoupled to the tapered fiber. The transmission spectrum is precisely controlled by changing the positions and the frequency detuning between the two cavities. Since the edge-located microtoroids with Q factors higher than 107 [20

20. I. S. Grudinin, H. Lee, O. Painter, and K. J. Vahala, “Phonon laser action in a tunable two-level system,” Phys. Rev. Lett. 104(8), 083901 (2010). [CrossRef] [PubMed]

, 21

21. G. Anetsberger, O. Arcizet, Q. P. Unterreithmeier, R. Rivière, A. Schliesser, E. M. Weig, J. P. Kotthaus, and T. J. Kippenberg, “Near-field cavity optomechanics with nanomechanical oscillators,” Nat. Phys. 5(12), 909–914 (2009). [CrossRef]

] and the normal (non edge-located) microtoroids with Q factors higher than 108 [17

17. D. K. Armani, T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Ultra-high-Q toroid microcavity on a chip,” Nature 421(6926), 925–928 (2003). [CrossRef] [PubMed]

] have already been fabricated, we expect to achieve narrower EIT-like spectral width in future by further optimizing the fabrication process and stability of the TEC heater. We believe that this all-optical analog to EIT on chip can be very useful in optical sensor [23

23. Y.-F. Xiao, V. Gaddam, and L. Yang, “Coupled optical microcavities: an enhanced refractometric sensing configuration,” Opt. Express 16(17), 12538–12543 (2008). [CrossRef] [PubMed]

], cavity optomechanics [20

20. I. S. Grudinin, H. Lee, O. Painter, and K. J. Vahala, “Phonon laser action in a tunable two-level system,” Phys. Rev. Lett. 104(8), 083901 (2010). [CrossRef] [PubMed]

, 24

24. T. J. Kippenberg and K. J. Vahala, “Cavity Optomechanics: Back-Action at the Mesoscale,” Science 321(5893), 1172–1176 (2008). [CrossRef] [PubMed]

], and quantum information processing [25

25. K. Di, C. D. Xie, and J. Zhang, “Coupled-resonator-induced transparency with a squeezed vacuum,” Phys. Rev. Lett. 106(15), 153602 (2011). [CrossRef] [PubMed]

, 26

26. A. Majumdar, A. Rundquist, M. Bajcsy, and J. Vuckovic, “Cavity Quantum Electrodynamics with a Single Quantum Dot Coupled to a Photonic Molecule,” arXiv:1201.6244v1.

].

Acknowledgments

This work was supported by the National Basic Research Program of China (Nos. 2012CB921804 and 2011CBA00205), the National Natural Science Foundation of China (Nos. 11104137 and 11021403), the Fundamental Research Funds for the Central Universities (1107021359) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

References and links

1.

S. E. Harris, “Electromagnetically induced transparency,” Phys. Today 50(7), 36–42 (1997). [CrossRef]

2.

J. Gea-Banacloche, Y. Li, S. Jin, and M. Xiao, “Electromagnetically induced transparency in ladder-type inhomogeneously broadened media: Theory and experiment,” Phys. Rev. A 51(1), 576–584 (1995). [CrossRef] [PubMed]

3.

M. Fleischhauer, A. Imamoglu, and J. P. Marangos, “Electromagnetically induced transparency: Optics in coherent media,” Rev. Mod. Phys. 77(2), 633–673 (2005). [CrossRef]

4.

M. D. Lukin and A. Imamoğlu, “Controlling photons using electromagnetically induced transparency,” Nature 413(6853), 273–276 (2001). [CrossRef] [PubMed]

5.

L. Maleki, A. B. Matsko, A. A. Savchenkov, and V. S. Ilchenko, “Tunable delay line with interacting whispering-gallery-mode resonators,” Opt. Lett. 29(6), 626–628 (2004). [CrossRef] [PubMed]

6.

