On feasibility of longitudinal characterisation of photonic structures via transverse excitation of whispering gallery modes

Remote side excitation of whispering gallery modes in photonic crystal structures such as hollow core fibres and homothetically scaled preforms (canes) reveals longitudinal properties of the structure normally requiring a long fibre length and its end-face access. By tuning the excitation to the maxima of observed morphology resonances, initiating axially expending whispering gallery modes in the fibre cladding and in its microstructure, characteristic spectral windows resembling ones at the fibre longitudinal transmission are observed. The results open up the possibility of detached characterization of rotationally-symmetric photonic structures in situ and in locations only assessable via side excitation using external light beams

Applied photometry, radiometry, and measurements of optical losses

Applied Photometry, Radiometry, and Measurements of Optical Losses reviews and analyzes physical concepts of radiation transfer, providing quantitative foundation for the means of measurements of optical losses, which affect propagation and distribution of light waves in various media and in diverse optical systems and components. The comprehensive analysis of advanced methodologies for low-loss detection is outlined in comparison with the classic photometric and radiometric observations, having a broad range of techniques examined and summarized: from interferometric and calorimetric, resonator and polarization, phase-shift and ring-down decay, wavelength and frequency modulation to pulse separation and resonant, acousto-optic and emissive - subsequently compared to direct and balancing methods for studying free-space and polarization optics, fibers and waveguides. The material is focused on applying optical methods and procedures for evaluation of transparent, reflecting, scattering, absorbing, and aggregated objects, and for determination of power and energy parameters of radiation and color properties of light

Photometry, radiometry, and measurements of optical losses

The revised 2nd edition of this practical book provides an expanded treatment and comparison of techniques used in advanced optical measurements, guiding its reader from fundamental radiometric and photometric concepts to the state-of-the-art in highly sensitive measurements of optical losses and in spectroscopic detection using coherent laser light and spontaneous radiation. The book describes and compares a broad array of high-sensitivity methods and techniques – from interferometric and/or calorimetric, acousto-optic and resonator or polarization to wavelength- and frequency-modulation, phase-shift and decay time studies, and direct-loss measurements for free-space, fiber- or waveguide-based systems and devices. Updated throughout, the new edition describes novel trends in spectral interferometry, frequency-comb and laser-excitation spectroscopy, reflected in the developments of Raman, Brillouin and FTIR (Fourier Transform Infra-Red) techniques for biomedical research, biotech sensing and detection. It also covers broad practical implementations of time- and frequency-domain terahertz spectroscopy measurements. This book reviews the physical concepts of radiation transfer, providing a quantitative foundation for the means of measurements of optical losses, which affect propagation and distribution of light waves in various media and in diverse optical systems and components. It focuses on the application of optical methods and procedures for the evaluation of transparent, reflecting, scattering, absorbing, and aggregated objects, and for determining the power and energy parameters of radiation and color properties of light. This updated new edition will serve as an up-to-date reference source and practical guide for those using photometric and radiometric techniques

Radiometry of partially coherent radiation

The origin of the photometric and radiometric concept is associated with the desire to observe and quantify radiation and to measure physical parameters of light beams via energy and power extents. Owing to the finiteness of the dimensions and time constants of visual and radiometric detectors, the observation and the measurement processes are defined not only by wave amplitudes of the electromagnetic oscillations observed, but also by the detector’s response to the squared amplitude of the wave averaged by detector time and space constants. The properties of the actual detectors define the space–time averages of radiant or luminous parameters of optical radiation and cause high-frequency filtration for observable radiation, leading to an evident lack of correlation between radiometric observation and the description of wave oscillations by electric and magnetic vector amplitudes (Rosenberg, Sov Phys Usp 20(1):55–79, 1977). Only in the electromagnetic field of a plane monochromatic wave, with the phase of its oscillation being an amplitude-invariable function of time, is it possible to construct a single-valued square correlation between the field intensity and its amplitude. Light waves emitted by sources are not strictly monochromatic owing to the finiteness of source dimensions and a great number of elementary dipoles affecting one another. Each light excitation made by a physical source is always given by a sum of Fourier decompositions to infinitely long individual monochromatic groups. Therefore, the wave amplitudes and phases of light in any actual wave field undergo certain irregular fluctuations within spectral width Δν of effective radiating frequency ν.</p

Systems of multiple reflections

As seen in Chaps. 2 and 5, expanding the effective optical path length or the number of light interactions with the object under study increases the sensitivity to the optical properties of the object.</p

Spectroscopic interferometry and laser-excitation spectroscopy

The underlying Michelson-Morley experiment [12.1] was made possible in an interferometer designed by Michelson for atomic spectroscopy in his attempt to establish a new meter standard using a suitably narrow spectral line, the red-line singlet not doublet of cadmium, via measuring visibility of a resultant two-beam interference pattern (see Chap. 3 ): V = (I max -I min )/(I max +I min ). </p

Photometers and radiometers

Spectrally Unselective Systems. As discussed in Chap. 2, by utilizing the thermoelectric reception, having practically equal to unity absorptance over a relatively broad spectral region.</p

Direct attenuation measurements

The actual means to increase the sensitivity of a given method for optical loss measurement are not necessarily restrained by limitations to the maximum number of light interactions with the object.</p