T. Mizumoto

T. Mizumoto
Tokyo Institute of Technology | TITech ·  Department of Electrical and Electronic Engineering

Degree of Engineering

About

309
Publications
12,312
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3,627
Citations
Additional affiliations
April 1984 - present
Tokyo Institute of Technology
Position
  • Professor (Full)

Publications

Publications (309)
Article
Optical isolators are necessary components in photonic integrated circuits to ensure system stability by blocking the back-reflected light waves. In this study, a transverse electric mode magneto-optical isolator based on an asymmetric microring resonator without additional polarization rotators in series is demonstrated. Cerium-substituted yttrium...
Article
Full-text available
We experimentally demonstrated a silicon optical isolator using a monolithically integrated cobalt ferrite (CFO) film as magneto-optical material, achieving an isolation ratio of 9.6 dB near 1550 nm wavelength. By virtue of the large Faraday rotation coefficient of CFO, the device has a compact footprint comparing to the current yttrium iron garnet...
Article
In photonic integrated circuits (PICs), optical isolators and circulators are essential to prevent lasers from backreflections and to reroute the light flow. In this paper, an integrated polarization-independent device that can be operated as an optical isolator or an optical circulator, based on an InP membrane on silicon platform, is demonstrated...
Preprint
Full-text available
A fundamental challenge of the quantum revolution is to efficiently interface the quantum computing systems operating at cryogenic temperatures with room temperature electronics and media for high data-rate communication. Current approaches to control and readout of such cryogenic computing systems use electrical cables, which prevent scalability d...
Article
This paper extends our previous work on the microring resonator-type serial-to-parallel conversion scheme aimed for all-optical label processing on the silicon photonic platform. In the previously proposed scheme, the architecture of the delay lines was silicon wires. This resulted in considerable propagation loss, confining multibit operation of s...
Article
As an indispensable component in the photonic integrated circuits, the design and fabrication of optical isolators, particularly in the transverse electric (TE) polarized mode, is a long-standing challenge. Herein, we present a TE mode magneto-optical isolator using adiabatic tapered waveguides to realize conversions between designated modes. The i...
Article
We propose a 3 dB polarization coupler in which the input light of the TE mode is converted into two out-of-phase TM modes, and the input light of the TM mode is split into two in-phase TM modes. This was designed with a 3-steps taper structure. When a Mach−Zehnder interferometer (MZI) is composed of the proposed 3 dB coupler, the polarization of t...
Article
Nonvolatile optical switches are promising components for low-power photonic integrated circuits with multiple functionalities. In this study, we experimentally demonstrate magneto-optical switches integrated with a magnet array. Optical switches in both microring and Mach-Zehnder configurations are fabricated on a high-quality single-crystalline m...
Article
We propose and demonstrate the fundamental operation of a novel on-chip microring resonator-type serial-to-parallel conversion scheme for all-optical label processing. We left out a delay between the simultaneously implemented pump pulses and probe bits to be extracted. This enabled us to utilize free-carrier dispersion effect to concurrently blue...
Article
Magneto-optical (MO) switches operate with a dynamically applied magnetic field. The MO devices presented in this paper consist of microring resonators (MRRs) fabricated on amorphous silicon-on-garnet platform. Two types of MO switches with MRRs were developed. In the first type, the switching state is controlled by an external magnetic field compo...
Article
In this study, we propose a novel all-optical switch that is controlled by the thermo-optic effect in a silicon ring resonator with a metal cladding layer. A pump light is efficiently converted into heat through absorption by a metal layer, causing a resonant wavelength shift. The burst-switching measurement reveals a switching on/off ratio of 5.7...
Conference Paper
Magneto-optical phase shift is effective to realize on-chip optical isolators. Optical isolators are fabricated on SOI platforms with isolation ratios of 30 and 16 dB for TM and TE mode input, respectively.
Article
Optical absorption of a guided light wave in a waveguide by a metal is undesirable in many photonic integrated devices. However, the heating due to the optical absorption enables to realize novel applications such as non-volatile optical memories and all-optical thermo-optic devices. We report an efficient heating due to the optical absorption of a...
Article
Full-text available
Silicon waveguide optical isolators were fabricated by direct bonding of magneto-optical (MO) garnet. The technique allowed efficient MO phase shift owing to the use of single-crystalline garnet and negligibly thin interlayer on the silicon core layer. A Mach–Zehnder interferometer (MZI) provided optical isolation utilizing the MO phase shift. High...
