Results 1 - 10 of 80351
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[en] An endoscope-compatible, submicrometer-resolution scanning confocal microscopy imaging system is presented. This approach, spectrally encoded confocal microscopy (SECM), uses a quasi-monochromatic light source and a transmission diffraction grating to detect the reflectivity simultaneously at multiple points along a transverse line within the sample. Since this method does not require fast spatial scanning within the probe, the equipment can be miniaturized and incorporated into a catheter or endoscope. Confocal images of an electron microscope grid were acquired with SECM to demonstrate the feasibility of this technique. copyright 1998 Optical Society of America
[en] Viscosity is one of the most important parameter in rheological and tribological properties of fluids. The objective of this study is to obtain the viscosity values from the simultaneous refractive-index measurements of lubricants, simply by dipping the fiber-optic probe into the oil to be measured. Due to the fact that these parameters are temperature dependent, within the interval under consideration, oil heated up steadily while measuring the viscosity and refractive index at the same time. The refractive index sensor, the digital viscometer and the thermometer were connected to a PC via an analog to digital converter and the values were acquired at the same time. The fiber optic refractive index sensor has been designed in our laboratory. By utilising Fresnel's fundamental reflection law, the intensity of reflected light from boundary surface (optic fiber core-motor oil) was measured at 660 nm wavelength and then refractive index of the oil was calculated. The derived refractive index values were converted viscosity values that acquired by using the calibration equation. The viscometer, used during the study, was the rotational Brookfield type
[en] Slow and fast light is an important and fascinating phenomenon in quantum optics. Here, we theoretically study how to achieve the ultraslow and ultrafast light in a passive-active optomechanical system, based on the ideal optomechanically induced transparency (OMIT). Under the conditions of the ideal OMIT, an abnormal (inverted) transparency window will emerge accompanied with a very steep dispersion, resulting that the ultraslow light can be easily achieved at the transparency window by adjusting the dissipation rates of the two cavities, even with usual mechanical linewidth (such as Hz linewidth). Particularly, as the decay rate of the passive cavity tends to the gain rate of the active cavity, the ideal stopped light can be achieved. Similarly, the ultrafast light can be achieved at transparency window by tuning the coupling strength and the decay rates in the system.
[en] In laser driven accelerators it is highly desirable to transport an intense radiation beam over a distance of many Rayleigh lengths. Without additional focusing mechanisms, a laser beam in vacuum diffracts on the scale of a Rayleigh length. For certain accelerator schemes, such as the beat wave accelerator, it is possible for the background plasma to provide the necessary focusing for laser transport over many Rayleigh lengths. The transport of laser beams through plasmas is studied both analytically and numerically. This analysis is based on an envelope equation derived from the ray equations of geometric optics. The resulting envelope equation describes the evolution of the mean radius of a radiation field which can be approximated by a Gaussian profile. This formulation describes propagation through plasmas with arbitrary density profiles
[en] The development of advanced photonics devices requires materials with large optical nonlinearities, fast response times and high optical transparency, while at the same time allowing for the micro/nano-processing needed for integrated photonics. In this context, glasses have been receiving considerable attention given their relevant optical properties which can be specifically tailored by compositional control. Corning Gorilla® Glass (strengthened alkali aluminosilicate glass) is well-known for its use as a protective screen in mobile devices, and has attracted interest as a potential candidate for optical devices. Therefore, it is crucial not only to expand the knowledge on the fabrication of waveguides in Gorilla Glass under different regimes, but also to determine its nonlinear optical response, both using fs-laser pulses. Thus, this paper reports, for the first time, characterization of the third-order optical nonlinearities of Gorilla Glass, as well as linear and nonlinear characterization of waveguide written with femtosecond pulses under the low repetition rate regime (1 kHz). (paper)
[en] The refractive index 𝑛(𝜆,𝑇) is a basic optical property of materials. The refractive index and the thermo-optic coefficient (d𝑛/d𝑇) are significant parameters of liquids for optically controlled systems, such as the direct measurement of liquid solution concentrations and optical paths. In this study, the variation in the refractive index of water in the liquid phase with temperature was measured with our self-designed fiber optic-based refractive index sensor and d𝑛/d𝑇 values were obtained with a full-width half-maximum method at wavelengths of 980, 1426, and 1550 nm, respectively. Water is the most abundant and life-critical substance in the world, and its optical properties pose challenging scientific problems that require knowledge of the refractive index to be resolved. The results indicate that the experimental refractive index values are compatible with both the theoretical and experimental data in the literature. We also tested the refraction index results with two theoretical models and obtained good agreement between the calculated and experimental values. The resolution of the fiber optic-based refractive index sensor was 10−5. Our designed sensor could measure the refractive index of liquids with temperature with accuracy. (author)
[en] Analytical signal formalism is used for derivation of expressions for a complex envelope of radiation with ultrabroadband spectrum and an arbitrary waveform, which occur rarely in modern texts on nonlinear optics. It is demonstrated that the envelope, phase, and instantaneous frequency of femtosecond radiation pulses with an ultrabroad spectrum in a transparent medium can exhibit oscillations with a characteristic time scale considerably shorter than one field cycle at the central frequency. The interference of pulses and the generation of multiple frequencies are among phenomena giving rise to such features. It is marked that the violation of conditions imposed by the theory of analytical signal leads to ambiguity of the complex envelope.
[en] We determine through numerical modelling the conditions for the generation of triangular-shaped optical pulses in a nonlinear, normally dispersive (ND) fibre and experimentally demonstrate triangular pulse formation in conventional ND fibre
[en] Two identical amplifying quantum optical taps, based on noiseless optical parametric amplification and twin beam quantum correlation, have been implemented in a series configuration and experimentally investigated. The result is an optical bus which we have shown to be robust with respect to downstream losses. copyright 1996 The American Physical Society
[en] We investigate the effects of quickly creating a plasma around a monochromatic electromagnetic source wave, on time scales on the order of a cycle of the wave. It is found that this results in an upshifting of the wave frequency, which can be varied by changing of the plasma density. It is also found that a substantial fraction of the B-field associated with the initial wave can be sustained in the plasma as a time-independent B field. Computer simulations have been used to study this process in detail, including the effects of finite ionization time. For long ionization times, strong plasma heating results