一般講演(15):光の干渉を起こさない真珠層のメカニズムについての考察

Interference caused by the multiple optical carriers in the broadband passive optical network (BPON) is reduced. This is achieved by modulating each multilongitudinal-mode laser diode with a strong sine wave to broaden optical spectral width. The results show that optical interference can be reduced to be minor, even when the optical spectra of all laser diodes overlap. Thus, the number of the optical carriers in the BPON system can be greatly extended. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14: 255–258, 1997.

A scheme to study the effect of residual phase gradients in an optical interference between two out-of-phase Gaussian beams is proposed. In a Sagnac interferometer configured to provide a null output, a variable linear phase swept across the null point unfolds an optical field rotation due to an apparently negligible residual phase gradient present orthogonal to the linear phase sweep. As the optical beam that rotates around its propagation axis carries orbital angular momentum, the experimental results presented in this Letter could provide an insight into the momentum change associated with the energy redistribution in the fundamental phenomenon of optical interference.

I systematically analyze the theory of optical frequency-modulated continuous-wave (FMCW) interference. There are three different versions of optical FMCW interference, discussed in detail: sawtooth-wave optical FMCW interference, triangular-wave optical FMCW interference, and sinusoidal-wave optical FMCW interference. The essential concepts and technical terms are clearly defined, the necessary simplifications are introduced according to the characteristics of optical waves, and the formulas used to calculate the signal intensities under two different situations (static and dynamic) are properly derived. Advantages and limitations of each version of optical FMCW interference are also discussed.

Multiple access interference (MAI) is a primary concern in optical coded division multiple access (OCDMA). To alleviate this issue, first cancellation stage of an optical serial interference cancellation (O-SIC) can be employed. In this paper, we investigate the effect of optical serial interference cancellation for the first cancellation stage on bit error rate (BER). We compare the first cancellation stage with the conventional correlation method by utilizing different threshold values with the various length and different number of users. We have successfully shown that the optical serial interference cancellation yields a better performance than the conventional correlation method by choosing the optimum value in the first cancellation stage. We provide the results of computer simulations showing the BER improvement when the first cancellation stage of optical serial interference cancellation (OPSIC) is used over the cancellation technique. The comparisons are done for several numbers of users.

We recognize that the superposed light beams do not interact with each other to re-distribute their energy in space or time in the absence of interacting material dipoles. This platform requires that we re-visit the physical model behind the generation of pulses from the so-called "mode-locked" lasers. In the process, we come across the mathematical models behind formulating (i) the autocorrelation due to pulsed light and (ii) the group velocity of pulse propagation are based on the direct summation (integration) of non-causal infinite Fourier frequencies as if the EM waves can actually modify their energy distribution in the time domain. Accordingly, we show by modeling results and proposed experiments that time-frequency Fourier theorem can give rise to self-contradictory predictions, verifiable by simple laboratory experiments. Based on these results, we propose that we replace the paradigm of "interference of light" by "superposition effects due to light beams" as reported by the material dipoles of detectors and beam splitters.

Experiments on the Fraunhofer diffraction and interference of light using computer-interfaced apparatus and data logging software are now available from suppliers of educational scientific equipment, and are a very useful tool for the teaching of these fundamental aspects of light. Clearly, however, cost imposes limits on the number of sets of apparatus which can be made available for student use. An alternative experimental arrangement is presented here, which results in a considerable cost saving by reducing the number of sensors and other apparatus required, while giving excellent quantitative results for comparison with theory.

The condensation of H2O on ice multilayers on Ru(001) was studied using both molecular beam and optical interference techniques as a function of surface temperature. From the beam reflection technique, the H2O sticking coefficient, S, was determined to be S = 0.99 ± 0.03 at temperatures between 85 and 150 K and was independent of incident angle (0−70°) and beam energy (1−40 kcal/mol). The condensation coefficient, α, was dependent on both the incident H2O flux and the desorption H2O flux at the various surface temperatures. The magnitude of α varied continuously from unity at T < 130 K to zero at higher temperatures. The optical interference experiments yielded condensation coefficients and sticking coefficients of α = S = 0.97 ± 0.10 at temperatures from 97 to 145 K where the H2O desorption flux was negligible with respect to the incident flux. The optical interference measurements monitored the ice film thickness versus H2O exposure time and were dependent on the refractive index, n, and the density, ρ, of the vapor-deposited ice. Consequently, the combined molecular beam and optical interference measurements provided a means to evaluate the refractive index and density for vapor-deposited ice as a function of surface temperature. The values of the refractive index varied from n = 1.27 at 90 K to n = 1.31 at 130 K. The calculated densities varied from ρ = 0.82 g/cm3 at 90 K to ρ = 0.93 g/cm3 at 130 K. Previous optical interference data were also reanalyzed to yield refractive indices and ice densities for films grown at surface temperatures between 20 and 150 K. Both the refractive index and density increased monotonically with increasing growth temperature. The lower refractive index and density at lower temperatures indicate that microporous ice films are formed when H2O deposits on substrates at T < 120 K.