M. F. Yanik, W. Suh, Z. Wang, and S. Fan, “Stopping Light in a Waveguide with an All-Optical Analog of Electromagnetically Induced Transparency,” Phys. Rev. Lett. 93(23), 233903 (2004). [CrossRef] [PubMed]

7.

D. D. Smith, H. Chang, K. A. Fuller, A. T. Rosenberger, and R. W. Boyd, “Coupled-resonator-induced transparency,” Phys. Rev. A 69(6), 063804 (2004). [CrossRef]

8.

A. Naweed, G. Farca, S. I. Shopova, and A. T. Rosenberger, “Induced transparency and absorption in coupled whispering-gallery microresonators,” Phys. Rev. A 71(4), 043804 (2005). [CrossRef]

9.

K. Totsuka, N. Kobayashi, and M. Tomita, “Slow light in coupled-resonator-induced transparency,” Phys. Rev. Lett. 98(21), 213904 (2007). [CrossRef] [PubMed]

10.

Q. Xu, S. Sandhu, M. L. Povinelli, J. Shakya, S. Fan, and M. Lipson, “Experimental Realization of an On-Chip All-Optical Analogue to Electromagnetically Induced Transparency,” Phys. Rev. Lett. 96(12), 123901 (2006). [CrossRef] [PubMed]

11.

R. W. Boyd and D. J. Gauthier, “Photonics: transparency on an optical chip,” Nature 441(7094), 701–702 (2006). [CrossRef] [PubMed]

12.

Q. Xu, P. Dong, and M. Lipson, “Breaking the delay-bandwidth limit in a photonic structure,” Nat. Phys. 3(6), 406–410 (2007). [CrossRef]

13.

X. Yang, M. Yu, D. L. Kwong, and C. W. Wong, “All-optical analog to electromagnetically induced transparency in multiple coupled photonic crystal cavities,” Phys. Rev. Lett. 102(17), 173902 (2009). [CrossRef] [PubMed]

14.

X. Yang, M. Yu, D. L. Kwong, and C. W. Wong, “Coupled resonances in multiple silicon photonic crystal cavities in all-optical solid-state analogy to electromagnetically induced transparency,” IEEE J. Sel. Top. Quantum Electron. 16(1), 288–294 (2010). [CrossRef]

15.

S. I. Shopova, Y. Sun, A. T. Rosenberger, and X. Fan, “Highly sensitive tuning of coupled optical ring resonators by microfluidics,” Microfluid Nanofluid 6(3), 425–429 (2009). [CrossRef]

16.

Y.-F. Xiao, L. He, J. Zhu, and L. Yang, “Electromagnetically induced transparency-like effect in a single polydimethylsiloxane coated silica microtoroid,” Appl. Phys. Lett. 94(23), 231115 (2009). [CrossRef]

17.

D. K. Armani, T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Ultra-high-Q toroid microcavity on a chip,” Nature 421(6926), 925–928 (2003). [CrossRef] [PubMed]

18.

M. Cai, O. Painter, and K. J. Vahala, “Observation of critical coupling in a fiber taper to a silica-microsphere whispering-gallery mode system,” Phys. Rev. Lett. 85(1), 74–77 (2000). [CrossRef] [PubMed]

19.

S. M. Spillane, T. J. Kippenberg, O. J. Painter, and K. J. Vahala, “Ideality in a fiber-taper-coupled microresonator system for application to cavity quantum electrodynamics,” Phys. Rev. Lett. 91(4), 043902 (2003). [CrossRef] [PubMed]

20.

I. S. Grudinin, H. Lee, O. Painter, and K. J. Vahala, “Phonon laser action in a tunable two-level system,” Phys. Rev. Lett. 104(8), 083901 (2010). [CrossRef] [PubMed]

21.

G. Anetsberger, O. Arcizet, Q. P. Unterreithmeier, R. Rivière, A. Schliesser, E. M. Weig, J. P. Kotthaus, and T. J. Kippenberg, “Near-field cavity optomechanics with nanomechanical oscillators,” Nat. Phys. 5(12), 909–914 (2009). [CrossRef]

22.