Article
Optical isolators and circulators are fundamental building block in photonic integrated circuits to block undesired reflections and routing light according to a prescribed direction. In silicon photonics, heterogeneous integration of magneto-optic garnet bonded on a pre-patterned silicon layer has been demonstrated to be an effective solution for m...
Article
We propose and demonstrate a novel low-loss waveguide optical isolator with tapered mode converter and magneto-optical phase shifter. The principle of operation of the isolator is based on the superposition of the TE and TM modes. The two different modes become direction-dependent due to a magneto-optical phase shift affecting the TM mode. We desig...
Article
In a planar waveguide including magneto-optical (MO) material with in-plane magnetization, a MO phase shift due to a first-order MO effect is induced. A Mach-Zehnder interferometer (MZI)-based optical isolator and circulator are fabricated by the direct bonding technique between silicon and MO garnets. The MZI can provide optical switching by dynam...
Article
Optical isolators and circulators are important elements in many photonic systems. These nonreciprocal devices are typically made of bulk optical components and are difficult to integrate with other elements of photonic integrated circuits. This article discusses the best performance for waveguide isolators and circulators achieved with heterogeneo...
Article
We demonstrate a novel self-holding function of a magneto-optical waveguide switch. The switching state is flipped by a pulsed current and maintained without any power supply by virtue of the non-volatility of the thin-film magnet. Extinction ratios up to 15.4 dB were demonstrated. The switch state was controlled by a 1-μs pulsed electrical current...
Conference Paper
A novel waveguide optical isolator operating for TE mode input is proposed with tapered mode converters and a magneto-optical phase shifter. A maximum isolation ratio of 6.4 dB is demonstrated at a wavelength of 1557 nm.
Conference Paper
A novel self-holding switch is demonstrated by a magneto-optical waveguide switch. The switching state is flipped by a pulsed current and maintained without any power supply by virtue of the non-volatility of thin-film magnet.
Conference Paper
Optical isolator and circulator are fabricated by directly bonding a single-crystalline magneto-optical garnet on silicon waveguides. An isolation of ≥30 dB has been obtained in fabricated devices.
Article
We demonstrate integrated optical isolators with broadband behavior for the standard silicon-on-insulator platform. We achieve over 20 dB of optical isolation across 18 nm of optical bandwidth. The isolator is completely electrically controlled and does not require a permanent magnet. Furthermore, we demonstrate the ability to tune the central oper...
Article
A wavelength selective switch is proposed for optical wavelength division multiplexing network applications with very short range interconnections. The proposed device uses a Mach–Zehnder interferometer configuration incorporating wavelength selective phase shifters composed of microring resonators between their two arms. Wavelength selectivity is...
Article
Optical circulators that unidirectionally route light could lead to bidirectional operations in applications in data centers and telecommunications, as well as sensors. In this work, to the best of our knowledge, we present the first realization of integrated optical circulators on silicon that are electrically driven and dynamically reconfigurable...
Article
In this work, we present optical isolators and circulators fabricated by bonding cerium-substituted yttrium iron garnet (Ce:YIG) on silicon microring resonators. A novel integrated electromagnet is fabricated by depositing a metal micro-strip on the bonded chip. We experimentally prove that it can be efficiently used to control the magnetic field n...
Article
We fabricated a magneto-optical (MO) isolator with a TE mode nonreciprocal phase shift. The isolator is based on a Mach-Zehnder interferometer composed of 3-dB directional couplers, a reciprocal phase shifter, and a nonreciprocal phase shifter. To realize TE mode operation in the optical isolator, we designed a novel waveguide structure composed of...
Conference Paper
A waveguide optical isolator operating in TE mode was demonstrated with an isolation of 17.9 dB. Amorphous silicon core along lateral walls of magneto-optical garnet was fabricated to induce nonreciprocal phase shift in TE mode.
Article
A waveguide optical isolator with a nonreciprocal phase shift is promising for obtaining high-optical isolation owing to its single-polarization operation. A typical configuration enables operation for only the TM mode input light. A silicon waveguide polarization rotator with asymmetric two parallel waveguides is implemented with the silicon waveg...
Article
Optical isolators are required to block undesired reflections in many photonic integrated circuits (PICs), but the performance of on-chip isolators using the magneto-optic effect has been limited due to high loss of such materials. Moreover, they require precise positioning of a permanent magnet close to the chip, increasing footprint and impeding...
