Research of microring lasers shows prospects of optical applications in electronics
A paper by Kazan Federal University appeared in IET Microwaves, Antennas & Propagation
2021-05-19
(Press-News.org) Problems for eigenmodes of a two-layered dielectric microcavity have become widespread thanks to the research of A.I. Nosich, E.I. Smotrova, S.V. Boriskina and others since the beginning of the 21st century. The KFU team first tackled this topic in 2014; undergraduates started working under the guidance of Evgeny Karchevsky, Professor of the Department of Applied Mathematics of the Institute of Computational Mathematics and Information Technology.
In this paper, the researchers discuss a model of a 2D active microcavity with a piercing hole and the possibility of a compromise between high directionality of radiation and low threshold gain. The analysis performed is based on the lasing eigenvalue problem (LEP) formalism. This LEP is a boundary value problem for the system of Maxwell equations with boundary and radiation conditions, adapted to study the threshold modes of open resonators with active regions. In LEP, each eigenvalue is a pair of two real numbers: the emission frequency and the threshold gain in the active region. This combination fits perfectly with the experimental results, which show that each mode has its own defined threshold, and that it is directly related to the field diagram and the location of the active region. When analyzing cavities of complex shape, we use the analytical regularization method in the form of a set of Müller boundary integral equations and reduce LEP to a nonlinear eigenvalue problem for a set of Fredholm integral equations of the second kind. To find a solution, a fast and accurate Galerkin method designed for this task is used. This method makes it possible to study symmetric and asymmetric modes separately, at the threshold of radiation that is not damped in time. The numerical results show that the directionality of the radiation of the operating modes in a given frequency range, together with their threshold gain values, is controlled by the size and location of the air hole in the resonator. In the developed code to study solutions of symmetric and asymmetric modes, the sine and cosine functions in the Galerkin scheme are used instead of exponentials. This makes the code resistant to jumps between mode families when numerically searching for eigenvalues and allows much smaller matrix equations to be used for computations with the order of machine precision. These modifications form the basis of this work. In addition, since the boundaries of the cavity and the hole are circles, this approach allows one to obtain explicit formulas for the matrix elements instead of double integrals. Thanks to all this, the algorithm is extremely fast and accurate. This makes it possible to perform an elementary optimization of the microlaser geometry, which ensures high directionality of the mode radiation while maintaining a low threshold value of the gain in the active region. This code is a promising engineering tool for microring lasers.
Dielectric microcavities have been the objects of intensive research in photonics and nano-optics for over 30 years. Laser radiation arising from the propagation of whispering gallery modes along the circumference of the microdisk resonators is not unidirectional. Due to a change in the structure of the laser (microcavity), it is possible to achieve unidirectional radiation with high directivity and low thresholds of its generation, which, in combination with its small size, the possibility of single-frequency generation and temperature stability, provides a wide range of applications. As an example, the authors can offer a quantum dot microcavity, which can be used to implement optical data transmission inside or between integrated circuits.
This topic can be expanded by considering and analyzing microcavities of complex structures. For example, a microcavity with several piercing holes arranged in a certain order (photonic crystal microcavity), or a microcavity with a quantum dot. Such complications will make it possible to generalize the results or to discover new dependencies.
INFORMATION:
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
2021-05-19
The last ice age ended almost 12 000 years ago in Norway. The land rebounded slowly as the weight of the ice disappeared and the land uplift caused many bays to become narrower and form lakes.
Fish became trapped in these lakes.
Sticklebacks managed to adapt when saltwater became freshwater, and they can still be found in today's coastal lakes along the Norwegian coast.
Saltwater gradually changed to brackish water and later to freshwater. This environmental change naturally led to a total replacement of the animal and plant life.
The exception is the tiny stickleback, which successfully adapted as saltwater became freshwater and ...
2021-05-19
A reason for these findings could be due to the fact that Parkinson's patients often also have many risk factors for a severe course of Covid-19. For the first time, the cross-sectional study provides detailed nationwide data. The research team led by Professor Lars Tönges reports in the journal Movement Disorders of 4 May 2021.
Nationwide analysis of hospital data
The team headed by Lars Tönges has analysed data on Parkinson's treatment in 1,468 hospitals. The data were taken from nationwide databases in which information on the treated diseases and of treatments carried out in hospitals is publicly collected, for example by the Institute for the Hospital Remuneration System or the Federal Statistical Office.
A comparison between the period of the first ...
2021-05-19
Blocked blood vessels in the brains of stroke patients prevent oxygen-rich blood from getting to cells, causing severe damage. Plants and some microbes produce oxygen through photosynthesis. What if there was a way to make photosynthesis happen in the brains of patients? Now, researchers reporting in ACS' Nano Letters have done just that in cells and in mice, using blue-green algae and special nanoparticles, in a proof-of-concept demonstration.
