We demonstrated a large aperture 1×16 silicon photonics OPA leveraging one-millimeter-long subwavelength grating antennas (SGA). The SGA is implemented by placing subwavelength silicon segments in the vicinity of the conventional strip waveguide so that they only interact with the evanescent field of the strip waveguide. The strength of the SGA can be conveniently controlled by tuning the location and size of the silicon segments. With the 1×16 OPA, a light beam of 0.1°×1.8° with a sidelobe suppression ratio > 10 dB is achieved.
We propose a multiwaveguide cavity which can significantly enlarge the mode volume of distributed feedback (DFB) cavity without increasing the cavity length. The cavity is constructed by combining λ/4 shifted DFB cavity with contra-directional couplers. Different from single-waveguide DFB cavity, the resonant mode is oscillating in multiple waveguides. A smaller threshold gain density is also obtained compared to single-waveguide DFB cavity. Theory model of the multiwaveguide cavity is established and finite-difference time-domain simulation is performed to verify the model.
Liquid crystal based phase only spatial light modulator has attracted many research interests since last decades because of its superior advantage. Until now the liquid crystal spatial light modulator has been applied in many fields, but the response speed of nematic LC limited its further application. In this paper, an optically addressed phase only LC spatial light modulator was proposed based on polymer network liquid crystal. Morphology effect on the light scattering of PNLC was studied, which was mainly consisted of fiber and fiber bundles. The morphology nearly determined the light scattering and electro-optical property. Due to the high threshold voltage, to address the PNLC phase modulator was also concerned. Optical addressing method was proposed, in which BSO crystal was selected to replace one of the glass substrate. The response speed of PNLC was so fast that the reorientation of liquid crystal director will follow the change of effective voltage applied on LC layer, which was related with the voltage signal and especially with electron transport of photo-induced carriers due to diffusion and drift. The on state dynamic response of phase change was investigated. Based on this device, beam steering was also achieved by loading 488nm laser strip on the optical addressed phase only spatial light modulator.
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