Kyushu University [Andrew Mark Spring (Associate Professor) Faculty of Engineering Sciences, Department of Internationalization and Future Conception]

Andrew Mark Spring

Last modified date：2024.04.14

Associate Professor / Department of Molecular and Materials Sciences (MMS) / Department of Internationalization and Future Conception / Faculty of Engineering Sciences

Papers

1.	Mahmoud Z. Basyouni, Mohammed F. Radwan, Mohamed E. Abdu, Andrew M. Spring, Synthesis, Characterization, and Optical Properties of Carbazole-Functionalized Poly(norbornene-dicarboximide) by ROMP, EVERGREEN, Vol. 11, Issue 01, pp207-213, March, 2024, 2024.04.
2.	Basyouni, Mahmoud Z, Ye, Jianhao, Spring, Andrew M., Conjugated Polymers and ROMP: Synthesis, Applications, and Prospects for Technological Innovations, International Exchange and Innovation Conference on Engineering and Sciences, Volume 9, Pages 405 - 4112023 9th International Exchange and Innovation Conference on Engineering and Sciences, IEICES 2023, 2023.10.
3.	Yurachat Janpatompong, Andrew M. Spring, Venukrishnan Komanduri, Raja U. Khan, and Michael L. Turner, Synthesis and Ring-Opening Metathesis Polymerization of o‑Dialkoxy Paracyclophanedienes, Macromolecules, Macromolecules 2022, 55, 24, 10854-10864., 2022.05.
4.	Lu, Guo-Wei; Hong, Jianxun; Qiu, Feng; Spring, Andrew M.; Kashino, Tsubasa; Oshima, Juro; Ozawa, Masa-aki; Nawata, Hideyuki; Yokoyama, Shiyoshi, High-temperature-resistant silicon-polymer hybrid modulator operating at up to 200 Gbit s-1 for energy-efficient data centres and harsh-environment applications, Nature Communications, 2020.10, To reduce the ever-increasing energy consumption in datacenters, one of the effective approaches is to increase the ambient temperature, thus lowering the energy consumed in the cooling systems. However, this entails more stringent requirements for the reliability and durability of the optoelectronic components. Herein, we fabricate and demonstrate silicon-polymer hybrid modulators which support ultra-fast single-lane data rates up to 200 gigabits per second, and meanwhile feature excellent reliability with an exceptional signal fidelity retained at extremely-high ambient temperatures up to 110 °C and even after long-term exposure to high temperatures. This is achieved by taking advantage of the high electro-optic (EO) activities (in-device n3r33 = 1021 pm V−1), low dielectric constant, low propagation loss (α, 0.22 dB mm−1), and ultra-high glass transition temperature (Tg, 172 °C) of the developed side-chain EO polymers. The presented modulator simultaneously fulfils the requirements of bandwidth, EO efficiency, and thermal stability for EO modulators. It could provide ultra-fast and reliable interconnects for energy-hungry and harsh-environment applications such as datacentres, 5G/B5G, autonomous driving, and aviation systems, effectively addressing the energy consumption issue for the next-generation optical communication..
5.	() Xiaoyang Cheng, Feng Qiu, Andrew M. Spring, Masaru Sasaki, Tsubasa Kashino, Masaaki Ozawa, Hideyuki Nawata, Tomohiro Kita, Okihiro Sugihara, and Shiyoshi Yokoyama, Camera sensor platform for high speed video data transmission using a wideband electro-optic polymer modulator, Optics Express, https://doi.org/10.1364/OE.27.001877, Vol. 27, No. 3 \| 4 Feb 2019 \| OPTICS EXPRESS 1877, 2019.01, In this work, 1 GHz video data was collected by a CMOS camera and successfully transmitted by the electro-optic (EO) modulator driven by an external modulation module integrated onto the same chip. For this application, the EO modulator component included a polymer waveguide modulator, which performed a 20 GHz bandwidth, clear eye diagram opening with a Q factor of 10.3 at 32 Gbit/s and a drive voltage of 1.5 V pp . By utilizing a thermally stable EO polymer, the wide-band polymer modular can yield a photonic integrated camera sensor system which is a reliable processing platform for real-time data processing..
6.	Hong, Jianxun; Spring, Andrew M.; Qiu, Feng; Yokoyama, Shiyoshi, A high efficiency silicon nitride waveguide grating coupler with a multilayer bottom reflector, Scientific Reports - Nature Research, 2019, 9(1), 1-8., 2019.09, We propose a high efficiency apodized grating coupler with a bottom reflector for silicon nitride photonic integrated circuits. The reflector consists of a stack of alternate silicon nitride and silicon dioxide quarter-wave films. The design, fabrication and optical characterization of the couplers has been presented. The measured fiber to detector insertion loss was −3.5 dB which corresponds to a peak coupling efficiency of −1.75 dB. A 3 dB wavelength bandwidth of 76.34 nm was demonstrated for the grating coupler with a 20-layer reflector. The fabrication process is CMOS-compatible and requires only a single etching step..
