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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 12 — Jun. 6, 2011
  • pp: 11415–11421
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Harmonic generation in silicon nitride ring resonators

Jacob S. Levy, Mark A. Foster, Alexander L. Gaeta, and Michal Lipson  »View Author Affiliations


Optics Express, Vol. 19, Issue 12, pp. 11415-11421 (2011)
http://dx.doi.org/10.1364/OE.19.011415


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Abstract

We demonstrate second- and third-harmonic generation in a centrosymmetric CMOS-compatible material using ring resonators and integrated optical waveguides. The χ(2) response is induced by using the nanoscale structure of the waveguide to break the bulk symmetry of silicon nitride (Si3N4) with the silicon dioxide (SiO2) cladding. Using a high-Q ring resonator cavity to enhance the efficiency of the process, we detect the second-harmonic output in the visible wavelength range with milliwatt input powers at telecom wavelengths. We also observe third-harmonic generation from the intrinsic χ(3) susceptibility of the silicon nitride. Phase matching of the harmonic processes occurs due to the near coincidence of indices of refraction of the fundamental mode at the pump frequency and the corresponding higher-order modes of the harmonic fields.

© 2011 OSA

1. Introduction

The emerging field of silicon photonics seeks to unify the high bandwidth of optical communications with complementary metal-oxide-semiconductor (CMOS) microelectronic circuits. Many components have been demonstrated for on-chip optical communications, including those that utilize the nonlinear optical properties of silicon [1

1. M. A. Foster, A. C. Turner, J. E. Sharping, B. S. Schmidt, M. Lipson, and A. L. Gaeta, “Broad-band optical parametric gain on a silicon photonic chip,” Nature 441(7096), 960–963 (2006). [CrossRef] [PubMed]

, 2

2. B. Corcoran, C. Monat, C. Grillet, D. J. Moss, B. J. Eggleton, T. P. White, L. O'Faolain, and T. F. Krauss, “Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides,” Nat. Photonics 3(4), 206–210 (2009). [CrossRef]

], silicon dioxide [3

3. T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity,” Phys. Rev. Lett. 93(8), 083904 (2004). [CrossRef] [PubMed]

, 4

4. T. Carmon and K. J. Vahala, “Visible continuous emission from a silica microphotonic device by third-harmonic generation,” Nat. Phys. 3(6), 430–435 (2007). [CrossRef]

] and silicon nitride [5

5. J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010). [CrossRef]

, 6

6. K. Ikeda, R. E. Saperstein, N. Alic, and Y. Fainman, “Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides,” Opt. Express 16(17), 12987–12994 (2008). [CrossRef] [PubMed]

]. Processes such as second harmonic (SH) generation, enabled by the second-order susceptibility, have not been developed in integrated optics since the bulk χ(2) vanishes in these centrosymmetric materials. Generating the lowest-order nonlinearity enables a new array of CMOS-compatible optical devices capable of nonlinear functionalities such as electro-optic modulation, sum frequency up-conversion, and difference frequency generation.

2. Design

Efficient SHG is possible by satisfying the phase-matching condition of matching the effective index of the fundamental waveguide mode in the IR to a higher order mode in the visible range. This method has previously been suggested for phase-matched third-harmonic generation in SiO2, in both microtoroids [4

4. T. Carmon and K. J. Vahala, “Visible continuous emission from a silica microphotonic device by third-harmonic generation,” Nat. Phys. 3(6), 430–435 (2007). [CrossRef]

] and microstructured fibers [17

17. J. K. Ranka, R. S. Windeler, and A. J. Stentz, “Optical properties of high-delta air silica microstructure optical fibers,” Opt. Lett. 25(11), 796–798 (2000). [CrossRef]

, 18

18. F. G. Omenetto, A. J. Taylor, M. D. Moores, J. Arriaga, J. C. Knight, W. J. Wadsworth, and P. S. J. Russell, “Simultaneous generation of spectrally distinct third harmonics in a photonic crystal fiber,” Opt. Lett. 26(15), 1158–1160 (2001). [CrossRef]

]. In order to determine which mode is best phase-matched, we use a finite difference method mode solver to calculate the effective index for both the pump and SH frequencies. This calculation solves for the effective refractive index for a waveguide bending with a radius equivalent to that of the fabricated ring resonator. By solving for the effective index instead of a centrosymmetric cavity mode, we are able to fully take into account material dispersion and track the phase-matching for a continuum of wavelengths. Figure 1(b), shows a plot of the effective index against wavelength for the first 8 modes of the waveguide at the SH wavelength and the fundamental mode at the pump wavelength. Since the phase-matching condition is satisfied when the effective index at the pump and corresponding SH wavelengths are equal, crossing points between the blue and red lines are perfectly phase-matched for the corresponding wavelength pair and mode number. As the plot shows, we have a phase-matching point near our experimental pump wavelength with the 6th transverse waveguide mode at the SH wavelength.

