Search results for "Acousto-optics"
showing 8 items of 8 documents
Accurate mode characterization of two-mode optical fibers by in-fiber acousto-optics.
2016
Acousto-optic interaction in optical fibers is exploited for the accurate and broadband characterization of two-mode optical fibers. Coupling between LP01 and LP1m modes is produced in a broadband wavelength range. Difference in effective indices, group indices, and chromatic dispersions between the guided modes, are obtained from experimental measurements. Additionally, we show that the technique is suitable to investigate the fine modes structure of LP modes, and some other intriguing features related with modes' cut-off.
Operational modes of a ferroelectric LCoS modulator for displaying binary polarization, amplitude, and phase diffraction gratings
2009
We analyze the performance of a ferroelectric liquid crystal on silicon display (FLCoS) as a binary polarization diffraction grating. We analyze the correspondence between the two polarization states emerging from the displayed grating and the polarization and intensity of the diffracted orders generated at the Fourier diffraction plane. This polarization-diffraction analysis leads, in a simple manner, to configurations yielding binary amplitude or binary phase modulation by incorporating an analyzer on the reflected beam. Based on this analysis, we present two useful variations of the polarization configuration. The first is a simplification using a single polarizer, which provides equival…
In-Fiber Acousto-Optics for the Broadband Measurement of the UV-Induced Refractive Index Change in Photosensitive Fibers
2019
In fiber acousto-optics has been demonstrated to be a versatile, highly sensitive technique that allows characterizing different parameters of singlemode or few-mode fibers, such as dispersion curves, radius or core refractive index, in a broadband wavelength range. The working principle of the technique relies in the fact that a variation in a parameter of the fiber leads to a shift in the optical wavelength that fulfills the acousto-optic phase matching condition. Thus, by measuring this wavelength shift it is possible to evaluate the change in the parameter under study. The technique shows a low detection limit: for example, it is as low as 10-8 for the core refractive index, in singlemo…
Thermally induced emission of light from a metallic diffraction grating, mediated by surface plasmons
1999
The angular emission of light of wavelength 710 and 810 nm from a gold diffraction grating was studied at about 700°C. A peak in the emission was found for defined angles. This contribution is purely TM-polarised and is attributed to thermally excited surface plasmons, coupled to light waves by the diffraction grating.
An approach to the measurement of the nonlinear refractive index of very short lengths of optical fibers
2018
A method for the measurement of the nonlinear-refractive index coefficient in single-mode optical fibers is presented. It takes advantage of the high sensitivity of the acousto-optic interaction effect in optical fibers to the fiber properties. Direct measurement of the nonlinear-refractive index change resulting from cross-phase modulation between a probe and a pump signal is obtained from the fiber's acousto-optic interaction performance. It is a non-interferometric method in which a very short length of fiber (<0.25 m) is required.
Achromatic diffraction of femtosecond light pulses
2003
Diffraction of electromagnetic waves in free space is a physical phenomenon that explicitly depends on the wavelength of light radiation. As an ultrashort-pulsed waveform consists of many frequency components that are coherently superposed, diffraction of a femtosecond pulse passing through an aperture radically differs from that under continuous wave (CW) monochromatic illumination. Note that the spectral width of a 5 fs pulsed beam is approximately 400 nm, which roughly corresponds to the entire visible spectrum bandwidth. The spectral distribution of the source results in the chromatic distortion, both lateral and axial, of the optical field diffracted by the aperture. This detrimental e…
400– to 1000–nm imaging spectrometer based on acousto-optic tunable filters
2004
An imaging spectrometer covering the 400-1000 nm band has been conceived and developed. The system is based on an Acousto-Optic Tunable Filter (AOTF) attached to a high performance digital camera. The AOTF permits the selection of spectral bands with an RF signal in the range of 70-210 MHz. The range is covered using two transducers attached to a single crystal. Although the idea is not new it covers a broader spectrum than previous systems. It includes a telecentric optical system that enhances system efficiency, by ensuring that the chief ray of each light cone emerges out of this doublet parallel to the optical axes. Additionally, an smart choice of integration time reduces the dependenc…