Takako Hirokawa

Takako Hirokawa
  • GlobalFoundries Inc.

About

61
Publications
4,240
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455
Citations
Introduction
Skills and Expertise
Current institution

Publications

Publications (61)
Conference Paper
We present optimized Ge shaping techniques that significantly reduce the back reflection of O-band Ge-on-Si photodetectors, achieving an optical return loss of -36dB in conjunction with ~60GHz 3-dB-EO-bandwidth, 0.95A/W responsivity and average dark current <30nA.
Conference Paper
We report the successful demonstration of monolithically integrated O-band Vgroove-based multi-tip SiN edge couplers, achieving 0.5/0.9dB insertion losses for two polarizations at 1310 nm, >280mW power handling and <-40dB optical-return-loss, surpassing IEEE 802.3 performance standards.
Conference Paper
Silicon photonics has emerged as a key solution for on-chip communication to improve computational systems especially for AI workloads. Testing of such photonic integrated circuits (PICs) is key to deliver known good dies to be co-packaged with the compute IC. The recent availability of commercial photonic testers has allowed for monitoring most op...
Article
Full-text available
We report the design and experimental realization of a deep subwavelength-engineered slotted photonic crystal fabricated using a commercial monolithic silicon photonics process with a minimum feature size near 40 nm. The deep subwavelength design includes a corrugated, slotted unit cell shape that leverages electromagnetic interface conditions to l...
Conference Paper
In this paper we discuss the latest developments in the GlobalFoundries Fotonix™ program, including enhancements in device performance, packaging, PDK compact models, and in-house test capabilities.
Conference Paper
We present scaled, bidirectional silicon photonic ring modulator and multi-channel coupled ring resonator models, offering advanced simulation capabilities for high-power and thermal time constant analysis, facilitating comprehensive on-chip EO system design with GlobalFoundries PDK.
Conference Paper
We demonstrate low-loss silicon nitride passive optical components including straight and bend waveguides, 1×2MMI, 2×2MMI, directional-coupler and waveguide crossings on a monolithic silicon photonics platform. Hardware performance statistics substantiate the mass manufacturability of the building-blocks.
Conference Paper
We introduce the concept of hybrid Si-SiN waveguides to mitigate substrate leakage on a monolithic-SiPh platform. Experimental data indicates añ80% reduction in TM-waveguide loss (resulting in ~0.3 dB/cm-attenuation) and a 9-fold TM-bend loss reduction.
Conference Paper
We present recent advancements in reducing polarization-dependent-losses (PDLs) for crucial SiPh components. Our link-budget analysis unveils a 1.45dB reduction in total PDL for representative receiver circuits, resulting in a mere 0.38dB TE-TM-path insertion-loss imbalance.
Conference Paper
We present recent progress in minimizing polarization-dependent-losses (PDLs) for critical SiPh components. Our link-budget analysis shows a noteworthy 1.45dB total PDL reduction for optical receiver circuits, leading to a mere 0.38dB imbalance in TE-TM-path insertion-loss.
Conference Paper
We report scalable foundry fabrication and characterization of photonic crystal nanobeam waveguides incorporating subwavelength-scale dielectric antislot unit cells. This work enables enhanced light-matter interaction and three-fold improvement in V π L when incorporated in Mach-Zehnder modulators.
Conference Paper
This paper reviews recent advancements in GlobalFoundries (GF) Fotonix TM technology: a 300-mm monolithic CMOS silicon photonics (SiPh) foundry platform. The discussion encompasses photonic and CMOS device libraries, advanced packaging, PDK compact models, reliability, and system-level demonstrations.
Conference Paper
We demonstrate low-loss SiN passive optical components, encompassing straight and bend waveguides, 1×2MMI, 2×2MMI, directional-coupler, waveguide crossings and cWDM, on a monolithic silicon photonics platform. Statistical hardware performance data validates the mass manufacturability of these building-blocks.
Conference Paper
We present hybrid Si-SiN waveguides as a solution to mitigate substrate leakage in a monolithic SiPh platform. Experimental results show an ~80% reduction in TM-waveguide-loss (leading to ~0.3 dB/cm-attenuation) and a 9-fold decrease in TM-bend-loss.
Article
