Nathalie Vermeulen | Universiteit Gent and Vrije Universiteit Brussel (original) (raw)
Papers by Nathalie Vermeulen
Journal of Physics: Photonics, 2018
We present a theoretical framework for nonlinear optics of graphene and other 2D materials in lay... more We present a theoretical framework for nonlinear optics of graphene and other 2D materials in layered structures. We derive a key equation to find the effective electric field and the sheet current density in the 2D material for given incident light beams. Our approach takes into account the effect of the surrounding environment and characterizes its contribution as a structure factor. We apply our approach to two experimental setups, and discuss the structure factors for several nonlinear optical processes including second harmonic generation, third harmonic generation, and parametric frequency conversion. Our systematic study gives a strict extraction method for the nonlinear coefficients, and provides new insights in how layered structures influence the nonlinear signal observed from 2D materials.
We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulat... more We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. We show by means of Raman spectroscopy and atomic force microscopy that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method. © 2015 Optical Society of America OCIS codes: (140.7090) Ultrafast lasers; (140.3390) Laser materials processing; (130.3120) Integrated optics devices. References and links 1. J.L. Cheng, N. Vermeulen, and J.E. Sipe, “Third order optical nonlinearity of graphene,” New J. Phys. 16, 053014 (2014)....
Novel nonlinear photonic functionalities in silicon nanowires
2012 Optical Interconnects Conference, 2012
ABSTRACT
Energy-per-bit and noise limits in plasmonic intergrated photodetectors
Integrated Optics: Physics and Simulations, 2013
ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for com... more ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications VI, 2007
ABSTRACT
Optical characterization of semiconductor microlenses using a Mach-Zehnder interferometer in the near-infrared region
We present a Mach-Zehnder interferometer to characterize semiconductor microlenses in transmissio... more We present a Mach-Zehnder interferometer to characterize semiconductor microlenses in transmission. We therefore make use of a wavelength of 1550nm with the possibility of expansion towards the IR spectrum. In this paper, the concept of our interferometer as well as the set-up is explained. We demonstrate the working principle and measurements on fused silica and silicon microlenses and benchmark the experimental results with measurement data obtained with well established micro-optics instrumentation tools.
Progress In Electromagnetics Research, 2013
Mitigating Heat Dissipation in Raman Lasers Using Coherent Anti-Stokes Raman Scattering
Physical Review Letters, 2007
We present a novel technique that intrinsically mitigates the quantum-defect heating in Raman las... more We present a novel technique that intrinsically mitigates the quantum-defect heating in Raman lasers. The basic principle of this so-called "coherent anti-Stokes Raman scattering (CARS)-based heat mitigation" is to suppress the phonon creation in the Raman medium by increasing the number of out-coupled anti-Stokes photons with respect to the number of out-coupled Stokes photons. We demonstrate with the aid of numerical simulations that for a hydrogen and a silicon Raman laser, CARS-based heat mitigation efficiencies of at least 30% and 35%, respectively, can be obtained.
Physical Review B, 2011
The prospect for low pump-power Raman amplification in silicon waveguides has recently been boost... more The prospect for low pump-power Raman amplification in silicon waveguides has recently been boosted by theoretical studies discussing the enhancement of nonlinear phenomena in slow-light structures. In principle, the slowing down of either the pump or the signal beam is equivalent in terms of Raman gain, but in the presence of losses, we show that they play different roles in determining the net signal gain. We also investigate the impact of the mode profile in realistic slow-light waveguides on the total gain, an effect that is usually neglected in the context of stimulated Raman scattering. By taking representative losses and mode shapes into account, we provide a realistic estimation of the achievable performance of slow-light photonic crystal waveguides.
