Luca Carletti

Amorphous silicon nanowires combining high nonlinearity, FOM and optical stability

We demonstrate optically stable amorphous silicon nanowires with both high nonlinear figure of merit (FOM) of ~5 and high nonlinearity Re(γ) = 1200W(-1)m(-1). We observe no degradation in these parameters over the entire course of our experiments including systematic study under operation at 2 W coupled peak power (i.e. ~2GW/cm(2)) over timescales of at least an hour.We demonstrate optically stable amorphous silicon nanowires with both high nonlinear figure of merit (FOM) of ~5 and high nonlinearity Re(γ) = 1200W -1 m -1 . We observe no degradation in these parameters over the entire course of our experiments including systematic study under operation at 2 W coupled peak power (i.e. ~2GW/cm 2 ) over timescales of at least an hour. References and links 1. J. Leuthold, C. Koos, and W. Freude, “Nonlinear silicon photonics,” Nat. Photonics 4, 535-544 (2010). 2. M. 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, 960-963 (2006). 3. F. Li, M. Pelusi, D. X. Xu, A. Densmore, R. Ma, S. Janz, and D. J. Moss, “Error-free all-optical demultiplexing at 160Gb/s via FWM in a silicon nanowire,” Opt. Express 18, 3905-3910 (2010). 4. H. Ji, M. Galili, H. Hu, M. Pu, L. K. Oxenlowe, K. Yvind, J. M. Hvam, and P. Jeppesen, “1.28-Tb/s demultiplexing of an OTDM DPSK data signal using a silicon waveguide,” IEEE Photon. Technol. Lett. 22, 1762-1764 (2010). 5. 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, 206-210 (2009). DOI: 10.1038/nphoton.2009.28. 6. B. Corcoran, C. Monat, M. Pelusi, C. Grillet, T. P. White, L. O’Faolain, T. F. Krauss, B. J. Eggleton, and D. J. Moss, “Optical signal processing on a silicon chip at 640Gb/s using slow-light,” Opt. Express 18, 7770-7781 (2010). 7. C. Xiong, C. Monat, A. S. Clark, C. Grillet, G. D. Marshall, M. J. Steel, J. Li, L. O’Faolain, T. F. Krauss, J. G. Rarity, and B. J. Eggleton, “Slow-light enhanced correlated photon pair generation in a silicon photonic crystal waveguide,” Opt. Lett. 36, 3413-3415 (2011). 8. S. Zlatanovic, J. S. Park, S. Moro, J. M. Chavez Boggio, I. B. Divliansky, N. Alic, S. Mookherjea, and S. Radic, “Mid-infrared wavelength conversion in silicon waveguides using ultracompact telecom-bandderived pump source,” Nat. Photonics 4, 561-564 (2010). 9. X. Liu, R. M. Osgood, Y. A. Vlasov, and W. J. Green, “Mid-infrared optical parametric amplifier using Si nanophotonic waveguides,” Nat. Photonics 4, 557-560 (2010). 10. B. Kuyken, X. Liu, G. Roelkens, R. Baets, R. M. Osgood, and W. J. Green, “50 dB parametric on-chip gain in silicon photonic wires,” Opt. lett. 36, 44014403 (2011). 11. B. Kuyken, X. Liu, R. M. Osgood, R. Baets, G. Roelkens, and W. J. Green, “Mid-infrared to telecom-band supercontinuum generation in highly nonlinear silicon-on-insulator wire waveguides,” Opt. Express 19, 20172-20181 (2011). 12. R. K. W. Lau, M. Menard, Y. Okawachi, M. A. Foster, A. C. Turner-Foster, R. Salem, M. Lipson, and A. Gaeta, “Continuous-wave mid-infrared frequency conversion in silicon nanowaveguides,” Opt. lett. 36, 1263-1265 (2011). 13. R. A. Soref, “Mid-infrared photonics in silicon and germanium,” Nat. Photonics 4, 495-497 (2010). 14. B. Jalali, “Silicon photonics: nonlinear optics in the mid-infrared,” Nat. Photonics 4, 506-508 (2010). 15. K. Ikeda, Y. M. Shen, and Y. Fainman, “Enhanced optical nonlinearity in amorphous silicon and its application to waveguide devices,” Opt. Express 15, 17761-17771 (2007). 16. S. K. O’Leary, S. R. Johnson, and P. K. Lim, “The relationship between the distribution of electronic states and the optical absorption spectrum of an amorphous semiconductor: an empirical analysis,” J. Appl. Phys. 82, 3334-3340 (1997). 17. Y. Shoji, T. Ogasawara, T. Kamei, Y. Sakakibara, S. Suda, K. Kintaka, H. Kawashima, M. Okano, T. Hasama, H. Ishikawa, and M. Mori, “Ultrafast nonlinear effects in hydrogenated amorphous silicon wire waveguide,” Opt. Express 18, 5668-5673 (2010). 