In recent years, standard CMOS microprocessors have approached their maximum power dissipation per unit area, effectively placing a limit on computational power. This highlights the urgent need to explore alternative technologies. One promising avenue is the use of superconductors, which demonstrate zero resistivity below a critical temperature. However, circuits based on superconductors necessitate the use of cryostats to maintain low temperatures, presenting challenges in data transfer with the room temperature environment. While coaxial cables are often employed for this purpose, they suffer from limited data transfer rates and contribute significantly to heat load. On the contrary, photonics integrated circuits (PICs) coupled with optical fibers present a viable solution. They enable scalable, cost-effective, and power-efficient optical interconnections capable of supporting high data transfer rates while minimizing heat transfer. In this presentation, We will discuss the latest advancements in cryogenic PICs, focusing on their application in interfacing with cryogenic computing systems such as single-flux-quantum logic circuits and superconducting qubits.
The nonreciprocal phase shift caused by the first-order magneto-optical effect is effective in realizing optical
nonreciprocal devices such as optical isolators and circulators in silicon waveguide platforms. The low refractive index
of the buried oxide layer in a Silicon-On-Insulator (SOI) waveguide enhances the magneto-optical phase shift, which
reduces the device footprints. In order to obtain the magneto-optical phase shift, it is required to integrate a magnetooptical
material on the silicon waveguide. A surface activated direct bonding technique was developed to integrate a
magneto-optical garnet single crystal on the silicon waveguides. Using this technique, a silicon waveguide optical
isolator based on the magneto-optical phase shift was demonstrated with an optical isolation of 30 dB at a wavelength of
1548 nm. Furthermore, a four port optical circulator was demonstrated with maximum isolations of 33.5 and 29.1 dB in
cross and bar ports, respectively, at a wavelength of 1543 nm. Excess insertion losses were 13 and 12.5 dB in the isolator
and circulator, respectively.
We developed a technique of bonding magneto-optic garnets to III/V compound semiconductors for integrating an optical isolator with a semiconductor optical device. Some approaches to realize an isolator integrated with a laser diode will be presented.
The wafer bonding of III-V semiconductor materials with garnet thin films has become of increasing technological importance in integration of optical components. The wafer bonding between InP wafer and GGG was demonstrated by using O2 plasma surface activation. The same process was applied to the bonding process of InP/Ce:YIG, which is indispensable for the fabrication of an integrated optical waveguide isolator.
KEYWORDS: Switches, Switching, Signal generators, Asynchronous transfer mode, Signal processing, Demultiplexers, Picosecond phenomena, Electronics, Data storage, Telecommunications
A novel unidirectional mode converter, which has the advantage
of a simple magnetization structure, is proposed for an application
to a waveguide-type optical isolator. The proposed mode converter
is constructed with in-plane magnetization in the whole device,
where the magnetization component along a light propagation
direction produces a mode conversion between TE0 and TM0 modes,
while the magnetization perpendicular to the propagation direction
provides a nonreciprocal phase shift to the TM0 mode. The
unidirectional mode converter, in which, in the backward direction,
100% TE-TM mode conversion is produced but, in the forward
direction, an input TE mode emerges as a TE mode, is realizable by
virtue of the nonreciprocal phase shift of the TM0 mode.
Design examples are shown by using the (LuBi)3Fe5O12 guiding
layer / (YBi)3Fe5O12 cladding layer / Gd3Ga5O12 substrate structure.
A typical length of the mode converter is 15.5 mm at the wavelength
of 1.152 .tm for the guiding layer thickness of O.575jim and with the
magnetization direction tilted by 87 degree from the light
propagation direction in the film plane. A relatively large device
length is reduced by using a magnetooptic material having a large
first-order magnetooptic coefficient.
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