7.	Andrew M. Spring Feng Qiu Jianxun Hong Alisa Bannaron Xiaoyang Cheng Shiyoshi Yokoyama, Adamantyl and carbazole containing trans-poly(norbornene-dicarboximide)s as electro-optic chromophore hosts, Polymer - Elsevier, 10.1016/j.polymer.2019.04.015, 172, 382-390, 2019.04, A selection of trans-poly(norbornene-dicarboximide) random copolymers incorporating adamantyl and carbazole groups have been prepared using the Grubbs 1st generation catalyst. The copolymer with the greatest carbazole content was employed as a host for a high activity chromophore guest. The adamantyl groups were able to elevate the glass transition and thermal decomposition temperatures of the host copolymers, while the carbazole groups were included to facilitate the dispersion of the added chromophores and enhance the poling process. The mass of the adamantyl pendant monomer was kept constant as the mass of the carbazole pendant monomer was increased gradually. The successful incorporation of the carbazole moiety into the copolymers was confirmed by 1H NMR integration. The polymers had a predominantly trans microstructure and the cis/trans ratio did not change significantly. The polymer molecular weights increased linearly from 25,758 g/mol to 56,827 g/mol as more carbazole-pendant monomer was incorporated. Polydispersities ranged from 1.29 to 1.70 and elemental analysis confirmed an ascending carbon% in the polymers from 72.29% to 76.26%. The glass transition temperatures decreased from 240 °C to 126 °C, with the thermal decomposition temperatures (10% loss) remaining relatively constant at between 423 °C to 394 °C, indicating the polymers had a good thermal stability. The chromophore guest concentration was increased gradually into the copolymer host from 15 wt% to 65 wt%. When poled at a field of 50 V/μm in thin film it was found that the optimum poling temperature decreased linearly from 150 °C to 90 °C as the chromophore concentration was increased, a maximum poling efficiency of 1.02 was achieved at a chromophore concentration of 55 wt%..
8.	Feng Qiu, Andrew. M. Spring, Jianxun Hong, and Shiyoshi Yokoyama, Plate-slot polymer waveguide modulator on silicon-on-insulator, Optical Society of America (OSA) - Optics Express, https://doi.org/10.1364/OE.26.011213, 26, 9, 11213-11221, 2018.04, Electro-optic (EO) modulators are vital for efficient “electrical to optical” transitions and high-speed optical interconnects. In this work, we applied an EO polymer to demonstrate modulators on silicon-on-insulator substrates. The fabricated Mach-Zehnder interferometer (MZI) and ring resonator consist of a Si and TiO2 slot, in which the EO polymer was embedded to realize a low-driving and large bandwidth modulation. The designed optical and electrical constructions are able to provide a highly concentrated TM mode with low propagation loss and effective EO properties. The fabricated MZI modulator shows a π-voltage-length product of 0.66 V·cm and a 3-dB bandwidth of 31 GHz. The measured EO activity is advantageous to exploit the ring modulator with a resonant tunability of 0.065 nm/V and a 3-dB modulation bandwidth up to 13 GHz..
9.	Jianxun Hong, Feng Qiu, Andrew M. Spring, and Shiyoshi Yokoyama, Silicon waveguide grating coupler based on a segmented grating structure, Optical Society of America (OSA) - Applied Optics, https://doi.org/10.1364/AO.57.003301, 57, 12, 3301-3305, 2018.04, We present the simulation, fabrication, and experimental results of a high-efficiency and wide-bandwidth segmented waveguide grating coupler on a silicon-on-insulator platform for near vertical optical coupling between the waveguide and optical fiber. The coupler comprises segmented gratings, which can increase vertical coupling to the optical fiber and reduce backward reflection. The proposed grating coupler has a 3 dB bandwidth of 71.4 nm and a coupling efficiency of 51.7% at a wavelength of 1550 nm. Compared with the standard uniform waveguide grating coupler, the coupling efficiency was improved by 25.64%..
10.	Hiroki Miura, Feng Qiu, Andrew M. Spring, Tsubasa Kashino, Takamasa Kikuchi, Masaaki Ozawa, Hideyuki Nawata, Keisuke Odoi, and Shiyoshi Yokoyama, High thermal stability 40 GHz electro-optic polymer modulators, Optical Society of America - Optics Express, https://doi.org/10.1364/OE.25.028643, 25, 23, 28643-28649, 2017.11, As a consequence of the urgent demand for an electro-optic (EO) polymer modulator with an elevated temperature stability, we have prepared a selection of EO polymers having glass transition temperatures of up to 194°C. The measured half-wave voltage characteristics of the fabricated Mach-Zehnder interference modulators revealed an excellent thermal resistance at 105°C for approximately 2,000 hours. By utilizing traveling-wave electrodes on the modulator, the high-frequency response at 10-40 GHz was evaluated under ascending temperatures. The advantage of such high-temperature stability EO polymer modulators was clearly demonstrated by the continuous frequency response up to 130°C..
11.	Qiu Feng, Spring Andrew M, Hong Jianxun, Miura Hiroki, Kashino Tsubasa, Kikuchi Takamasa, Ozawa Masaaki, Nawata, Hideyuki, Odoi Keisuke, Yokoyama, Shiyoshi, Electro-optic Polymer Ring Resonator Modulator on a Flat Silicon-on-Insulator, Wiley - Laser and Photonics Reviews, https://doi.org/10.1002/lpor.201700061, 11, 6, 1700061, 2017.11, Optical polymers are a promising material of choice in the development of hybrid silicon photonics devices. Particularly, recent progress in electro-optic (EO) active polymers has shown a strong Pockels effect. A ring resonator modulator is a vital building block for practical applications, such as signal processing, routing, and monitoring. However, the properties of the hybrid silicon and EO polymer ring modulators are still far from their theoretical limits. Here, we demonstrate a unique design of a hybrid ring resonator modulator simply located onto a silicon-on-insulator (SOI) substrate. Extra doping and etching of the SOI wafer is not required, even so we measured an in-device electro-optic coefficient r33 = 129 pm/V. The ring modulator exhibited a high sensitivity of the electrically tunable resonance, which enabled a 3 dB bandwidth of up to 18 GHz. The proposed technique will enable efficient mass-production of the micro-footprint modulators and promote the development of integrated silicon photonics..
