Abstract
We proposed a design of a fundamental TM mode waveguide optical isolator using lithium niobate on insulator (LNOI) and deposited magneto-optical film. The optical isolator adopts an asymmetric Mach-Zehnder interferometer (MZI) structure composed of two 1 × 2 MMIs, non-reciprocal and reciprocal waveguides. We used three methods to calculate the non-reciprocal phase shift (NRPS) of the lithium niobate (LN)/ Ce: YIG composite waveguide and got similar results. The device shows about 51.98 nm 30 dB isolation bandwidth and 1.20 dB simulated insertion loss at the wavelength of 1550 nm. The fabrication tolerances and a suitable process are also discussed to meet the state-of-art technology and material properties.
Highlights
In optical communication systems, non-reciprocal optical devices, such as optical isolators and optical circulators, control the unidirectional transmission of light in waveguides or optical fibers
We proposed an optical isolator for fundamental TM mode on lithium niobate on insulator (LNOI) platform
As can be seen from the previous section, non-reciprocal phase shift (NRPS) determines the length of the nonreciprocal waveguide, and affects the loss and compactness, so solving the magnitude of NRPS is the key to design devices
Summary
Non-reciprocal optical devices, such as optical isolators and optical circulators, control the unidirectional transmission of light in waveguides or optical fibers. Sugimoto et al realized an isolator with insertion loss lower than 3.2 dB and isolation over 25 dB in the 1.5 μm wavelength band, which was integrated on PLC platform [12]. Shoji using this method [19] It showed an isolation ratio of 21 dB and an insertion loss of 8 dB at the wavelength of 1559 nm. With a device footprint of 0.94 mm ×0.33 mm, the isolator reached a maximum isolation ratio of 30 dB at the wavelength of 1574.5 nm and an ~5 dB insertion loss. These devices mostly adopted the structure of radiative-coupled magneto-optical waveguides. We conceived a reasonable process flow suitable for the device
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