Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.apt.2024.104713

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1007/s10934-024-01663-z

DOI： https://doi.org/10.1007/s10934-024-01663-z

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.molstruc.2024.138001

DOI： https://doi.org/10.1016/j.molstruc.2024.138001

Language：English   Publishing type：Research paper (scientific journal)  

Repository Public URL： https://hdl.handle.net/2324/7172257

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Repository Public URL： https://hdl.handle.net/2324/7318877

Language：English   Publishing type：Research paper (scientific journal)  

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.

Repository Public URL： https://hdl.handle.net/2324/7318872

Language：English   Publishing type：Research paper (scientific journal)  

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.

Repository Public URL： https://hdl.handle.net/2324/7318868

Language：English   Publishing type：Research paper (scientific journal)  

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%.

DOI： 10.1016/j.polymer.2019.04.015

Repository Public URL： https://hdl.handle.net/2324/7318867

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/OE.27.001877

Repository Public URL： https://hdl.handle.net/2324/7318869

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/OE.26.011213

Repository Public URL： https://hdl.handle.net/2324/7318863

Language：English   Publishing type：Research paper (scientific journal)  

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%.

DOI： https://doi.org/10.1364/AO.57.003301

Repository Public URL： https://hdl.handle.net/2324/7318861

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1016/j.eurpolymj.2017.10.022

Repository Public URL： https://hdl.handle.net/2324/7239430

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/OE.25.028643

Repository Public URL： https://hdl.handle.net/2324/7318857

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1002/lpor.201700061

Repository Public URL： https://hdl.handle.net/2324/7318855

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/OME.7.002182

Repository Public URL： https://hdl.handle.net/2324/7318852

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： doi:10.1038/s41598-017-04851-x

Repository Public URL： https://hdl.handle.net/2324/7239718

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.1016/j.polymer.2017.05.005

Repository Public URL： https://hdl.handle.net/2324/7239429

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.1364/OE.25.000768

Repository Public URL： https://hdl.handle.net/2324/7239431

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1016/j.eurpolymj.2016.09.012

Repository Public URL： https://hdl.handle.net/2324/7239418

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.1063/1.4966272

Repository Public URL： https://hdl.handle.net/2324/7239425

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1039/c6py01186a

Repository Public URL： https://hdl.handle.net/2324/7239427

Language：English   Publishing type：Research paper (scientific journal)  

[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.

DOI： 10.1039/c6ob00885b

Repository Public URL： https://hdl.handle.net/2324/7239428

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1021/acsphotonics.5b00695

Repository Public URL： https://hdl.handle.net/2324/7239422

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1063/1.4931490

Repository Public URL： https://hdl.handle.net/2324/7239402

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： DOI:10.1021/ph500450n

Repository Public URL： https://hdl.handle.net/2324/7239410

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： doi:10.1038/srep08561

Repository Public URL： https://hdl.handle.net/2324/7239414

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.1016/j.polymer.2014.11.043

Repository Public URL： https://hdl.handle.net/2324/7239400

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： DOI 10.1007/s00289-014-1283-2

Repository Public URL： https://hdl.handle.net/2324/7239384

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.1063/1.4893925

Repository Public URL： https://hdl.handle.net/2324/7239375

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： DOI:10.1364/OE.22.014101

Repository Public URL： https://hdl.handle.net/2324/7239383

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： dx.doi.org/10.1021/ma500009s

Repository Public URL： https://hdl.handle.net/2324/7238804

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： doi:10.1038/pj.2014.26

Repository Public URL： https://hdl.handle.net/2324/7238805

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： http://dx.doi.org/10.7567/JJAP.53.01AF04

Repository Public URL： https://hdl.handle.net/2324/7239371

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1016/j.tsf.2013.06.071

Repository Public URL： https://hdl.handle.net/2324/7239385

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1063/1.4809818

Repository Public URL： https://hdl.handle.net/2324/7238796

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1002/lpor.201300089

Repository Public URL： https://hdl.handle.net/2324/7238792

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1063/1.4790440

Repository Public URL： https://hdl.handle.net/2324/7238799

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1002/pola.26505

Repository Public URL： https://hdl.handle.net/2324/7238803

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/JOSAB.29.003069

Repository Public URL： https://hdl.handle.net/2324/7238785

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： https://doi.org/10.1364/OL.37.004086

Repository Public URL： https://hdl.handle.net/2324/7238786

Language：English   Publishing type：Research paper (scientific journal)  

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

DOI： 10.1021/ma901966g

Repository Public URL： https://hdl.handle.net/2324/7178739

Language：English   Publishing type：Research paper (scientific journal)  

Excellent control in the synthesis of MEH-PPV can be achieved by microwave assisted, ring-opening metathesis polymerization
(ROMP) of [2.2]paracyclophanedienes.

DOI： 10.1039/b901075k

Repository Public URL： https://hdl.handle.net/2324/7238775

Language：English   Presentation type：Oral presentation (general)  

Venue：63rd SPSJ Symposium on Macromolecules, Nagasaki, Japan.   Country：Japan  

Over the last decade, organic electro-optic (NLO) materials have undergone significant developments in both the range of polymer architectures available and the selection of photonic devices which they can be utilized in. Key material properties include the ability to exhibit a large EO coefficient, optical transparency as not to impede device utilization, thermal stability to survive the harsh poling conditions and lastly but not least important, they should be highly soluble in a range of common organic solvents to facilitate their solution casting onto a range of conductive substrates. Poly(norbornene-dicarboximide) (NDI) homopolymers as well as polymer brushes derived from an NDI backbone, with methyl methacrylate (MMA) side arms display many of these important features.

Language：English   Presentation type：Oral presentation (general)  

Venue：The 10th SPSJ International Polymer Conference (IPC2014)   Country：Japan  

The academic interest in poly(norbornene-dicarboximides) (poly(NDI)s) has increased substantially as a consequence of their favorable thermal, mechanical and optical properties, giving them a range of practical uses in optics. Provided that the cyclic monomers exhibit a high ring strain and low steric hindrance ROMP allows the preparation of well-defined homopolymers, random copolymers, block copolymers and polymer brushes.

An optimal organic electro-optic (EO) material must exhibit a large EO coefficient, optical transparency, thermal stability, temporal stability and a good solubility. These key requirements can be met by the use of poly(norbornene-dicarboximide) (NDI) homopolymers and polymer brushes with an NDI backbone and methyl methacrylate (MMA) side arms. The EO affect quantifies the relationship between the refractive index change (Δn) of a material upon application of an electric field (E). The magnitude of this change is related to the materials EO coefficient (r33) as described by the equation: Δn=-1/2n3r33E. Typical FTC chromophores encompass a strongly donating aromatic amine, an extended thiophene bridge and a strong tricyano containing heterocyclic electron accepting moiety. We have manipulated the structures of FTC chromophores in order to tune the properties, enhancing the hyperpolarizability and steric interactions and investigated the feasibility of using various Poly(norbornene)dicarboximide homopolymers, copolymers and polymer brushes as hosts for such chromophores.