12.	Xiaoyang Cheng, Jianxun Hong, Andrew M. Spring, and Shiyoshi Yokoyama, Fabrication of a high-Q factor ring resonator using LSCVD deposited Si3N4 film, Optical Society of America - Optical Materials Express, https://doi.org/10.1364/OME.7.002182, 7, 7, 2182-2187, 2017.07, High-quality silicon nitride (Si3N4) films with a low stress and optical loss were deposited at low temperature (150°C) using liquid source chemical vapor deposition (LSCVD). The refractive index of the Si3N4 film was optimized by changing the composition ratio and deposition temperature. An integrated photonic structure of micro-ring resonator based on the as-deposited Si3N4 layer has been demonstrated to exemplify its viability as a photonic integration platform. Bragg gratings are fabricated at both ends of the bus waveguide to improve coupling efficiency and testing flexibility. A measured waveguide loss of 2.9 dB/cm and a high Q-factor of 5.2 × 104 are achieved. The LSCVD deposited Si3N4 is therefore a highly promising photonic integration platform for various integrated photonic applications..
13.	Hong Jianxun, Qiu Feng, Cheng Xiaoyang, Spring Andrew M, Yokoyama Shiyoshi, A high-speed electro-optic triple-microring resonator modulator, Nature Research - Scientific Reports, doi:10.1038/s41598-017-04851-x, 7, 4682, 2017.07, The coupling intensity modulator based on a triple-microring structure was proposed and numerically investigated for a high speed and a low bit error ratio (BER) operation. The modulator consists of a dual-microring optical cavity and a gate-microring energy feedback path. The optical cavity ensures a high energy storing efficiency, and the feedback path enables modulation with little intracavity energy decay. The bandwidth of 103 GHz and modulation depth of 6.2 dB at 2.0 Vpp were theoretically verified by the analysis of the sinusoidal modulation performance. Pulse modulation resulted in a data rate of 160 Gbps, an extinction ratio of 16.84 dB, and a BER of 1 × 10−8. The proposed modulator is applicable for compact, high-speed, and low-energy photonic integration..
14.	Sato Hiromu, Miura Hiroki, Qiu Feng, Spring Andrew M, Kashino Tsubasa, Kikuchi Takamasa, Ozawa Masaaki, Nawata Hideyuki, Odoi Keisuke, Yokoyama Shiyoshi, Low driving voltage Mach-Zehnder interference modulator constructed from an electro-optic polymer on ultra-thin silicon with a broadband operation, Optical Society of America (OSA) - Optics Express, http://dx.doi.org/10.1364/OE.25.000768, 25, 2, 768-775, 2017.01, An electro-optic (EO) polymer waveguide using an ultra-thin silicon hybrid has been designed and fabricated. The silicon core has the thickness of 50 nm and a width of 5 μm. The waveguide was completed after covering the cladding with the high temperature stable EO polymer. We have demonstrated a low half-wavelength voltage of 0.9 V at the wavelength of 1.55 μm by using a Mach-Zehnder interference modulator with TM mode operation. The measured modulation corresponded to an effective in-device EO coefficient of 165 pm/V. By utilizing the traveling-wave electrode on the modulator the high-frequency response was tested up to 40 GHz. The 3 dB modulation bandwidth was measured to be 23 GHz. In addition, the high frequency sideband spectral measurement revealed that a linear response of the modulation index against the RF power was confirmed up to 40 GHz signal..
15.	Spring Andrew M, Qiu Feng, Hong Jianxun, Bannaron Alisa, Kashino Tsubasa, Kikuchi Takamasa, Ozawa Masaaki, Nawata Hideyuki, Odoi Keisuke, Yokoyama Shiyoshi, Crosslinked poly(norbornene-dicarboximide)s as electro-optic chromophore hosts, Elsevier - European Polymer Journal, https://doi.org/10.1016/j.eurpolymj.2017.10.022, 97, 263-271, 2017.12, A series of crosslinked poly(norbornene-dicarboximide)s have been prepared by ring opening metathesis polymerization. Increasing quantities of a bifunctional norbornene-dicarboximide crosslinker was doped into a high Tg cyclohexyl-substituted norbornene-dicarboximide monomer before polymerization. The wt% of the crosslinker was increased from 0.00 to 4.40 wt%, after which the polymers became gelated. Polymer molecular weights increased drastically from 23,500 to 2,135,000 g/mol, the polydispersities increased from 1.18 to 73.47 and the viscosities increased from 5.27 to 538.7 mPa·s as the wt% of the crosslinker was increased. The trans:cis vinylene ratio remained constant at 1:0.18 as well as the Tg and Td with average values of 210 °C and 392 °C being measured. Five of the crosslinked polymers and the reference homopolymer were utilized as hosts for the high activity tert-butyldiphenylsilyl substituted FTC chromophore guest. The polymer host containing 1.96 wt% crosslinker was foundto have amaximum r33 of 78 pm/V whenpolled at 150 °C withan electric ﬁeldstrength of 100 V/μm. The r33 increased linearly from 63 to 78 pm/V as the wt% of the crosslinker was increased from 0.00 to 1.96wt%. The thermal and temporal stability was found to increase slightly with the 0.00 wt% polymer exhibiting a stability of 77%, while the 1.96 wt%polymer exhibited a stability of79% when both were heated to 85 °C and aged for 500 h in air..
