Aug 7, 2013
Long range air-hole assisted subwavelength waveguide targets high-density photonic ICs
A straight optical waveguide is a fundamental building block for photonic integrated circuits. To meet the demands of high-density photonic integration, subwavelength confinement in the integrated plane of the circuit, chip-scale long propagation length, highly efficient waveguide bends with compact footprints, and tiny centre-to-centre separation between adjacent waveguides with negligible crosstalk are the four indispensable requirements. So far, few waveguides can satisfy all of these design features simultaneously.
In a recent study, scientists in China describe a metal-dielectric-metal (MDM)-photonic crystal (PC)-hybrid waveguide with promising characteristics. The configuration, dubbed a long-range air-hole assisted subwavelength (LR-AHAS) waveguide, can be considered as the equivalent combination of a MDM waveguide with a PC waveguide.
By taking full advantage of the ultra-low propagation loss of a PC waveguide, the high-absorptive metal can be partly isolated, and the loss of the hybrid waveguide can be significantly reduced. Meanwhile, by utilizing the high reflectivity with the mirror symmetry of a metal as well as the strong mode confinement of a MDM structure resulting from the evanescent field effect, the lateral periodic number and the entire width of a PC waveguide can be largely decreased.
Simulation and testing
The results reveal that the figure of merit (FOM) of the proposed waveguide is as high as 6 × 108, the propagation length is 15.2 mm with a lateral mode width of between 511.3 nm and 564.3 nm, and waveguide isolation of over 36 dB with tiny centre-to-centre separation at the wavelength of 1.55 µm. In addition, broad optical bandwidth, high efficiency 90° and 120° direct bends, and low radiation loss of the metallic gaps in the new waveguide are also demonstrated.
These excellent features show that the proposed waveguide could be an ideal candidate for high-density photonic integrations.
Full details can be found in the journal Nanotechnology 24 235203.
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About the author
Wen Zhou is a graduate student in the School for Information and Optoelectronic Science and Engineering at South China Normal University, under the supervision of Prof. Xu Guang Huang. One of Zhou’s major research interests deals with the design and development of novel waveguides and related functional devices, in particular – the realization of subwavelength mode confinement and low-loss propagation properties based on photonic crystal waveguides, plasmonic waveguides and their hybrid descendants. Dr Xu Guang Huang is a Professor in the School for Information and Optoelectronic Science and Engineering at South China Normal University. He has published more than 80 peer-reviewed papers in international academic journals, and several patents. His research interests include integrated optics, nanophotonics, fibre-optic communications, and fibre sensors.