Ultrafast all-optical switching in a silicon-based photonic crystal
TL;DR: In this paper, the effect of two-photon absorption and Kerr nonlinearity on the optical properties of a one-dimensional photonic crystal made with amorphous silicon and SiO2 was studied.
Abstract: We study the effect of two-photon absorption and Kerr nonlinearity on the optical properties of a one-dimensional photonic crystal made with amorphous silicon and SiO2. A stop band appearing near 1.5 μm is monitored with a weak probe beam and modulated by changes in the refractive index caused by a pump pulse at 1.71 μm with 18 GW/cm2 peak intensity. Nonlinear optical characterization of the sample using Z-scan points out to two-photon absorption as the main contributor to free carrier excitation in silicon at that power level. Modulation in the transmittance near the band edge is found to be dominated by the optical Kerr effect within the pulse overlap (∼400 fs) whereas free carrier index changes are observed for 12 ps.
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TL;DR: The experimental demonstration of fast all-optical switching on silicon using highly light-confining structures to enhance the sensitivity of light to small changes in refractive index and confirm the recent theoretical prediction of efficient optical switching in silicon using resonant structures.
Abstract: Photonic circuits, in which beams of light redirect the flow of other beams of light, are a long-standing goal for developing highly integrated optical communication components1,2,3. Furthermore, it is highly desirable to use silicon—the dominant material in the microelectronic industry—as the platform for such circuits. Photonic structures that bend, split, couple and filter light have recently been demonstrated in silicon4,5, but the flow of light in these structures is predetermined and cannot be readily modulated during operation. All-optical switches and modulators have been demonstrated with III–V compound semiconductors6,7, but achieving the same in silicon is challenging owing to its relatively weak nonlinear optical properties. Indeed, all-optical switching in silicon has only been achieved by using extremely high powers8,9,10,11,12,13,14,15 in large or non-planar structures, where the modulated light is propagating out-of-plane. Such high powers, large dimensions and non-planar geometries are inappropriate for effective on-chip integration. Here we present the experimental demonstration of fast all-optical switching on silicon using highly light-confining structures to enhance the sensitivity of light to small changes in refractive index. The transmission of the structure can be modulated by up to 94% in less than 500 ps using light pulses with energies as low as 25 pJ. These results confirm the recent theoretical prediction16 of efficient optical switching in silicon using resonant structures.
1,506 citations
TL;DR: A unified theoretical platform that not only can be used for understanding the underlying physics but should also provide guidance toward new and useful applications is provided.
Abstract: Several kinds of nonlinear optical effects have been observed in recent years using silicon waveguides, and their device applications are attracting considerable attention. In this review, we provide a unified theoretical platform that not only can be used for understanding the underlying physics but should also provide guidance toward new and useful applications. We begin with a description of the third-order nonlinearity of silicon and consider the tensorial nature of both the electronic and Raman contributions. The generation of free carriers through two-photon absorption and their impact on various nonlinear phenomena is included fully within the theory presented here. We derive a general propagation equation in the frequency domain and show how it leads to a generalized nonlinear Schrodinger equation when it is converted to the time domain. We use this equation to study propagation of ultrashort optical pulses in the presence of self-phase modulation and show the possibility of soliton formation and supercontinuum generation. The nonlinear phenomena of cross-phase modulation and stimulated Raman scattering are discussed next with emphasis on the impact of free carriers on Raman amplification and lasing. We also consider the four-wave mixing process for both continuous-wave and pulsed pumping and discuss the conditions under which parametric amplification and wavelength conversion can be realized with net gain in the telecommunication band.
877 citations
TL;DR: In this paper, the authors describe the way in which strongly modulated photonic crystals differ from other optical media, and clarify what they can do, including light confinement, frequency dispersion and spatial dispersion.
Abstract: Recently, strongly modulated photonic crystals, fabricated by the state-of-the-art semiconductor nanofabrication process, have realized various novel optical properties. This paper describes the way in which they differ from other optical media, and clarifies what they can do. In particular, three important issues are considered: light confinement, frequency dispersion and spatial dispersion. First, I describe the latest status and impact of ultra-strong light confinement in a wavelength-cubic volume achieved in photonic crystals. Second, the extreme reduction in the speed of light is reported, which was achieved as a result of frequency dispersion management. Third, strange negative refraction in photonic crystals is introduced, which results from their unique spatial dispersion, and it is clarified how this leads to perfect imaging. The last two sections are devoted to applications of these novel properties. First, I report the fact that strong light confinement and huge light–matter interaction enhancement make strongly modulated photonic crystals promising for on-chip all-optical processing, and present several examples including all-optical switches/memories and optical logics. As a second application, it is shown that the strong light confinement and slow light in strongly modulated photonic crystals enable the adiabatic tuning of light, which leads to various novel ways of controlling light, such as adiabatic frequency conversion, efficient optomechanics systems, photon memories and photons pinning.
403 citations
TL;DR: In this paper, the authors proposed ultrafast and low-power photonic-crystal all-optical switching based on strong optical nonlinearity enhancement due to excited-state interelectron transfer.