16.	Spring Andrew M, Qiu Feng, Hong Jianxun, Bannaron Alisa, Yokoyama Shiyoshi, Electro-optic properties of a side chain poly(norbornene-dicarboximide) system with an appended phenyl vinylene thiophene chromophore, Elsevier - Polymer, http://dx.doi.org/10.1016/j.polymer.2017.05.005, 119, 13-27, 2017.06, A side chain EO copolymer series has been synthesized by ROMP using the Grubbs 3rd generation initiator and quenched with ethyl vinyl ether. The copolymers were prepared by combining two norbornene-dicarboximide monomers, one with a cyclohexyl substituent and another substituted with an FTC chromophore. The mol% of the chromophore-substituted monomer was varied from 0.00 mol% to 22.92 mol%, all polymers were obtained in a yield of between 83 and 92% and a purity of between 97 and 98%. The cis:trans vinylene ratio remained constant at 1:1, conﬁrming the polymers were amorphous. Peak molecular weights increased from 29,541 g/mol to 142,113 g/mol and the PDI increased from 1.36 to 4.01 respectively. Glass transition and thermal decomposition temperatures decreased from 206 C to 168 C and 433 C to 382 C as the mol% of the chromophore-substituted monomer was increased. UV evis absorbance spectroscopy was used to quantify the chromophore content. A close correlation (68 e95%) between the measured and calculated absorbance was found. The polymer containing 22.92 mol% of the chromophore-substituted monomer had a maximum r33 of 70 pm/V when polled at an optimum ﬁeld of 60 V/mm at a polling temperature of 200 C. This equates to a high polling efﬁciency of 1.16. High current ﬂow in this polymer ﬁlm at elevated ﬁeld strength caused a breakdown of the electrode, preventing access to an elevated electro-optic coefﬁcient. This polymer was found to have an excellent stability of 76% when aged at 85 C for 1000 h in air..
17.	Lidster Benjamin J, Kumar Dharam R, Spring Andrew M, Yu Chin-Yang, Helliwell Madeleine, Raftery James, Turner, Michael L, Alkyl substituted [2.2]paracyclophane-1,9-dienes, Royal Society of Chemistry (RSC) - Organic & Biomolecular Chemistry, 10.1039/c6ob00885b, 14, 25, 6079-6087, 2016.05, [2.2]Paracyclophane-1,9-dienes substituted with n-octyl chains have been synthesised from the corresponding dithia[3.3]paracyclophanes using a benzyne induced Stevens rearrangement. The use of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and tetra-n-butylammonium fluoride as the in situ benzyne source gave significantly improved yields over traditional sources of benzyne and enabled the preparation of n-octyl substituted [2.2]paracyclophane-1,9-dienes on a multi-gram scale..
18.	Lidster Benjamin J, Kumar Dharam R, Spring, Andrew M, Yu, Chin-Yang, Turner Michael L, Alkyl substituted poly(p-phenylene vinylene)s by ring opening metathesis polymerisation, Royal Society of Chemistry (RSC) - Polymer Chemistry, 10.1039/c6py01186a, 7, 35, 5544-5551, 2016.06, The ring opening metathesis polymerisation (ROMP) of three n-octyl substituted [2.2]paracyclophane1,9-dienes, initiated by Grubbs ruthenium carbene complexes is reported. The molecular weight of the resulting alkyl-substituted poly(p-phenylene vinylene)s is determined by the monomer to initiator ratio and the polymers are isolated with relatively narrow polydispersities and control of the end groups. Only the pseudo-geminal isomer of the tetra-alkyl substituted [2.2]paracyclophane-1,9-diene was susceptible to ROMP. The optical properties of the two series of polymers was investigated..
19.	Qiu Feng, Miura Hiroki, Spring Andrew M, Hong Jianxun, Maeda Daisuke, Ozawa Masa-aki, Odoi Keisuke, Yokoyama Shiyoshi, An electro-optic polymer-cladded TiO2 waveguide modulator, Applied Physics Letter (APL), http://dx.doi.org/10.1063/1.4966272, 109, 17, 173301-1-173301-4, 2016.10, Organic electro-optic (EO) materials and their hybrid systems have received considerable attention for high-performance modulators. In this work, we demonstrate the design and fabrication of an EO modulator with a low half-wave voltage (Vp) and a RF modulation response up to at least 10GHz. The polymer used in this work has a glass transition temperature of 172C, which makes it stable even under high temperature RF sputtering. As a result, an EO polymer-cladded titanium dioxide (TiO2) waveguide structure can be utilized to enlarge the conﬁnement factor, and thus, enable a low Vp. The response of the modulator from 4 to 10GHz has been measured, which shows a ﬂat frequency response up to 10 GHz and a potential for the application in several tens GHz..
20.	Qiu Feng Spring Andrew M, Miura Hiroki, Maeda Daisuke, Ozawa Masa-aki, Odoi, Keisuke, Yokoyama, Shiyoshi, Athermal Hybrid Silicon/Polymer Ring Resonator Electro-optic Modulator, American Chemical Society (ACS) Photonics, 10.1021/acsphotonics.5b00695, 3, 5, 780-783, 2016.05, In this work, we have demonstrated a hybrid silicon/polymer ring resonator electro-optic (EO) modulator with a temperature-independent modulation. The waveguide consisted of an ultrathin silicon core with an EO polymer cladding. Using ultrathin silicon is advantageous, as it allows a reduction in the side-wall scattering loss and also oﬀers excellent light distribution to enable athermal operation. With a radius of 60 μm, the ring exhibited a 9.7 dB extinction depth and a Q value of 1.25 × 104. After poling of the EO polymer, the ring resonator functioned well as an EO modulator and operated in a stable manner between 25 and 55 °C..
