The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kent D Choquette - One of the best experts on this subject based on the ideXlab platform.
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vertical cavity surface emitting laser operating with photonic crystal seven Point Defect structure
Applied Physics Letters, 2003Co-Authors: Noriyuki Yokouchi, Aaron J Danner, Kent D ChoquetteAbstract:A vertical-cavity surface-emitting laser with a two-dimensional photonic crystal (PC) structure has been investigated for single lateral mode operation. The PC confined mode can be controlled by the lattice constant, the hole diameter, the etching depth, and the Defect structure. A seven-Point Defect structure is proposed to enhance the confinement effect, which is diluted by finite hole depth of the PC structure. We obtained a pure PC confined mode under room-temperature cw conditions with a PC lattice constant of 2 μm, hole diameters of 1.0 and 1.4 μm, and depths of 1.85 and 1.92 μm, respectively.
Susumu Noda - One of the best experts on this subject based on the ideXlab platform.
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time domain response of Point Defect cavities in two dimensional photonic crystal slabs using picosecond light pulse
Applied Physics Letters, 2006Co-Authors: Takashi Asano, Wataru Kunishi, Bongshik Song, Susumu NodaAbstract:Time-domain responses of Point-Defect cavities in two-dimensional photonic crystal slabs are directly investigated. Point-Defect cavities are excited by picosecond light pulses and time evolutions of the light emissions are measured by using cross-correlation method. The obtained signals clearly show delays in initial rises and tailings in later stages which reflect photon lifetimes of the cavities. The signals are analyzed by comparing with numerical simulations where Gaussian input pulses and linear responses of the systems are assumed. Photon lifetimes are evaluated to be <1, 3, and 9ps for the Point-Defect cavities having Q factors of 500, 3800, and 10 000, respectively. We believe that the results obtained here will contribute to the time-domain manipulation of photons utilizing artificial Defects in photonic crystals.Time-domain responses of Point-Defect cavities in two-dimensional photonic crystal slabs are directly investigated. Point-Defect cavities are excited by picosecond light pulses and time evolutions of the light emissions are measured by using cross-correlation method. The obtained signals clearly show delays in initial rises and tailings in later stages which reflect photon lifetimes of the cavities. The signals are analyzed by comparing with numerical simulations where Gaussian input pulses and linear responses of the systems are assumed. Photon lifetimes are evaluated to be <1, 3, and 9ps for the Point-Defect cavities having Q factors of 500, 3800, and 10 000, respectively. We believe that the results obtained here will contribute to the time-domain manipulation of photons utilizing artificial Defects in photonic crystals.
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investigation of Point Defect cavity formed in two dimensional photonic crystal slab with one sided dielectric cladding
Applied Physics Letters, 2006Co-Authors: Yoshinori Tanaka, Takashi Asano, Ranko Hatsuta, Susumu NodaAbstract:Three-missing-hole Point-Defect cavities formed in a two-dimensional photonic crystal slab with a silicon-on-insulator structure are investigated. It is theoretically revealed that radiation loss to the SiO2-cladding side is four times higher than that to the air-cladding side due to the smaller refractive index contrast. In addition, in-plane radiation due to transverse electric-transverse magnetic (TE-TM) coupling occurs due to the vertical structural asymmetry. The amount of TE-TM coupling loss is comparable with that of radiation loss to the SiO2 cladding. Experimental results agreed well with theoretical predictions. This treatment can be applied to Point-Defect cavities in one-sided dielectric cladding structures and in three-dimensional configurations.
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investigation of Point Defect cavity formed in two dimensional photonic crystal slab with one sided dielectric cladding
Applied Physics Letters, 2006Co-Authors: Yoshinori Tanaka, Takashi Asano, Ranko Hatsuta, Susumu NodaAbstract:Three-missing-hole Point-Defect cavities formed in a two-dimensional photonic crystal slab with a silicon-on-insulator structure are investigated. It is theoretically revealed that radiation loss to the SiO2-cladding side is four times higher than that to the air-cladding side due to the smaller refractive index contrast. In addition, in-plane radiation due to transverse electric-transverse magnetic (TE-TM) coupling occurs due to the vertical structural asymmetry. The amount of TE-TM coupling loss is comparable with that of radiation loss to the SiO2 cladding. Experimental results agreed well with theoretical predictions. This treatment can be applied to Point-Defect cavities in one-sided dielectric cladding structures and in three-dimensional configurations.
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line Defect waveguide laser integrated with a Point Defect in a two dimensional photonic crystal slab
Applied Physics Letters, 2005Co-Authors: Atsushi Sugitatsu, Takashi Asano, Susumu NodaAbstract:We realize an active two-dimensional (2D) photonic crystal laser with a combination of line Defects and Point Defects. Based on a line-Defect–waveguide laser in a 2D photonic crystal slab, we observe laser emission from the Point Defect at the waveguide mode-edge frequency when there is a frequency mismatch with the Point-Defect mode. This phenomenon is due to the wide-field distribution at the waveguide mode edge and its distortion by the adjacent Point Defect. Numerical calculations estimate the emission efficiency and are in good agreement with experimental results.
