Xiaoguang Tu - Academia.edu (original) (raw)

Papers by Xiaoguang Tu

We demonstrate a 1×4 coarse wavelength division-multiplexing (CWDM) planar concave grating multip... more We demonstrate a 1×4 coarse wavelength division-multiplexing (CWDM) planar concave grating multiplexer/demultiplexer and its application in re-configurable optical add/drop multiplexer (ROADM) system in silicon-on-insulator substrate. The wavelengths of the demonstrated concave grating multiplexer align well with the ITU-T standard. We demonstrate a prototype of ROADM comprising two such concave gratings and four wide-band thermo-optical MZI switches. Undercut technology which removes the underneath silicon substrate is adopted in optical switches in order to minimize the operation power. For all the thermal heaters, the operation voltage is smaller than 1.5 V, and the switch power is ~2.4 mW. High throughput pseudorandom binary sequence (PRBS) data transmission with up to 100 Gb/s is demonstrated, showing the high-performance ROADM functionality.

The first pn-type carrier-induced silicon Bragg-grating filter is demonstrated. The extinction-ra... more The first pn-type carrier-induced silicon Bragg-grating filter is demonstrated. The extinction-ratio modulations are 11.5 dB and 10 dB with reverse and forward biases, respectively. 8-Gpbs data rate is achieved with a reverse bias.

2017 Optical Fiber Communications Conference and Exhibition (OFC), 2017

Benefiting from the new 193nm lithography, a narrow tip with width of 100 nm can be fabricated on... more Benefiting from the new 193nm lithography, a narrow tip with width of 100 nm can be fabricated on IME's MPW platform. Based on the new capability, we optimized the suspended coupler and realized the state-of-the-art coupling loss less than −1.3 dB/facet with cleaved single mode fiber. A uniformity of 0.4 dB across wafers has also been confirmed, the best performance to our knowledge realized in public-available silicon photonics platform.

World Academy of Science, Engineering and Technology, International Journal of Chemical and Molecular Engineering, 2016

Conference on Lasers and Electro-Optics, 2016

We propose an electrically programmable, multi-level non-volatile photonics memory cell (PMC) fab... more We propose an electrically programmable, multi-level non-volatile photonics memory cell (PMC) fabricated by standard CMOS compatible processes. A micro-ring resonator (MRR) was built using the PMC to demonstrate programmable and erase functions.

電子情報通信学会技術研究報告 Ope 光エレクトロニクス, Oct 18, 2012

2015 IEEE International Conference on Electron Devices and Solid-State Circuits (EDSSC), 2015

We present silicon-based WDM photonics link for 240 Gb/s data transmission on 1.3 μm with above 5... more We present silicon-based WDM photonics link for 240 Gb/s data transmission on 1.3 μm with above 50 GHz silicon modulator and 20GHz Germanium photo-detector. Photonics link has a bandwidth of 53.4GHz limited by the impedance mismatch.

Conference on Lasers and Electro-Optics 2012, 2012

ABSTRACT Silicon photonics, being an important technology platform for a wide range of applicatio... more ABSTRACT Silicon photonics, being an important technology platform for a wide range of applications, demands an easily assessable fabrication foundry with the flexibility desired for research and development of integrated photonics circuits, as well as with the manufacturing path required for volume production.

2014 IEEE 16th Electronics Packaging Technology Conference (EPTC), 2014

High-performance silicon optical modulator is demonstrated with up to 50-Gb/s data rate upon 1.3-... more High-performance silicon optical modulator is demonstrated with up to 50-Gb/s data rate upon 1.3-Vpp. The measured extinction ratios of the optical eye-diagrams are respectively 5.97-dB, 5.13-dB and 4.44-dB at 28-Gb/s, 40-Gb/s and 50-Gb/s data rate.

Optical Fiber Communication Conference, 2014

ABSTRACT A mode converter is fabricated with SiON to reduce coupling loss between SiN waveguide a... more ABSTRACT A mode converter is fabricated with SiON to reduce coupling loss between SiN waveguide and cleaved single-mode-fiber. The coupling loss is 1.2 and 1.4dB/facet for TE and TM mode with 3dB alignment tolerance of ±3.5µm

Optics express, Jan 3, 2014

We proposed a microring resonator (MRR) enhanced photodetector (PD) structure. Resonance waveleng... more We proposed a microring resonator (MRR) enhanced photodetector (PD) structure. Resonance wavelength enhanced by the MRR amplifies the PD response. At L-band wavelengths, responsivity was doubled for an ultra-short germanium PD of 4 µm employing the MRR structure. Data rates of up to 40 Gb/s were also demonstrated at 1600 nm.

