Browsing by Author "Chen, Ming Syuan"

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All-optically controlled light valve assembled by photorefractive crystal and PDLC hybrid structure
(2015-01-01)
Marinova, Vera
;
Liu, Ren Chung
;
Chen, Ming Syuan
;
Lin, Shiuan Huei
;
Lin, Yi Hsin
A light-valve device, assembled by Ru-doped Bi12SiO20 (BSO) photoconductive substrate and polymer dispersed liquid crystal layer is proposed, in which all the processes are controlled by the near infrared light. Laser beam illumination (Gaussian shape) on BSO:Ru crystal caused charge carriers generation, which migrate and form an inhomogeneous distribution and subsequent space charge field. This surface-localized electromagnetic field penetrates into the PDLC layer and modulate the orientation of the liquid crystals, that caused reverse of the device initial opaque state to the highly transparent one. The proposed structure is simple and easy to fabricate, without requirements of ITO contacts and alignment layers and opens further possibilities for near-infrared applications.
Graphene-based spatial light modulator operating at near infrared spectral range
(2019-04-01)
Marinova, Vera
;
Lin, Shiuan Huei
;
Petrov, Stefan
;
Chen, Ming Syuan
;
Lin, Yi Hsin
In this paper, a near infrared operating spatial light modulator is demonstrated, assembled in a way to combine the excellent photoconductivity of Ru-doped Bi12SiO20 (BSO:Ru) crystal, strong birefringence of liquid crystal (LC) and exceptionally high transparency and conductivity of graphene. A photo-alignment method instead of mechanical rubbing is used to simplify the fabrication procedure and to prevent detachment of the graphene layer from the substrate. The proposed device operates at low driving voltage (competitive to a reference device using ITO electrodes) moreover requires much less near infrared intensity for the light modulation. It is assumed the effect is due to the photo-induced space charge exchange between BSO:Ru and graphene allowing charge redistribution and optical doping effect resulting in a modulation of graphene's properties. The voltage-dependent transmittance and phase retardation show high contrast ratio with the response time of similar to 100 ms at 1064 nm. In addition, by projecting a video image through the proposed structure the response of modulated pump light intensity is demonstrated which supports device ability to work as near infrared optically addressed spatial light modulator (OASLM). The obtained performances reveal great potentials of graphene-based electro-optic devices for near infrared applications.