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AIP Conference Proceedings [Author(s) 4TH ELECTRONIC AND GREEN MATERIALS INTERNATIONAL CONFERENCE 2018 (EGM 2018) - Bandung, Indonesia (27–28 July 2018)] - Design and analysis of fiber Bragg grating tunable filter utilizing thermal technique
摘要： In this paper a tunable filter based on fiber Bragg grating (FBG) utilizing thermal technique is theoretically investigated and experimentally validated. According to the results, a tuning range is achieved about 1.5 nm in C-band region. While, for L-band region the wavelength shift is slightly greater than in the C-band region about 1.6 nm. This shifting is due to changing in thermo-optic and thermal expansion of fiber, which causes changing in refractive index and then Bragg wavelength. The experimental validation is done at wavelength 1552.7 nm, the tunability is about 1.2428 nm when the temperature is varied from 21°C to 61°C.
关键词： thermal expansion,fiber Bragg grating,thermo-optic effect,thermal technique,tunable filter
更新于2025-09-23 15:23:52
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Chiral coding metasurfaces with integrated vanadium dioxide for thermo-optic modulation of terahertz waves
摘要： In the field of electromagnetics, there are many limitations to achieve simultaneous polarization conversion and wavefront control. The chiral coding metasurface based on the Pancharatnam-Berry (PeB) phase effectively helps to alleviate these restrictions and shows strong control over the terahertz radiation field. In this paper, the principle of chirality is theoretically analyzed and verified by simulation results. The circular dichroism DR (chiral effect) achieves 0.8. By combining the chirality and thermo-optic effect of vanadium dioxide (VO2), we propose three switchable metasurfaces for quantitative splitting and high-efficiency focusing (low-efficiency divergence) of terahertz beams. The amplitude switching efficiency of the circularly polarized (CP) and linearly polarized (LP) pencil beams is above 0.85. Under the excitation of LP waves, the first two chiral metasurfaces have one and two temperature-switchable reflective right-handed circularly polarized (RCP) pencil beams, respectively. The third chiral metasurface generates high-efficiency focusing for RCP waves and low-efficiency divergence for left-handed circularly polarized (LCP) waves. This work provides new methods for more flexible modulation of CP and LP waves and promotes the application of terahertz coding metasurfaces in communication.
关键词： Pancharatnam-Berry (PeB) phase,Vanadium dioxide,Thermo-optic effect,Chiral coding metasurface
更新于2025-09-23 15:19:57
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On-chip integrated optical switch based on polymer waveguides
摘要： Optical polymer is one of the promising materials for photonic integrated devices that can be processed with simple, flexible and semiconductor compatible technology. Especially, optical polymer with the advantages of high thermo-optic (TO) and electro-optic (EO) coefficients has been widely applied in optical waveguide switches. However, most of the current optical switches are independent with single function. It is essential to develop an on-chip integrated device with multilayer for signal manipulation. In this paper, we propose an on-chip 3-dimensional integrated optical switch based on the EO polymer-clad waveguide incorporate with the TO tunable vertical coupler. The proposed integrated optical switch could realize the function-integration of the adjustable 3D optical connection and the high-speed modulation. A typical fabricated switch shows an insertion loss of 16.3 dB and an extinction ratio of 16.0 dB at the driving power of 48.2 mW. The dynamic characteristics of TO and EO switching functions of the device were also measured in this work.
关键词： Polymer waveguide,Thermo-optic effect,Electro-optic effect,Optical communication,Optical switch
更新于2025-09-16 10:30:52
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Investigation of Temperature Sensitivity of a Polymer-Overlaid Microfiber Mach-Zehnder Interferometer
摘要： The temperature sensitivity of the free spectral range (FSR) for a polymer-overlaid microfiber Mach-Zehnder interferometer (MZI) is investigated both theoretically and experimentally. The waist diameter of the optical microfiber can be controlled to alter the thermal expansion and optic properties of the polymer-coated MZI. Inserting an optical microfiber with a strong evanescent field into the MZI, a low index polymer with high thermal characteristics is deposited on the surface of the microfibers to realize a polymer-overlaid microfiber MZI. It was found that the thermal expansion factor in the proposed MZI plays an important role in the temperature sensitivity of the FSR. The temperature sensitivity of the polymer-overlaid microfiber MZI is improved, which is measured to be ?8.29 nm/?C at 25 ?C. The optical transmission spectrum of the polymer-overlaid microfiber MZI is converted to the spatial frequency spectrum via fast Fourier transform. The temperature sensitivity of the spatial frequency in the proposed polymer-overlaid MZI is estimated to be 18.31 pm?1 ?C?1, which is 17 times higher than that of the microfiber MZI without polymer coating (1.04 pm?1 ?C?1).
关键词： temperature sensors,thermo-optic effect,thermal expansion effect,microfibers,microfiber Mach-Zehnder interferometers
更新于2025-09-10 09:29:36
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Highly c-axis oriented crystal growth induced giant unusual saturable absorption behavior in wet chemically grown ZnO thin films
摘要： Wet-chemical sol-gel spin coating technique was considered to fabricate ZnO thin films on bare glass substrates with different thickness values (30 nm, 90 nm, 110 nm, 150 nm). The XRD reflections showed a transition from semi-polar crystal growth orientation to polar crystal growth orientation when the thickness was reduced to 30 nm. The nonlinear characteristics of prepared nano-films were quantized by performing open aperture and closed aperture Z-scan measurements under a continuous wavelength regime. The open aperture Z-scan transmittance curves showed a remarkable transition from normalized valley to normalized peak in 30 nm thick ZnO film. The presence of normalized valley and peak were attributed to reverse saturable absorption (RSA) and saturable absorption (SA) behavior respectively. The RSA behavior was attributed to well known two-photon absorption (TPA) mechanisms and the SA behavior was due to the reduction in electron-hole wave function overlapping along c-axis. The closed aperture Z-scan measurement of 30 nm thick ZnO film revealed the violation of two parabolic band (TPB) and Kramer-Kronig relations by exhibiting self-focusing mechanism. The self-focusing mechanism was attributed to thermal effects due to the smaller thickness of ZnO. However, self-defocusing behavior was observed in 90 nm, 110 nm, and 150 nm thick ZnO films.
关键词： electron-hole wavefunction,saturable absorption,polar ZnO,thermo-optic effect,self-focusing
更新于2025-09-09 09:28:46