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Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides.

Husko C, Wulf M, Lefrancois S, Combrié S, Lehoucq G, De Rossi A, Eggleton BJ, Kuipers L - Nat Commun (2016)

Bottom Line: We develop an analytic formalism describing the free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude.We confirm these observations with a numerical nonlinear Schrödinger equation model.These results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), Institute of Photonics and Optical Science (IPOS), School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia.

ABSTRACT
Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing the free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrödinger equation model. These results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.

No MeSH data available.


Related in: MedlinePlus

Spectral transmission and time-resolved near-field microscopy of soliton fission.(a) Spectral transmission properties of the optical pulse measured at the waveguide output. (b) Time-resolved near-field optical microscope (NSOM) apparatus used in the experiment. (c) Experimental cross-correlation measurements as a function of power (vertical axis) at two spatial positions along the nanostructured photonic waveguide. It is clear that as the power is increased a break up of the pulse occurs as it propagates.
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f1: Spectral transmission and time-resolved near-field microscopy of soliton fission.(a) Spectral transmission properties of the optical pulse measured at the waveguide output. (b) Time-resolved near-field optical microscope (NSOM) apparatus used in the experiment. (c) Experimental cross-correlation measurements as a function of power (vertical axis) at two spatial positions along the nanostructured photonic waveguide. It is clear that as the power is increased a break up of the pulse occurs as it propagates.

Mentions: The structure under study is a two-dimensional PhCWG made of air-holes etched in a GaInP slab (see Methods, Supplementary Note 1 and Supplementary Table 1 for additional details). These structures are known to enhance the nonlinear optical properties due to slow light in the periodic medium18. We note the increased group index ng=15.1 is achieved using the dispersion-engineered design outlined in ref. 19 in a region away from the band edge so as to avoid scattering losses20 and minimize TOD21. The earliest investigations of nonlinear evolution of optical pulses in PhCWGs examined the pulse spectra after the pulse propagated through the waveguide22. Figure 1a shows the measured spectral transmission in our current experiment (solid) at the waveguide output for low and high power levels for the optical pulse of 2.2 ps (TFWHM, full-width at half-maximum of a hyperbolic secant). Note that the oscillations in the measured spectra arise from disorder in the periodic media20. The measured waveguide transmission spectrum is shown as Supplementary Fig. 1. The dashed curves are the result of model calculations detailed below. Spectra measured at different power levels are shown in Supplementary Fig. 2 and described in Supplementary Note 2. We observe a clear spectral blueshift at high power due to FCD7, as well as a less intense satellite peak. Such satellite peaks have in the past been attributed to soliton fission in fibres, though no similar observations in semiconductor waveguides have been reported to date.


Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides.

Husko C, Wulf M, Lefrancois S, Combrié S, Lehoucq G, De Rossi A, Eggleton BJ, Kuipers L - Nat Commun (2016)

Spectral transmission and time-resolved near-field microscopy of soliton fission.(a) Spectral transmission properties of the optical pulse measured at the waveguide output. (b) Time-resolved near-field optical microscope (NSOM) apparatus used in the experiment. (c) Experimental cross-correlation measurements as a function of power (vertical axis) at two spatial positions along the nanostructured photonic waveguide. It is clear that as the power is increased a break up of the pulse occurs as it propagates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835551&req=5

f1: Spectral transmission and time-resolved near-field microscopy of soliton fission.(a) Spectral transmission properties of the optical pulse measured at the waveguide output. (b) Time-resolved near-field optical microscope (NSOM) apparatus used in the experiment. (c) Experimental cross-correlation measurements as a function of power (vertical axis) at two spatial positions along the nanostructured photonic waveguide. It is clear that as the power is increased a break up of the pulse occurs as it propagates.
Mentions: The structure under study is a two-dimensional PhCWG made of air-holes etched in a GaInP slab (see Methods, Supplementary Note 1 and Supplementary Table 1 for additional details). These structures are known to enhance the nonlinear optical properties due to slow light in the periodic medium18. We note the increased group index ng=15.1 is achieved using the dispersion-engineered design outlined in ref. 19 in a region away from the band edge so as to avoid scattering losses20 and minimize TOD21. The earliest investigations of nonlinear evolution of optical pulses in PhCWGs examined the pulse spectra after the pulse propagated through the waveguide22. Figure 1a shows the measured spectral transmission in our current experiment (solid) at the waveguide output for low and high power levels for the optical pulse of 2.2 ps (TFWHM, full-width at half-maximum of a hyperbolic secant). Note that the oscillations in the measured spectra arise from disorder in the periodic media20. The measured waveguide transmission spectrum is shown as Supplementary Fig. 1. The dashed curves are the result of model calculations detailed below. Spectra measured at different power levels are shown in Supplementary Fig. 2 and described in Supplementary Note 2. We observe a clear spectral blueshift at high power due to FCD7, as well as a less intense satellite peak. Such satellite peaks have in the past been attributed to soliton fission in fibres, though no similar observations in semiconductor waveguides have been reported to date.

Bottom Line: We develop an analytic formalism describing the free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude.We confirm these observations with a numerical nonlinear Schrödinger equation model.These results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), Institute of Photonics and Optical Science (IPOS), School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia.

ABSTRACT
Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing the free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrödinger equation model. These results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.

No MeSH data available.


Related in: MedlinePlus