H. A. Haus, Waves and Fields in Optoelectronics (Prentice-Hall, Englewood Cliffs, NJ,1984).

23.

Y.-F. Xiao, V. Gaddam, and L. Yang, “Coupled optical microcavities: an enhanced refractometric sensing configuration,” Opt. Express 16(17), 12538–12543 (2008). [CrossRef] [PubMed]

24.

T. J. Kippenberg and K. J. Vahala, “Cavity Optomechanics: Back-Action at the Mesoscale,” Science 321(5893), 1172–1176 (2008). [CrossRef] [PubMed]

25.

K. Di, C. D. Xie, and J. Zhang, “Coupled-resonator-induced transparency with a squeezed vacuum,” Phys. Rev. Lett. 106(15), 153602 (2011). [CrossRef] [PubMed]

26.

A. Majumdar, A. Rundquist, M. Bajcsy, and J. Vuckovic, “Cavity Quantum Electrodynamics with a Single Quantum Dot Coupled to a Photonic Molecule,” arXiv:1201.6244v1.

OCIS Codes
(140.3945) Lasers and laser optics : Microcavities
(230.4555) Optical devices : Coupled resonators

ToC Category:
Optical Devices

History
Original Manuscript: June 26, 2012
Revised Manuscript: July 17, 2012
Manuscript Accepted: July 19, 2012
Published: July 25, 2012

Citation
Can Zheng, Xiaoshun Jiang, Shiyue Hua, Long Chang, Guanyu Li, Huibo Fan, and Min Xiao, "Controllable optical analog to electromagnetically induced transparency in coupled high-Q microtoroid cavities," Opt. Express 20, 18319-18325 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-16-18319