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coupling between a Point Defect cavity and a line Defect waveguide in three dimensional photonic crystal
Physical Review B, 2003Co-Authors: Makoto Okano, Shinichi Kako, Susumu NodaAbstract:The properties of the coupling between a Point-Defect cavity and a line-Defect waveguide in three-dimensional (3D) photonic crystal are investigated theoretically using plane-wave expansion and 3D finite-difference time-domain methods. It is shown that for the symmetric structure where the Point and line Defects are on the same rod within the photonic crystal, a state is created in which the Point- and line-Defect modes are completely decoupled due to the mismatch in modal symmetry, while coupled states can be formed by introducing asymmetry. In these asymmetric structures, the strength of coupling between Point- and line-Defect modes is estimated as a function of the position of the end of the line-Defect waveguide by estimating the quality factor of the Point-Defect cavity. The quality factor is found to oscillate with small changes in the position of the waveguide. For instance, the quality factor changes by a factor of up to ∼ 1.1 1×10 4 with small positional change. In addition, the quality factor and light extraction efficiency are estimated when the size of the photonic crystal is finite, as in experimental circumstances. These findings provide very useful design rules for controlling the transfer of light from the Point-Defect cavity to the line-Defect waveguide. These coupling structures are thought to be an important component in 3D photonic crystal optical circuits.
Noriyuki Yokouchi - One of the best experts on this subject based on the ideXlab platform.
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vertical cavity surface emitting laser operating with photonic crystal seven Point Defect structure
Applied Physics Letters, 2003Co-Authors: Noriyuki Yokouchi, Aaron J Danner, Kent D ChoquetteAbstract:A vertical-cavity surface-emitting laser with a two-dimensional photonic crystal (PC) structure has been investigated for single lateral mode operation. The PC confined mode can be controlled by the lattice constant, the hole diameter, the etching depth, and the Defect structure. A seven-Point Defect structure is proposed to enhance the confinement effect, which is diluted by finite hole depth of the PC structure. We obtained a pure PC confined mode under room-temperature cw conditions with a PC lattice constant of 2 μm, hole diameters of 1.0 and 1.4 μm, and depths of 1.85 and 1.92 μm, respectively.
Xinbing Zhao - One of the best experts on this subject based on the ideXlab platform.
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Point Defect engineering of high performance bismuth telluride based thermoelectric materials
Advanced Functional Materials, 2014Co-Authors: Lipeng Hu, Xinbing ZhaoAbstract:Developing high-performance thermoelectric materials is one of the crucial aspects for direct thermal-to-electric energy conversion. Herein, atomic scale Point Defect engineering is introduced as a new strategy to simultaneously optimize the electrical properties and lattice thermal conductivity of thermoelectric materials, and (Bi,Sb)2(Te,Se)3 thermoelectric solid solutions are selected as a paradigm to demonstrate the applicability of this new approach. Intrinsic Point Defects play an important role in enhancing the thermoelectric properties. Antisite Defects and donor-like effects are engineered in this system by tuning the formation energy of Point Defects and hot deformation. As a result, a record value of the figure of merit ZT of ≈1.2 at 445 K is obtained for n-type polycrystalline Bi2Te2.3Se0.7 alloys, and a high ZT value of ≈1.3 at 380 K is achieved for p-type polycrystalline Bi0.3Sb1.7Te3 alloys, both values being higher than those of commercial zone-melted ingots. These results demonstrate the promise of Point Defect engineering as a new strategy to optimize thermoelectric properties.
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high performance mg2 si sn solid solutions a Point Defect chemistry approach to enhancing thermoelectric properties
Advanced Functional Materials, 2014Co-Authors: Guangyu Jiang, Tiejun Zhu, Xiaohua Liu, Xinbing ZhaoAbstract:A Point Defect chemistry approach to improving thermoelectric (TE) properties is introduced, and its effectiveness in the emerging mid-temperature TE material Mg2(Si,Sn) is demonstrated. The TE properties of Mg2(Si,Sn) are enhanced via the synergistical implementation of three types of Point Defects, that is, Sb dopants, Mg vacancies, and Mg interstitials in Mg2Si0.4Sn0.6-xSbx with high Sb content (x > 0.1), and it is found that i) Sb doping at low ratios tunes the carrier concentration while it facilitates the formation of Mg vacancies at high doping ratios (x > 0.1). Mg vacancies act as acceptors and phonon scatters; ii) the concentration of Mg vacancies is effectively controlled by the Sb doping ratio; iii) excess Mg facilitates the formation of Mg interstitials that also tunes the carrier concentration; vi) at the optimal Sb-doping ratio near x ≈ 0.10 the lattice thermal conductivity is significantly reduced, and a state-of-the-art figure of merit ZT > 1.1 is attained at 750 K in 2 at% Zn doped Mg2Si0.4Sn0.5Sb0.1 specimen. These results demonstrate the significance of Point Defects in thermoelectrics, and the promise of Point Defect chemistry as a new approach in optimizing TE properties.
Qingyuan Meng - One of the best experts on this subject based on the ideXlab platform.
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tunable thermal transport properties of graphene by single vacancy Point Defect
Applied Thermal Engineering, 2017Co-Authors: Yuhang Jing, Xiaochuan Li, Qingyuan MengAbstract:Abstract Graphene, a representative two-dimensional nanomaterial, possess great potential in the field of nanoelectronics. However, the Defects which are usually unavoidable in the fabrication of graphene may cause significant thermal effects in real applications. Thus, the effective and precise manipulation of thermal transport is critical for the practical applications of graphene-based electronic devices. In this paper, the effect of single-vacancy Point Defect on thermal transport properties of graphene was analyzed with non-equilibrium molecular dynamics (NEMD) method. We found that the existence of single-vacancy Point Defect can reduce the thermal conductivities of graphene. However, different from previous conclusions, the thermal conductivity of graphene depends not only on the Defect density, but also on the topological configuration of Defect. Our present results revealed that thermal conductivity of graphene with randomly distributed Defects decreases monotonously with the increase of Defect density. On the contrary, the thermal conductivity of graphene with regularly distributed Defects expresses obvious non-monotonicity for the same case. This phenomenon was furthermore explained by performing the analysis of phonon properties. These results indicate that the precise manipulation on the thermal conductivity of nanodevices can be realized by regulating the topological configuration of Defect on graphene. These understandings will provide important references for the development of nanoelectronic devices.