18. K. Narayanan, and S. F. Preble, “Optical nonlinearities in hydrogenated amorphous silicon waveguides,” Opt. Express 18, 8998-9905 (2010). 19. S. Suda, K. Tanizawa, Y. Sakakibara, T. Kamei, K. Nakanishi, E. Itoga, T. Ogasawara, R. Takei, H. Kawashima, S. Namiki, M. Mori, T. Hasama, and H. Ishikawa, “Pattern-effect-free all-optical wavelength conversion using a hydrogenated amorphous silicon waveguide with ultra-fast carrier decay,” Opt. Lett. 37, 1382-1384 (2012). 20. K-Y. Wang, and A. C. Foster, “Ultralow power continuous-wave frequency conversion in hydrogenated amorphous silicon waveguides,” Opt. Lett. 37, 1331-1333 (2012). 21. B. Kuyken, S. Clemmen, S. K. Selvaraja, W. Boagaerts, D. Thourhout, P. Emplit, S. Massar, G. Roelkens, and R. Baets, “On-chip parametric amplification with 26.5dB gain at telecommunication wavelengths using CMOS-compatible hydrogenated amorphous silicon waveguides,” Opt. Lett. 36, 552-554 (2011). 22. B. Kuyken, H. Ji, S. Clemmen , S. K. Selvaraja, H. Hu, M. Pu, M. Galili, P. Jeppesen, G. Morthier, S. Massar, L. K. Oxenlowe, G. Roelkens, and R. Baets, “Nonlinear properties of and nonlinear processing in hydrogenated amorphous silicon waveguides,” Opt. Express 19, B146-B153 (2011). 23. H. K. Tsang, R. V. Penty, I. H. White, R. S. Grant, W. Sibbett, J. B. D. Soole, H. P. Leblanc, N. C. Andreadakis, R. Bhat, and M. A. Koza, “Two-photon absorption and self-phase modulation in InGaAsP/InP multi-quantum well waveguides,” J. Appl. Phys. 70, 3992-3994 (1991). 24. O. Boyraz, T. Indukuri, and B. Jalali, “Self-phase-modulation induced spectral broadening in silicon waveguides,” Opt. Express 12, 829-834 (2004). 25. E. Dulkeith, Y. A. Vlasov, X. Chen, N. C. Panoiu, and R. M. Osgood, “Self-phase-modulation in submicron silicon-on-insulator photonic wires,” Opt. Express 14, 5524-5534 (2006). 26. X. Liu, J. B. Driscoll, J. I. Dadap, R. M. Osgood, S. Assefa, Y. A. Vlasov, and W. M. J. Green, “Selfphase modulation and nonlinear loss in silicon nanophotonic wires near the mid-infrared two-photon absorption edge,” Opt. Express 19, 7778-7789 (2011). 27. K. Narayanan, A. W. Elshaari, and S. F. Preble, “Broadband all-optical modulation in hydrogenatedamorphous silicon waveguides,” Opt. Express 18, 9809-9814 (2010). 28. C. Sciancalepore, B. Ben Bakir, X. Letartre, J. Harduin, N. Olivier, C. Seassal, J. M. Fedeli, and P. Viktorovitch, “CMOS-compatible ultra-compact 1.55uf06dm emitting VCSELs using double photonic crystal mirrors,” IEEE Photon. Technol. Lett. 24, 455 (2012). 29. R. Orobtchouk, S. Jeannot, B. Han, T. Benyattou, J. M. Fedeli, and P. Mur, “Ultra compact optical link made in amorphous silicon waveguide,” Proc. SPIE 6183, conf. on Integrated Optics, Silicon Photonics, and Photonic Integrated Circuits, Strasbourg, paper 618304 (2006). 30. K.-Y. Wang, K. G. Petrillo, M. A. Foster, and A. C. Foster, “Ultralow-power 160-Gb/s all-optical demultiplexing in hydrogenated amorphous silicon waveguides,” in Integrated Photonics Research, Silicon and Nanophotonics, OSA Technical Digest (online), paper IW4C.3 (2012). 31. J. M. Fedeli, M. Migette, L. Di Cioccio, L. El Melhaoui, R. Orobtchouk, C. Seassal, P. Rojo-Romeo, F. Mandorlo, D. Marris-Morini, L. Vivien, “Incorporation of a photonic layer at the metallization levels of a CMOS circuit,” in proceedings of 3rd IEEE International Conf. on Group IV Photonics, 200-202 (2006). 32. J. M. Fedeli, R. Orobtchouk, C. Seassal, and L. Vivien, “Integration issues of a photonic layer on top of a CMOS circuit,” Proc. SPIE 6125, conf. on Silicon Photonics, San Jose, paper 61250H (2006). 33. J. M. Fedeli, L. Di Cioccio, D. Marris-Morini, L. Vivien, R. Orobtchouk, P. Rojo-Romeo, C. Seassal, and F. Mandorlo, “Development of silicon photonics devices using microelectronic tools for the integration on top of a CMOS wafer,” Adv. Optical Technol. 2008, doi:10.1155/2008/412518 (2008).