Optics Express, 2014
We present an iterative design method for the coupling and the mode conversion of arbitrary modes... more We present an iterative design method for the coupling and the mode conversion of arbitrary modes to focused surface plasmons using a large array of aperiodically randomly located slits in a thin metal film. As the distance between the slits is small and the number of slits is large, significant mutual coupling occurs between the slits which makes an accurate computation of the field scattered by the slits difficult. We use an accurate modal source radiator model to efficiently compute the fields in a significantly shorter time compared with three-dimensional (3D) full-field rigorous simulations, so that iterative optimization is efficiently achieved. Since our model accounts for mutual coupling between the slits, the scattering by the slits of both the source wave and the focused surface plasmon can be incorporated in the optimization scheme. We apply this method to the design of various types of couplers for arbitrary fiber modes and a mode demultiplexer that focuses three orthogonal fiber modes to three different foci. Finally, we validate our design results using fully vectorial 3D finite-difference time-domain (FDTD) simulations.
Optics Express, 2011
We present a generic approach to determine the phase mismatch for any optical nonlinear process. ... more We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying this approach, which is based on the evaluation of local phase changes, to Raman-and Kerr-based four-wave mixing in silicon waveguides, we obtain an expression for the phase mismatch which is more accurate as compared to the conventional definition; and which contains additional contributions due to the dispersion of the four-wave-mixing processes. Furthermore, starting from the general propagation equations for the involved pump, Stokes and anti-Stokes waves, we investigate the impact of this four-wave-mixing dispersion in silicon waveguides and examine how it is influenced by changing the frequency difference between the pump and Stokes input waves. We show by means of numerical simulations that, by detuning this frequency difference slightly away from Raman resonance, the four-wave-mixing conversion efficiency can be more than doubled, but can also lead to a decrease in efficiency of more than 10 dB. We also discuss how the pump-Stokes frequency difference that is optimal for wavelength conversion varies with the length of the silicon waveguides and with their dispersion characteristics. Finally, starting from the newly introduced phase mismatch formula we simplify the set of propagation equations such that they are less computationally intensive to solve while still giving accurate estimates of the optimal pump-Stokes frequency difference and the corresponding wavelength conversion efficiency.
Optics Communications, 2006
We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thuliu... more We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 • 10 18 cm À3 was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF 2 prism and a single set of optics.
Low-loss wavelength tuning of a mid-infrared Cr2+:ZnSe laser using a Littrow-mounted resonant diffraction grating
Laser Physics Letters, 2011
ABSTRACT We report the first demonstration of resonant-grating-based laser wavelength tuning in t... more ABSTRACT We report the first demonstration of resonant-grating-based laser wavelength tuning in the mid-infrared spectral domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe laser that this tuning technique is much more wavelength selective than prism-based tuning, while inducing very low cavity losses (around 2%), which are at least two times smaller than in the case of a standard metal grating. Furthermore, the resonant grating allows tuning the Cr:ZnSe laser over as much as 400 nm around a center wavelength of 2.38 µm. This shows the potential of employing Littrow-mounted resonant diffraction gratings for controlling and tuning the emission wavelength of lasers emitting in the mid-infrared spectral domain and other wavelength regions. (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Coherent anti-Stokes Raman scattering in Raman lasers and Raman wavelength converters
Laser & Photonics Reviews, 2010
ABSTRACT
Enhancement methods for CARS-based heat mitigation and application to near- and mid-infrared silicon-based Raman lasers
We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel ... more We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel approach for reducing the quantum-defect heating in Raman lasers. More specifically, we discuss the influence of the CARS-related phase mismatch and of backward Raman scattering on our CARS-based heat mitigation technique and explain how these heat-mitigation-affecting factors should be managed to enhance the effectiveness of our technique. To illustrate the feasibility of obtaining efficient CARS-based heat mitigation, we discuss to what extent the described effectiveness-enhancing methods can be applied to near- and mid-infrared silicon-based Raman lasers. Finally, we numerically demonstrate that for near-infrared silicon-based Raman lasers a heat mitigation efficiency of 15% can be obtained, whereas the corresponding efficiency for their mid-infrared counterparts can be as high as 35%.
