V. S. Terent’ev

A reflection interferometer with a noninverted response function based on a phase grating

It is shown that the inclusion of a simple phase grating in the optical scheme of a resonator provides the possibility of performing spectral investigations in reflected light with characteristics of a Fabry-Perot interferometer. The response function of the interferometer is examined, and experimental results are presented.

Noninverted interference fringes upon light reflection from a Fabry-Perot interferometer with an asymmetric diffraction mirror

This paper describes the calculation, fabrication, and experimental investigation of a reflection two-mirror interferometer whose front mirror is asymmetric in reflection and made as a thin-layer diffraction metal structure (Al, Ag) in combination with a dielectric coating (MgF2, ZnS). In reflection, this interferometer creates in the zero diffraction order a transmission-like pattern similar to that produced by an ordinary Fabry-Perot interferometer operating in transmitted light.

Numerical simulation of a reflective diffraction fiber interferometer

Numerical simulation was used to demonstrate the possibility of designing a two-mirror multibeam reflective diffraction interferometer using a single-mode fiber with a cladding. The method is based on the calculation of the multimode and multibeam interference of the cladding modes in the fiber describing the diffraction on a diffuser made in the form of an insert of a different fiber as part of one of the interferometer mirrors. It is shown based on bulk optics that using certain optimization, one can obtain a reflection-response function profile of this interferometer similar to that of the transmission-response function of a Fabry-Perot interferometer.

Measurement of the phase parameter of dielectric mirrors

A method for measuring the composed phase parameter ϑ=Ψ1+Ψ2−2Ф1 (where Ψ1 and Ψ2 are the phases of the mirror reflectances and Ψ1 is the phase of the mirror transmittance) of dielectric mirrors with small absorption coefficients is proposed. This method is based on the use of the properties of a laser with a three-mirror cavity, and the mirror under study is the internal mirror of this cavity. It is shown that the value of the parameter Ψ, differing slightly from π, can be measured, and the results of the measurement are independent of the character of saturation of the laser active medium. The phase parameter was also measured for mirrors with reflectances below 0.8 by using an external method in which the interferometer with the mirror under study was placed outside of the laser cavity. It turned out that the intracavity laser method for measuring Ψ has a number of advantages and ensures an appreciably higher accuracy in measuring the parameter ε=Ψ−π than do extracavity techniques.

Experimental method of fabrication of a matched metal–dielectric structure for a sensor based on the effect of frustrated total internal reflection

An experimental method of fabrication of a sensor based on a metal–dielectric structure (Al + ZnS) and optimization of its characteristics is described. The coefficient of light reflection (p-polarization) from the aluminum layer is studied as a function of the layer thickness for different angles of incidence at the wavelength of 532 nm. Based on calculations, which are qualitatively consistent with experimental results, a structure consisting of matched layers of aluminum and zinc sulfide is fabricated; this structure has a higher angular resolution than the aluminum film with no dielectric coating. The detection limit of angular measurements by the sensor based on this structure is estimated as 2.6 · 10-5 RIU (refraction index units).

Frequency selection of the radiation of a fiber laser with a reflection interferometer

This paper considers the results of using a two-mirror multiple-beam reflection interferometer (RI) which has a response function in reflection similar to the response function of a Fabry-Perot interferometer in transmission. The two-mirror cavity of the RI included two flat mirrors, one of which was highly reflective, and the other had an asymmetric coefficient of reflection from different sides. The light reflected from the RI was brought to an optical fiber through a collimator lens. The optical fiber, collimator, and RI constituted an integrated fiber RI, which was first used for continuous tuning of the wavelength of an erbium ring fiber laser with a continuous generation in the spectral range 1520–1566 nm.

FABRICATION OF NANO-HOLES IN THIN ALUMINUM FILM BY FEMTOSECOND LASER ABLATION FOR SINGLE-MOLECULAR FLUORESCENCE SPECTROSCOPY

Представлены экспериментальные результаты по созданию наноотверстий методом фемтосекундной (270 фс) ультрафиолетовой лазерной абляции в пленке алюминия толщиной 100 нм, осажденной на стеклянную поверхность методом вакуумного магнетронного напыления. Исследованы зависимости диаметра наноотверстий от энергии импульсов в диапазоне от 10 до 25 нДж и от числа фемтосекундных лазерных импульсов в диапазоне от 5 до 50 импульсов. Показано, что минимальный диаметр наноотверстий достигается при энергии импульсов 10 нДж и количестве импульсов 50. Продемонстрированы наноотверстия диаметром <150 нм, которые представляют собой волноводы нулевой моды. Экспериментальная проверка работоспособности наноотверстий производилась в белом свете сразу после их изготовления, а также непосредственно в схеме многоканального ДНК-секвенатора типа Pacific Biosciences при регистрации испущенного из них флуоресцентного сигнала малой интенсивности (≈103 фотонов/с). Результаты работы подтверждают потенциальную применимость изготовленных наноотверстий в одномолекулярной флуоресцентной спектроскопии. Ключевые слова: фемтосекундная лазерная абляция, тонкие металлические пленки, ДНК-секвенатор, волновод нулевой моды, одномолекулярная спектроскопия, изготовление наноотверстий.

Spectral properties of a metal–dielectric sensor structure

Numerical analysis of the spectral characteristics of a two-layer structure is performed in the processes of fabrication, measurement, and application of this structure as a sensor of the refractive index of the external medium. The effect of environmental conditions and parameters of the metal and dielectric layers on the sensor sensitivity is discussed. The results of model calculations are confirmed by experimental studies.

Calculating the spatial fluorescence distribution of a thick fluorophore layer in a multichannel confocal microscope

The propagation of rays in the optical system of a multichannel confocal microscope is numerically modelled in the Gaussian approximation, making it possible to estimate the shape of the image profile of a focused laser beam in a thick phosphor layer. The proposed method creates the possibility of calculating the signal-to-background-illumination-noise ratio of a confocal system in the case of a large number of parallel channels without using extensive computer resources. The results are compared with experimental measurements made by successively scanning a thick fluorophore layer in depth.

Diagnosing the direction of temperature drift from the asymmetry of the fringes in a reflecting interferometer

This paper describes the design of a metal–dielectric structure intended to be used as a thermometric sensor. As the temperature varies, the fringes in the light reflected from a three-mirror interferometer become asymmetric. The asymmetry has different signs, depending on whether the object is being heated or cooled.