3. Experimental results

3.1 Second-harmonic conversion

We measure the SH wavelength in the waveguide coupled to the resonator for input pump powers as low as 3 mW. A tunable diode laser is amplified using an erbium-doped fiber amplifier and coupled to the waveguide using a tapered lensed fiber. We use a polarization controller to launch light in the fundamental quasi-TE mode of the waveguide. The pump wavelength λP is tuned into the resonance of the ring cavity near 1554 nm and, with suitable power levels, we are able to observe generation of the second harmonic (Fig. 2(a)
Fig. 2 The visible and spectral output from the generated SH light. (a). Top view visible CCD camera image of the microresonator generating red light. IR light, invisible to this camera, is launched from the left and couples into the ring. The power builds-up in the ring generating SH which couples back into the waveguide propagating out to the right. (b) The output from the waveguide, pumped at 1554.2 nm, is collected into an optical spectrometer. The visible emitted light occurs only at the expected SH wavelength
). We use a spectrometer to measure the wavelength of the visible emitted light. Figure 2(b) shows the output with the generated SH wavelength λSH measured to be 777.1 nm which, as expected, is λP/2. Since only the SH wavelength is detected, we conclude we are not generating broadband photoluminescence which has been previously described in silicon nitride [19

19. A. Serpengüzel and S. Tanriseven, “Controlled photoluminescence in amorphous-silicon-nitride microcavities,” Appl. Phys. Lett. 78(10), 1388–1390 (2001). [CrossRef]

, 20

20. M. Barth, N. Nusse, J. Stingl, B. Lochel, and O. Benson, “Emission properties of high-Q silicon nitride photonic crystal heterostructure cavities,” Appl. Phys. Lett. 93(2), 021112–021113 (2008). [CrossRef]

]. To measure the power of the SH, both the IR pump and the visible signal are collected into an optical spectrum analyzer (OSA). The powers measured by the OSA are corrected to the absolute power values coming out of the waveguide, taking into consideration the coupling efficiencies from the waveguide to the fiber and to the OSA for both pump and SH wavelengths, respectively. The OSA confirms the wavelength measurement for both the pump and SH. We observe a maximum conversion efficiency of −35 dB with 100 µW of SH generated for a pump of 315 mW. At increased pump powers, the ring’s resonance experiences a thermal shift which prevents efficient coupling from the waveguide to the resonator.

3.2 Modal profile image

The captured mode image of the waveguide output (Fig. 3
Fig. 3 Modal cross-section profiles for phase-mathched SH generation. (a) The simulated cross-section mode profile for the sixth-order mode of our waveguide at 777.1 nm. (b) The captured mode image of the visible emission from our waveguide showing good agreement with the simulated mode profile.
) corresponds well to the simulated mode profile for the 6th order SH mode which optimizes the phase-matching condition. Since the ring and bus waveguide cross-sections are identical, we expect the same-order mode generated in the ring resonator to couple to the waveguide. To effectively image the mode, we polish away the nanotapers [21

21. V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett. 28(15), 1302–1304 (2003). [CrossRef] [PubMed]

], used to increase coupling efficiency, at the output of the waveguide. We collect the output light with a high NA objective to focus the image on a CCD camera. There are three distinct lobes in the mode showing a good match with the simulated mode.

3.3 Third-harmonic generation

In addition to SH, we also observe third-harmonic generation in the ring resonators as shown in Fig. 4(a)
Fig. 4 Third-harmonic generation in silicon nitride resonators. (a) Top view CCD image of waveguide coupled ring resonator generating visible TH from an IR pump tuned to the cavity resonance. (b) Spectrometer output from the waveguide shown in (a). The monochromatic response confirms the wavelength and that THG is occurring.
. The intrinsic χ (3) nonlinearity of the silicon nitride induces the third order process in which three pump photons generate a single photon at the third-harmonic frequency. Efficient THG requires meeting the same phase-matching condition as SHG: the effective index of the pump must equal the effective index at the TH wavelength. By performing similar simulations as before we find the fundamental mode of the pump is closest in refractive index to the 18th order mode at the third-harmonic wavelength.

