There has been a rapid technological development in the field of polymer-based photonic devices in recent times due to advanced fabrication techniques. Though, effective way to couple the light into the polymer devices is a difficult task. In this paper, we propose a novel technique to overcome the challenges in coupling the light from an optical fibre to a polymer-based photonic device. Unlike in silicon photonic devices where usually grating couplers are used to couple light, the same technique is quite ineffective to couple the light in polymer-based photonic devices due to small refractive index contrast and poor confinement. The proposed device has been theoretically analyzed using Lumerical MODE Solutions in the wavelength range of 1520-1580 nm. The proposed structure consists of a conventional 4-port, add-drop, racetrack resonator with a high-quality factor of 5316.7 for the notch at 1527.8 nm on top of cylindrical pillars of radius 6 μm. The free spectral range of the device is 11.42 nm. Two-photon polymerization based direct laser writing technique has been used to fabricate the device, using IP-DIP polymer. The micro-pillars provide a degree of freedom and lift the entire resonator structure to the desired height, thereby relaxing the vertical mismatch between fibre and the resonator. This method provides a simple method to couple light without using grating couplers or etching the fibre.
The advancement of fabrication techniques, especially in the field of polymer-based photonic devices, has led to the implementation of novel designs with increased flexibility. In this paper, we propose a polymer-based whispering gallery spiral waveguide, which has been tapered down to nano-dimension for the detection of gold nanoparticles. Gold nanoparticles are being explored extensively in the areas of catalysis, imaging, therapeutic agents, drug delivery in various chemical and medical applications. Though, detection of gold nanoparticles in low concentration with high sensitivity is still a challenge. The proposed structure can be used to detect a single gold nanoparticle. It consists of two interleaved spirals; the inner ends of the spirals are connected by semicircular-arcs of a circle forming an S-shaped structure whereas the outer ends of the spirals serve as input and output ports of the waveguide. By nano-tapering, the center of the spiral, we observe enhanced evanescent field in the tapered region. The interaction of the evanescent field with the gold nanoparticle causes a shift in the characteristic wavelength of the device. The capability of the device to detect gold nanoparticle of different radius (10 nm-100 nm) has been theoretically analyzed. As the shift in the characteristic wavelength depends on the size of the gold nanoparticle, it provides a size selective detection of nanoparticles and this is regarded as an extrinsic size effect. The proposed device has been fabricated by two-photon polymerization based direct laser writing technique.
A wrinkle-network structure of Mn doped ZnO is presented in this paper. The undoped and Mn doped ZnO thin film samples have been prepared on ITO coated glass substrates by sol-gel spin coating technique as it is a simple and lowcost method to deposit semiconductor thin films. High resolution X-ray diffraction technique confirms the formation of hexagonal wurtzite structure with diffraction pattern corresponding to ZnO. Mn related phases have not been observed within the detection limit of HR-XRD. The incorporation of Mn dopant in the sample has been confirmed by energy dispersive X-ray spectroscopy (EDS). Both the undoped and Mn doped samples have high optical transmittance in the wavelength range of 300 nm – 800 nm, with a maximum of 88% as recorded by UV-VIS spectroscopy. There is an increase in the bandgap of ZnO thin films by the introduction of Mn dopants which has been calculated by Tauc plot.
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