Optical Fiber Communication Conference/National Fiber Optic Engineers Conference 2013, 2013

ABSTRACT A carrier-induced silicon-waveguide Bragg-grating filter with a pin junction is demonstr... more ABSTRACT A carrier-induced silicon-waveguide Bragg-grating filter with a pin junction is demonstrated. The bandwidth and the extinction ratio of the filter are 0.3nm and 14dB, respectively. It can be tuned by both forward and reverse biases.

Optical Fiber Communication Conference/National Fiber Optic Engineers Conference 2013, 2013

We demonstrate a cost-effective silicon microring-based bio/chemical sensor, which integrates ver... more We demonstrate a cost-effective silicon microring-based bio/chemical sensor, which integrates vertical grating couplers, two cascaded microrings for optical sensing and electrical tracing, and Ge photodetector for direct sensing interrogation. Detection limit of 1.5×10-5 is demonstrated.

Optics express, Jan 22, 2014

High-index-contrast (HIC) waveguide such as Si and Si3N4 has small mode size enabling compact int... more High-index-contrast (HIC) waveguide such as Si and Si3N4 has small mode size enabling compact integration. However, the coupling loss with single mode fiber is also remarkable owning to the mode mismatching. Therefore, mode size converter, as the interface between HIC waveguide and optical fiber, takes an important role in the field of integrated optics. The material with refractive index (RI) between HIC waveguide and optical fiber can be used as a bridge to reduce the mode mismatching loss. In this letter, we employ silicon oxynitride (SiON) with RI about 1.50 as the intermediate material and optimize the structure of the SiON waveguide to match with cleaved single mode fiber and HIC waveguide separately. Combined with inverse taper and suspended structure, the mismatching loss is reduced and the dependence to the dimension of the structure is also released. The coupling loss is 1.2 and 1.4 dB/facet for TE and TM mode, respectively, with 3 dB alignment tolerance of ± 3.5 μm for Si...

Optics express, Jan 22, 2014

A silicon Mach-Zehnder Interferometer (MZI) optical modulator with a shield coplanar waveguide (C... more A silicon Mach-Zehnder Interferometer (MZI) optical modulator with a shield coplanar waveguide (CPW) transmission line electrode design was demonstrated. This shield-CPW electrode suppresses the signal distortion caused by the parasitic slot-line (SL) mode and improves the electrical bandwidth and the electro-optical (EO) bandwidth. With the shield-CPW electrodes and 5.5 mm-long phase shifters, the silicon MZI optical modulator delivered an EO bandwidth of above 24 GHz and a V (π) = 3.0 V was achieved at λ = 1310 nm. When modulated at 28-Gb/s data rate, it achieved an extinction ratio of 5.66 dB under a driving voltage of V (pp) = 1.3 V, corresponding to a power consumption of 0.8 pJ/bit.

Optical Fiber Communication Conference, 2012

ABSTRACT We demonstrate a 4-channel 2×2 colorless WSS with channel spacing of 20nm, the total tra... more ABSTRACT We demonstrate a 4-channel 2×2 colorless WSS with channel spacing of 20nm, the total transmission loss of ~10dB, power consumption of ~2.5mW, and switching time of ~006μs. High-throughput data transmission of 80Gb/s is demonstrated.

Optics Express, 2014

We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a wave... more We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a waveguide loop. We theoretically investigate the forbidden band and conduction band conditions in an infinite periodic lattice. We also discuss the reflection-and transmission-spectra, group delay in finite periodic structures. Light has a larger group delay at the band edge in a periodic structure. The flat band pass filter and flat-top group delay can be realized in a non-periodic structure. Scattering matrix method is used to calculate the effects of waveguide loss on the optical characteristics of these structures. We also introduce a tunable coupling loop waveguide to compensate for the fabrication variations since the coupling coefficient of the directional coupler in the loop waveguide is a critical factor in determining the characteristics of a loop CROW. The loop CROW structure is suitable for a wide range of applications such as band pass filters, high Q microcavity, and optical buffers and so on.

