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Emitters as topic

Optical emitters are devices that produce light or electromagnetic radiation. They are essential components in a wide range of applications, including lighting, displays, sensing, and communication. Optical emitters can be classified into two broad categories: spontaneous emitters and stimulated emitters. 
Spontaneous optical emitters include incandescent lamps and light-emitting diodes (LEDs). Incandescent lamps generate light through the heating of a filament, while LEDs use a semiconductor material to produce light through a process called electroluminescence. Spontaneous emitters are generally less efficient than stimulated emitters, but they are easier to manufacture and can be used in a wider range of applications.
Stimulated optical emitters, such as lasers, produce coherent light through the process of stimulated emission. In a laser, a gain medium such as a crystal or gas is excited by an external energy source, causing the atoms or molecules in the medium to emit photons in a particular direction. These photons then stimulate other atoms or molecules to emit photons in the same direction, creating a coherent beam of light. Lasers have many applications, including in scientific research, telecommunications, and materials processing.
Overall, optical emitters play a critical role in many areas of modern technology, and ongoing research aims to improve their performance and develop new types of emitters with novel properties.

Silicon Microspheres for Super-Planckian Light Sources in the Mid Infrared

Advanced Optical Materials 2300135 (2023)
R. Fenollosa, F. Ramiro-Manzano, M. Garín, and F. Meseguer

Silicon microspheres with a diameter in the range of 2–3 micrometers constitute photonic nanocavities that emit light through their Mie resonances when heated at high temperatures. At 500–600 °C these microresonators show a particular mid-infrared (MIR) emission dominated by the lowest order modes. Such resonances feature a large free spectral range, about 600 cm−1, and a high proximity to the critical coupling condition. In fact, resonances with high-quality factor, around 160 are found. It corresponds to the limit of detection of their measuring setup, being 600 the theoretical value. Most importantly, several modes emit light above the calculated black body limit because they feature an optical absorption cross-section larger than their geometric one. All these characteristics set silicon microspheres as very promising zero-dimensional materials for developing micrometric and sub-wavelength light sources in the MIR.

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Silicon Microspheres/Resonators as emitters in the MidIR

Supporting information: Silicon Microspheres for Super-Planckian Light Sources in the Mid Infrared

Advanced Optical Materials 2300135 (2023)
R. Fenollosa, F. Ramiro-Manzano, M. Garín, and F. Meseguer

Supporting information with additional figures and explanations.

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Transmittance and photoluminescence oscillations, perovskite crystal

Optical properties of organic/inorganic perovskite microcrystals through the characterization of Fabry–Pérot resonances

Dalton Transactions, 49, 12798 (2020)
F. Ramiro-Manzano, R. García-Aboal, R. Fenollosa, S. Biasi, I. Rodriguez, P. Atienzar and F. Meseguer

A precise knowledge of the optical properties, specifically the refractive index, of organic/inorganic perovskites, is essential for pushing forward the performance of the current photovoltaic devices that are being developed from these materials. Here we show a robust method for determining the real and the imaginary part of the refractive index of MAPbBr3 thin films and micrometer size single crystals with planar geometry. The simultaneous fit of both the optical transmittance and the photoluminescence spectra to theoretical models defines unambiguously the refractive index and the crystal thickness. Because the method relies on the optical resonance phenomenon occurring in these microstructures, it can be used to further develop optical microcavities from perovskites or from other optical materials.

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Thermal emission of Silicon sphereical resonators. High-Q

Thermal Emission of Silicon at Near-Infrared Frequencies Mediated by Mie Resonances

ACS Photonics, 6, 3174–3179 (2019)
R. Fenollosa, F. Ramiro-Manzano, M. Garín, R. Alcubilla

Planck’s law constitutes one of the cornerstones in physics. It explains the well-known spectrum of an ideal blackbody consisting of a smooth curve, whose peak wavelength and intensity depend on the temperature of the body. This scenario changes drastically, however,
when the size of the emitting object is comparable to the wavelength of the emitted radiation. Here we show that a silicon microsphere (2−3 μm in diameter) heated to around 800 °C yields a thermal emission spectrum consisting of pronounced peaks that are associated with Mie resonances. We experimentally demonstrate in the near-infrared the existence of modes with an ultrahigh quality factor, Q, of 400, which is substantially higher than values reported so far, and set a new benchmark in the field of thermal emission. Simulations predict that the thermal response of the microspheres is very fast, about 15 μs. Additionally, the possibility of achieving light emission above the Planck limit at some frequency ranges is envisaged.

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Fernando Ramiro Manzano, PhD 
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(+34) 96 387 9841
CTF-ITQ, UPV, Edificio 8B, Avda. Los Naranjos SN, 46360 - Valencia, Spain
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