Abstract: Photonic crystals, materials with periodic dielectric structures, are able to control the propagation states of photons owing to the so-called photonic-bandgap effect1. Nonlinear photonic crystals, whose refractive-index distribution can be tuned optically, have been used to demonstrate all-optical switching2. However, a high pump intensity is usually required because the nonlinear optical coefficient of conventional materials is relatively small3. Here we report ultrafast and low-power photonic-crystal all-optical switching based on strong optical nonlinearity enhancement due to excited-state interelectron transfer. Compared with the case without nonlinearity enhancement, the switching operation power is reduced by four orders of magnitude while the ultrafast response time, of the order of a picosecond, is maintained. This provides a strategy for constructing photonic materials with large nonlinearity and studying ultrafast low-power integrated photonic devices.
266 citations
Cites background from "Ultrafast all-optical switching in ..."
...However, there exists an upper limit to the intensity of light that can be used before the photonic crystals are destroyed and, unfortunately, high pump intensities, often of the order of GW cm −2 , are required to achieve a large switching efficienc...
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References
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TL;DR: If a three-dimensionally periodic dielectric structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission can be rigorously forbidden.
Abstract: It has been recognized for some time that the spontaneous emission by atoms is not necessarily a fixed and immutable property of the coupling between matter and space, but that it can be controlled by modification of the properties of the radiation field. This is equally true in the solid state, where spontaneous emission plays a fundamental role in limiting the performance of semiconductor lasers, heterojunction bipolar transistors, and solar cells. If a three-dimensionally periodic dielectric structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission can be rigorously forbidden.
12,787 citations
TL;DR: A new mechanism for strong Anderson localization of photons in carefully prepared disordered dielectric superlattices with an everywhere real positive dielectrics constant is described.
Abstract: A new mechanism for strong Anderson localization of photons in carefully prepared disordered dielectric superlattices with an everywhere real positive dielectric constant is described. In three dimensions, two photon mobility edges separate high- and low-frequency extended states from an intermediate-frequency pseudogap of localized states arising from remnant geometric Bragg resonances. Experimentally observable consequences are discussed.
9,067 citations
TL;DR: In this paper, a single-beam technique for measuring both the nonlinear refractive index and nonlinear absorption coefficient for a wide variety of materials is reported, including a comprehensive theoretical analysis.
Abstract: A sensitive single-beam technique for measuring both the nonlinear refractive index and nonlinear absorption coefficient for a wide variety of materials is reported. The authors describe the experimental details and present a comprehensive theoretical analysis including cases where nonlinear refraction is accompanied by nonlinear absorption. In these experiments, the transmittance of a sample is measured through a finite aperture in the far field as the sample is moved along the propagation path (z) of a focused Gaussian beam. The sign and magnitude of the nonlinear refraction are easily deduced from such a transmittance curve (Z-scan). Employing this technique, a sensitivity of better than lambda /300 wavefront distortion is achieved in n/sub 2/ measurements of BaF/sub 2/ using picosecond frequency-doubled Nd:YAG laser pulses. >
7,717 citations
TL;DR: Single crystals of silicon inverse opal with a complete three-dimensional photonic bandgap centred on 1.46 µm are described, produced by growing silicon inside the voids of an opal template of close-packed silica spheres that are connected by small ‘necks’ formed during sintering, followed by removal of the silica template.
Abstract: Photonic technology, using light instead of electrons as the information carrier, is increasingly replacing electronics in communication and information management systems. Microscopic light manipulation, for this purpose, is achievable through photonic bandgap materials1,2, a special class of photonic crystals in which three-dimensional, periodic dielectric constant variations controllably prohibit electromagnetic propagation throughout a specified frequency band. This can result in the localization of photons3,4,5,6, thus providing a mechanism for controlling and inhibiting spontaneous light emission that can be exploited for photonic device fabrication. In fact, carefully engineered line defects could act as waveguides connecting photonic devices in all-optical microchips7, and infiltration of the photonic material with suitable liquid crystals might produce photonic bandgap structures (and hence light-flow patterns) fully tunable by an externally applied voltage8,9,10. However, the realization of this technology requires a strategy for the efficient synthesis of high-quality, large-scale photonic crystals with photonic bandgaps at micrometre and sub-micrometre wavelengths, and with rationally designed line and point defects for optical circuitry. Here we describe single crystals of silicon inverse opal with a complete three-dimensional photonic bandgap centred on 1.46 µm, produced by growing silicon inside the voids of an opal template of close-packed silica spheres that are connected by small ‘necks’ formed during sintering, followed by removal of the silica template. The synthesis method is simple and inexpensive, yielding photonic crystals of pure silicon that are easily integrated with existing silicon-based microelectronics.
1,520 citations
TL;DR: In this paper, the in-plane phase-matching resonances are given by a nonlinear Bragg law and a related nonlinear Ewald construction, which can be used for multiple-beam second-harmonic generation (SHG), ring cavity SHG, or multiple wavelength frequency conversion.
Abstract: Nonlinear frequency conversion in 2D ${\ensuremath{\chi}}^{(2)}$ photonic crystals is theoretically studied. Such a crystal has a 2D periodic nonlinear susceptibility, and a linear susceptibility which is a function of the frequency, but constant in space. It is an in-plane generalization of 1D quasi-phase-matching structures and can be realized in periodic poled lithium niobate or in GaAs. An interesting property of these structures is that new phase-matching processes appear in the 2D plane as compared to the 1D case. It is shown that these in-plane phase-matching resonances are given by a nonlinear Bragg law, and a related nonlinear Ewald construction. Applications as multiple-beam second-harmonic generation (SHG), ring cavity SHG, or multiple wavelength frequency conversion are envisaged.
696 citations