Optical Fiber Communication Conference, 2014

ABSTRACT We demonstrate the first silicon-based parallel-fed travelling-wave photodetector array ... more ABSTRACT We demonstrate the first silicon-based parallel-fed travelling-wave photodetector array (TWPDA). Impedance-matched travelling-wave electrode is designed considering periodic loading effect. The demonstrated up to 4-channel TWPDAs show >10GHz 3-dB bandwidths and ~0.75A/W responsivity using 30µm-length PDs.

2014 The European Conference on Optical Communication (ECOC), 2014

We report a compact dual-polarization quadrature phase-shift keying (DP-QPSK) modulator module ac... more We report a compact dual-polarization quadrature phase-shift keying (DP-QPSK) modulator module accommodating a silicon DP-QPSK modulator chip and driver amplifiers in a package in a dimension of 15×35×4.5 mm3. 128-Gb/s DP-QPSK transmission in 1000-km single-mode fibre is confirmed with the compact modulator module.

Optics Express, 2014

We propose a novel three-dimensional (3D) monolithic optoelectronic integration platform. Such pl... more We propose a novel three-dimensional (3D) monolithic optoelectronic integration platform. Such platform integrates both electrical and photonic devices in a bulk silicon wafer, which eliminates the high-cost silicon-on-insulator (SOI) wafer and is more suitable for process requirements of electronic and photonic integrated circuits (ICs). For proofof-concept, we demonstrate a three-dimensional photodetector and WDM receiver system. The Ge is grown on a 8-inch bulk silicon wafer while the optical waveguide is defined in a SiN layer which is deposited on top of it, with ~4 µm oxide sandwiched in between. The light is directed to the Ge photodetector from the SiN waveguide vertically by using grating coupler with a Aluminum mirror on top of it. The measured photodetector responsivity is ~0.2 A/W and the 3-dB bandwidth is ~2 GHz. Using such vertical-coupled photodetector, we demonstrated an 8-channel receiver by integrating a 1 × 8 arrayed waveguide grating (AWG). High-quality optical signal detection with up to 10 Gbit/s data rate is demonstrated, suggesting a 80 Gbit/s throughput. Such receiver can be applied to on-chip optical interconnect, DRAM interface, and telecommunication systems.

We demonstrate a 1×4 coarse wavelength division-multiplexing (CWDM) planar concave grating multip... more We demonstrate a 1×4 coarse wavelength division-multiplexing (CWDM) planar concave grating multiplexer/demultiplexer and its application in re-configurable optical add/drop multiplexer (ROADM) system in silicon-on-insulator substrate. The wavelengths of the demonstrated concave grating multiplexer align well with the ITU-T standard. We demonstrate a prototype of ROADM comprising two such concave gratings and four wide-band thermo-optical MZI switches. Undercut technology which removes the underneath silicon substrate is adopted in optical switches in order to minimize the operation power. For all the thermal heaters, the operation voltage is smaller than 1.5 V, and the switch power is ~2.4 mW. High throughput pseudorandom binary sequence (PRBS) data transmission with up to 100 Gb/s is demonstrated, showing the high-performance ROADM functionality.

The first pn-type carrier-induced silicon Bragg-grating filter is demonstrated. The extinction-ra... more The first pn-type carrier-induced silicon Bragg-grating filter is demonstrated. The extinction-ratio modulations are 11.5 dB and 10 dB with reverse and forward biases, respectively. 8-Gpbs data rate is achieved with a reverse bias.

2017 Optical Fiber Communications Conference and Exhibition (OFC), 2017

Benefiting from the new 193nm lithography, a narrow tip with width of 100 nm can be fabricated on... more Benefiting from the new 193nm lithography, a narrow tip with width of 100 nm can be fabricated on IME's MPW platform. Based on the new capability, we optimized the suspended coupler and realized the state-of-the-art coupling loss less than −1.3 dB/facet with cleaved single mode fiber. A uniformity of 0.4 dB across wafers has also been confirmed, the best performance to our knowledge realized in public-available silicon photonics platform.

World Academy of Science, Engineering and Technology, International Journal of Chemical and Molecular Engineering, 2016

Conference on Lasers and Electro-Optics, 2016

We propose an electrically programmable, multi-level non-volatile photonics memory cell (PMC) fab... more We propose an electrically programmable, multi-level non-volatile photonics memory cell (PMC) fabricated by standard CMOS compatible processes. A micro-ring resonator (MRR) was built using the PMC to demonstrate programmable and erase functions.

