The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Taco D Visser - One of the best experts on this subject based on the ideXlab platform.
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plasmon switching observation of dynamic surface plasmon steering by selective Mode excitation in a sub wavelength slit
Optics Express, 2012Co-Authors: Shreyas B Raghunathan, Philippe Lalanne, T Van Dijk, Hugo F Schouten, W Ubachs, Taco D VisserAbstract:We report a plasmon steering method that enables us to dynamically control the direction of surface plasmons generated by a two-Mode slit in a thin metal film. By varying the phase between different coherent beams that are incident on the slit, individual waveguide Modes are excited. Different linear combinations of the two Modes lead to different diffracted fields at the exit of the slit. As a result, the direction in which surface plasmons are launched can be controlled. Experiments confirm that it is possible to distribute an approximately constant surface plasmon intensity in any desired proportion over the two launching directions. We also find that the anti-Symmetric Mode generates surface plasmons more efficiently than the fundamental Symmetric Mode.
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plasmon switching observation of dynamic surface plasmon steering by selective Mode excitation in a sub wavelength slit
Optics Express, 2012Co-Authors: Shreyas B Raghunathan, Philippe Lalanne, Hugo F Schouten, W Ubachs, Choon How Gan, T Van Dijk, Ea B Kim, Taco D VisserAbstract:We report a plasmon steering method that enables us to dynamically control the direction of surface plasmons generated by a two-Mode slit in a thin metal film. By varying the phase between different coherent beams that are incident on the slit, individual waveguide Modes are excited. Different linear combinations of the two Modes lead to different diffracted fields at the exit of the slit. As a result, the direction in which surface plasmons are launched can be controlled. Experiments confirm that it is possible to distribute an approximately constant surface plasmon intensity in any desired proportion over the two launching directions. We also find that the anti-Symmetric Mode generates surface plasmons more efficiently than the fundamental Symmetric Mode.
Albert P. Pisano - One of the best experts on this subject based on the ideXlab platform.
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micromachined one port aluminum nitride lamb wave resonators utilizing the lowest order Symmetric Mode
IEEE\ ASME Journal of Microelectromechanical Systems, 2014Co-Authors: Chihming Lin, Yung-yu Chen, Jie Zou, Ventsislav Yantchev, Albert P. PisanoAbstract:The characteristics of one-port aluminum nitride (AlN) Lamb wave resonators utilizing the lowest-order Symmetric Mode with electrically open, grounded, and floating bottom electrode configurations are theoretically and experimentally investigated in this paper. Finite element analysis is performed to take an insight into the static capacitance characteristics of the AlN Lamb wave resonators with various bottom surface conditions. Without sacrificing the transduction efficiency, the floating bottom electrode is capable of reducing the static capacitance in the AlN thin plate and then promotes an efficient improvement in the effective coupling coefficient (k2eff). In addition, in comparison with the grounded bottom electrode, the employment of the floating bottom electrode offers simple fabrication processes for the micromachined Lamb wave resonators. Experimentally, the AlN Lamb wave resonators without the bottom electrode exhibit an average loaded quality factor (Q) as high as 2676 at the series resonance frequency, but a low average k2eff of 0.19%. On the contrary, the Lamb wave resonators with the electrically floating bottom electrode show the largest average k2eff up to 1.13% among the three topologies but a low average loaded Q of 800 at the series resonance frequency. In contrast to the floating bottom electrode, the Lamb wave resonators with the electrically grounded bottom electrode show a smaller average k2eff of 0.78% and a similar average loaded Q of 758 at the series resonance frequency.
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thermally stable sio 2 aln sio 2 lamb wave resonators utilizing the lowest order Symmetric Mode at high temperatures
Internaltional Ultrasonics Symposium, 2013Co-Authors: Jie Zou, Debbie G. Senesky, Chihming Lin, Albert P. PisanoAbstract:Thermal compensation at high temperatures for Lamb wave resonators utilizing the lowest Symmetric (S0) Mode in a SiO2/AlN/SiO2 sandwiched structure is theoretically investigated in this work. When temperature raises from room temperature to 600°C, the deformation and displacement caused by the thermal expansion mismatch in the SiO2/AlN/SiO2 Symmetric composite plate is much less than a conventional temperature compensation plate, i.e. the AlN/SiO2 composite plate. Acoustic characteristics of the SiO2/AlN/SiO2 Symmetric membrane with three main electrode configurations are investigated, exhibiting higher phase velocity and larger electromechanical coupling coefficient than the common AlN/SiO2 layered structure since the Symmetric sandwiched plate traps more acoustic waves in the AlN layer. In addition, with proper thicknesses of the AlN and SiO2 layers, the S0 Mode can simultaneously achieve a turnover temperature at high temperatures and a large intrinsic k2 in the SiO2/AlN/SiO2 sandwiched structure.
