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A highly efficient GeSn electroabsorption modulator using higher-order-mode is proposed for mid-infrared photonics. Proposed structure is suitable for monolithic integration on Ge-on-Si platform and > 10 dB enhancement of the extinction ratio is possible.
Fully three-dimensional wavefront matching method for waveguide discontinuity problem is newly developed. In principle, the developed method can be applied to optimize any geometries including reflection. The application for Si mode converters (TE0-TE1, and TE0-TE2) are demonstrated and ultrasmall structure with low-loss is obtained.
A five-mode multiplexer/demultiplexer based on a partially elongated five-core fiber is presented. Multiplexing operation is experimentally verified. Mode selectivity higher than 95% at 1550 nm, for both the LP11 and the LP21 mode, is achieved.
We propose a low-loss and low-crosstalk Mach-Zehnder mode multi/demultiplexer for WDM/MDM transmission. A broadband 3dB mode divider, which is also newly devised here, makes it possible to compose Mach-Zehnder filter for “mode” and “wavelength” simultaneously.
A novel GeSn electroabsorption modulator using vertical multimode interference is proposed for mid-infrared photonics. The size of the proposed device is 1/3 with lower loss and larger extinction ratio compared with conventional structure.
Material characteristics (optical gain/absorption, refractive index change) of GeSn/SiGeSn quantum wells in mid-IR region is theoretically investigated based on many-body theory. The strategies for designing quantum wells having large material gain or absorption under applied electric field are discussed.
A three-mode exchanger composed of symmetric and asymmetric directional couplers is proposed for mode-division-multiplexing system. Theoretical design shows low-loss and highly efficient mode exchanging is possible. Fabricated device exhibits successful mode exchanging for LP01 mode.
A novel scrambling-type mode multiplexer is proposed for future large-mode-number mode-division-multiplexing. 3-mode multiplexer design based on silica PLC shows low-loss and small wavelength dependence multiplexing is possible and a proof-of-concept device is fabricated.
Multi-stage mode conversion technique, using asymmetric directional couplers and tapered mode converters, for launching LP21b and LP02 mode on PLC for six mode multi/demultiplexer is proposed. Successful excitation of these modes are demonstrated.
Impulse response of coupled six-core fibers is analyzed based on nonlinear Schrödinger equation, showing good agreement between theory and reported measured results. It is shown that air-hole added structure reduced the group delay spread further.
The wavefront matching method for the waveguide discontinuity problem is newly developed in this study. The developed method can be applied to optimize the waveguides including reflection. The application for silicon mode converters are demonstrated and ultrasmall and low-loss structure is obtained.
A simple and versatile design method for suppressing the reflection of photonic crystal (PC) cavities is proposed. The proposed method only requires the tuning of the waveguide width and distance between the waveguide and cavity, without changing the structure of cavity itself.
We demonstrate optimized design of 4LP-mode multicore fibers (MCFs) with low differential mode delay (DMD) for high spatial multiplicity and find that 4LP-mode 19-core fiber can achieve the highest reported relative core multiplicity factor (RCMF) with a cladding diameter (CD) of less than 250 pm.
A compact and low-loss PLC-based mode rotator is proposed. The mode rotator with curved trench is devised based on wavefront matching method. The proposed structure is 60% in size and low-loss (1/5) compared with conventional structure with straight trench.
We fabricated a lumped-electrode type EADFB laser module using a flip-chip interconnection technique which provides a large modulation bandwidth. We obtained clear 56-Gbaud 4-PAM signal after 10-km SMF transmission with no equalizer using this module.
An air-hole added six-core fiber with extremely small group delay spread is proposed for mode-division-multiplexing-system. A principal mode analysis reveals that 95% reduction of the group delay spread is possible compared with conventional coupled-six-core fibers.
Using a lumped-electrode EADFB laser with a modulation bandwidth of ∼59 GHz, we demonstrated single-wavelength single-polarization direct-detection 4-PAM transmission with the record net data rate of 200 Gbit/s.
In a class focused on practical programming, it is not uncommon to find a large difference in student ability levels. When such a gap in proficiency exists, students with a high level of understanding tend to find the class too simple and as a result their motivation decreases. Up until this point, we have been responding to students who have a lower level of understanding by providing them with supplementary...
We demonstrated a six-spatial-mode multiplexer using effective index matching and adiabatic mode transition. Six-mode multiplexing including the equal effective indices of LP21b and LP02 was successfully achieved with a fabricated PLC on one chip.
Quantum-confined Stark effect of Ge(Sn)/SiGe(Sn) quantum wells (QWs) is analyzed by many-body theory. Calculated absorption spectra of Ge/SiGe-QWs are in good agreement with the experiment. Also, the effect of Sn-incorporation is investigated for mid-infrared applications.
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