21.	Spring, Andrew M, Qiu, Feng, Yokoyama Shiyoshi, High stability poly(N-adamantyl-exo-norbornene-5,6-dicarboximide) and phenyl vinylene thiophene electro-optic host-guest system, Elsevier - European Polymer Journal, https://doi.org/10.1016/j.eurpolymj.2016.09.012, 84, 89-99, 2016.11, Poly(N-adamantyl-exo-norbornene-5,6-dicarboximide) was prepared by ring opening metathesis polymerization. This was achieved in chloroform using the Grubbs 1st generation initiator and quenched with ethyl vinyl ether. The polymer had a weight average molecular weight of 27,000 g/mol with a polydispersity index of 2.19, a high glass transition temperature of 281 °C and a high thermal decomposition temperature of 385 °C (10% loss). The trans:cis vinylene ratio was 1.00:0.19 making the polymer amorphous. The polymer was used as a host for 5 guest nonlinear optical chromophores. The relationship between the chromophore structure and the electro-optic coefficient was investigated. A range of chromophore concentrations were evaluated and it was found that the ideal chromophore structure included a bulky tert-butyldiphenylsilane side group. A maximum r33 of 80 pm/V was obtained at a chromophore concentration of 45 wt% and a poling temperature of 160 °C. A host-guest system containing 35 wt% of the tert-butyldiphenylsilane substituted chromophore had a stability of 85% at a temperature of 85 °C for 500 h. The stability at 105 °C was 72%. In comparison amorphous polycarbonate under the same conditions achieved a stability of just 58% at 85 °C, while poly(methyl methacrylate) had a stability of 0% at 85 °C..
22.	Qiu Feng, Spring Andrew M, Maeda Daisuke, Ozawa Masa-aki, Odoi Keisuke, Otomo Akira, Aoki Isao, Yokoyama, Shiyoshi, A hybrid electro-optic polymer and TiO2 double-slot waveguide modulator, Nature research - Scientific Reports, doi:10.1038/srep08561, 5, 8561, 1-6, 2015.02, An electro-optic (EO) modulator using a TiO2 slot hybrid waveguide has been designed and fabricated. Optical mode calculations revealed that the mode was primarily confined within the slots when using a double-slot configuration, thus achieving a high EO activity experimentally. The TiO2 slots also acted as an important barrier to induce an enhanced DC field during the poling of the EO polymer and the driving of the EO modulator. The hybrid phase modulator exhibited a driving voltage (Vπ) of 1.6 V at 1550 nm, which can be further reduced to 0.8 V in a 1 cm-long push-pull Mach–Zehnder interferometer (MZI) structure. The modulator demonstrated a low propagation loss of 5 dB/cm and a relatively high end-fire coupling efficiency..
23.	Qiu Feng, Spring Andrew M and Yokoyama, Shiyoshi, Athermal and High-Q Hybrid TiO2–Si3N4 Ring Resonator via an Etching-Free Fabrication Technique, American Chemical Society (ACS) Photonics, DOI:10.1021/ph500450n, 2, 3, 405-409, 2015.03, In this work, we have demonstrated a hybrid TiO2−Si3N4 ring resonator with a high-Q and a temperature-insensitive resonance. The waveguide consists of a thermo-optic positive Si3N4 slab and a negative TiO2 overcladding. The TiO2 layer has a shallow ridge structure, which has been designed to realize an athermal operation and maintain a low scattering loss. During the fabrication of this waveguide, there was no need to utilize the dryetching process. The method aﬀords a straightforward fabrication and a precise control over the waveguide dimensions. As a result, the ring resonator exhibits a high Q value of 1.55 × 105,a low propagation loss of 0.4 dB/cm, and a small temperature-dependent wavelength shift of 0.14 pm/°C between 25 and 60 °C..
24.	Qiu Feng, Sato Hiromu, Spring Andrew M, Maeda Daisuke, Ozawa Masa-aki, Odoi Keisuke, Aoki Isao, Otomo Akira, Yokoyama, Shiyoshi, Ultra-thin silicon/electro-optic polymer hybrid waveguide modulators, Applied Physics Letters (APL), https://doi.org/10.1063/1.4931490, 107, 12, 123302-1-123302-5, 2015.09, Ultra-thin silicon and electro-optic (EO) polymer hybrid waveguide modulators have been designed and fabricated. The waveguide consists of a silicon core with a thickness of 30nm and a width of 2lm. The cladding is an EO polymer. Optical mode calculation reveals that 55% of the optical ﬁeld around the silicon extends into the EO polymer in the TE mode. A Mach-Zehnder interferometer (MZI) modulator was prepared using common coplanar electrodes. The measured half-wave voltage of the MZI with 7lm spacing and 1.3cm long electrodes is 4.6V at 1550nm. The evaluated EO coefﬁcient is 70pm/V, which is comparable to that of the bulk EO polymer ﬁlm. Using ultra-thin silicon is beneﬁcial in order to reduce the side-wall scattering loss, yielding a propagation loss of 4.0dB/cm. We also investigated a mode converter which couples light from the hybrid EO waveguide into a strip silicon waveguide. The calculation indicates that the coupling loss between these two devices is small enough to exploit the potential fusion of a hybrid EO polymer modulator together with a silicon micro-photonics device..
25.	Andrew M. Spring, Daisuke Maeda, Masaaki Ozawa, Keisuke Odoi, Feng Qiu, Kazuhiro Yamamoto, Shiyoshi Yokoyama, An analysis of the structural, thermal and optical characteristics as well as the electrical resistivity of tert-butyldiphenylsilyl substituted poly(norbornene-dicarboximide)s, Elsevier - Polymer, http://dx.doi.org/10.1016/j.polymer.2014.11.043, 56, 15, 189-198, 2014.12, A sequence of well controlled tert-butyldiphenylsilyl substituted poly(norbornene-dicarboximide)s with ascending mol. wts. have been prepd. using the Grubbs 1st generation catalyst in anhyd. chloroform. The kinetics of the polymn. was examd. using NMR spectroscopy and gel permeation chromatog. By decreasing the Grubbs catalyst concn., the polymer mol. wts. increased linearly. The glass transition temps. and thermal decompn. temps. initially increased with polymer mol. wt., then reached a plateau. Regardless of mol. wt. the polydispersities remained narrow. The polymers exhibited a predominantly trans microstructure and matrix-assisted laser desorption/ionization mass spectrometry was utilized to det. polymer end groups and to calc. the abs. mol. wts. The residual ruthenium content of the polymers was quantified using inductively coupled plasma mass spectrometry and the influence on the resistivity, refractive indexes and thin film optical transmittance was evaluated..