Strokes result in the deaths of 5 million people worldwide every year, according to the World Health Organization. Millions more survive, but they often experience disabilities, such as difficulties with speech, swallowing or memory. The most common cause is a blood vessel blockage in the brain, and the best way to ...
2021-05-19
WASHINGTON, DC (May 19, 2021) - Human genetics and genomics contributed $265 billion to the U.S. economy in 2019 and has the potential to drive significant further growth given major new areas of application, according to a new report issued today by the American Society of Human Genetics (ASHG). The findings indicate that this research and industry sector has seen its annual impact on the U.S. economy grow five-fold in the last decade and outlined at least eight areas of expanding impact for human health and society. ASHG commissioned and funded the report and is grateful for generous additional contributions from Invitae and Regeneron. ...
2021-05-19
An international research team led by Professor Charles Gauthier from the Institut national de la recherche scientifique (INRS) has discovered a new molecule with potential to revolutionize the biosurfactant market. The team's findings have been published in Chemical Science, the Royal Society of Chemistry's flagship journal.
Surfactants are synthesized from petroleum and are the main active ingredient in most soaps, detergents, and shampoos. Biosurfactants, produced by bacteria, are safer and can replace synthetic surfactants.
Rhamnolipid molecules are some ...
2021-05-19
Pregnant women made only modest dietary changes after being diagnosed with gestational diabetes, according to a study by researchers at the National Institutes of Health. Women with gestational diabetes are generally advised to reduce their carbohydrate intake, and the women in the study did cut their daily intake of juice and added sugars. They also increased their intake of cheese and artificially sweetened beverages. However, certain groups of women did not reduce their carbohydrate intake, including women with obesity, had more than one child, were Hispanic, had a high school degree or less, or were between the ages of 35-41 years.
The study was led by Stefanie N. Hinkle, Ph.D., of the Epidemiology Branch at NIH's Eunice Kennedy Shriver ...
2021-05-19
WASHINGTON (May 19, 2021)--Early online support for the Boogaloos, one of the groups implicated in the January 2021 attack on the United States Capitol, followed the same mathematical pattern as ISIS, despite the stark ideological, geographical and cultural differences between their forms of extremism. That's the conclusion of a new study published today by researchers at the George Washington University.
"This study helps provide a better understanding of the emergence of extremist movements in the U.S. and worldwide," Neil Johnson, a professor of physics at GW, said. "By identifying hidden common patterns in what seem to be completely unrelated movements, topped with a rigorous mathematical description of how they develop, our ...
2021-05-19
DALLAS, May 19, 2021 -- Steps to ensure safety and mitigate the spread of COVID-19 have had some unintended consequences on the management of chronic conditions such as high blood pressure, a leading cause of heart disease and health disparities in the United States. COVID-19 has disproportionately affected people from different racial and ethnic groups, those who are from under-resourced populations and communities that face historic or systemic disadvantages. Discussions and research are ongoing to address what many experts label as long-existing inequities in the U.S. health system, according to information published today in the Journal of the American Heart Association, an open access journal of the American Heart Association.
"Media coverage has examined how ...
2021-05-19
Chronic exposure to second-hand smoke results in lower body weight and cognitive impairments that more profoundly affects males, according to new research in mice led by Oregon Health & Science University.
The study published today in the journal Environmental Health Perspectives.
"The hope is that we can better understand these effects for policymakers and the next generation of smokers," said lead author Jacob Raber, Ph.D., professor of behavioral neuroscience in the OHSU School of Medicine. "Many people still smoke, and these findings suggest that that the long-term health effects can be quite serious for people who are chronically exposed to second-hand smoke."
The research examined daily exposure of 62 mice over a period of 10 months. Researchers used a specially designed ...
2021-05-19
A new article from Liverpool ocular researchers demonstrates that small uveal (intraocular) melanomas are not always harmless, as the current paradigm suggests.
Instead, a reasonable proportion of them have molecular genetic alterations, which categorises them as highly metastatic tumours. The article recommends that they should not be observed but rather treated immediately, to improve patients' chances of survival.
The paper shows that uveal melanoma patients with small tumours, when treated within a certain time frame in Liverpool, do indeed have improved outcomes.
The study was undertaken by researchers ...
LAST 30 PRESS RELEASES:
[Press-News.org] Research of microring lasers shows prospects of optical applications in electronics
A paper by Kazan Federal University appeared in IET Microwaves, Antennas & Propagation
