Analysis and characterization of electro-optic coefficient for multi-layer polymers: dependence on measurement wavelengths.

We report a significant improvement in the measurement accuracy of electro-optic (EO) coefficients for low-loss EO polymers on substrates of sol-gel silica and indium tin oxide (ITO). Initially, we apply the standard Teng and Man reflection ellipsometric method, which results in substantial variability in the measured EO coefficients across a wavelength spectrum with changes as small as <1 nm. This variance leads to unreliable EO coefficient values ranging from a few to 70 pm/V at the 1.31 and 1.55 µm wavelengths. By adopting a transmission method for our experiments, we effectively mitigate the dependence of the measured EO coefficient on the wavelength variance of 0.2 nm. As a result, this new approach enables a more accurate and reliable measurement of the EO coefficients. This breakthrough presents a significant step forward in the field of EO research, paving the way for further exploration into the behavior and properties of EO polymers. Additionally, our findings highlight the importance of selecting an appropriate measurement method in accordance with the unique properties of the material under investigation.

A Novel Optical Biosensing System Using Mach-Zehnder-Type Optical Waveguide for Influenza Virus Detection.

In order to minimize the damage from viral epidemics, early detection of the causative agent of a viral epidemic and prevention of its immediate spread are urgent social demands. Therefore, in this study, we evaluated the utility of a Mach-Zehnder-type optical waveguide as a sensing device for influenza virus detection. However, it is impossible to detect a 100-nm-size virus using a sol-gel optical biosensor because sol-gel glass has a pore size of only a few nanometers, which makes it impossible for the virus to diffuse into the silica thin film. In order to construct the influenza-specific Mach-Zehnder optical biosensor for influenza detection, a stable antibody immobilization method with resulting high density on the sol-gel surface is strongly required. In this study, the sol-gel glass surface was modified with amino and carboxyl groups, and an anti-H1N1/HA1 antibody was covalently immobilized using a cross-linking agent. We successfully prepared a carboxyl-modified sol-gel surface, using NHS/EDC as the cross-linker, for antibody immobilization, and confirmed the detection of influenza virus using the antibody-immobilized sol-gel glass. After treatment with a 100 µg/mL influenza virus solution for 15 min, a peak wavelength shift (~24 nm) was observed in the output light spectrum.

Sol-Gel Material-Enabled Electro-Optic Polymer Modulators.

Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the optical loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low optical loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The optical loss is influenced by the propagation loss in the device, as well as the losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed.

Mesoporous sol-gel silica cladding for hybrid TiO2/electro-optic polymer waveguide modulators.

We report the efficient poling of an electro-optic (EO) polymer in a hybrid TiO(2)/electro-optic polymer multilayer waveguide modulator on mesoporous sol-gel silica cladding. The mesoporous sol-gel silica has nanometer-sized pores and a low refractive index of 1.24, which improves mode confinement in the 400-nm-thick EO polymer film in the modulators and prevents optical absorption from the lower Au electrode, thereby resulting in a lower half-wave voltage of the modulators. The half-wave voltage (Vπ) of the hybrid modulator fabricated on the mesoporous sol-gel silica cladding is 6.0 V for an electrode length (Le) of 5 mm at a wavelength of 1550 nm (VπLe product of 3.0 V·cm) using a low-index guest-host EO polymer (in-device EO coefficient of 75 pm/V).

Enhanced conductivity of sol-gel silica cladding for efficient poling in electro-optic polymer/TiO2 vertical slot waveguide modulators.

We report the enhanced conductivity of sol-gel silica under-cladding for efficient poling of electro-optic (EO) polymer in a hybrid EO polymer/TiO2 vertical slot waveguide modulator. The electrical volume conductivity of sol-gel silica cladding increases approximately 30 times when the calcining time of the cladding layer is critically reduced to 45 minutes, which increases the in-device EO coefficient of the 600-nm-thick EO polymer film in modulators and reduces the lower halfwave voltage (Vπ) of the modulators. The lowest driving voltage (Vπ) of the TiO2 slot waveguide modulator is 2.0 V for an electrode length (Le) of 10 mm and wavelength of 1550 nm (VπLe = 2.0 V·cm) for the low-index guest-host EO polymer SEO125. The optical propagation loss is reduced to 7 dB/cm.