Abstract:
A photorefractive composition and a photorefractive device comprising the composition are disclosed. The composition is configured to be photorefractive upon irradiation by a laser having a wavelength in the visible light spectrum and comprises a polymer, a non linear optical chromophore, and a plasticizer. In an embodiment, the percentage of polymer recurring units that comprise a charge transport moiety is less than 30 %. In an embodiment, the polymer is selected from the group consisting of polycarbonate, polyurea, polyurethane, poly(meth)acrylate, polyester, polyimide, and combinations thereof. Preferably, the composition has a diffraction efficiency of about 30 % or greater upon irradiation with a visible light laser.
Abstract:
Holographic methods for recording fast movies whose speed is limited by the laser pulse duration if the recording material has sufficient sensitivity to reliably record a frame of the fast event with a single pulse. The method uses the selectivity of multiplexed holograms to resolve frames that are recorded with adjacent pulses. Specially designed pulse generators (62, 64, 66) are used to generate the pulse train that illuminates an object (71) and a reference pulse train. The signal and reference pulse trains are then directed to a recording medium (10). We experimentally demonstrate the system by making movies of laser induced shock waves with a temporal resolution of 5.9ns, limited by the pulse width of the Q-switched Nd:YAG laser used in the experiments.
Abstract:
The present invention provides a multi-channel tunable filter and methods for making such a filter. In one embodiment, the filter (100) comprises a bank of gratings (111) imprinted into a filter material (130), such as Lithium Niobate. In another embodiment, the filter comprises a bank of gratings imprinted on a thin-film filter. An optical read-head comprising a pair of lenses is configured to pass light from within an optical fiber carrying multiple wavelengths through an appropriate grating to extract or drop a specific wavelength. To ensure continous data transmission, the filter is tuned to a wavelength by configuring the read-head to move in a hitless manner. In one embodiment, the gratings are recorded by the interference of two beams. A first wave reflects off a first mirror stack and a second plane wave reflects off a second stack. In another embodiment, the gratings are recorded by a phase masking method.
Abstract:
The invention relates to an optical switch which includes a paraelectric photorefractive material (10), storing a hologram (24), possibly a latent hologram, whose reconstruction, or activation and reconstruction, is controllable by means of an applied electric field (12, 14). The hologram may be formed by spatial modulation of refractive index of the paraelectric photorefractive material, which arises from the quadratic electro-optic effect induced by the combined action of a spatially modulated space charge within the paraelectric photorefractive material and an external applied electric field. The switch may be used in a switching network, such as a multistage network for optical communication.
Abstract:
A system for recording multiple volume Bragg gratings (VBGs) in a photo thermo- refractive material is configured to implement a method which provides for irradiating the material by a coherent light through a phase mask. The system has a plurality of actuators operative to displace the light source, phase mask and material relative to one another so as to mass produce multiple units of the material each having one or more uniformly configured VBGs.
Abstract:
Described herein are optical devices comprising a photorefractive layer and at least two inert layers, such that the photorefractive layer is sandwiched between the two inert layers. The photorefractive layer may include a photorefractive composition that is photorefractive upon irradiation by a laser beam. In some embodiments, the photorefractive composition is formulated such that a grating that is irradiated into the photorefractive composition can be read out of the photorefractive composition without applying an external bias voltage. Furthermore, a grating that is written into the composition may be controlled using thermal treatment.