IEEE Photonics Technology Letters, 2000
We propose a silicon ring Raman converter based on a low-loss nanowire ring, in which the spatial... more We propose a silicon ring Raman converter based on a low-loss nanowire ring, in which the spatial variation of the Raman gain for transverse-electric polarization is used to quasi-phase-match the wavelength conversion process. When using the intrinsic silicon-on-insulator platform, this quasi-phase-matching scheme, combined with the low propagation losses, can give rise to conversion efficiencies that exceed 0 dB at modest pump powers, and that are more than 6 dB higher than those of silicon ring Raman converters in which perfect phase-matching is established through dispersion engineering.
Modeling mid-infrared continuous-wave silicon-based Raman lasers
We present the first modeling results for the Stokes and anti-Stokes output of a mid-infrared con... more We present the first modeling results for the Stokes and anti-Stokes output of a mid-infrared continuous-wave silicon-based Raman laser. These emission characteristics are generated by the use of an iterative resonator model, the loss terms of which we adapted for the case of silicon-based Raman lasers operating in the mid-infrared spectral domain. These loss terms contain besides linear losses also
Energy-per-bit and noise limits in plasmonic intergrated photodetectors
ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for com... more ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
Continuous-wave fiber-pumped Cr: ZnSe laser
ABSTRACT
We present a generic approach to determine the phase mismatch for any optical nonlinear process. ... more We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying this approach, which is based on the evaluation of local phase changes, to Raman- and Kerr-based four-wave mixing in silicon waveguides, we obtain an expression for the phase mismatch which is more accurate as compared to the conventional definition; and which contains additional contributions due to the dispersion of the four-wave-mixing processes. Furthermore, starting from the general propagation equations for the involved pump, Stokes and anti-Stokes waves, we investigate the impact of this four-wave-mixing dispersion in silicon waveguides and examine how it is influenced by changing the frequency difference between the pump and Stokes input waves. We show by means of numerical simulations that, by detuning this frequency difference slightly away from Raman resonance, the four-wave-mixing conversion efficiency can be more than doubled, but can also lead to a decrease in...
Journal of Physics: Photonics, 2018
We present a theoretical framework for nonlinear optics of graphene and other 2D materials in lay... more We present a theoretical framework for nonlinear optics of graphene and other 2D materials in layered structures. We derive a key equation to find the effective electric field and the sheet current density in the 2D material for given incident light beams. Our approach takes into account the effect of the surrounding environment and characterizes its contribution as a structure factor. We apply our approach to two experimental setups, and discuss the structure factors for several nonlinear optical processes including second harmonic generation, third harmonic generation, and parametric frequency conversion. Our systematic study gives a strict extraction method for the nonlinear coefficients, and provides new insights in how layered structures influence the nonlinear signal observed from 2D materials.
We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulat... more We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. We show by means of Raman spectroscopy and atomic force microscopy that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method. © 2015 Optical Society of America OCIS codes: (140.7090) Ultrafast lasers; (140.3390) Laser materials processing; (130.3120) Integrated optics devices. References and links 1. J.L. Cheng, N. Vermeulen, and J.E. Sipe, “Third order optical nonlinearity of graphene,” New J. Phys. 16, 053014 (2014)....
Novel nonlinear photonic functionalities in silicon nanowires
2012 Optical Interconnects Conference, 2012
ABSTRACT
Energy-per-bit and noise limits in plasmonic intergrated photodetectors
Integrated Optics: Physics and Simulations, 2013
ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for com... more ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications VI, 2007
ABSTRACT
Optical characterization of semiconductor microlenses using a Mach-Zehnder interferometer in the near-infrared region
We present a Mach-Zehnder interferometer to characterize semiconductor microlenses in transmissio... more We present a Mach-Zehnder interferometer to characterize semiconductor microlenses in transmission. We therefore make use of a wavelength of 1550nm with the possibility of expansion towards the IR spectrum. In this paper, the concept of our interferometer as well as the set-up is explained. We demonstrate the working principle and measurements on fused silica and silicon microlenses and benchmark the experimental results with measurement data obtained with well established micro-optics instrumentation tools.
