Magneto-Optical Nonreciprocal Devices for Silicon Photonics

Abstract

Silicon waveguide optical non-reciprocal devices based on the magneto-optical effect are reviewed. The non-reciprocal phase shift caused by the first-order magneto-optical effect is effective in realizing optical non-reciprocal devices in silicon waveguide platforms. In a silicon-on-insulator waveguide, the low refractive index of the buried oxide layer enhances the magneto-optical phase shift, which reduces the device footprints. A surface activated direct bonding technique was developed to integrate a magneto-optical garnet crystal on the silicon waveguides. A silicon waveguide optical isolator based on the magneto-optical phase shift was demonstrated with an optical isolation of 30 dB and insertion loss of 13 dB at a wavelength of 1548 nm. Furthermore, a four port optical circulator was demonstrated with maximum isolations of 15.3 and 9.3 dB in cross and bar ports, respectively, at a wavelength of 1531 nm.

Reconfigurable optomechanical circulator and directional amplifier

“…Nonetheless, it is still a challenge to obtain devices with non-reciprocal or active gain properties. Especially the non-reciprocal devices, including the most common isolator and circulator, have attracted great efforts for both fundamental and practical considerations [2][3][4][5][6][7]. Although their bulky counterparts play a vital role in daily applications of optics, the requirement of strong external bias magnetic field and the magnetic field shields, and also the compatibility of lossy mageto-optics materials prevent the miniaturization [8].Owing to the general principle of Lorentz reciprocity or time-reversal symmetry in optics, nonlinear optical effects are the remain option to come round the obstacle [9][10][11].…”

Proposal of Si waveguide optical isolator based on nonreciprocal TE-TM mode conversion using magneto-optical phase shift for TM mode

“…That is, the propagation constant of the TM mode is slightly decreased compared with a non-magnetized case. The TE mode is not affected by the magnetooptical effect [1]. Because of this, the interference spectrum is shifted to a shorter wavelength side in case of the forward propagation.…”

“…There have been proposed and demonstrated several types of SOI waveguide optical isolators. We demonstrated a silicon waveguide optical isolator based on a Mach-Zehnder interferometer with a high isolation of >30 dB [1]. Also, temperature-insensitive optical isolation >20 dB was realized in a temperature range of 20-60 ℃ [2].…”

Optical Nonreciprocal Devices Fabricated with Directly Bonded Magneto-Optical Garnet

“…An MO material is placed as an upper cladding layer and is magnetized in the film plane transverse to the light propagation direction in the MO phase shifter. When the TM-mode light wave is propagated in such a waveguide, it experiences the phase shift caused by the first-order MO effect, which is dependent on the light propagation direction as well as the magnetization direction of MO material [3]. Different MO phase shifts are induced in MZI arms by applying external magnetostatic fields in antiparallel directions in the two arms.…”