Asi Solodar

Infrared to visible image up-conversion using optically addressed spatial light modulator utilizing liquid crystal and InGaAs photodiodes

Combination of InGaAs/InP heterojunction photodetector with nematic liquid crystal (LC) as the electro-optic modulating material for optically addressed spatial light modulator for short wavelength infra-red (SWIR) to visible light image conversion was designed, fabricated, and tested. The photodetector layer is composed of 640 × 512 photodiodes array based on heterojunction InP/InGaAs having 15 μm pitch on InP substrate and with backside illumination architecture. The photodiodes exhibit extremely low, dark current at room temperature, with optimum photo-response in the SWIR region. The photocurrent generated in the heterojunction, due to the SWIR photons absorption, is drifted to the surface of the InP, thus modulating the electric field distribution which modifies the orientation of the LC molecules. This device can be attractive for SWIR to visible image upconversion, such as for uncooled night vision goggles under low ambient light conditions.

Optimized depth of field methodology using annular liquid crystal modulator assisted by image processing

An optical-digital tunable depth of field (DOF) methodology is presented. The suggested methodology forms a fused image based on the sharpest similar depth regions from a set of source images taken with different phase masks. Each phase mask contains a different degree of DOF extension and is implemented by using an annular liquid crystal spatial light modulator, which consists of 16-ring electrodes positioned in the pupil plane. A detailed description of the optical setup and characterization of selected pupil phase masks as well as optimization of the binary phase mask for maximal DOF extension is presented. Experimental results are investigated both qualitatively and quantitatively. In addition, the algorithms results are compared with those of some well-known fusion algorithms and proved its supremacy.

Tailored liquid crystal devices for specific imaging applications

Following the mature liquid crystals (LCs) display technology, there is a significant interest in implementing these devices into other non-display applications. Hence the emerging field of LC photonics is becoming increasingly active in which the strong electrooptic properties of LCs are harnessed for these applications particularly for imaging such as the use of SLMs, tunable focus lenses, tunable filters and polarization control devices. In this paper we review our recently developed LC devices integrated into full field optical coherence tomography system, into multi-spectral skin diagnosis system and in extended depth of focus imaging system.

Ultrafast laser induced nanostructured ITO for liquid crystal alignment and higher transparency electrodes

Femtosecond laser nanostructured indium tin oxide (ITO) coated glass is shown to act both as a liquid crystal (LC) alignment layer and as an electrode with higher transparency. The nanopatterns of the 120 nm period were created using ultrashort laser pulses directly on ITO films without any additional spin coating materials or lithography process. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO confirming the follow-up of the LC director to the line orientation. The device interfacial anchoring energy was found to be ∼ 1 μ J / m 2, comparable to the anchoring energy of nematic LC on photosensitive polymers. The transparency as an electrode was found to improve due to the better antireflection and lower absorption expected from a nanostructured surface.Femtosecond laser nanostructured indium tin oxide (ITO) coated glass is shown to act both as a liquid crystal (LC) alignment layer and as an electrode with higher transparency. The nanopatterns of the 120 nm period were created using ultrashort laser pulses directly on ITO films without any additional spin coating materials or lithography process. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO confirming the follow-up of the LC director to the line orientation. The device interfacial anchoring energy was found to be ∼ 1 μ J / m 2, comparable to the anchoring energy of nematic LC on photosensitive polymers. The transparency as an electrode was found to improve due to the better antireflection and lower absorption expected from a nanostructured surface.

Liquid crystal alignment on ultrafast laser nanostructured ITO coated glass

Liquid crystal (LC) devices are widely used as building blocks of many electro-optical systems including linear polarization rotators, dynamical wave plate retarders, and pixilated devices for displays, spatial light modulators, and tunable filters [1]. Precise alignment of the LC molecules is required for high quality components. The anisotropic nature of LC molecules allows them to align on solid surfaces. This can be achieved either due to physicochemical interaction such as photo-alignment on surfaces using polarized blue light or due to the elastic interaction when aligned along nanogrooves created by mechanical rubbing or lithography techniques [2]. Although numerous methods enabling the manufacturing of LC devices have been reported, the technological flexibility and precision remains a problem.

Dataset for Form-Birefringence in ITO Thin Films Engineered by Ultrafast Laser Nanostructuring

Dataset for Cerkauskaite, A., Drevinskas, R., Solodar, A., Abdulhalim, I., & Kazansky, P. (2017). Form-Birefringence in ITO Thin Films Engineered by Ultrafast Laser Nanostructuring. ACS Photonics.