RESUMEN
We present an original acousto-optic tunable filter that is able to filter visible light from 400 to 650 nm and is designed to interact simultaneously with two polarizations. The filter shows an adjustable optical bandwidth and apodization capabilities. These features make it suitable for practical spectroscopic applications. Experimental validation is also presented.
RESUMEN
Phase imaging microscopy with incoherent object illumination is convenient and affordable for biomedical research and clinics since it provides easy integration with a variety of bright-field optical microscopes. We report the design of a new hyperspectral imaging system based on a combination of a spatial light modulator (SLM) and an acousto-optic tunable filter (AOTF) for phase imaging microscopy. Contrast of phase-only objects originates from matched spectral and spatial filtering performed by the SLM and the AOTF located in Fourier-conjugate optical planes in the back-end of the optical system. The system is designed as an add-on to a standard optical microscope with incoherent diascopic sample illumination.
RESUMEN
Acousto-optic tunable filters are known as efficient instruments for spectral and spatial filtering of light. In this paper, we analyze the bandwidth dependence of a double-pass filter. The interaction geometry chosen allows the simultaneous diffraction of the ordinary and the extraordinary optical modes by a single ultrasonic frequency. We present the main parameters of a custom device (design, optical range, driving frequency) and experimental results concerning the angular deviation of the beams including the effect of optical birefringence. The spectral resolution and the side lobes' significance are discussed. Spectral bandwidth of such a system is analyzed.
RESUMEN
A cascaded system of two acousto-optical cells is proposed and experimentally demonstrated for optical notch rejection filtering in the spectral range from 1400 nm to 1600 nm. Two similar paratellurite acousto-optical devices for unpolarized light are used in a free-space gap of a fiber line. Compensation for birefringence in anisotropic paratellurite devices provides a diffraction regime that is insensitive to polarization of light. High extinction ratios up to 40 dB are measured.
RESUMEN
We study simultaneous photonic and phononic crystal slabs created in Z-cut lithium niobate membranes. Bandgaps for guided waves are identified using the three-dimensional finite element method (FEM). Three lattices are considered: the square, the hexagonal, and the honeycomb lattices. We investigate the evolution of band gaps as a function of geometrical parameters such as hole radius and membrane thickness. We show the existence of dual photonic and phononic bandgaps in the triangular lattice for suitable geometrical parameters and specific modal symmetries for both the elastic and the electromagnetic fields.
RESUMEN
In the paper, bandwidth parameters of acousto-optical deflectors (AODs) are analyzed from the point of view of acoustical anisotropy. Equations for bandwidth and central frequency of AOD are derived for arbitrary propagation direction of ultrasound in optically uniaxial crystals. The phenomenon of bandwidth shift due to phase mismatch at the central frequency is studied theoretically and verified experimentally.
RESUMEN
A wide bandwidth tunable optical low-frequency shifter is presented in this work. It is based on two acousto-optic devices operating in tandem. The relevant parameters of the specific configurations of acousto-optic interactions in paratellurite material are detailed. Results from numerical computations leading to the practical design parameters are given. The low-frequency shifter has been experimentally tested at a visible wavelength λ0=514 nm and a high efficiency (>60%) has been measured. The tuning capability of the optical shifter covers a bandwidth Δf=26 MHz.
RESUMEN
We propose a method for filtering convergent light beams with arbitrary polarization. For this purpose, a tandem of similar acousto-optic tunable filters was applied. Owing to the special mutual orientation of the cells, two coincident beams with ordinary and extraordinary polarizations were diffracted by the first crystal and the second crystal, respectively.
RESUMEN
A cascaded system of two acousto-optical cells is proposed for equalization of multichannel optical signal satisfying coarse wavelength-division multiplexing standard. Two similar acousto-optical modulators for unpolarized light on the basis of 10 degrees-cut paratellurite crystals were used in a free-space gap of a fiber line. The system controlled intensity of several optical carriers in the spectral range from 1200 to 1700 nm. The device was tested in a four-channel regime of operation in the range 1510-1570 nm. Overall optical insertion losses did not exceed -2 dB and less than 1 W electric power per channel was necessary for -20 dB intensity attenuation of the signal in a continuous operation mode. Compensation for birefringence in paratellurite provided diffraction regime that was insensitive to polarization of light. Interchannel crosstalk was less than -10 dB.
RESUMEN
We present a bifrequency acousto-optic tunable filter (AOTF) for applications using polychromatic laser beams. The acousto-optic device is based on two successive anisotropic interactions in paratellurite: the first takes place with an acoustic shear wave tilted at 10 degrees from the [110] axis, while the latter is provided by the acoustic shear wave propagating collinear to the [110] axis. It is then demonstrated that the sidelobes of the impulse response to optical wavelengths of such a bifrequency AOTF are greatly reduced. General expressions of operating frequencies, spectral bandwidths, and acoustic powers are derived. Numerical computations have been drawn for paratellurite. The bifrequency AOTF has been tested using a multiline beam radiated by an argon laser. According to the spectral power distribution of this polychromatic laser beam, the most critical configurations of wavelength filtration have been considered. Experimental results confirm the theoretical predictions.