By pumping at a resonance near 1560 nm, we generate the TH and measure the light to be exactly one third of the pump wavelength (Fig. 4). We are able to measure picowatts of output power with for the same pump strength as used to generate SH light. This is on the same order as shown in a silicon photonic crystal [2

2. B. Corcoran, C. Monat, C. Grillet, D. J. Moss, B. J. Eggleton, T. P. White, L. O'Faolain, and T. F. Krauss, “Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides,” Nat. Photonics 3(4), 206–210 (2009). [CrossRef]

], but here light is coupled and guided in the bus waveguide as opposed to out of plane emission.

4. Analysis

5. Conclusions

Our demonstration of guided on-chip visible light generation opens the available spectrum for Si-based devices from the IR to the visible, increasing bandwidth and enabling potential integration of silicon photodetectors to on-chip optical networks. We have demonstrated an integrated coupling of both the second and third harmonics from a cavity to a waveguide for the first time on a silicon platform. Additionally, the doubly resonant SH generation presented here could produce squeezed states [23

23. S. F. Pereira, M. Xiao, H. J. Kimble, and J. L. Hall, “Generation of squeezed light by intracavity frequency doubling,” Phys. Rev. A 38(9), 4931–4934 (1988). [CrossRef] [PubMed]

] of both the pump and SH frequencies for quantum optics studies. Finally, the induced second-order nonlinearity could be used for difference frequency generation to combine two near infrared pumps to generate a mid-infrared source [24

24. N. K. Hon, K. K. Tsia, D. R. Solli, and B. Jalali, “Periodically poled silicon,” Appl. Phys. Lett. 94(9), 091116–091113 (2009). [CrossRef]

].

Acknowledgements

The authors would like to acknowledge DARPA for supporting this work under the MTO POPS Program. This work was performed in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECS-0335765).

References and links

1.

M. A. Foster, A. C. Turner, J. E. Sharping, B. S. Schmidt, M. Lipson, and A. L. Gaeta, “Broad-band optical parametric gain on a silicon photonic chip,” Nature 441(7096), 960–963 (2006). [CrossRef] [PubMed]

2.

B. Corcoran, C. Monat, C. Grillet, D. J. Moss, B. J. Eggleton, T. P. White, L. O'Faolain, and T. F. Krauss, “Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides,” Nat. Photonics 3(4), 206–210 (2009). [CrossRef]

3.

T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity,” Phys. Rev. Lett. 93(8), 083904 (2004). [CrossRef] [PubMed]

4.

T. Carmon and K. J. Vahala, “Visible continuous emission from a silica microphotonic device by third-harmonic generation,” Nat. Phys. 3(6), 430–435 (2007). [CrossRef]

5.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010). [CrossRef]

6.

K. Ikeda, R. E. Saperstein, N. Alic, and Y. Fainman, “Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides,” Opt. Express 16(17), 12987–12994 (2008). [CrossRef] [PubMed]

7.

D. T. H. Tan, K. Ikeda, P. C. Sun, and Y. Fainman, “Group velocity dispersion and self phase modulation in silicon nitride waveguides,” Appl. Phys. Lett. 96(6), 061101–061103 (2010). [CrossRef]

8.

N. Bloembergen, R. K. Chang, S. S. Jha, and C. H. Lee, “Optical Second-Harmonic Generation in Reflection from Media with Inversion Symmetry,” Phys. Rev. 174(3), 813–822 (1968). [CrossRef]

9.

H. W. K. Tom, T. F. Heinz, and Y. R. Shen, “Second-Harmonic Reflection from Silicon Surfaces and Its Relation to Structural Symmetry,” Phys. Rev. Lett. 51(21), 1983–1986 (1983). [CrossRef]

10.

J. E. Sipe, D. J. Moss, and H. M. van Driel, “Phenomenological theory of optical second- and third-harmonic generation from cubic centrosymmetric crystals,” Phys. Rev. B Condens. Matter 35(3), 1129–1141 (1987). [CrossRef] [PubMed]

11.

Y. R. Shen, “Surface properties probed by second-harmonic and sum-frequency generation,” Nature 337(6207), 519–525 (1989). [CrossRef]

12.

S. Lettieri, S. D. Finizio, P. Maddalena, V. Ballarini, and F. Giorgis, “Second-harmonic generation in amorphous silicon nitride microcavities,” Appl. Phys. Lett. 81(25), 4706–4708 (2002). [CrossRef]

13.

