Ultranarrow resonance peaks in the transmission and reflection spectra of a photonic crystal cavity with Raman gain

The Raman gain of a probe light in a three-state $\Lambda$-scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit \textit{simultaneously} occurring narrow peaks (resonances) whose position is determined by the Raman resonance. Transmission and reflection coefficients can be larger than unity at pump intensities of order tens of $\mu$W/cm$^{2}$. When the pump intensity is outside this region, the peak in the transmission spectrum turns into a narrow dip. The nature of narrow resonances is attributed to a drastic dispersion of the nonlinear refractive index in the vicinity of the Raman transition, which leads to a significant reduction of the group velocity of the probe wave.Comment: 9 pages, 3 figure

Geometric phase and o-mode blue shift in a chiral anisotropic medium inside a Fabry-P\'erot cavity

Anomalous spectral shift of transmission peaks is observed in a Fabry--P\'erot cavity filled with a chiral anisotropic medium. The effective refractive index value resides out of the interval between the ordinary and the extraordinary refractive indices. The spectral shift is explained by contribution of a geometric phase. The problem is solved analytically using the approximate Jones matrix method, numerically using the accurate Berreman method and geometrically using the generalized Mauguin--Poincar\'e rolling cone method. The $o$-mode blue shift is measured for a 4-methoxybenzylidene-4'-$n$-butylaniline twisted--nematic layer inside the Fabry--P\'erot cavity. The twist is electrically induced due to the homeoplanar--twisted configuration transition in an ionic-surfactant-doped liquid crystal layer. Experimental evidence confirms the validity of the theoretical model.Comment: the text is available both in English (Timofeev2015en.tex) and in Russian (download: other formats - source - Timofeev2015ru.tex, Timofeev2015rus.pdf

Inversionless gain in a three-level system driven by a strong field and collisions

Inversionless gain in a three-level system driven by a strong external field and by collisions with a buffer gas is investigated. The mechanism of populating of the upper laser level contributed by the collision transfer as well as by relaxation caused by a buffer gas is discussed in detail. Explicit formulae for analysis of optimal conditions are derived. The mechanism developed here for the incoherent pump could be generalized to other systems.Comment: RevTeX, 9 pages, 4 eps figure

Coherent control of light-pulse propagation in a Raman induced grating

We study light-pulse propagation in a dynamically controllable periodic structure (grating) resulting from Raman interaction of a weak probe pulse with a standing-wave pump and a second control laser field inN-type four-level atomic media. The grating is induced due to periodic spatial modulation of the Raman gain in a standing pump field (Raman gain grating). We show that it is possible to control both the probe pulse amplitude and the group velocity of the pulse from subluminal to superluminal by varying the pump or control field. Such a grating is of interest forall-optical switches and transistors

Ienversionless gain in an optically-dense resonant Doppler-broadened medium

Resonant nonlinear-optical interference processes in four-level Doppler-broadened media are studied. Specific features of amplification and optical switching of short-wavelength radiation in a strongly-absorbing resonant gas under coherent quantum control with two longer wavelength radiations, are investigated. The major outcomes are illustrated with virtual experiments aimed at inversionless short-wavelength amplification, which also address deficiencies in this regard in recent experiments. With numerical simulations related to the proposed experiment in optically-dense sodium dimer vapor, we show optimal condition for optical switching and the expected gain of the probe radiation, which is above the oscillation threshold.Comment: 7 pages, 12 eps figures. Video/audio clips of the related virtual experiments are available on http://kirensky.krasn.ru/popov/opa/opa.ht

ВАКУУМНАЯ ЛИНЕЙНАЯ УСТАНОВКА ДЛЯ НАНЕСЕНИЯ ГИДРОФОБНОГО ПРОСВЕТЛЯЮЩЕГО ПОКРЫТИЯ НА СЕНСОРНЫЕ ДИСПЛЕИ

The aim of the work is to develop vacuum technological equipment for deposition an interference antireflection coating with the evaporation of a hydrophobic protective layer in a single vacuum cycle. To deposition an interference antireflection coating, the method of magnetron reactive sputtering in the alternating current mode with a frequency of 20 kHz is used. This method allows using of a wide range of sputtered materials and obtains stable and high-quality coatings on various substrates. To determine the optical characteristics, a spectrophotometer was used, which evaluated the transmittance and reflection in the visible region of the spectrum of electromagnetic radiation. To check the physical characteristics of the hydrophobic coating, abrasion test of the coating with metal wool with a load of 1 kg/cm2 was used. The novelty of the presented method is the combination of the liquid-phase coating method together with physical deposition in a vacuum without interrupting the process. This method allows increasing productivity and yield of suitable parts since the number of operations at the multi-stage stage of production of the touch display is reduced. After the development and adjustment of the Aurora G5 linear vacuum equipment, a stable and reproducible process for producing hydrophobic anti-reflective coatings over large areas with high performance was obtained. An antireflection coating was obtained with an average reflection coefficient of less than 0.6 % in the wavelength range of 400 to 700 nm. The adhesion test showed grade 0 according to the ISO classification. The resulting coatings have high hardness >9 H and abrasion resistance >5000 cycles. The result of this development and research is the introduction of vacuum processing equipment in the manufacturing process for the manufacture of anti-reflective hydrophobic coatings on touch displays.Целью работы является разработка вакуумного технологического оборудования для напыления интерференционного просветляющего покрытия с последующим нанесением гидрофобного защитного слоя в едином вакуумном цикле. Для напыления интерференционного просветляющего покрытия используется метод магнетронного реактивного распыления в режиме переменного тока с частотой 20 кГц. Данный метод позволяет использовать широкий спектр распыляемых материалов и получать стабильные и качественные покрытия на различных подложках. Для определения оптических характеристик использовали спектрофотометр, которым оценивали коэффициенты пропускания и отражения в видимой области спектра электромагнитного излучения. Для проверки физических характеристик гидрофобного покрытия использовали тест на истирание покрытия металлической ватой с нагрузкой 1 кг/см2. Новизной представленного метода является совмещение жидкофазного метода нанесения покрытий совместно с физическим распылением в вакууме без разрыва технологического процесса. Данный метод позволяет добиться увеличения производительности и выхода годных деталей, так как уменьшается количество операций на многоступенчатом этапе производства сенсорного дисплея. После разработки и настройки линейного вакуумного оборудования Aurora G5 был получен стабильный и воспроизводимый технологический процесс получения гидрофобных просветляющих покрытий на большие площади с высокой производительностью. Получено просветляющее покрытие со средним коэффициентом отражения менее 0,6 % в диапазоне длин волн 400 до 700 нм. Проверка адгезии показала 0 класс согласно классификации ISO. Полученные покрытия имеют высокие твердость >9H и стойкость к истиранию >5000 циклов. Итогом данной разработки и исследования является внедрение вакуумного технологического оборудования в производственный процесс изготовления просветляющих гидрофобных покрытий на сенсорные дисплеи