Conference Paper
We investigated carrier lifetime in a micro-crystalline silicon wire waveguide at 1550 nm using an orthogonal pump-probe method. By a cross amplitude modulation measurement, the carrier lifetime was characterized to be 21 ns, which was longer than that of amorphous and single-crystalline silicon waveguides.
Article
We fabricated a magneto-optical (MO) switch with a hydrogenated amorphous silicon waveguide on an MO garnet. The switch is composed of a 2 × 2 Mach-Zehnder interferometer (MZI). The switch state is controlled by an MO phase shift through a magnetic field generated by a current flowing in an electrode located on the MZI. The switching operation was...
Conference Paper
We have investigated magneto-optical nonreciprocal devices on silicon waveguide platforms. An optical isolator is the one-way device that transmits lightwaves in a pre-determined direction and prevents the light propagation in the other directions. An optical circulator is important for building functional photonic circuits that process reflected o...
Article
We fabricated a wavelength-selective switch composed of microring resonators as wavelength filters and Mach–Zehnder-interferometer-based thermo-optic switches as routing switches. Nonblocking wavelength-selective switching operations for several channels were successfully demonstrated. A wavelength-selective transmittance change of 9.7 dB was obtai...
Article
Silicon waveguide optical nonreciprocal devices that use the magneto-optical phase shift are reviewed. The phase shift caused by the first-order magneto-optical effect is effective in realizing optical nonreciprocal devices on semiconductor waveguide platforms. In a silicon-on-insulator waveguide, the low refractive index of the buried oxide layer...
Conference Paper
We demonstrate an integrated four-port optical circulator on silicon with 12dB isolation ratio. By locally switching the direction of the magnetic field on chip, we can dynamically reconfigure or shut off the circulation.
Conference Paper
For the first time, an ultra-compact integrated isolator without use of permanent magnets is designed and fabricated by bonding Ce:YIG on a silicon microring. Record isolation of 32dB and low 2.3dB excess loss were achieved.
Article
Optical isolators play unique roles in photonic circuits. We have developed an optical isolator with silicon waveguides, based on a Mach-Zehnder interferometer. The device characteristics were temperature dependent. We investigated the temperature dependence of the refractive index (dn/dT) and the magneto-optical coefficient (d θf/dT) of a magneto-...
Conference Paper
We investigate a single-trench waveguide TE-TM mode converter in the GalnAsP waveguide of which structure is compatible with a GaInAsP waveguide optical isolator. A TE-TM mode conversion efficiency of 91.6 % is achieved at a wavelength of 1.55 μm in the fabricated device with a 200-μm conversion length.
Conference Paper
An optical isolator employing a nonreciprocal guided-radiation mode conversion is described. The optical isolator is comprised of a strip-loaded magneto-optic waveguide. Only backward-traveling TM modes can couple to TE radiation modes. The optical isolator was designed at 1.55 /m depending on the refractive index of a strip. Wavelength dependence...
Conference Paper
An optical add-drop multiplexer (OADM) is demonstrated by integrating silicon waveguide optical circulators and a waveguide Bragg reflector. Two magneto-optical circulators and one vertical groove grating Bragg reflector is successfully integrated on a silicon-on-insulator platform to achieve optical add and drop operations with a 10-nm wavelength...
Conference Paper
A magneto-optical (MO) switch with amorphous silicon waveguides on a magneto-optic garnet is fabricated. The device uses the MO phase shift where the magnetic field is applied by the current flow in an electric wiring. The switch exhibited an extinction ratio of 11.7 dB at a wavelength of 1550 nm.
Article
In the telecom wavelength range, the magnetooptical effect of cobalt ferrites is approximately 10 times larger than that of conventional magnetooptical materials such as yttrium iron garnets. In this study, we focus on an application of cobalt ferrite to a magnetooptical isolator that is to be miniaturized and made suitable for integration. First,...
Article
A Si waveguide optical isolator is integrated with an asymmetrical slit Si waveguide TE-TM mode converter. A maximum isolation of 26.7 dB is demonstrated at a wavelength of 1553 nm for TE mode input light.
Article
Full-text available
Optical and magnetic microstructures are directly fabricated inside a film of cerium-substituted yttrium iron garnet (Ce:YIG) by using a direct femtosecond laser writing. The laser irradiation induces local changes in both optical and magnetic properties of Ce:YIG. A quantitative phase imaging technique proves that the refractive index is increased...
Article
Optical nonreciprocal devices such as isolators and circulators are fabricated on silicon waveguide platforms. Magneto-optical materials play an essential role in obtaining optical nonreciprocity. The authors have developed a direct bonding technique that enables integration of magneto-optical garnet on a silicon waveguide. Using this technique, op...
