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GaN waveguide directional coupler for optical quantum information processing systems (Conference Presentation)
Author(s): Junya Miwa; Masafumi Kihira; Keishi Shiomi; Yasufumi Fujiwara; Masahiro Uemukai; Ryuji Katayama
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Paper Abstract

Waveguide Mach-Zehnder interferometers (MZIs) composed of two directional couplers (DCs) are widely used as basic building blocks in the optical communications systems and photonic quantum circuits. Since nitride semiconductors have a strong electro-optic effect, they are suitable for implementation of the fast electric-field driven phase shifters in MZIs. In addition, based on its strong optical nonlinearity, the nitride semiconductors can be applied to the quantum light source of 800 nm band via an optical parametric down conversion process. By integration of the nitride-based waveguide MZI devices and the InGaN laser diodes pumped high-efficiency quantum light sources, novel quantum information processing systems made of single material can be expected. In this work, we report on the design, fabrication and evaluation of two types of waveguide DCs: rib waveguide and strip waveguide. As for the design the DC which splits an incident wave at a wavelength of 810 nm into two waves with equal power, 3D beam propagation method simulations were performed. The DCs with different coupled waveguide lengths were fabricated by RIE using Ni hard masks. After a SiO2 cladding layer deposition, the devices were diced and end facets were polished. The splitting characteristics of the rib waveguide DCs were evaluated using a DFB laser, and almost 1:1 splitting ratio was successfully obtained. Measured data shows that we can control the splitting ratio by changing coupled waveguide length. In addition to the above results on rib waveguide DC, we will report on the fabrication and evaluation of the strip waveguide DCs.

Paper Details

Date Published: 13 March 2019
Proc. SPIE 10918, Gallium Nitride Materials and Devices XIV, 109180J (13 March 2019); doi: 10.1117/12.2510634
Show Author Affiliations
Junya Miwa, Osaka Univ. (Japan)
Masafumi Kihira, Osaka Univ. (Japan)
Keishi Shiomi, Osaka Univ. (Japan)
Yasufumi Fujiwara, Osaka Univ. (Japan)
Masahiro Uemukai, Osaka Univ. (Japan)
Ryuji Katayama, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 10918:
Gallium Nitride Materials and Devices XIV
Hiroshi Fujioka; Hadis Morkoç; Ulrich T. Schwarz, Editor(s)

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