All fiber optical current transducers (FOCTs) are widely used and it is urgent demand to monitor and check the FOCTs. In this paper, a novel method to examine the state of the FOCT system and its components is proposed and demonstrated theoretically. Taking the reflective FOCT as an example, the transmittance of the FOCT, which is a function of wavelength is deduced using Jones matrix and the relationship between the transmittance and the parameters (phase shift and alignment angle) of the components such as modulator, high birefringent delay fiber, quarter wavelength plate is discussed respectively. By measuring the spectrum of the output light and processing the transmittance data, each of the parameters can be calculated and then the states of the components and whole system can be evaluated in some simple situations.
Lasing properties of the two-dimensional (2D) distributed feedback (DFB) lasers can be engineered by replacing either the gain medium or periodic structures necessary for the feedback mechanism. Quasicrystals are the intermediate class between the periodic and random structures. They have high rotational symmetry and more favorable for the generation of photonic bandgap as compared to periodic structures. In our experiment, we designed a pentagonal prism for the holographic lithography to construct a long-range 10-fold rotational symmetry, which exhibits 2D quasiperiodic structures. A solution-processable colloidal quantum dots (CQDs) was spin-coated on the resultant 2D quasicrystals. An analytical model based on the cavity mode coupling effect was developed to predict the output performance of the 2D DFB CQDs photonic quasicrystals laser. The respective optically pumped 2D photonic quasicrystal samples exhibit multi-wavelength lasing emission in different directions due to long-range rotational symmetry. The five DFB lasing spots are symmetrically distributed in the 2D space, the center of the lasing spots is similar to a star shape. The derived analytical model predictions are in line with the experimental results.
In this work, a temperature tunable capillary-based polymer whispering gallery modes laser was proposed. The WGM laser device was fabricated by filling the liquid polymer into the capillary tubes. Due to the thermal-optic effect of the polymer, the emission wavelength of the laser device can be continuously tuned from 601.4 nm to 581.9 nm with the varying temperature. Moreover, the suppression of modes was observed owing to the two-ring coupling effect in the capillary cavity. The easy-fabricated and very low-cost method of the temperature tunable WGM laser was verified which exhibits the potentiality for applications of photothermic and sensing devices.
The performance of distributed feedback (DFB) polymer lasers was adjusted by changing the cavity coupling. The microcavity of DFB polymer lasers was fabricated by two-beam multi-exposure interference lithography. With the different angles between two gratings, the coupling strength of the cavity modes was controlled. Reducing the coupling strength of cavity modes, the threshold of the polymer lasers decreased. According to the experimental results, the azimuthally polarized output was changed by tuning the cavity coupling. This method provides a facile way to realize low threshold and azimuthally polarized DFB polymer laser.
Metallic photonic crystals (MPCs) with different periods have been fabricated by solution-processed method. Scanning electron microscopy images show that the structures with their period larger than 400 nm can easily maintain their morphologies during the high temperature lift-off process. The optical properties of the waveguided MPCs with different periods have been investigated. With an increase in the period, high-order coupling between particle plasmon resonance and the waveguide resonance modes can be observed in the spectra. We found that the ±2 orders coupling of the structure with its period of 880 nm has similar tuning properties to the ±1 st orders coupling of the 430 nm period structures, which infers us that we can use the structures with larger period that can be controllably fabricated to replace the ones with smaller period. The results we obtained in this work provide reference for further applications of the MPCs.
We demonstrate the fabrication of two-dimensional (2D) metallic photonic crystals (MPCs) based on colloidal gold
nanoparticles, where laser interference ablation combining subsequent high temperature annealing is employed for the
construction of 2D gold nano-dot arrays in square lattices. The microscopic and spectroscopic properties of the 2-D
MPCs are systematically characterized by the scanning electron microscope and the angle-resolved optical extinction
spectroscopic measurements, the strong coupling between the waveguide resonance mode and the particle plasmon
resonance of the MPCs imply the success of the fabrication method, which show potential applications in optoelectronic
devices and sensors.
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