China
Africa
Explore chapters and articles related to this topic
Strong Coupling in Cavity Magnonics
Published in Gianluca Gubbiotti, Three-Dimensional Magnonics, 2019
Angelo Leo, Silvia Rizzato, Anna Grazia Monteduro, Giuseppe Maruccio
Beyond MSMs, a YIG sphere can also support photonic whispering gallery modes (WGMs), and MW-to-light conversion can be achieved through spin–orbit interaction [53, 54]. In this respect, recent developments of cavity optomagnonics were carried out by impinging an infrared 1.5 μm laser with Ω0 frequency on a YIG sphere strongly coupled in a 3D resonator using the experimental setup shown in Fig. 11.10a, where light through an optical fiber interacts with the WGMs of a magnetically saturated YIG sphere (shown in Fig. 11.10b). The spatially uniform spin precession of YIG spheres is the basis of the pronounced nonreciprocity and asymmetry in the sideband signals generated by the FMR magnon-induced Brillouin light scattering of light (Fig. 11.10c), which is reported in this work [54]. The thermal bistability of magnons excited in the same configuration was demonstrated [55]. All the aforementioned properties arise from the geometric birefringence of the WGMs photons in YIG at FMR under a polarized optical signal, driving the MW photon–FM magnon–optical photon system in a nonreciprocal triple-resonance condition. Haigh et al. employed prism coupling to the magnetic sphere for precise mode identification [56].
Nanophotonics silicon solar cells
Published in Klaus D. Sattler, Silicon Nanomaterials Sourcebook, 2017
Despite the effective light trapping by metallic nanoparticles, the obvious disadvantage is that it is challenging to avoid the absorption loss of the particle which prevents the solar cell performance from further improving. Therefore, lossless dielectric nanoparticles are proposed to be integrated into the solar cells for light management. For instance, TiO2 nanoparticles have been demonstrated on top of the c-Si solar cells to act as antireflective coatings, thereby increasing the longer wavelength light-path length. In addition, closely packed SiO2 nanoparticles have been applied on top of solar cells to generate whispering gallery modes (WGMs) to enhance the light absorption [28–32]. Dielectric nanoparticles can successfully avoid the shadowing problem and the parasitic absorption existing in the metal nanoparticles. High-index nanoparticles, Si for example, can support Mie resonance modes which yield almost zero reflection over the entire spectrum range when placed on an Si substrate. For nanostructure integrated solar cells, novel nanocone and nanowire structures have been demonstrated for efficient light coupling to guided modes from the top surface of the solar cells. The above mentioned dielectric nanoparticles and nanostructures can provide effective light trapping schemes for thin-film solar cells. Detail discussions will be given in the following sections.
Recent Progress in Optical Microcavity Experiments
Published in Hiroyuki Yokoyama, Ujihara Kikuo, Spontaneous Emission and Laser Oscillation in Microcavities, 2020
It is well known that microspheres made by liquid or solid dielectric materials act as cavities having high Q values for certain modes. These resonant modes are called whispering gallery (WG) modes, and they propagate azimuthally near the inside surface of a sphere due to total intemal reflection. So far, dye-molecule-embedded spheres tens of micron in size have been used for láser oscillation experiments.9-11 If the sphere size is decreased to the order of the emitted light wavelength, the emission lifetime of molecules coupled to a WG mode is modified.9 From the application point of view, this cavity structure has a large problem in coupling the light out with high efficiency.
Optical gain and photo-bleaching of organic dyes, quantum dots, perovskite nanoplatelets and nanodiamonds
Published in Liquid Crystals, 2023
Mahendran Vellaichamy, Miha Škarabot, Igor Muševič
The aim of this study is to measure the optical gain and rate of photo-bleaching of a variety of materials that are used, or are considered to be used in liquid crystal microdroplet lasers. Typically, LC microdroplet lasers are droplets of a nematic [14,15], chiral nematic [16] or even ferroelectric liquid crystals [17] dispersed in another medium that does not mix with that particular LC. For example, nematic droplets of 5CB are dispersed in water with added surfactants to control the surface anchoring, which controls the internal director structure of the droplet [15]. Whispering Gallery Mode (WGM) lasing is obtained from such a droplet, if optical gain is added to the LC, and is excited by external light pulses. The optical gain material is usually fluorescent organic dye that easily dissolves in LC and has large quantum yield. The excitation of electronic transitions within gain fluorescent molecules will give rise to spontaneous and stimulated emission of light. Because a LC droplet is an optical cavity that sustains WGMs, lasing will take place from these modes, generating characteristic WGM spectrum of sharp lines [14,15]. In a WGM microlaser, made of nematic droplet with dissolved fluorescent dye, the typical lasing threshold fluences of the excitation (pump) pulsed beam is of the order of ~1 mJ/cm2 and typical pulse duration is ~1 ns.
Determination of refractive index by a U-shaped multimode fiber sensor
Published in Instrumentation Science & Technology, 2018
Yong Zhang, Ming Lei, Haifeng Hu, Yong Zhao, Jin Li, Han Gao
Besides the whispering gallery and the cladding modes, another part of the incident light is coupled into the leakage mode and leads to bending loss in power intensity. To reduce the power loss during measurement, the multimode fiber is used to fabricate the U-shaped structure. As is well known, the multimode fiber has the graded index profile whose phase difference between each two core modes is wavelength independent, but the multimode fiber has step index profile whose phase difference between each two core modes is wavelength dependent. Only the interference between the WGM and core mode is what we need. Therefore, to avoid the modal interference among the core modes in multimode fiber, the graded index multimode fiber is selected.
Optimization of light absorption in ultrathin elliptical silicon nanowire arrays for solar cell applications
Published in Journal of Modern Optics, 2022
Seyedeh Leila Mortazavifar, Mohammad Reza Salehi, Mojtaba Shahraki, Ebrahim Abiri
For nanowire-shaped SCs, there are whispering-gallery modes that are caused by a global curvature in the structure, and they lead to the accumulation of a field near the surface of the structure and light entrapment. In the case of nanowires, these modes are observed at significantly low wavelengths. The reason behind the development of these modes is continuity of the overall reflection on the surface, in such a way that they establish the intensification conditions. These modes are highly dependent on the appearance of the structure, and they are visible as accumulated fields on the surface of the nanowires.