S. Lettieri, F. Gesuele, P. Maddalena, M. Liscidini, L. C. Andreani, C. Ricciardi, V. Ballarini, and F. Giorgis, “Second-harmonic generation in hydrogenated amorphous-Si 1 - xN x doubly resonant microcavities with periodic dielectric mirrors,” Appl. Phys. Lett. 87(19), 191110 (2005). [CrossRef]

14.

A. Gondarenko, J. S. Levy, and M. Lipson, “High confinement micron-scale silicon nitride high Q ring resonator,” Opt. Express 17(14), 11366–11370 (2009). [CrossRef] [PubMed]

15.

A. C. Turner, M. A. Foster, A. L. Gaeta, and M. Lipson, “Ultra-low power parametric frequency conversion in a silicon microring resonator,” Opt. Express 16(7), 4881–4887 (2008). [CrossRef] [PubMed]

16.

M. Ferrera, L. Razzari, D. Duchesne, R. Morandotti, Z. Yang, M. Liscidini, J. E. Sipe, S. Chu, B. E. Little, and D. J. Moss, “Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures,” Nat. Photonics 2(12), 737–740 (2008). [CrossRef]

17.

J. K. Ranka, R. S. Windeler, and A. J. Stentz, “Optical properties of high-delta air silica microstructure optical fibers,” Opt. Lett. 25(11), 796–798 (2000). [CrossRef]

18.

F. G. Omenetto, A. J. Taylor, M. D. Moores, J. Arriaga, J. C. Knight, W. J. Wadsworth, and P. S. J. Russell, “Simultaneous generation of spectrally distinct third harmonics in a photonic crystal fiber,” Opt. Lett. 26(15), 1158–1160 (2001). [CrossRef]

19.

A. Serpengüzel and S. Tanriseven, “Controlled photoluminescence in amorphous-silicon-nitride microcavities,” Appl. Phys. Lett. 78(10), 1388–1390 (2001). [CrossRef]

20.

M. Barth, N. Nusse, J. Stingl, B. Lochel, and O. Benson, “Emission properties of high-Q silicon nitride photonic crystal heterostructure cavities,” Appl. Phys. Lett. 93(2), 021112–021113 (2008). [CrossRef]

21.

V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett. 28(15), 1302–1304 (2003). [CrossRef] [PubMed]

22.

R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic Press, San Diego, 2008).

23.

S. F. Pereira, M. Xiao, H. J. Kimble, and J. L. Hall, “Generation of squeezed light by intracavity frequency doubling,” Phys. Rev. A 38(9), 4931–4934 (1988). [CrossRef] [PubMed]

24.

N. K. Hon, K. K. Tsia, D. R. Solli, and B. Jalali, “Periodically poled silicon,” Appl. Phys. Lett. 94(9), 091116–091113 (2009). [CrossRef]

OCIS Codes
(130.3120) Integrated optics : Integrated optics devices
(190.2620) Nonlinear optics : Harmonic generation and mixing
(190.4400) Nonlinear optics : Nonlinear optics, materials

ToC Category:
Nonlinear Optics

History
Original Manuscript: April 28, 2011
Revised Manuscript: May 22, 2011
Manuscript Accepted: May 23, 2011
Published: May 26, 2011

Citation
Jacob S. Levy, Mark A. Foster, Alexander L. Gaeta, and Michal Lipson, "Harmonic generation in silicon nitride ring resonators," Opt. Express 19, 11415-11421 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-12-11415