Progress In Electromagnetics Research, 2013
Mitigating Heat Dissipation in Raman Lasers Using Coherent Anti-Stokes Raman Scattering
Physical Review Letters, 2007
We present a novel technique that intrinsically mitigates the quantum-defect heating in Raman las... more We present a novel technique that intrinsically mitigates the quantum-defect heating in Raman lasers. The basic principle of this so-called "coherent anti-Stokes Raman scattering (CARS)-based heat mitigation" is to suppress the phonon creation in the Raman medium by increasing the number of out-coupled anti-Stokes photons with respect to the number of out-coupled Stokes photons. We demonstrate with the aid of numerical simulations that for a hydrogen and a silicon Raman laser, CARS-based heat mitigation efficiencies of at least 30% and 35%, respectively, can be obtained.
Physical Review B, 2011
The prospect for low pump-power Raman amplification in silicon waveguides has recently been boost... more The prospect for low pump-power Raman amplification in silicon waveguides has recently been boosted by theoretical studies discussing the enhancement of nonlinear phenomena in slow-light structures. In principle, the slowing down of either the pump or the signal beam is equivalent in terms of Raman gain, but in the presence of losses, we show that they play different roles in determining the net signal gain. We also investigate the impact of the mode profile in realistic slow-light waveguides on the total gain, an effect that is usually neglected in the context of stimulated Raman scattering. By taking representative losses and mode shapes into account, we provide a realistic estimation of the achievable performance of slow-light photonic crystal waveguides.
Optics Express, 2014
We present an iterative design method for the coupling and the mode conversion of arbitrary modes... more We present an iterative design method for the coupling and the mode conversion of arbitrary modes to focused surface plasmons using a large array of aperiodically randomly located slits in a thin metal film. As the distance between the slits is small and the number of slits is large, significant mutual coupling occurs between the slits which makes an accurate computation of the field scattered by the slits difficult. We use an accurate modal source radiator model to efficiently compute the fields in a significantly shorter time compared with three-dimensional (3D) full-field rigorous simulations, so that iterative optimization is efficiently achieved. Since our model accounts for mutual coupling between the slits, the scattering by the slits of both the source wave and the focused surface plasmon can be incorporated in the optimization scheme. We apply this method to the design of various types of couplers for arbitrary fiber modes and a mode demultiplexer that focuses three orthogonal fiber modes to three different foci. Finally, we validate our design results using fully vectorial 3D finite-difference time-domain (FDTD) simulations.
Optics Express, 2011
We present a generic approach to determine the phase mismatch for any optical nonlinear process. ... more We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying this approach, which is based on the evaluation of local phase changes, to Raman-and Kerr-based four-wave mixing in silicon waveguides, we obtain an expression for the phase mismatch which is more accurate as compared to the conventional definition; and which contains additional contributions due to the dispersion of the four-wave-mixing processes. Furthermore, starting from the general propagation equations for the involved pump, Stokes and anti-Stokes waves, we investigate the impact of this four-wave-mixing dispersion in silicon waveguides and examine how it is influenced by changing the frequency difference between the pump and Stokes input waves. We show by means of numerical simulations that, by detuning this frequency difference slightly away from Raman resonance, the four-wave-mixing conversion efficiency can be more than doubled, but can also lead to a decrease in efficiency of more than 10 dB. We also discuss how the pump-Stokes frequency difference that is optimal for wavelength conversion varies with the length of the silicon waveguides and with their dispersion characteristics. Finally, starting from the newly introduced phase mismatch formula we simplify the set of propagation equations such that they are less computationally intensive to solve while still giving accurate estimates of the optimal pump-Stokes frequency difference and the corresponding wavelength conversion efficiency.
Optics Communications, 2006
We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thuliu... more We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 • 10 18 cm À3 was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF 2 prism and a single set of optics.
