Ultrashort free-carrier lifetime in low-loss silicon nanowaveguides

Turner-Foster, Amy C.; Foster, Mark A.; Levy, Jacob S.; Poitras, Carl B.; Salem, Reza; Gaeta, Alexander L.; Lipson, Michal

doi:10.1364/oe.18.003582

Cited by 194 publications

(137 citation statements)

References 49 publications

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“…At higher data rates, self-phase modulation is compromized 28 and compression cannot occur. To circumvent this problem, methods such as ion implantation 31 or reverse biased P-I-N junctions 32 may be used to greatly reduce free-carrier lifetimes to below 20 ps and in so forth, eliminate free-carrier accumulation at higher data rates. Furthermore, these methods can reduce FCA limitations on nonlinear phase acquisition at higher peak powers.…”

Section: Discussionmentioning

confidence: 99%

Monolithic nonlinear pulse compressor on a silicon chip

2010

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Projected demands in information bandwidth have resulted in a paradigm shift from electrical to optical interconnects. Switches, modulators and wavelength converters have all been demonstrated on complementary metal-oxide semiconductor compatible platforms, and are important for all optical signal and information processing. Similarly, pulse compression is crucial for creating short pulses necessary for key applications in high-capacity communications, imaging and spectroscopy. In this study, we report the first demonstration of a chip-scale, nanophotonic pulse compressor on silicon, operating by nonlinear spectral broadening from self-phase modulation in a nanowire waveguide, followed by temporal compression with an integrated dispersive element. Using a low input peak power of 10 W, we achieve compression factors as high as 7 for 7 ps pulses. This compact and efficient device will enable ultrashort pulse sources to be integrated with systems level photonic circuits necessary for future optoelectronic networks.

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Section: Discussionmentioning

confidence: 99%

Monolithic nonlinear pulse compressor on a silicon chip

2010

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“…(1) and (2) using the split-step Fourier method [19], with values n 2 9 × 10 −14 cm 2 ∕W, γ 3PA 0.025 cm 3 ∕GW 2 , σ 3.7 × 10 −21 m 2 , and μ 4.7, as taken from the literature [22][23][24]. We use a value of 10 ns for the free-carrier lifetime, taken as an upper estimate from the measurements of smaller but similar devices [25].…”

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confidence: 99%

Octave-spanning mid-infrared supercontinuum generation in silicon nanowaveguides

et al. 2014

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We report, to the best of our knowledge, the first demonstration of octave-spanning supercontinuum generation (SCG) on a silicon chip, spanning from the telecommunications c-band near 1.5 μm to the mid-infrared region beyond 3.6 μm. The SCG presented here is characterized by soliton fission and dispersive radiation across two zero group-velocity dispersion wavelengths. In addition, we numerically investigate the role of multiphoton absorption and free carriers, confirming that these nonlinear loss mechanisms are not detrimental to SCG in this regime. It is well known that pumping in the anomalous wavelength region near the zero group-velocity dispersion (ZGVD) wavelength may result in broadband SCG predominantly governed by soliton fission and dispersive wave generation [5]. Furthermore, it has been shown theoretically and experimentally that under suitable conditions, a second ZGVD wavelength on the opposite side of the pump will result in even broader SCG due to the generation of redshifted dispersive waves [3,4]. While silicon-based SCG in the MIR wavelength range has been previously demonstrated [11,12], the generated spectrum was limited to 990 nm, as the spectral broadening was mainly due to modulation instability with a single dispersive wave at lower wavelengths.In this Letter, we present a fundamentally different SCG, characterized by soliton fission and dispersive radiation across both ZGVD wavelengths, which enables us to achieve MIR spectra spanning 1.3 octaves, from 1.51 to 3.67 μm, in a silicon wire waveguide. This demonstration represents, to the best of our knowledge, the first octave-spanning SCG from a silicon chip.The silicon-on-insulator (SOI) waveguide used in our experiments has a cross section of 320 nm by 1210 nm, and a length of 2 cm, and is engineered to exhibit a ZGVD wavelength on each side of the 2.5 μm pump. Figure 1 shows the group-velocity dispersion (GVD) of the waveguide for the fundamental transverse electric (TE) mode, modeled using a custom finitedifference mode solver. The GVD is anomalous within the tuning range of the pump and falls to zero near 2.1 and 3.0 μm. The waveguide cross section and mode profile at λ 2.5 μm are shown in the inset. Fig. 1. Simulated group-velocity dispersion (GVD) curve for fundamental TE mode of an SOI waveguide with a cross section of 320 nm by 1210 nm, which results in anomalous GVD near the pump wavelength of 2.5 μm and zero-GVD wavelengths near 2.1 and 3.0 μm. The waveguide cross section and the mode profile are shown in the inset.