Enabling cost-effective and power-efficient laser source on a silicon photonics (SiPh) platform is a major goal that has been highly sought after. In the past two decades, tremendous effort has been made to develop various on-chip integration techniques to enhance SiPh circuits with efficient light-emitting materials. Here we review our recent adva...
Article
We report the scalable fabrication and characterization of photonic crystal (PhC) nanobeam waveguides incorporating subwavelength-scale dielectric anti-slot unit cells. These anti-slot PhCs were fabricated using deep UV lithography on a monolithic silicon photonics technology. The dielectric band edge mode is characterized by strong field localizat...
Conference Paper
We simulated and experimentally characterized the differential group delay induced from polarization mode dispersion (PMD) of key components on a monolithic SiPh platform. Strategy for compensating PMD was introduced for high-speed applications beyond 100 Gbit/s.
Conference Paper
We experimentally demonstrated V-groove-based self-aligned SiN edge coupler (EC) on a monolithic CMOS-SiPh platform. <0.6/0.8 dB TE/TM SMF-EC transmission efficiency, in conjunction with <-39 dB back reflection and >520 mW power handling capability were achieved.
Conference Paper
We report a study on moisture effect on optical performance of monolithic silicon photonics technologies featuring V-grooves for self-aligned fiber attach. Chip-level hermetic sealing was achieved by implementing moisture barrier for the fiber coupler.
Conference Paper
We report deep subwavelength-engineered slotted photonic crystal nanobeams with minimum features <70 nm fabricated using a 90 nm monolithic silicon photonics technology at GlobalFoundries. This work enables potential for scalable, advanced integrated photonics applications.
Article
We demonstrate a 2.5 mm silicon photonics traveling-wave Mach-Zehnder modulator with on-chip tunable termination to study termination mismatching as a technique for optimizing modulator performance by leveraging the monolithic integration of electronic and photonic devices. Time domain reflectometry measurements demonstrate the tunability of the te...
Conference Paper
An algorithm based on point set operations is developed to solve the waveguide length-balancing problem in silicon photonics layout. The method is applicable to complex photonic circuits incorporating multiple waveguide levels (e.g. Si and SiN).
Conference Paper
We demonstrate a waveguide-integrated germanium-on-silicon avalanche pho-todiode in a monolithic silicon photonics technology, with TE responsivity of 26 A/W at 1310 nm wavelength at -5 V operating bias with a 3-dB bandwidth of > 30 GHz.
Conference Paper
We demonstrate a novel C-band wavelength selective switch well equipped to handle the demands of scaling access at the edge. The 1x4 switch block has two drops per port with thermo-optic tuning. © 2022 The Author(s)
Conference Paper
We report a hybrid flip-chip-integrated laser attach technology on a monolithic SiPh platform. Efficient laser-to-PIC butt-coupling with optical power up to 11dBm was demonstrated through a combination of precise mechanical stops and optical alignment features.
Conference Paper
A comprehensive set of SiN building blocks was demonstrated on a monolithic SiPh platform. Low-loss SiN waveguides (<0.35dB/cm), Si-SiN transitions (0.026dB), efficient polarization splitters/rotators, and compact ring WDM filters were realized at O-band.
Article
As datacenters continue to scale in size, energy efficiency for short reach (<2 km) links is a major factor for networks that may connect hundreds of thousands of servers. We demonstrate that links based on analog coherent detection (ACD) offer a promising path to simultaneously achieving significantly larger link budgets and improved link energy e...
Article
Wavelength-selective switches have been proposed for datacenter use to enhance the scalability of their networks to help in meeting ever-increasing traffic demands. We have previously demonstrated a 4x4 ring-based crossbar silicon photonic switch in which each cross-point contained three ring pairs to partition the free spectral range (FSR) into th...
Article
Full-text available
We present a comparison of design trade-offs for transimpedance, sensitivity, DC voltage offset cancellation, group-delay variation (GDV), common-mode rejection, and overload for transimpedance amplifiers (TIA) based on balanced, unbalanced, and pseudodifferential topologies. The TIAs are implemented monolithically in the IHP 250-nm SiGe BiCMOS EPI...