26.	Jia Yue, Spring Andrew M, Yu Feng, Yamamoto Kazuhiro, Aoki Isao, Otomo Akira, Yokoyama, Shiyoshi, A Norbornene Polymer Brush for Electro-optic Applications, Elsevier - Thin Solid Films, https://doi.org/10.1016/j.tsf.2013.06.071, 554, 175-179, 2013.07, Norbornenedicarboximide derived polymer brushes containing Disperse Red 1 appended chromophores have been prepared by sequencial ring opening metathesis polymerization and atom transfer radical polymerization. This brush was then employed as an electro-optic polymer host for high molecular hyperpolarizability phenyl vinylene thiophene vinylene (FTC) bridge chromophores in a binary chromophore system. The r33 of the polymer brush/bi-chromophore network was evaluated via in situ poling and was measured as 94 pm/V compared to the benchmark polymethylmethacrylate (PMMA) system of 76 pm/V with an identical chromophore. Furthermore, our polymer brush/bi-chromophore network exhibited an enhanced poling efﬁciency of 1.37 (nm/V)2 as compared to a simple PMMA - FTC host - guest 0.70 (nm/V)2..
27.	Andrew M. Spring, Daisuke Maeda, Masaaki Ozawa, Keisuke Odoi, Feng Qiu, Kazuhiro Yamamoto, Shiyoshi Yokoyama, Glass transition temperature control by poly(norbornene-dicarboximide) copolymers, Springer - Polymer Bulletin, DOI 10.1007/s00289-014-1283-2, 72, 3, 503-521, 2014.12, By the precise combination of both cyclohexyl- and octyl-substituted norbornene-dicarboximide monomers, a series of copolymers were prepd. by ring-opening metathesis polymn. utilizing the Grubbs first-generation initiator. This allowed an excellent control over the glass transition temp. between 215 and 126 °C depending upon the percentage of the octyl moiety in the copolymer. Initially two homopolymers, poly(N-cyclohexyl-exo-norbornene-5,6-dicarboximide) and poly(N-octyl-exo-norbornene-5,6-dicarboximide), were prepd. to det. the desirable conditions for copolymer prepn. The kinetics of the two homopolymers were monitored using proton NMR spectroscopy and size-exclusion chromatog., with monomer conversion being achieved after 120 min in both cases..
28.	Qiu Feng, Spring Andrew M, Maeda Daisuke, Ozawa Masa-Aki, Odoi Keisuke, Aoki Isao, Otomo Akira, Yokoyama Shiyoshi, TiO2 ring-resonator-based EO polymer modulator, The Optical Society of America (OSA) - Optics Express, DOI:10.1364/OE.22.014101, 22, 14101-14107, 2014.06, In this work, an electro-optic (EO) ring resonator modulator was designed and fabricated in a waveguide consisting of a titanium dioxide (TiO2) core, silicon dioxide (SiO2) buffer layer, EO polymer claddings, and electrodes. By optimizing the thickness of the TiO2 and SiO2 layers, the modulator could satisfy the single-mode requirement; furthermore 52.5% TM mode was confined in the active EO polymer layers. The designed modulator could also pole the EO polymer effectively regardless of its resistivity. Therefore, the EO modulator was obsd. to show a high resonance wavelength shift of 2.25 × 10-2 nm/V. The intensity modulation at 1550 nm showed a Vp-p = 1.9 V for a 3dB distinction ratio..
29.	Feng Qiu, Andrew M. Spring, Daisuke Maeda, Masa-aki Ozawa, Keisuke Odoi, Isao Aoki, Akira Otomo, and Shiyoshi Yokoyama, A straightforward electro-optic polymer covered titanium dioxide strip line modulator with a low driving voltage, Applied Physics Letters (AIP), http://dx.doi.org/10.1063/1.4893925, 105, 073305-1-073305-4, 2014.08, An electrooptic (EO) modulator composed of an EO polymer/TiO2 (TiO2) hybrid waveguide was designed and fabricated. By using a TiO2 strip line (0.3 × 0.3 μm2 cross-section) as the core, the confinement factor in the EO polymer is optimized, thus achieving a high EO activity. The coplanar electrode spacing is tuned to enable an effective poling and a small propagation loss. The measured in-device EO coeff. is 100 pm/V at 1550 nm, with a driving voltage (Vπ) 3.2 V for the 12 mm-electrode length. The results also predict a possible Vπ of ∼1 V in a push-pull MZI structure. The EO activity of the modulator exhibited an excellent temporal stability at 85° for 500 h due to the high glass transition temp. of the EO polymer and the temp.-insensitive TiO2 strip line..