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theoretical investigation of lamb wave characteristics in aln 3c sic composite membranes
Applied Physics Letters, 2010Co-Authors: Chihming Lin, Yung-yu Chen, Albert P. PisanoAbstract:Cubic silicon carbide (3C–SiC) layer can provide advantages of high frequency and high quality factor for Lamb wave devices due to the superior properties of high acoustic velocity and low acoustic loss. In this study, Lamb wave propagation characteristics in composite membranes consisting of a c-axis oriented aluminum nitride (AlN) film and an epitaxial 3C–SiC (100) layer are investigated by theoretical calculation. The lowest Symmetric Mode Lamb wave propagating along the [011] direction exhibits a phase velocity higher than 10 000 m/s and an electromechanical coupling coefficient above 2% in the AlN/3C–SiC multilayered membranes.
Shreyas B Raghunathan - One of the best experts on this subject based on the ideXlab platform.
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plasmon switching observation of dynamic surface plasmon steering by selective Mode excitation in a sub wavelength slit
Optics Express, 2012Co-Authors: Shreyas B Raghunathan, Philippe Lalanne, T Van Dijk, Hugo F Schouten, W Ubachs, Taco D VisserAbstract:We report a plasmon steering method that enables us to dynamically control the direction of surface plasmons generated by a two-Mode slit in a thin metal film. By varying the phase between different coherent beams that are incident on the slit, individual waveguide Modes are excited. Different linear combinations of the two Modes lead to different diffracted fields at the exit of the slit. As a result, the direction in which surface plasmons are launched can be controlled. Experiments confirm that it is possible to distribute an approximately constant surface plasmon intensity in any desired proportion over the two launching directions. We also find that the anti-Symmetric Mode generates surface plasmons more efficiently than the fundamental Symmetric Mode.
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plasmon switching observation of dynamic surface plasmon steering by selective Mode excitation in a sub wavelength slit
Optics Express, 2012Co-Authors: Shreyas B Raghunathan, Philippe Lalanne, Hugo F Schouten, W Ubachs, Choon How Gan, T Van Dijk, Ea B Kim, Taco D VisserAbstract:We report a plasmon steering method that enables us to dynamically control the direction of surface plasmons generated by a two-Mode slit in a thin metal film. By varying the phase between different coherent beams that are incident on the slit, individual waveguide Modes are excited. Different linear combinations of the two Modes lead to different diffracted fields at the exit of the slit. As a result, the direction in which surface plasmons are launched can be controlled. Experiments confirm that it is possible to distribute an approximately constant surface plasmon intensity in any desired proportion over the two launching directions. We also find that the anti-Symmetric Mode generates surface plasmons more efficiently than the fundamental Symmetric Mode.
Junqi Liu - One of the best experts on this subject based on the ideXlab platform.
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high power substrate emitting quantum cascade laser with a Symmetric Mode
IEEE Photonics Technology Letters, 2017Co-Authors: Fengmin Cheng, Jinchuan Zhang, Zhiwei Jia, Yue Zhao, Dongbo Wang, Ning Zhuo, Shenqiang Zhai, Lijun Wang, Junqi Liu, Shuman LiuAbstract:We demonstrate a buried grating coupled substrate emitting distributed-feedback quantum cascade laser with high power room temperature continuous wave (cw) operation at $4.97~\mu \text{m}$ . A second-order semiconductor/semiconductor grating is used for in-plane feedback and vertical out-coupling. A surface emitting power of 248 mW is attained in cw operation at 20 °C. Single-Mode operation is obtained with a good linear wavelength tuning with injection current. The far field shows a low divergence about 0.14° $ \times 16$ °, indicating that the device operates in Symmetric Mode.