電子情報通信学会技術研究報告 Ope 光エレクトロニクス, Oct 18, 2012

2015 IEEE International Conference on Electron Devices and Solid-State Circuits (EDSSC), 2015

We present silicon-based WDM photonics link for 240 Gb/s data transmission on 1.3 μm with above 5... more We present silicon-based WDM photonics link for 240 Gb/s data transmission on 1.3 μm with above 50 GHz silicon modulator and 20GHz Germanium photo-detector. Photonics link has a bandwidth of 53.4GHz limited by the impedance mismatch.

Conference on Lasers and Electro-Optics 2012, 2012

ABSTRACT Silicon photonics, being an important technology platform for a wide range of applicatio... more ABSTRACT Silicon photonics, being an important technology platform for a wide range of applications, demands an easily assessable fabrication foundry with the flexibility desired for research and development of integrated photonics circuits, as well as with the manufacturing path required for volume production.

2014 IEEE 16th Electronics Packaging Technology Conference (EPTC), 2014

High-performance silicon optical modulator is demonstrated with up to 50-Gb/s data rate upon 1.3-... more High-performance silicon optical modulator is demonstrated with up to 50-Gb/s data rate upon 1.3-Vpp. The measured extinction ratios of the optical eye-diagrams are respectively 5.97-dB, 5.13-dB and 4.44-dB at 28-Gb/s, 40-Gb/s and 50-Gb/s data rate.

Optical Fiber Communication Conference, 2014

ABSTRACT A mode converter is fabricated with SiON to reduce coupling loss between SiN waveguide a... more ABSTRACT A mode converter is fabricated with SiON to reduce coupling loss between SiN waveguide and cleaved single-mode-fiber. The coupling loss is 1.2 and 1.4dB/facet for TE and TM mode with 3dB alignment tolerance of ±3.5µm

Optics express, Jan 3, 2014

We proposed a microring resonator (MRR) enhanced photodetector (PD) structure. Resonance waveleng... more We proposed a microring resonator (MRR) enhanced photodetector (PD) structure. Resonance wavelength enhanced by the MRR amplifies the PD response. At L-band wavelengths, responsivity was doubled for an ultra-short germanium PD of 4 µm employing the MRR structure. Data rates of up to 40 Gb/s were also demonstrated at 1600 nm.

Optical Fiber Communication Conference/National Fiber Optic Engineers Conference 2013, 2013

ABSTRACT A carrier-induced silicon-waveguide Bragg-grating filter with a pin junction is demonstr... more ABSTRACT A carrier-induced silicon-waveguide Bragg-grating filter with a pin junction is demonstrated. The bandwidth and the extinction ratio of the filter are 0.3nm and 14dB, respectively. It can be tuned by both forward and reverse biases.

Optical Fiber Communication Conference/National Fiber Optic Engineers Conference 2013, 2013

We demonstrate a cost-effective silicon microring-based bio/chemical sensor, which integrates ver... more We demonstrate a cost-effective silicon microring-based bio/chemical sensor, which integrates vertical grating couplers, two cascaded microrings for optical sensing and electrical tracing, and Ge photodetector for direct sensing interrogation. Detection limit of 1.5×10-5 is demonstrated.

Optics express, Jan 22, 2014

High-index-contrast (HIC) waveguide such as Si and Si3N4 has small mode size enabling compact int... more High-index-contrast (HIC) waveguide such as Si and Si3N4 has small mode size enabling compact integration. However, the coupling loss with single mode fiber is also remarkable owning to the mode mismatching. Therefore, mode size converter, as the interface between HIC waveguide and optical fiber, takes an important role in the field of integrated optics. The material with refractive index (RI) between HIC waveguide and optical fiber can be used as a bridge to reduce the mode mismatching loss. In this letter, we employ silicon oxynitride (SiON) with RI about 1.50 as the intermediate material and optimize the structure of the SiON waveguide to match with cleaved single mode fiber and HIC waveguide separately. Combined with inverse taper and suspended structure, the mismatching loss is reduced and the dependence to the dimension of the structure is also released. The coupling loss is 1.2 and 1.4 dB/facet for TE and TM mode, respectively, with 3 dB alignment tolerance of ± 3.5 μm for Si...