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References

  1. S. E. Harris, “Electromagnetically induced transparency,” Phys. Today50(7), 36–42 (1997). [CrossRef]
  2. J. Gea-Banacloche, Y. Li, S. Jin, and M. Xiao, “Electromagnetically induced transparency in ladder-type inhomogeneously broadened media: Theory and experiment,” Phys. Rev. A51(1), 576–584 (1995). [CrossRef] [PubMed]
  3. M. Fleischhauer, A. Imamoglu, and J. P. Marangos, “Electromagnetically induced transparency: Optics in coherent media,” Rev. Mod. Phys.77(2), 633–673 (2005). [CrossRef]
  4. M. D. Lukin and A. Imamoğlu, “Controlling photons using electromagnetically induced transparency,” Nature413(6853), 273–276 (2001). [CrossRef] [PubMed]
  5. L. Maleki, A. B. Matsko, A. A. Savchenkov, and V. S. Ilchenko, “Tunable delay line with interacting whispering-gallery-mode resonators,” Opt. Lett.29(6), 626–628 (2004). [CrossRef] [PubMed]
  6. M. F. Yanik, W. Suh, Z. Wang, and S. Fan, “Stopping Light in a Waveguide with an All-Optical Analog of Electromagnetically Induced Transparency,” Phys. Rev. Lett.93(23), 233903 (2004). [CrossRef] [PubMed]
  7. D. D. Smith, H. Chang, K. A. Fuller, A. T. Rosenberger, and R. W. Boyd, “Coupled-resonator-induced transparency,” Phys. Rev. A69(6), 063804 (2004). [CrossRef]
  8. A. Naweed, G. Farca, S. I. Shopova, and A. T. Rosenberger, “Induced transparency and absorption in coupled whispering-gallery microresonators,” Phys. Rev. A71(4), 043804 (2005). [CrossRef]
  9. K. Totsuka, N. Kobayashi, and M. Tomita, “Slow light in coupled-resonator-induced transparency,” Phys. Rev. Lett.98(21), 213904 (2007). [CrossRef] [PubMed]
  10. Q. Xu, S. Sandhu, M. L. Povinelli, J. Shakya, S. Fan, and M. Lipson, “Experimental Realization of an On-Chip All-Optical Analogue to Electromagnetically Induced Transparency,” Phys. Rev. Lett.96(12), 123901 (2006). [CrossRef] [PubMed]
  11. R. W. Boyd and D. J. Gauthier, “Photonics: transparency on an optical chip,” Nature441(7094), 701–702 (2006). [CrossRef] [PubMed]
  12. Q. Xu, P. Dong, and M. Lipson, “Breaking the delay-bandwidth limit in a photonic structure,” Nat. Phys.3(6), 406–410 (2007). [CrossRef]
  13. X. Yang, M. Yu, D. L. Kwong, and C. W. Wong, “All-optical analog to electromagnetically induced transparency in multiple coupled photonic crystal cavities,” Phys. Rev. Lett.102(17), 173902 (2009). [CrossRef] [PubMed]
  14. X. Yang, M. Yu, D. L. Kwong, and C. W. Wong, “Coupled resonances in multiple silicon photonic crystal cavities in all-optical solid-state analogy to electromagnetically induced transparency,” IEEE J. Sel. Top. Quantum Electron.16(1), 288–294 (2010). [CrossRef]
  15. S. I. Shopova, Y. Sun, A. T. Rosenberger, and X. Fan, “Highly sensitive tuning of coupled optical ring resonators by microfluidics,” Microfluid Nanofluid6(3), 425–429 (2009). [CrossRef]
  16. Y.-F. Xiao, L. He, J. Zhu, and L. Yang, “Electromagnetically induced transparency-like effect in a single polydimethylsiloxane coated silica microtoroid,” Appl. Phys. Lett.94(23), 231115 (2009). [CrossRef]
  17. D. K. Armani, T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Ultra-high-Q toroid microcavity on a chip,” Nature421(6926), 925–928 (2003). [CrossRef] [PubMed]
  18. M. Cai, O. Painter, and K. J. Vahala, “Observation of critical coupling in a fiber taper to a silica-microsphere whispering-gallery mode system,” Phys. Rev. Lett.85(1), 74–77 (2000). [CrossRef] [PubMed]
  19. S. M. Spillane, T. J. Kippenberg, O. J. Painter, and K. J. Vahala, “Ideality in a fiber-taper-coupled microresonator system for application to cavity quantum electrodynamics,” Phys. Rev. Lett.91(4), 043902 (2003). [CrossRef] [PubMed]
  20. I. S. Grudinin, H. Lee, O. Painter, and K. J. Vahala, “Phonon laser action in a tunable two-level system,” Phys. Rev. Lett.104(8), 083901 (2010). [CrossRef] [PubMed]
  21. G. Anetsberger, O. Arcizet, Q. P. Unterreithmeier, R. Rivière, A. Schliesser, E. M. Weig, J. P. Kotthaus, and T. J. Kippenberg, “Near-field cavity optomechanics with nanomechanical oscillators,” Nat. Phys.5(12), 909–914 (2009). [CrossRef]
  22. H. A. Haus, Waves and Fields in Optoelectronics (Prentice-Hall, Englewood Cliffs, NJ,1984).
  23. Y.-F. Xiao, V. Gaddam, and L. Yang, “Coupled optical microcavities: an enhanced refractometric sensing configuration,” Opt. Express16(17), 12538–12543 (2008). [CrossRef] [PubMed]
  24. T. J. Kippenberg and K. J. Vahala, “Cavity Optomechanics: Back-Action at the Mesoscale,” Science321(5893), 1172–1176 (2008). [CrossRef] [PubMed]
  25. K. Di, C. D. Xie, and J. Zhang, “Coupled-resonator-induced transparency with a squeezed vacuum,” Phys. Rev. Lett.106(15), 153602 (2011). [CrossRef] [PubMed]
  26. A. Majumdar, A. Rundquist, M. Bajcsy, and J. Vuckovic, “Cavity Quantum Electrodynamics with a Single Quantum Dot Coupled to a Photonic Molecule,” arXiv:1201.6244v1.

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