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high efficiency single lobe surface emitting dfb dbr quantum cascade lasers
Optics Express, 2016Co-Authors: Yinghui Liu, Jinchuan Zhang, Zhiwei Jia, Ning Zhuo, Shenqiang Zhai, Lijun Wang, Fangliang Yan, Fengqi Liu, Ping Liang, Junqi LiuAbstract:We demonstrate a surface-emitting quantum cascade laser (QCL) based on second-order buried distributed feedback/distributed Bragg reflector (DFB/DBR) gratings for feedback and outcoupling. The grating fabricated beneath the waveguide was found to fundamentally favor lasing in Symmetric Mode either through analysis or experiment. Single-lobe far-field radiation pattern with full width at half maximum (FWHM) of 0.18° was obtained along the cavity-length direction. Besides, the buried DFB/DBR grating structure successfully provided an efficient vertical outcoupling mechanism with low optical losses, which manages to achieve a high surface outcouping efficiency of 46% in continuous-wave (CW) operation and 60% in pulsed operation at room temperature. Single-Mode emission with a side-Mode suppression ratio (SMSR) about 25 dB was continuously tunable by heat sink temperature or injection current. Our work contributes to the realization of high efficiency surface-emitting devices with high far-field beam quality that are significantly needed in many application fields.
L J Mawst - One of the best experts on this subject based on the ideXlab platform.
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high power surface emitting quantum cascade laser operating in a Symmetric grating Mode
Applied Physics Letters, 2016Co-Authors: C Boyle, C Sigler, J D Kirch, D Lindberg, T Earles, D Botez, L J MawstAbstract:Grating-coupled surface-emitting (GCSE) lasers generally operate with a double-lobed far-field beam pattern along the cavity-length direction, which is a result of lasing being favored in the antiSymmetric grating Mode. We experimentally demonstrate a GCSE quantum-cascade laser design allowing high-power, nearly single-lobed surface emission parallel to the longitudinal cavity. A 2nd-order Au-semiconductor distributed-feedback (DFB)/distributed-Bragg-reflector (DBR) grating is used for feedback and out-coupling. The DFB and DBR grating regions are 2.55 mm- and 1.28 mm-long, respectively, for a total grating length of 5.1 mm. The lasers are designed to operate in a Symmetric (longitudinal) grating Mode by causing resonant coupling of the guided optical Mode to the antiSymmetric surface-plasmon Modes of the 2nd-order metal/semiconductor grating. Then, the antiSymmetric Modes are strongly absorbed by the metal in the grating, causing the Symmetric Mode to be favored to lase, which, in turn, produces a single-lobed beam over a range of grating duty-cycle values of 36%–41%. Simulations indicate that the Symmetric Mode is always favored to lase, independent of the random phase of reflections from the device's cleaved ends. Peak pulsed output powers of ∼0.4 W were measured with nearly single-lobe beam-pattern (in the longitudinal direction), single-spatial-Mode operation near 4.75 μm wavelength. Far-field measurements confirm a diffraction-limited beam pattern, in agreement with simulations, for a source-to-detector separation of 2 m.
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design for high power single lobe grating surface emitting quantum cascade lasers enabled by plasmon enhanced absorption of antiSymmetric Modes
Applied Physics Letters, 2014Co-Authors: C Sigler, J D Kirch, T Earles, L J Mawst, D BotezAbstract:Resonant coupling of the transverse-magnetic polarized (guided) optical Mode of a quantum-cascade laser (QCL) to the antiSymmetric surface-plasmon Modes of 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antiSymmetric-Mode absorption. In turn, lasing in the Symmetric Mode, that is, surface emission in a single-lobe far-field beam pattern, is strongly favored over controllable ranges in grating duty cycle and tooth height. By using core-region characteristics of a published 4.6 μm-emitting QCL, grating-coupled surface-emitting (SE) QCLs are analyzed and optimized for highly efficient single-lobe operation. For infinite-length devices, it is found that when the antiSymmetric Mode is resonantly absorbed, the Symmetric Mode has negligible absorption loss (∼0.1 cm−1) while still being efficiently outcoupled, through the substrate, by the DFB grating. For finite-length devices, 2nd-order distributed Bragg reflector (DBR) gratings are used on both sides of the DFB grating to prevent uncontrolled reflections from cleaved facets. Equations for the threshold-current density and the differential quantum efficiency of SE DFB/DBR QCLs are derived. For 7 mm-long, 8.0 μm-wide, 4.6 μm-emitting devices, with an Ag/InP grating of ∼39% duty cycle, and ∼0.22 μm tooth height, threshold currents as low as 0.45 A are projected. Based on experimentally obtained internal efficiency values from high-performance QCLs, slope efficiencies as high as 3.4 W/A are projected; thus, offering a solution for watt-range, single-lobe CW operation from SE, mid-infrared QCLs.