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“…In order to arrive to a stable multisoliton comb, it is necessary to properly adjust the FCT (here τ eff 320 ps). As shown in [3,18], this can be achieved by tuning the reverse bias voltage applied to a PIN structure embedding the microring: τ eff 320 ps corresponds to about 2 V bias.…”

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confidence: 99%

Mid-infrared soliton and Raman frequency comb generation in silicon microrings

2014

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We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cwpumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described. higher nonlinearity compared to silica, coupled with vanishing two-photon absorption (TPA) and associated free-carrier absorption (FCA) and dispersion (FCD) for photon energies below the silicon half-bandgap [2]. Recent experiments have demonstrated that siliconchip-based MIR frequency comb generation is critically dependent upon the possibility of reducing the lifetime of free carriers generated by three-photon absorption (3PA) [3]. In this work we present a numerical study of MIR frequency comb generation in silicon microresonators, which demonstrates that a proper control of the free-carrier lifetime (FCT) may enable a new route for stable soliton self-mode-locking of the comb. Indeed, multiphoton-absorption-induced FCD introduces a dynamic nonlinear cavity detuning, which replaces the need for a nonzero linear cavity detuning [4,5]. We also predict the highly efficient generation of MIR Raman frequency combs [6] from silicon microresonators.Time dynamics of frequency comb generation in silicon microresonators is described by a generalized nonlinear envelope equation for the field envelope A W p ∕m, which includes linear loss and dispersion, the Kerr effect, Raman scattering, TPA and 3PA, FCA and FCD [2,[5][6][7][8][9][10],coupled with the evolution equation for the averaged carrier density hN c τi,where τ is a continuous (slow) temporal variable that replaces the round-trip number, v g c∕n g and n g are the group velocity and refractive index at the pump carrier frequency ω 0 , k 0 ω 0 ∕c, τ sh 1∕ω 0 , and t is a retarded (fast) time. In Eq. (2), brackets denote average over the cavity circulation time t R : hXτi 1∕t R R t R ∕2 −t R ∕2 Xt; τdt, so that Eq. (2) describes the buildup of carriers within the cavity over many round trips, supposing that the FCT τ eff ≫ t R . The group-velocity dispersion (GVD) operator D reads asIn Eq.(1) the linear loss coefficient α α 0 ∕L with α 0 α d L θ∕2, α d represents distributed cavity loss and θ is the transmission coefficient between the resonator of length L and the bus waveguide. Moreover, σ is the FCA coefficient, μ is the FCD coefficient, β TPA is the TPA coefficient, δ 0 δ 0 ∕L ω R − ω 0 t R ∕L is the linear cavity detuning (where ω R is the closest linear cavity resonance to the pump frequency ω 0 ), f 0 θ p ∕LA in and A in the injected cw pump amplitude. The cavity boundary conditions impose the field to be t-periodic with period t R , i.e., Aτ; t Aτ; t t R . The nonlinear polarization reads as where ⊗ denotes convolution product, n 2 is the nonlinear index, and γ R is the Ra...

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Ultrashort free-carrier lifetime in low-loss silicon nanowaveguides

Cited by 194 publications

References 49 publications

Monolithic nonlinear pulse compressor on a silicon chip

Monolithic nonlinear pulse compressor on a silicon chip

Octave-spanning mid-infrared supercontinuum generation in silicon nanowaveguides

Mid-infrared soliton and Raman frequency comb generation in silicon microrings

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