Conference Paper
The first chip-scale wavelength-selective silicon photonic switch in the O-band is demonstrated. We describe the design and report results from the crossbar switch, which utilizes three pairs of microring resonators per crossing for wavelength selectivity.
Article
We present a strictly nonblocking 4×4 electrooptic silicon photonic switch fabric with on-chip gain. The switch integrates 12 Mach-Zehnder cells in a 3-stage topology equipped with fast electrooptic phase shifters, and thermooptic phase trimmers. To compensate for the losses of the fabric, a 4-channel GaInAsP/InP semiconductor optical amplifier arr...
Conference Paper
Full-text available
We have developed three light-based educational outreach activities targeted towards pre-university students, emphasizing experiential hands-on components for core learning via challenges the students must complete. These activities leverage photonics concepts from two active research areas at the Univ. of California Santa Barbara: integrated optic...
Conference Paper
Military imaging requirements demand continuous improvements in Focal Plane Array (FPA) resolution, size, sensitivity and frame rate, driving the need for high-speed interconnects between the FPA, located inside a cryogenic Dewar, to the processing electronics in the ambient environment. Significant advances in operational bandwidth are needed to s...
Conference Paper
We report a monolithically-integrated photoreceiver with a pseudo-differential Cherry-Hooper transimpedance amplifier (TIA) in a 250nm BiCMOS process. High sensitivity 50Gbps operation in demonstrated, and the TIA architecture is analyzed.
Conference Paper
We present a silicon photonic switch assembly integrating a nonblocking 4×4 Mach-Zehnder switch and a flip-chipped SOA array. The switch provides close to net-neutral-loss in the full C-band for all states and shows nanosecond-scale reconfiguration time.
Article
Full-text available
We present an on-chip wavelength reference with a partial drop ring resonator and germanium photodetector. This approach can be used in ring-resonator-based wavelength-selective switches where absolute wavelength alignment is required. We use the temperature dependence of heater resistance as a temperature sensor. Additionally, we discuss locking s...
Article
In this paper, we demonstrate that forward bias (+0.9V) of a high-speed silicon (Si) optical Mach-Zehnder Modulator (MZM) increases the radio-frequency (RF) link gain by 30 dB when compared to reverse bias operation (-8V). RF applications require tunable, narrowband electro-optic conversion with high gain to mitigate noise of the optical receiver a...
Article
Full-text available
In this paper, we demonstrate that forward bias (+0.9V) of a high-speed silicon (Si) optical Mach-Zehnder modulator (MZM) increases the radio-frequency (RF) link gain by 30 dB when compared to reverse bias operation (−8V). RF applications require tunable, narrowband electro-optic conversion with high gain to mitigate noise of the optical receiver a...
Conference Paper
Full-text available
We present an 8×8 ring resonator based crossbar switch for WDM networks in data centers. The switch can dynamically allocate bandwidth and is equipped with an on-chip wavelength reference for tuning the ring resonators to the specific channels.
Article
Full-text available
In response to national calls to better align physics laboratory courses with the way physicists engage in research, we have developed an epistemology and expectations survey to assess how students perceive the nature of physics experiments in the contexts of laboratory courses and the professional research laboratory. The Colorado Learning Attitud...
Article
Full-text available
The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) was developed as a broadly applicable assessment tool for undergraduate physics lab courses. At the beginning and end of the semester, the E-CLASS assesses students views about their strategies, habits of mind, and attitudes when doing experiments in lab classes...
Article
Optical lattice clocks based on ensembles of neutral atoms have the potential to operate at the highest levels of stability due to the parallel interrogation of many atoms. However, the control of systematic shifts in these systems is correspondingly difficult due to potential collisional atomic interactions. By tightly confining samples of ultraco...

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