30.	Yue Jia, Andrew M. Spring, Feng Qiu, Feng Yu, Kazuhiro Yamamoto, Isao Aoki, Akira Otomo, and Shiyoshi Yokoyama, Electro-optic properties of a bi-chromophore norbornene polymer brush system, IOP Science - Japanese Journal of Applied Physics (JJAP)*, http://dx.doi.org/10.7567/JJAP.53.01AF04, 53, 01AF04, 01AF041-01AF04-5, 2013.12, A selection of poly(norbornene-exo-dicarboximide) brush-type polymers decorated with a pendent azobenzene dye have been prepared for use as electro-optic (EO) hosts. These polymer brushes were employed as EO polymer hosts for a high molecular hyperpolarizability phenyl vinylene thiophene vinylene (FTC) chromophore guest. These polymer brushes contained methoxy or cyano azobenzene substituents, which were able to manipulate the electronic polarization, refractive index, and EO activity. The concentration of the azobenzene dye was increased from 6 to 38%, in order to ﬁnd the optimum and to maximise the EO coefﬁcient. The refractive index of the mixtures could also be tuned by changing the azobenzene content. Ultimately an EO coefﬁcient of nearly 95 pm/V could be realized using a methoxy substituted azobenzene brush at a concentration of 25% with an added FTC chromophore..
31.	Andrew M Spring, Feng Yu, Feng Qiu, Kazuhiro Yamamoto and Shiyoshi Yokoyama, The preparation of well-controlled poly(N-cyclohexyl-exo-norbornene-5,6-dicarboximide) polymers, Nature Publishing Group - Polymer Journal, doi:10.1038/pj.2014.26, 46, 576-583, 2014.03, We have studied the ring-opening metathesis polymerization of N-cyclohexyl-exo-norbornene-5,6-dicarboximide using the following 4 initiators: Grubbs 1, Grubbs 2, Hoveyda–Grubbs 1 (HG1) and Hoveyda–Grubbs 2 (HG2). Only the Grubbs 1 initiator was able to precisely control the polymer molecular weight. Polymerizations initiated by the HG1, Grubbs 2 and HG2 initiators could not be controlled well. Both the Grubbs 1 and HG1 yielded polymers with a high trans % (85–98%), whereas Grubbs 2 and HG2 yielded polymers with a lower trans % (50–52%). The level of molecular weight control for the four initiators decreased in the order Grubbs 14HG14HG24Grubbs 2. We also demonstrated that, in the case of polymers produced using Grubbs 1, the refractive indices (RIs) of the polymers decreased in a linear and controllable fashion from 1.539 to 1.534 at 633 nm, as the molecular weight was increased from 6700 to 26 400. This change represented a decrease in the RI of 0.005..
32.	Andrew M. Spring, Leandro A. Estrada, Svetlana V. Vasilyeva, Andrew G. Rinzler, and John R. Reynolds, Carbon Nanotube Adsorptive Materials Derived from Acid Degradable Poly(acetals), American Chemical Society (ACS) - Macromolecules, dx.doi.org/10.1021/ma500009s, 47, 2556-2560, 2014.04, In this paper, we report the synthesis and characterization of a well-controlled and acid degradable poly(acetal) which can adsorb strongly to the surface of carbon nanotubes (CNTs). These polymers, generated via acyclic diene metathesis (ADMET), incorporate pendant pyrene groups that are well-known to associate strongly to CNTs by noncovalent interactions. Films and solutions of the polymer were degraded through the controlled addition of aqueous hydrochloric acid in ethanol. The polymer’s ability to adsorb to and be removed from a CNT ﬁlm was also evaluated..
33.	Yu Feng, Spring Andrew M, Li Lu, Qiu Feng, Yamamoto Kazuhiro, Maeda Daisuke, Ozawa Masaaki, Odoi Keisuke, Yokoyama Shiyoshi, An Enhanced Host-Guest Electro-Optical Polymer System Using Poly(norbornene-dicarboximides) via ROMP, About Wiley Online Library - Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.26505, 51, 1278-1284, 2012.11, High glass transition temperature poly(N-cyclohexyl-5-norbornene-2,3-dicarboximide)s (NDI)s prepared by ring opening metathesis polymerization yielded polymers with a narrow polydispersity and well-controlled molecular weight materials when using the Grubbs first generation initiator. Polymers produced using the Grubbs second generation initiator could not be controlled easily. By initiator selection it was also possible to synthesize polymers with either 98 or 52% trans microstructures. These materials were employed as electro-optic (EO) polymer hosts for high molecular hyperpolarizability phenyl vinylene thiophene vinylene bridge chromophores. This chromophore was modified by the incorporation of a tert-butyldiphenylsilane group. The addition was able to further increase its EO coefficient (r33) to reach 93 pm/V in a trans rich poly(NDI) produced by the Grubbs first generation initiator, compared to a benchmark chromophore / polymer combination. We investigated in detail the relationship between polymer microstructure and their absolute molecular weight on forming the best host–guest with the high polarizability chromophore. Our results indicate that by utilizing a very simple host–guest system a high r33 can be realized..
34.	Qiu Feng, Spring Andrew M, Yu Feng, Yokoyama Shiyoshi, Complementary Metal-Oxide-Semiconductor compatible athermal Silicon Nitride/Titanium Dioxide Hybrid Micro Ring Resonators, American Institute of Physics (AIP) - Applied Physics Letters (APL), https://doi.org/10.1063/1.4790440, 102, 051106 1-051106-3, 2013.02, Micro-ring resonators have been widely utilized in silicon photonics. However they often exhibit a high sensitivity to ambient temperature ﬂuctuations. In this letter, we have demonstrated a complementary metal–oxide–semiconductor compatible athermal micro-ring resonator made from titanium dioxide (TiO2) and silicon nitride (SiNx). We have exploited the negative thermo–optic coefﬁcient of TiO2 to counterbalance the positive coefﬁcient of SiNx. By a precise control over the TiO2 layer thickness, an athermal condition remarkably consistent with the simulation can be achieved. Therefore, a SiNx–TiO2 hybrid micro-ring resonator with a temperature dependent wavelength shift of 0073 pm/C has been realized..
