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x)As distributed Bragg reflectors on InP substrates for 1.3 - 1.5 μm wavelengths
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
Semiconductor distributed Bragg reflectors (DBRs) are a key element in a wide variety of opto-electronic devices, such as vertical cavity surface emitting lasers [1]. For high reflectivity there must be a large refractive index difference An between the two alternate layers in the DBR, and the two layers must be transparent at operating wavelengths. High-reflectivity DBRs operating at shorter wavelengths have been made using AlAs/GaAs stacks (▵n=0.6). At 1.55 μm wavelengths, InP/InGaAsP DBRs have also been demonstrated [2]. Owing to the small ▵n (0.27) of InP/InGaAsP, however, many pairs are required for effective reflectivity in the long wavelength range. Recently, several material systems including the antimonide compounds, such as AlAsSb/GaAsSb [3], AlAsSb/InGaAs [4], and AlPSb/GaPSb [5] have been proposed for high-reflectivity DBRs at 1.55 μm. This is because the AlAsSb and AlPSb can be lattice-matched to InP substrates and have a low refractive index. However, there has been no report for the 1.3-μm DBRs.
Advanced Optoelectronic Device Processing
Published in Wengang (Wayne) Bi, Hao-chung (Henry) Kuo, Pei-Cheng Ku, Bo Shen, Handbook of GaN Semiconductor Materials and Devices, 2017
Instead of using metals as a reflector, distributed Bragg reflector (DBR) is also widely used in lateral LEDs. The DBR structure is generally formed from a repeated periodical stack of alternating high and low index layers, the thickness of each layer is a one-quarter wavelength of the light. As the refraction indexes of the two materials are different, Fresnel reflection will occur at the interfaces. Better reflection effect can be obtained if the difference of refractive index is larger. Usually, the difference of the refraction index between the two materials is not large so that the reflection effect is not good at each interface. Increasing the periods of DBRs can effectively increase the total reflectivity to close to 100%. The two materials of DBR for nitride LEDs are normally SiO2 and TiO2.27,28 With proper design, the reflectivity of the DBR can be higher than that of the metallic reflectors. The DBR can also be integrated in the epistructure during epitaxial growth, in the form of Al0.2Ga0.8N/GaN repeating layers.29–31
Vertical-Cavity Surface-Emitting Lasers
Published in Joachim Piprek, Handbook of Optoelectronic Device Modeling and Simulation, 2017
Tomasz Czyszanowski, Leszek Frasunkiewicz, Maciej Dems
Unlike typical edge-emitting lasers, in VCSELs the optical cavity is formed between the mirrors above and below the active region (Figure 34.1). The laser light resonates in the vertical direction. Inside the laser structure, the light passes the active region in the vertical direction—i.e., gain is provided over a short distance only and the amplification per photon round-trip is small. Therefore, the mirrors must be highly reflective (over 99% for the emitting mirror and almost 100% for the opposite one) so that the photons make many round-trips before they are emitted. High reflectivity is provided by DBRs composed of stacks of two alternating layers with high refractive index contrast. With quarter-wavelength layer thicknesses, the reflected waves from all DBR interfaces add up constructively, allowing for a total DBR reflectance of over 99%. Such layers are composed of 50 or more semiconductor layers. The current is injected vertically, similar to edge-emitting devices. However, in VCSELs, optical resonance occurs in the vertical direction.
Numerical analysis of a miniaturized design of a Fabry–Perot resonator based on silicon strip and slot waveguides for bio-sensing applications
Published in Journal of Modern Optics, 2019
M. A. Butt, S. N. Khonina, N. L. Kazanskiy
A Fabry–Perot resonator is an optical oscillator, consisting of two distributed Bragg reflectors (DBRs) with a spacer medium in between. The transmission spectrum of this resonator has numerous resonance peaks, which occur at positions where the phase shift ϕ of the resonator is a multiple of 2π. The modal properties of our sensor design are inspected by means of the finite-element method (FEM) using COMSOL Multiphysics with the scattering boundary condition (SBC). The sub-domains in the WG cross-section were divided into triangular mesh elements. The grid size is set to λ/9 for the air medium and λ/10 for WGs geometry in order to obtain accurate simulation results within the available computation resources. In our first sensor design, the corrugated Bragg gratings and a cavity are structured on both sides of a Si strip WG as shown in Figure 1. We used TE-polarized light for the wavelength range of 1540–1590 nm to calculate the transmission spectrum of the FP-resonator. These simulation parameters are used throughout the paper.
Flexible distributed Bragg reflectors as optical outcouplers for OLEDs based on a polymeric anode
Published in Journal of Information Display, 2021
Carmela Tania Prontera, Marco Pugliese, Roberto Giannuzzi, Sonia Carallo, Marco Esposito, Giuseppe Gigli, Vincenzo Maiorano
This paper demonstrates the possibility of realizing a TOLED based on a PEDOT:PSS bottom electrode deposited on top of a dielectric Bragg reflector (DBR)-modified flexible polyimide substrate. A DBR is a periodic structure obtained by alternating dielectric layers that can be used to obtain a high degree of reflection in a certain range of wavelengths, by exploiting the differences in the refractive indices of the dielectric layers and their thickness [18]. By combining the reflectivity properties of the DBR with the conductivity and flexibility of the polymeric electrode, flexible TOLEDs can be fabricated with the replacement of the bottom thin metal film electrode.
Nonlinear optical response properties of a quantum dot embedded in a semiconductor microcavity: possible applications in quantum communication platforms
Published in Journal of Modern Optics, 2021
Vijay Bhatt, Sabur A. Barbhuiya, Pradip K. Jha, Aranya B. Bhattacherjee
The model proposed in this article is shown in Figure 1. Here we consider a single semiconductor quantum dot (QD) inside a semiconductor micro cavity. The micro-cavity can be fabricated by a set of distributed Bragg reflectors (DBR). Light confinement along the longitudinal and transverse direction in the DBR can be achieved by known techniques [53]. DBR mirrors are generally quarter-wavelength thick, a high and lower refractive index which leads to tunable reflectivity [54].