Comparisons are made between the visualization of fingerprint corrosion ridge detail on fired brass cartridge casings, where fingerprint sweat was deposited prefiring, using both ultraviolet (UV) and visible (natural daylight) light sources. A reflected ultraviolet imaging system (RUVIS), normally used for visualizing latent fingerprint sweat deposits, is compared with optical interference and digital color mapping of visible light, the latter using apparatus constructed to easily enable selection of the optimum viewing angle. Results show that reflected UV, with a monochromatic UV source of 254nm, was unable to visualize fingerprint ridge detail on any of 12 casings analyzed, whereas optical interference and digital color mapping using natural daylight yielded ridge detail on three casings. Reasons for the lack of success with RUVIS are discussed in terms of the variation in thickness of the thin film of metal oxide corrosion and absorption wavelengths for the corrosion products of brass.

A study of the optical readout head used in compact disc players provides an insight into the various optical principles involved in reading the data and in maintaining correct tracking and focusing on the disc surface. A detailed analysis of the design of this widely-used consumer item can be used to illustrate how diode laser technology, dielectric coatings, optical interference and diffraction effects, low-aberration collimating and focusing optics, holographic gratings, and a quadrant silicon detector are all combined in a single unit which is designed to read data from the optical disc. This paper will describe the operation of the optical readout head and some simple experiments which can be performed to illustrate the function of the various components in the head.

Optical interference and refractive index of silica glass in the infrared absorption region

In the present study, we successfully obtained nonstaining blood flow images of a developing fish egg embryo using optical interference caused by the Doppler shift. The spectral distribution of light reflected by moving objects such as the heart and red cells was found to be different from that of the incident light because of the Doppler effect. Interference between different frequency components was observed in an interferogram through heterodyne interaction using an imaging-type two-dimensional Fourier spectroscopic system, and information on the intensities of the spectral components was obtained by Fourier transformation. Beat signals with specific frequencies due to the heart beating and blood flow of the fish egg embryo were detected. When the signals were plotted in two dimensions, the heart part and vessel flows were clearly visualized without staining. In addition, near-infrared (NIR) images were produced using absorbance spectra of the molecular vibrations of O-H and C-H groups included in water, hydrocarbons, and aliphatic compounds. Obtaining nonstaining blood flow images using heterodyne optical interference and images of molecular distribution using molecular vibrational information simultaneously manifests an exciting advance in NIR imaging.

Introduction. In the post-pandemic period, when all universities are switching to full–time education, the problem of the meaning and place of virtual laboratory work (hereinafter referred to as VLR) in physics at a technical university has arisen in a new way. The following questions have become relevant: about the frequency of the use of different types of VLR in universities in Russia and abroad; about the effectiveness of their use for the formation of practical and intellectual experimental skills; about methods and means of training that allow to increase the effectiveness of the formation of experimental skills when performing VLR in physics. Materials and methods. Our research is based on the methodology of conducting a physical experiment and the requirements of digital learning. The methods of analysis of modern sources on the problem of the use of VLR in physics, questioning of teachers and testing of students on the problem of the formation of experimental skills when conducting VLR in physics in technical universities were used. The questionnaire was attended by physics teachers of MGUPP and the National Research University "MPEI". Testing was conducted among students of 1-2 courses of the named universities. Results. The most common types of VLR are VLR animations and VLR videos and the frequency of their use in technical universities. It was found that the frequency of using VRL animations is 24%, and VRL videos – 53%. It is proved that VLR animations with an interactive component make it possible to effectively form the practical and intellectual skills of students in laboratory classes. To strengthen the independence of students when performing VLR, methods of using interactive tests and using Excel calculation tables are proposed. In the Moodle environment, tests for 15 VLRs have been developed, an example of a test for VLR "Light Interference" is given. 10 Excel calculation tables have been created to monitor the results of laboratory work by students. Such tables for the VLR "Ohm's Law" and "Determination of the Poisson ratio by the Reichardt method" are given in the article. Conclusion. The prospects for further research include the creation of electronic lecture notes and their inclusion together with interactive tests and calculation tables in a demonstration and information complex on general physics.

Human-made agro-ecosystems lack negative feedback controls, which may result in rodent population explosions, causing considerable economic loss and thus increasing human-wildlife conflicts. The traditional solution is the extensive use of rodenticides, which have a negative impact on the environment. In Beit-Sheaan Valley, Israel, which is located on a major route for migrating birds, poisoning of voles may result in the death of birds that prey on the dead voles (e.g. storks and herons). In the present essay we discuss some integrated methods, based on the implementation of ecological principles in agro-ecosystems, that could be used to decrease the use of rodenticides. The first method is light interference during winter (long scotophase), which can result in the death of the social vole Microtus socialis kept in enclosures under natural conditions. Under laboratory conditions such interference causes a decrease in thermoregulatory ability in the cold. As light interference is a source of pollution, only active vole burrows should be illuminated. The second method involves using the mobile irrigation pipelines to flood the vole burrows and force them to escape into the open, where diurnal birds such as storks and herons will prey on them. The third method involves the use of nesting boxes for barn owls and stands for diurnal raptors, both of which prey on voles. The great advantage of using an integrated approach is that voles cannot become adapted to any one of the methods. Such integrated methods, together with appropriate treatment of alfalfa fields by farmers, can provide an efficient and sustainable pest control approach.

New gap detection method using two lasers optical heterodyne interference for X-ray lithography

Presbyopia, accommodation, and mature catenary