Nonlinear optical response of low loss silicon germanium waveguides in the mid-infrared

We have investigated the nonlinear optical response of low loss Si(0.6)Ge(0.4) / Si waveguides in the mid-infrared wavelength range from 3.25- 4.75μm using picosecond optical pulses. We observed and measured the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index. The dynamics of the spectral broadening suggests that, in addition to multiphoton absorption, the corresponding higher order nonlinear refractive phenomena also needs to be included when high optical pulse intensities are used at mid-infrared wavelengths in this material.

Mid-infrared nonlinear optical response of Si-Ge waveguides with ultra-short optical pulses

We characterize the nonlinear optical response of low loss Si(0.6)Ge(0.4) / Si waveguides in the mid-infrared between 3.3 μm and 4 μm using femtosecond optical pulses. We estimate the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index from the experimental measurements. The effect of multiphoton absorption on the optical nonlinear Kerr response is evaluated and the nonlinear figure of merit estimated providing some guidelines for designing nonlinear optical devices in the mid-IR. Finally, we compare the impact of free-carrier absorption at mid-infrared wavelengths versus near-infrared wavelengths for these ultra-short pulses.

Mid-infrared nonlinear optics in SiGe waveguides

Comprehensive mid-IR nonlinear measurements of SiGe waveguides performed in the picosecond and femtosecond regime and compared to numerical calculations are reported. Nonlinear properties of SiGe waveguides in the mid-IR are extracted.

Hydrogenated amorphous silicon nanowires with high nonlinear figure of merit and stable nonlinear optical response

The nonlinear characteristics of hydrogenated amorphous silicon nanowires are experimentally measured. A nonlinear coefficient, γ, with a high real part Real(γ)= 690W-1m-1, combined with a low imaginary part Im(γ)= 10 W-1m-1, resulted in a high nonlinear FOM of 5.5. Furthermore, systematic studies over hours of operational time under 2.2W of pulse peak power revealed no degradation of the optical response.The nonlinear characteristics of hydrogenated amorphous silicon nanowires are experimentally demonstrated. A high nonlinear refractive index, n2=1.19 x 10-17 m2/W, combined with a low two-photon absorption, 0.14 x 10-11 m/W, resulted in a high nonlinear FOM of 5.5. Furthermore, systematic studies over hours of operational time under 2.2W of pulse peak power revealed no degradation of the optical response.

Mid-infrared integrated photonics on a SiGe platform

The mid-infrared is of great interest for a huge range of applications such as medical and environment sensors, security, defense and astronomy. I will give a broad overview of the different activities recently launched in INL Lyon, in close collaboration with several French and Australian institutions, under the umbrella of “Mid-IR integrated photonics” with a particular focus on novel integrated sources for the Mid-IR exploiting a nonlinear SiGe platform.

Mid-IR integrated photonics for sensing applications

The mid-infrared (mid-IR, wavelength range between 2 and 10 μm) is of great interest for a huge range of applications such as medical and environment sensors, security, defense and astronomy. I will give a broad overview of the different activities recently launched in INL Lyon, in close collaboration with several French and Australian institutions, under the umbrella of “Mid-IR integrated photonics” with a particular focus on novel integrated sources for the Mid-IR including hybrid III-V semiconductors on SiGe sources, thermal sources and nonlinear sources.

Nonlinear optical properties of SiGe waveguides in the mid-infrared

We measure the nonlinear response of CMOS-compatible SiGe waveguides in the mid-infrared. Comparing with numerical calculations, we extract the multi-photon absorption coefficients and the induced free-carrier absorptions for wavelengths between 3μm and 5μm.

Nonlinear response of SiGe waveguides in the mid-infrared

The linear and nonlinear optical response of SiGe waveguides in the mid-infrared are experimentally measured. By cutback measurements we find the linear losses to be less than 1.5dB/cm between 3μm and 5μm, with a record low loss of 0.5dB/cm at a wavelength of 4.75μm. By launching picosecond pulses between 3.25μm and 4.75μm into the waveguides and measuring both their self-phase modulation and nonlinear transmission we find that nonlinear losses can be significant in this wavelength range due to free-carrier absorption induced by multi-photon absorption. This should be considered when engineering SiGe photonic devices for nonlinear applications in the mid-IR.

Experimental characterization of hydrogenated amorphous silicon photonic crystal waveguides

Summary form only given. Photonic crystal (PhC) slab waveguides are very compact structures that are able to tightly confine light. This property makes them fundamental in the conception of highly integrated photonic devices. In our work we report the first experimental results, to our knowledge, of PhC waveguides fabricated using the hydrogenated amorphous silicon (a-Si:H) platform. From recent investigations, a-Si:H has emerged as a possible new material platform for nonlinear photonics [1-4]. The associated fabrication process can be fully CMOS compatible. Furthermore, a-Si:H can exhibit both high nonlinear Kerr index (n2) and low two-photon absorption (βTPA) at telecom wavelengths. Its nonlinear figure of merit (FOM=n2/ (βTPA*λ)) can be as high as 5 [4], which is critical for creating efficient nonlinear photonic devices. In comparison, crystalline silicon (c-Si) exhibit a high Kerr coefficient but its poor FOM (~0.3-0.5) prevents it from being used in some applications.