35.	Qiu Feng, Spring Andrew M, Yu Feng, Aoki Isao, Otomo Akira, Yokoyama Shiyoshi, Thin TiO2 Core and Electro-optic Polymer Cladding Waveguide Modulators, American Institute of Physics (AIP) - Applied Physics Letters (APL), https://doi.org/10.1063/1.4809818, 102, 233504-1-2335043, 2013.06, In this letter, we have fabricated a thin TiO2 core and electro-optic (EO) polymer cladding derived rib-waveguide and demonstrated its optical modulation at 1550 nm with a VpL ﬁgure of merit of 3.3 V cm. We utilized the high refractive index TiO2 to conﬁne a large fraction of light in the relatively low refractive index EO polymer layer. Furthermore, this TiO2 core enables the modulator to be constituted without a transparent top cladding and also can increase the EO activity to a much higher level. As a result, the waveguide has an enhanced in-device r33, corresponding to a VpiL of 165 V cm in a pushpull MachZehnder interferometer structure..
36.	Qiu Feng, Spring Andrew M, Yu Feng, Aoki Isao, Otomo Akira, Yokoyama Shiyoshi, Electro-optic Polymer/Titanium Dioxide Hybrid Core Ring Resonator Modulators, Laser and Photonics Reviews, https://doi.org/10.1002/lpor.201300089, 7, L84-L88, 2013.04, Compact electro-optic (EO) modulators are desirable for a number of applications. In this study, a ring modulator has been fabricated in the titanium dioxide (TiO2) core and EO polymer cladding waveguide structure. A 250-nm thick TiO2 core was utilized to minimize the ring radius down to 100 μm, to avoid using the top cladding between the EO polymer and the electrode, and to improve the poling efﬁciency. The resonance obtained by the ring modulator was observed to shift by 0.02 nm/V due to the enhanced in-device EO coefﬁcient of 105 pm/V. A modulation depth of 3 dB was observed at the frequency response function at 20 kHz using 2-V Vp–p clock signal..
37.	Qiu Feng, Yu Feng, Spring Andrew M, Yokoyama Shiyoshi, Athermal Silicon Nitride Ring Resonator by Photobleaching of Disperse Red 1-Doped Poly(methylmethacrylate) Polymer, Optical Society of America (OSA) - Optics Letters, https://doi.org/10.1364/OL.37.004086, 19, 4086-4088, 2012.07, To fabricate athermal silicon nitride waveguides, the dimensions of both the core and cladding, refractive index, and thermo-optic coefficients must be controlled precisely. We present a simple and effective method for the postfabrication trimming of silicon nitride ring resonators that overcomes the highly demanding fabrication. In order to manipulate the polymer’s refractive index and thermo-optic coefficient, we bleached the Disperse Red 1-doped poly(methyl methacrylate) (DR1/PMMA) top cladding using UV irradiation. After a suitable bleaching time, the temperature-dependent wavelength shift of the ring resonator was reduced from −9.8 to −0.018 pm∕°C, which is the lowest shift that we are aware of for an athermal waveguide realized by overlaying a polymer cladding to date..
38.	Feng Qiu Feng Yu, Andrew M. Spring, and Shiyoshi Yokoyama, Thermal Sensitive Wavelength Filter Based on Polymer Waveguide and Polarization-maintaining Fiber, Journal of the Optical Society of America B (OSA) Optical Physics, https://doi.org/10.1364/JOSAB.29.003069, 29, 3069-3071, 2012.10, A simple thermal tuning wavelength filter is experimentally demonstrated by using a high polarization extinction ratio polymer waveguide and a polarization-maintaining fiber. This filter can be tuned with its free spectral range, on/off ratio, and filtered wavelength. The large temperature dependence wavelength shift of 0.65 nm=°C also makes it a suitable candidate of thermal sensors..
39.	Andrew M. Spring, Chin-Yang Yu, Masaki Horie and Michael L. Turner, MEH-PPV by microwave assisted ring-opening metathesis polymerisation, Royal Society of Chemistry (RSC) - Chemical Communications*, 10.1039/b901075k, 19, 2676-2678, 2009.03, Excellent control in the synthesis of MEH-PPV can be achieved by microwave assisted, ring-opening metathesis polymerization (ROMP) of [2.2]paracyclophanedienes..
40.	Chin-Yang Yu, Masaki Horie, Andrew M. Spring, Kim Tremel, and Michael L. Turner, Homopolymers and Block Copolymers of p-Phenylenevinylene-2,5-diethylhexyloxy-p-phenylenevinylene and m-Phenylenevinylene-2,5-diethylhexyloxy-p-phenylenevinylene by Ring-Opening Metathesis Polymerisation, American Chemical Society (ACS) - Macromolecules*, 10.1021/ma901966g, 43, 222-232, 2009.10, p-Phenylenevinylene-2,5-diethylhexyloxypphenylenevinylene and m-phenylenevinylene-2,5-diethylhexyloxy-p-phenylenevinylene homopolymers have been prepared by the ring-opening metathesis polymerization (ROMP) of strained cyclophanedienes, initiated by the second generation Grubbs catalyst. The as-formed polymers have a backbone of alternating cis- and trans-vinylene linkages due to the opening of only one vinylene of the cyclophanediene. Irradiation with UV light results in an isomerization to an all-trans-vinylene microstructure for all polymers. The polymer chain ends remain active after complete consumption of the cyclophanediene, and block copolymers can be prepared by addition of further cyclophanediene. The optical and electronic properties of the homopolymers and block copolymers are reported.

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