Low-loss wavelength tuning of a mid-infrared Cr2+:ZnSe laser using a Littrow-mounted resonant diffraction grating
Laser Physics Letters, 2011
ABSTRACT We report the first demonstration of resonant-grating-based laser wavelength tuning in t... more ABSTRACT We report the first demonstration of resonant-grating-based laser wavelength tuning in the mid-infrared spectral domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe laser that this tuning technique is much more wavelength selective than prism-based tuning, while inducing very low cavity losses (around 2%), which are at least two times smaller than in the case of a standard metal grating. Furthermore, the resonant grating allows tuning the Cr:ZnSe laser over as much as 400 nm around a center wavelength of 2.38 µm. This shows the potential of employing Littrow-mounted resonant diffraction gratings for controlling and tuning the emission wavelength of lasers emitting in the mid-infrared spectral domain and other wavelength regions. (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Coherent anti-Stokes Raman scattering in Raman lasers and Raman wavelength converters
Laser & Photonics Reviews, 2010
ABSTRACT
Enhancement methods for CARS-based heat mitigation and application to near- and mid-infrared silicon-based Raman lasers
We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel ... more We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel approach for reducing the quantum-defect heating in Raman lasers. More specifically, we discuss the influence of the CARS-related phase mismatch and of backward Raman scattering on our CARS-based heat mitigation technique and explain how these heat-mitigation-affecting factors should be managed to enhance the effectiveness of our technique. To illustrate the feasibility of obtaining efficient CARS-based heat mitigation, we discuss to what extent the described effectiveness-enhancing methods can be applied to near- and mid-infrared silicon-based Raman lasers. Finally, we numerically demonstrate that for near-infrared silicon-based Raman lasers a heat mitigation efficiency of 15% can be obtained, whereas the corresponding efficiency for their mid-infrared counterparts can be as high as 35%.
IEEE Photonics Technology Letters, 2000
We propose a silicon ring Raman converter based on a low-loss nanowire ring, in which the spatial... more We propose a silicon ring Raman converter based on a low-loss nanowire ring, in which the spatial variation of the Raman gain for transverse-electric polarization is used to quasi-phase-match the wavelength conversion process. When using the intrinsic silicon-on-insulator platform, this quasi-phase-matching scheme, combined with the low propagation losses, can give rise to conversion efficiencies that exceed 0 dB at modest pump powers, and that are more than 6 dB higher than those of silicon ring Raman converters in which perfect phase-matching is established through dispersion engineering.
Modeling mid-infrared continuous-wave silicon-based Raman lasers
We present the first modeling results for the Stokes and anti-Stokes output of a mid-infrared con... more We present the first modeling results for the Stokes and anti-Stokes output of a mid-infrared continuous-wave silicon-based Raman laser. These emission characteristics are generated by the use of an iterative resonator model, the loss terms of which we adapted for the case of silicon-based Raman lasers operating in the mid-infrared spectral domain. These loss terms contain besides linear losses also
Energy-per-bit and noise limits in plasmonic intergrated photodetectors
ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for com... more ABSTRACT The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
Continuous-wave fiber-pumped Cr: ZnSe laser
ABSTRACT
We present a generic approach to determine the phase mismatch for any optical nonlinear process. ... more We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying this approach, which is based on the evaluation of local phase changes, to Raman- and Kerr-based four-wave mixing in silicon waveguides, we obtain an expression for the phase mismatch which is more accurate as compared to the conventional definition; and which contains additional contributions due to the dispersion of the four-wave-mixing processes. Furthermore, starting from the general propagation equations for the involved pump, Stokes and anti-Stokes waves, we investigate the impact of this four-wave-mixing dispersion in silicon waveguides and examine how it is influenced by changing the frequency difference between the pump and Stokes input waves. We show by means of numerical simulations that, by detuning this frequency difference slightly away from Raman resonance, the four-wave-mixing conversion efficiency can be more than doubled, but can also lead to a decrease in...