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References

  1. M. A. Foster, A. C. Turner, J. E. Sharping, B. S. Schmidt, M. Lipson, and A. L. Gaeta, “Broad-band optical parametric gain on a silicon photonic chip,” Nature 441(7096), 960–963 (2006). [CrossRef] [PubMed]
  2. B. Corcoran, C. Monat, C. Grillet, D. J. Moss, B. J. Eggleton, T. P. White, L. O'Faolain, and T. F. Krauss, “Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides,” Nat. Photonics 3(4), 206–210 (2009). [CrossRef]
  3. T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity,” Phys. Rev. Lett. 93(8), 083904 (2004). [CrossRef] [PubMed]
  4. T. Carmon and K. J. Vahala, “Visible continuous emission from a silica microphotonic device by third-harmonic generation,” Nat. Phys. 3(6), 430–435 (2007). [CrossRef]
  5. J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010). [CrossRef]
  6. K. Ikeda, R. E. Saperstein, N. Alic, and Y. Fainman, “Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides,” Opt. Express 16(17), 12987–12994 (2008). [CrossRef] [PubMed]
  7. D. T. H. Tan, K. Ikeda, P. C. Sun, and Y. Fainman, “Group velocity dispersion and self phase modulation in silicon nitride waveguides,” Appl. Phys. Lett. 96(6), 061101–061103 (2010). [CrossRef]
  8. N. Bloembergen, R. K. Chang, S. S. Jha, and C. H. Lee, “Optical Second-Harmonic Generation in Reflection from Media with Inversion Symmetry,” Phys. Rev. 174(3), 813–822 (1968). [CrossRef]
  9. H. W. K. Tom, T. F. Heinz, and Y. R. Shen, “Second-Harmonic Reflection from Silicon Surfaces and Its Relation to Structural Symmetry,” Phys. Rev. Lett. 51(21), 1983–1986 (1983). [CrossRef]
  10. J. E. Sipe, D. J. Moss, and H. M. van Driel, “Phenomenological theory of optical second- and third-harmonic generation from cubic centrosymmetric crystals,” Phys. Rev. B Condens. Matter 35(3), 1129–1141 (1987). [CrossRef] [PubMed]
  11. Y. R. Shen, “Surface properties probed by second-harmonic and sum-frequency generation,” Nature 337(6207), 519–525 (1989). [CrossRef]
  12. S. Lettieri, S. D. Finizio, P. Maddalena, V. Ballarini, and F. Giorgis, “Second-harmonic generation in amorphous silicon nitride microcavities,” Appl. Phys. Lett. 81(25), 4706–4708 (2002). [CrossRef]
  13. S. Lettieri, F. Gesuele, P. Maddalena, M. Liscidini, L. C. Andreani, C. Ricciardi, V. Ballarini, and F. Giorgis, “Second-harmonic generation in hydrogenated amorphous-Si 1 - xN x doubly resonant microcavities with periodic dielectric mirrors,” Appl. Phys. Lett. 87(19), 191110 (2005). [CrossRef]
  14. A. Gondarenko, J. S. Levy, and M. Lipson, “High confinement micron-scale silicon nitride high Q ring resonator,” Opt. Express 17(14), 11366–11370 (2009). [CrossRef] [PubMed]
  15. A. C. Turner, M. A. Foster, A. L. Gaeta, and M. Lipson, “Ultra-low power parametric frequency conversion in a silicon microring resonator,” Opt. Express 16(7), 4881–4887 (2008). [CrossRef] [PubMed]
  16. M. Ferrera, L. Razzari, D. Duchesne, R. Morandotti, Z. Yang, M. Liscidini, J. E. Sipe, S. Chu, B. E. Little, and D. J. Moss, “Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures,” Nat. Photonics 2(12), 737–740 (2008). [CrossRef]
  17. J. K. Ranka, R. S. Windeler, and A. J. Stentz, “Optical properties of high-delta air silica microstructure optical fibers,” Opt. Lett. 25(11), 796–798 (2000). [CrossRef]
  18. F. G. Omenetto, A. J. Taylor, M. D. Moores, J. Arriaga, J. C. Knight, W. J. Wadsworth, and P. S. J. Russell, “Simultaneous generation of spectrally distinct third harmonics in a photonic crystal fiber,” Opt. Lett. 26(15), 1158–1160 (2001). [CrossRef]
  19. A. Serpengüzel and S. Tanriseven, “Controlled photoluminescence in amorphous-silicon-nitride microcavities,” Appl. Phys. Lett. 78(10), 1388–1390 (2001). [CrossRef]
  20. M. Barth, N. Nusse, J. Stingl, B. Lochel, and O. Benson, “Emission properties of high-Q silicon nitride photonic crystal heterostructure cavities,” Appl. Phys. Lett. 93(2), 021112–021113 (2008). [CrossRef]
  21. V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett. 28(15), 1302–1304 (2003). [CrossRef] [PubMed]
  22. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic Press, San Diego, 2008).
  23. S. F. Pereira, M. Xiao, H. J. Kimble, and J. L. Hall, “Generation of squeezed light by intracavity frequency doubling,” Phys. Rev. A 38(9), 4931–4934 (1988). [CrossRef] [PubMed]
  24. N. K. Hon, K. K. Tsia, D. R. Solli, and B. Jalali, “Periodically poled silicon,” Appl. Phys. Lett. 94(9), 091116–091113 (2009). [CrossRef]

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