Conference Paper
The temperature dependences of the refractive index and magneto-optic coefficient of magneto-optic garnet Ce: YIG are characterized to be 2.5×10-4 K-1 and 13 deg/cm/K, respectively. The design of a temperature insensitive waveguide optical isolator is proposed.
Conference Paper
A polarization-independent optical isolator with amorphous silicon waveguide is proposed and designed. The amorphous silicon waveguide is formed along the lateral wall of magneto-optic garnet to provide nonreciprocal phase shifts for TE and TM modes.
Conference Paper
An optical isolator is fabricated with an amorphous silicon waveguide core deposited using a plasma-enhanced chemical-vapor-deposition technique on a magneto-optical garnet Ce:YIG. An isolation ratio of 17 dB is demonstrated.
Conference Paper
Integrating technique between a laser diode and an optical isolator can be realized by photosensitive adhesive bonding. Coupling efficiency between a laser diode and a magneto-optic waveguide was calculated by means of beam propagation method.
Article
A magneto-optical isolator is indispensable for optical fiber communication to protect active devices from unwanted reflections. A ferrite garnet such as yttrium iron garnet (YIG) is typically used because of its transparency and relatively large magneto-optic effect for near-infrared light (~0.8 eV). However, a YIG film must be epitaxially grown o...
Article
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...
Article
Full-text available
Many novel materials and device designs have been proposed as photonic analogs to electrical diodes over the last four decades. This paper seeks to revisit these materials and designs as advanced technologies may enable experimental realization that was not possible upon conception of several of these designs. The background behind integration chal...
Article
We demonstrate a silicon Mach-Zehnder interferometer (MZI) based magneto-optical isolator having an 8 nm bandwidth for more than 20 dB isolation. The operational bandwidth of the isolator is determined by the wavelength dependence of a reciprocal phase difference provided by the asymmetric path length of the MZI. Although a shorter path length requ...
Article
Full-text available
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...
Article
Full-text available
With the goal of creating magneto-optical devices, we demonstrated forming nanostructures inside a substrate of cerium-substituted yttrium iron garnet (Ce:YIG) by means of direct laser writing. Laser irradiation changed both the optical and magnetic properties of Ce:YIG. The measurements showed that the refractive index was increased by 0.015 (abou...
Conference Paper
A silicon Mach-Zehnder interferometer-based optical isolator is fabricated by directly bonding a magneto-optical garnet Ce:YIG. By reducing the length of reciprocal phase shifter, an optical isolation > 20 dB is obtained in 8 nm wavelength width.
Article
Full-text available
We fabricated a waveguide optical isolator with a GaInAsP guiding layer integrated with spot size converters (SSCs) for efficient coupling to optical fibers. The isolator is constructed with a Mach-Zehnder interferometer (MZI), which is composed of multi-mode interference (MMI) couplers, as well as nonreciprocal and reciprocal phase shifters. The n...
Conference Paper
Optical nonreciprocal devices such as isolators and circulators play unique roles in photonic circuits. The optical nonreciprocal devices are discussed that are based on magneto-optical materials bonded on silicon waveguides.
Article
Full-text available
An optical isolator for transverse electric (TE) polarized light is demonstrated by adhesive bonding of a ferrimagnetic garnet die on top of a 380 nm thick silicon waveguide circuit. Polarization rotators are implemented in the arms of a nonreciprocal Mach-Zehnder interferometer to rotate the polarization to transverse magnetic in the nonreciprocal...
Conference Paper
The magneto-optic effect is important to realize the optical nonreciprocal devices such as isolators and circulators. In this article, magneto-optical nonreciprocal devices are discussed that are based on silicon waveguide platforms.
Article
A four-port optical circulator based on a Mach–Zehnder interferometer is fabricated in a silicon nanowire waveguide. A magneto-optical garnet is directly bonded to the silicon waveguide using a surface activated bonding technique. Four-port circulator operation is demonstrated with a maximum isolation of 15.3 dB at a wavelength of 1531 nm.
Article
Full-text available
A classical 3-port optical circulator is demonstrated on the silicon-on-insulator (SOI) platform. A garnet die with a magneto-optical cerium-doped yttrium iron garnet (Ce:YIG) layer is bonded on top of a Mach-Zehnder interferometer circuit using a thin adhesive bonding layer. The power transmission between different ports is characterized in the pr...