1,721,240 research outputs found
Manipulating wavelength-selective emission with heterogeneous photonic crystals
No full textThe usual near-field radiation profile of a light beam emanating from a photonic crystal waveguide (PCW) has a main lobe at the center line of the waveguide. However, a centrally symmetric profile for the emission pattern with two sidelobes can be required in some applications, e.g., Y-type power dividers, wavelength multiplexers, and semiconductor lasers. With such motivations in mind, we present the design of a compact structure that deflects the beam propagation direction in this manner. The idea utilizes the manipulation of the dispersion diagram of cascaded photonic crystals by exploiting the bandgap and self-collimation properties. The waveguide mode in the PCW can be transformed from a propagating mode into a diffusive one by altering the filling factor, which, in turn, leads to off-axis light emission. By using the finite-difference time-domain method, we show that the emission takes place into free space at the inclined output surfaces of the PCW with deviation angles of +/- 45 degrees. (C) 2011 Optical Society of AmericaTechnological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T306]; Turkish Academy of Sciences (TUBA GEBIP)Turkish Academy of SciencesThe author gratefully acknowledges the financial support of the Technological Research Council of Turkey (TUBITAK) under project no. 110T306. H. Kurt also acknowledges support from the Turkish Academy of Sciences Distinguished Young Scientist Award (TUBA GEBIP)
Optimal Design of Omni-directional Optical Cloaking by Annular Sectorized Unit-cells
No full textIn this manuscript, we demonstrate the design and experimental proof of an optical cloaking structure which multi-directionally conceals a perfectly electric conductor (PEC) object from an incident plane wave. The dielectric modulation around the highly reflective scattering PEC object is determined by an optimization process for multi-directional cloaking purposes
All-Optical Half Subtractor Circuit Based on Inverse- Designed Logic Gates
No full textWe present a half-subtractor circuit consisting of the combination of AND and NOT gates designed with topology optimization. We could achieve good performance, making our design suitable for various photonic circuit applications
Inverse design of compact multimode waveguide bends leveraging enhanced Bezier curve techniques
No full textWe designed two compact multimode silicon waveguide bends (MWBs) leveraging the Bezier curve with added structural parameters, achieving simulated outcomes with minimal insertion loss (<0.11 dB and <0.16 dB) and inter-modal crosstalk (<-19.4 dB and <-20.3 dB)
Channel Phase-Error Initialization via Inverse Designed On-Chip Silicon Metalens
No full textWe propose a method for phase initialization and error correction using silicon on-chip metalens. Leveraging inverse design techniques, we engineered on-chip metalens with high-performance characteristics of 61.3% focusing efficiency and 0.39 numerical aperture at 1550 nm wavelength, with a broad operation bandwidth of 380 nm
Experimental demonstration of silicon-based on-chip neuromorphic optical computing
No full textWe propose an experimental demonstration of a silicon-based neuromorphic computing scheme with optical interconnects. The device consists of 4-channel input grating coupler arrays to guide 1550 nm light through the waveguide, tunable Mach-Zehnder Interferometer (MZI) mesh for matrix-vector multiplication, micro-ring resonator (MRR)-based MZI to implement nonlinear activation function, and 4-channel radiator array for free-space radiation. Depending on the different input information (i.e., image, voice, text, etc.), the radiated beam is focused in different directions to perform the classification task. Our proposed on-chip optical computing scheme can pave the way for future AIs, providing a small footprint, high-speed, cost-effective, and power-efficient
Inverse Design of a 4-by-2 Silicon-Based Photonic Encoder Circuit Using Topology Optimization
No full textWe propose a 4-to-2 inverse-designed photonic encoder, occupying 30 μm 2, operating at 1.52 μm–1.60 μm. Employing topology optimization to design our device, we achieved efficient performance of encoder functions
Theoretical Study of Directional Emission Enhancement From Photonic Crystal Waveguides With Tapered Exits
No full textWe utilize an approach based on the idea of tapering waveguide exits to increase the directional emission of the light waves emitted from photonic crystal waveguides. It is shown that the enhancement of the directional beaming can be achieved under certain tapered configurations due to the interference pattern created at the exit of the waveguide. The output radiation profile is observed with the finite-difference time-domain method and a 75% reduction in the divergence angle of the out-coupled beam is achieved with the modified waveguide ends.
Wide-angle field-of-view air-hole metalens based on quadratic phase profile
No full textWe investigate an air-hole metalens based on quadratic phase profiles. The engineered metalens provides a field of view of 160°, approximately 80% focusing efficiency and 0.80 numerical aperture at 1550 nm wavelength
Limited-diffraction light propagation with axicon-shape photonic crystals
No full textElectromagnetic beams are subject to spatial spreading as they propagate. I have investigated the light propagation passing through a finite-aperture, which is obtained by two-dimensional square-lattice photonic crystals (PCs). It is found that the beam that is coupled to the free-space by exiting the axicon-shape PC resists considerably against the diffraction. The inspection of the beam profile in the transverse to the propagation direction reveals the appearance of the side-lobes, and I have attributed the limited-diffraction beam propagation to these artificially created lobes. I optimize the length of the aperture while keeping the width constant and show that an order of magnitude improvement for beating the diffraction length is achievable. The advantages of the presented PC-based axicon over the bulk refractive axicons are the compactness and integrated nature of the former one, in addition to the flexibility of engineering individual unit cells of PC structure. (C) 2009 Optical Society of America
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