visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2024-08-16 11:00 
일시 11am, 16th august 2024 (friday) 
장소 E6 1322 (no zoom broadcasting) 
연사 Hikaru Saito (Associate Professor at Kyushu University) 
Abstract: Cathodoluminescence (CL) is a powerful imaging technique to visualize emitters with a high spatial resolution far beyond the diffraction limit. Electron beams are truly “white” excitation sources that can excite coherent and incoherent light emission in any frequency range, covering a variety of nanophotonic materials such as photonic crystals and plasmonic resonators, and optoelectronics materials including wide-gap semiconductors. In this talk, I will introduce three cutting-edge analysis examples that take advantage of the strengths of CL.
The first topic is topological plasmonic waveguides. Valley polarization has recently been adopted in optics, offering robust waveguiding and angular momentum sorting. The success of valley systems in photonic crystals suggests a plasmonic counterpart that can merge topological photonics and topological condensed matter systems, for instance, two-dimensional materials with the enhanced light-matter interaction. However, a valley plasmonic waveguide with a sufficient propagation distance in the near-infrared (NIR) or visible spectral range was challenging due to ohmic loss inside the metal. My colleagues and I employed gap surface plasmons for high index contrasting and realized a wide-bandgap valley plasmonic crystal, allowing waveguiding in the NIR–visible range. The edge mode with a propagation distance of 5.3 μm in the range of 1.31–1.36 eV was experimentally confirmed by visualizing the field distributions with a scanning transmission electron microscope CL technique, suggesting a practical platform for transferring angular momentum between photons and carriers in mesoscopic active devices [1]. The second topic is time-correlation CL applied to halide perovskites. Time-resolved or time-correlation CL has an attractive potential to reveal carrier dynamics at the nanoscale. However, halide perovskites, which are promising optoelectronic materials, exhibit significantly different decay dynamics in their CL and photoluminescence (PL). My colleagues and I conducted time-correlation CL measurements of CsPbBr3 using Hanbury Brown-Twiss interferometry and compared them with time-resolved PL. The measured CL decay time was on the order of subnanoseconds and was faster than PL decay at an excited carrier density of 2.1 × 1018 cm–3. Our experiment and analytical model revealed the CL dynamics induced by individual electron incidences, which are characterized by highly localized carrier generation followed by a rapid decrease in carrier density due to diffusion. This carrier diffusion can play a dominant role in the CL decay time for undoped semiconductors, in general, when the diffusion dynamics are faster than the carrier recombination [2].
The last topic is plasmon enhanced luminescence nanoscopically visualized by CL. The extremely broadband excitation characteristics of electron beams can sometimes be detrimental. For example, in emitter-resonator systems, electron beams inevitably excite not only the emitters but also the coherent electromagnetic modes of the resonators. This problem has made it difficult for CL analysis to quantify luminescence from the emitter that enhanced by the resonators. Here, to discriminate incoherent emissions from coherent emissions in integrated emitter-resonator systems, a simple new method utilizing CL saturation is proposed.
 
Contact: Yongsoo Yang (yongsoo.yang@kaist.ac.kr)
번호 날짜 장소 제목
563 2024-10-17 16:00  온라인 (https://kaist.zoom.us/j/89289652931?pwd=eNz6xnTFrEMGXYj9fXpdBJsW9fEpJX.1)  Photonic Methods for Quantum Levitodynamics Beyond the Rayleigh Regime
562 2024-10-14 11:00  KI Building(E4), Matrix Hall(2nd Floor)  [RSVP, Oct 14th Mon] Ambassador of Hungary to Republic of Korea Special Lecture file
561 2024-10-02 12:00  E6-2, #3441  Data-driven discovery of neural computations through brain-wide and cell-type-specific dynamical systems file
560 2024-09-26 14:00  KAIST, Physics Bldg. (E6-2) / (Rm. 3441)  Quantum spin nematic phase in a square-lattice iridate
559 2024-09-03 12:00  자연과학동(E6-2) 1323  2024 가을학기 물리학과 특별세미나 전체 일정 (응집물리 및 광학분야) file
558 2024-09-02 16:00  자연과학동 1501호(공동강의실)  2024학년도 가을학기 물리학과 콜로키움(Physics Colloquium) file
557 2024-08-22 16:00  RM #C303, Creation Hall (3F), KAIST Munji Campus  [CAPP seminar] Development of a 12-20 GHz CO Intensity Mapping Receiver for Capturing the Star-formation History in the Early Universe file
» 2024-08-16 11:00  E6 1322 (no zoom broadcasting)  Cathodoluminescence for nanophotonics: Applications to plasmonic bandgap materials and perovskite semiconductors file
555 2024-08-14 11:00  E6, #3441  Pair Density Waves and Supercurrent Diode Effect in Altermagnets
554 2024-07-25 16:00  Rm. 3441, E6-2 (Advanced Physics Lecture Hall)  Generation and Certification of Optical Quantum States for Information Processing file
553 2024-07-23 16:00  KI Building(E4) Matrix Hall(2F)  Spin Conversion Research Towards Novel Spintronic Functionalities file
552 2024-07-22 14:00  E6-2 #3441  Nonthermal electronic orders in photo-doped Mott insulators
551 2024-07-18 11:00  E6-2 #1323  Acousto-electric non-local detection of magnon-phonon coupling
550 2024-07-10 16:00  E6-2 #2502  [High Energy Theory Seminar] The Weak Gravity Conjecture in Perturbative String Theory
549 2024-07-03 16:00  E6-2 #2502  [High Energy Theory Seminar] Holographic duals of Higgsed Dpb(BCD)
548 2024-06-13 16:00  E6-2, #1323  Magnonic $\varphi$ Josephson junction and its non-Hermitian Josephson diode effect
547 2024-06-13 16:00  Zoom  [CAPP seminars]Simulation, design and fabrication of Josephson Parametric Amplifiers for axion search file
546 2024-06-12 16:00  E6-2, #1323  New high Tc superconductivity and symmetric pseudogap metal in the bilayer nickelate La3Ni2O7-Part2 file
545 2024-06-12 13:30  E6, #1501  Competition between superconductivity and density waves in spin-degenerate and spin-orbit-coupled Bernal bilayer graphene
544 2024-06-05 10:00  E6, #2501  Moir\’e fractals in supermoir\’e structures