In this work, the transverse optical trapping of spherical particle with strong absorption is studied in geometrical optics
model by numerical simulation. In our work, the exact expressions of wave vector are used instead of traditional
approximate expressions, and the transverse optical trapping force acting on a spherical particle due to strong absorption
is calculated when the particle is illuminated by a focused Gaussian beam of TEM00 mode. The calculated results show
that stable transverse optical trapping positions only exist when the center of the spherical particle is located in front of
the focus of the beam. Our results also reveal that the trapping positions are decided by the radius of the beam waist ω0.
The magnitude of transverse optical trapping force and the stiffness of optical trapping decrease with the increase in ω0.
Optical heterodyne interferometry has been widely used in precision measurements. In this paper, we develop a modified
Mach-Zehnder interferometer for measurement of light polarization state in real time by using two heterodyne frequency
reference beams. Two collinear linearly polarized reference beams with different frequency, ωp and ωs, interfere simultaneously with the measured beam with frequency ω0. The polarization directions of the two reference beams are perpendicular to each other. The light intensity of the interference fringe is monitored by a photodetector. The heterodyne signals, ωp and ωs - ω0, give the amplitudes and the phase difference of the orthogonal polarization components of the measured beam projected to the polarization directions of the reference beams. We analyze the beat frequency signals by Fourier and inverse Fourier transform and realize accurate measurement of polarization state experimentally.
Waveguide is the basic component of integrated optical device. In this work, we introduced a new method to realize switchable waveguide on electric-optical crystals slice. We wrote ferroelectric-domain-inversed pattern in LiNbO3 crystal slice. When we added external electric field on the slice, electric-optical effect operates and the refractive index difference appears in domain-inversed part and its surroundings. Under appropriate configuration, incident beam could be guided along the domain structure. We produced successfully waveguides with width from 10 to 100 μm. Experimental results show that the capability of the waveguides inside LiNbO3 crystal slice could be adjusted by changing the external electric field on the crystal slice. Compared with other production method of waveguide such as ion diffusion, our method is more flexible and more suitable to produce design-free waveguide devices.
Optical microstructures are very important for the realization of multifunctional optics and photonics devices. In the last decade, with the development of commercial femtosecond laser, it has been proven that micro-structuring with femtosecond laser pulses is an excellent tool for free design micro-fabrication of almost all kinds of materials. With the filament, spatially scanning and other methods, many types of 0 to 3-dimensional optical microstructures, including optical memory, waveguides, gratings, couplers and photonic crystals, were produced successfully inside a wide variety of transparent materials of solid state and also liquid state. Here we reviewed the proceeding of the micro-fabrication technology by femtosecond laser pulses in the last few years.
Angular selectivity of volume grating limits the capacity of holographic 3-dimensional storage. In this work, we investigated experimentally the influence of wavefront shapes of the writing beams on the angular selectivity of thick grating in a LiNbO3 crystal. The experimental results showed that longer wavefront curvature results in more critical Bragg angular selectivity.
In photorefractive holographic storages, the superimposed holograms make the refractive index of the media irregular. The readout beam is scattered by the media and the noise is added onto the reproduced messages. In this paper, we introduced a simple way to suppress the noise caused by the superimposition. In our method, holograms were recorded by convergent reference beam. We made the convergent point of the beam overlap the curvature center of a concave mirror. The reflected beam from the concave mirror was used to readout the holograms. By this method, we suppressed the noise caused by superimposition and realized noise-free readout in holographic storage.
We investigated the infrared spectra of the optical damage caused by laser diode at 808 nm in iron-doped lithium niobate crystals. The spectra show that the OH− absorption band in the region of the optical damage exhibits a structure consisting of three peaks. Comparing to the spectra at the non-damage region the main peak moves to red. The result will be helpful to microphotonic device applications.
We propose and demonstrate a new method to fabricate volume phase mask in LiNbO3:Fe crystal by photorefractive effect, for the first time to our knowledge. First, we image an amplitude mask with corresponding intensity distribution at the incident face of a photorefractive LiNbO3:Fe crystal. After an exposure of proper time, due to photorefractive effect, the distribution of refractive index in the crystal is changed. Therefore we get the volume phase mask we want. The influence of the anisotropy of photorefractive nonlinearity on volume phase mask can be overcome by controlling experimental conditions. We can see an intensity-modulation image in the image plane of the volume phase mask. The intensity distribution of the image of the volume phase mask is inverse from the one of input amplitude mask. It can be explained by waveguide theory. Volume phase mask can be used to get modulated amplitude pattern by modulating the phase of incident light. It has the advantage of low energy loss over amplitude mask and real-time. Our method is very simple. It can be used to fabricate many kinds of complex phase masks and phase components used in optical information processing and Integrated Optics.
To the best of our knowledge, we have demonstrated for the first time that ring waveguides can be written and stored in photovoltaic and self-defocusing photorefractive medium LiNbO3:Fe crystals. The interactions between the ring solitons, such as the fusion and the birth of ring solitons, have been experimentally observed.
Based on the Li set vacancy model, we analyze the incorporation process of Mg ion in LiNbO3:Mg crystals with increasing MgO doping concentration. The obtained results are in good agreement with the experimental data reported in the literature. The congruent melting compositions are predicted according to our suggested incorporation model when the (Li2O-MgO-Nb2O5) system is considered as a ternary one.A procedure is suggested to find out the congruent melting compositions of LiNbO3:Mg crystals.
In this paper, we analyze the characters of all damage- resistant dopants' valences and electronic shell configurations found up to now in LiNbO3 crystals. We show that all damage-resistant dopants have only one valence state. We also show that these damage-resistant ions' electronic shell configurations are filled fully, as are the cases of the inert elements. From this point of view, we conclude that the anti-site NbLi5+ should be involved in the charge transport process, while the Li vacancy VLi is not involved in the charge transport process. It also can give us some insights about how to select a damage-resistant dopant for LiNbO3 crystal.
KEYWORDS: Modulation, Optical signal processing, Signal processing, Absorption, Mass attenuation coefficient, Interference (communication), Molecules, Signal to noise ratio, Proteins, Differential equations
In this paper, we analyzed theoretically the modulated transmission property of bR film under two beams of light, yellow light and purple light, illuminate the bR film simultaneously. Using the transmission property of bR film, we can realize the winner-take-all thresholding operation. Based on this thresholding operation, we realized some useful optical signal process.
In this paper we demonstrated the advantage of the fanning- noise-free double doped photorefractive LiNbO3 crystals for the 3D storage. The fanning noise can be completely suppressed. The SNR and the line resolution of the holographic reconstructed patterns in these kinds of crystal are very high. It is simple and convenient to practice using double doped LiNbO3 crystal to suppress the fanning noise.
In this paper, we examined the saturation absorption nonlinearity of Azo doped polymers, based on which we successfully realize a novel optical filter for improvement in contrast of images.
In this paper, we report a new effect -- the threshold effect of incident light intensity for the photorefractive light-induced scattering in LiNbO3:Fe, Mg crystals, which could be used as a simple, effective technique to suppress the photorefractively light-induced scattering and is useful for us to get the noise-free photorefractive devices.
In this paper, we introduce a new technology for picking-up images and one-way aberration- free image communication through a phase-disturbing medium using photorefractive four- wave mixing and theoretically analyze this photorefractive process using the photorefractive four-wave coupling equations. We also experimentally realize this operation in the LiNbO3:Fe crystal.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.