Optics express, Jan 22, 2014

A silicon Mach-Zehnder Interferometer (MZI) optical modulator with a shield coplanar waveguide (C... more A silicon Mach-Zehnder Interferometer (MZI) optical modulator with a shield coplanar waveguide (CPW) transmission line electrode design was demonstrated. This shield-CPW electrode suppresses the signal distortion caused by the parasitic slot-line (SL) mode and improves the electrical bandwidth and the electro-optical (EO) bandwidth. With the shield-CPW electrodes and 5.5 mm-long phase shifters, the silicon MZI optical modulator delivered an EO bandwidth of above 24 GHz and a V (π) = 3.0 V was achieved at λ = 1310 nm. When modulated at 28-Gb/s data rate, it achieved an extinction ratio of 5.66 dB under a driving voltage of V (pp) = 1.3 V, corresponding to a power consumption of 0.8 pJ/bit.

Optical Fiber Communication Conference, 2012

ABSTRACT We demonstrate a 4-channel 2×2 colorless WSS with channel spacing of 20nm, the total tra... more ABSTRACT We demonstrate a 4-channel 2×2 colorless WSS with channel spacing of 20nm, the total transmission loss of ~10dB, power consumption of ~2.5mW, and switching time of ~006μs. High-throughput data transmission of 80Gb/s is demonstrated.

Optics Express, 2014

We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a wave... more We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a waveguide loop. We theoretically investigate the forbidden band and conduction band conditions in an infinite periodic lattice. We also discuss the reflection-and transmission-spectra, group delay in finite periodic structures. Light has a larger group delay at the band edge in a periodic structure. The flat band pass filter and flat-top group delay can be realized in a non-periodic structure. Scattering matrix method is used to calculate the effects of waveguide loss on the optical characteristics of these structures. We also introduce a tunable coupling loop waveguide to compensate for the fabrication variations since the coupling coefficient of the directional coupler in the loop waveguide is a critical factor in determining the characteristics of a loop CROW. The loop CROW structure is suitable for a wide range of applications such as band pass filters, high Q microcavity, and optical buffers and so on.

Optical Fiber Communication Conference, 2014

ABSTRACT We demonstrate the first silicon-based parallel-fed travelling-wave photodetector array ... more ABSTRACT We demonstrate the first silicon-based parallel-fed travelling-wave photodetector array (TWPDA). Impedance-matched travelling-wave electrode is designed considering periodic loading effect. The demonstrated up to 4-channel TWPDAs show >10GHz 3-dB bandwidths and ~0.75A/W responsivity using 30µm-length PDs.

2014 The European Conference on Optical Communication (ECOC), 2014

We report a compact dual-polarization quadrature phase-shift keying (DP-QPSK) modulator module ac... more We report a compact dual-polarization quadrature phase-shift keying (DP-QPSK) modulator module accommodating a silicon DP-QPSK modulator chip and driver amplifiers in a package in a dimension of 15×35×4.5 mm3. 128-Gb/s DP-QPSK transmission in 1000-km single-mode fibre is confirmed with the compact modulator module.

Optics Express, 2014

We propose a novel three-dimensional (3D) monolithic optoelectronic integration platform. Such pl... more We propose a novel three-dimensional (3D) monolithic optoelectronic integration platform. Such platform integrates both electrical and photonic devices in a bulk silicon wafer, which eliminates the high-cost silicon-on-insulator (SOI) wafer and is more suitable for process requirements of electronic and photonic integrated circuits (ICs). For proofof-concept, we demonstrate a three-dimensional photodetector and WDM receiver system. The Ge is grown on a 8-inch bulk silicon wafer while the optical waveguide is defined in a SiN layer which is deposited on top of it, with ~4 µm oxide sandwiched in between. The light is directed to the Ge photodetector from the SiN waveguide vertically by using grating coupler with a Aluminum mirror on top of it. The measured photodetector responsivity is ~0.2 A/W and the 3-dB bandwidth is ~2 GHz. Using such vertical-coupled photodetector, we demonstrated an 8-channel receiver by integrating a 1 × 8 arrayed waveguide grating (AWG). High-quality optical signal detection with up to 10 Gbit/s data rate is demonstrated, suggesting a 80 Gbit/s throughput. Such receiver can be applied to on-chip optical interconnect, DRAM interface, and telecommunication systems.