Characteristics of electric field from a coupled mode inside an optical fiber under perturbation by three-dimensional (3D) printed long-period fiber grating (LPFG) device have been observed in this work by the experiment and simulation. The various periodic index differences referring to the weights of perturbation by 3D printed LPFG device are applied on the single-mode fiber. The experimental results show that the resonant wavelength shift is a linear function of the grating period with the maximum coefficient of determination R² of 0.9995. Some of resonant wavelengths are chosen to run simulations to investigate the electric field distribution. The scattering direction of the electric field states the magnitude of leaking optical power when the light transmits through the grating region applied to the single-mode fiber. Both the experimental and simulation results demonstrate that our proposed scheme can usefully be applied to selective tunable filters, intruder sensors, etc.

We suggested a plasmonic platform based on a cubic pattern of gold spheres for surface enhanced Raman spectroscopy (SERS). In the case of linear polarization along the symmetry axes, the SERS enhancement per area is identical to hexagonally patterned surfaces. The validity of this model was tested using the simulation package of COMSOL Multiphysics- Modeling Software. We found an improved sensitivity in the near infrared and visible region of the electromagnetic spectrum. This method considered tolerance towards stacking faults and suggested a plasmonic platform for ultra-sensing applications. The design can be extended towards the molecular detection if the proposed plasmonic platform is used with SERS.

An abrupt change in optical transmission characteristic of a graphene oxide (GO) coated optical planar waveguide was observed. This observation was based on the peculiar characteristics of the graphene oxide film, namely its high transverse-electric polarized light propagation loss, highly selective permeability of water, and change in optical propagation characteristic in the presence of water. The as-fabricated GO-coated optical waveguide showed a large polarization dependent loss of ~32 dB in the C-band optical fiber communication window (1550 nm). The response of the proposed sensor was first tested by using water. When a drop of water was applied onto the GO coating, the large polarization dependent loss was fully suppressed almost instantaneously. This effect was reversible as the polarization dependent loss was restored after complete water evaporation from the GO coating. All-optical measurement of water content in alcohol was then demonstrated by using the GO-coated optical waveguide. By analyzing the drying profile of the water-alcohol mixture, water content in the range of 0.2 volume % – 100 volume % could be measured. These measurements were carried out by using solution volume of 1.0 μL only. The all-optical sensing nature of the proposed sensor has potential applications in in-situ monitoring of water content in alcohol.

We propose a highly refractive index sensor based on plasmonic Bow Tie configuration. The sensitivity of the resonator design is enhanced by incorporating a nanowall (NW) in a modified Bow Tie design where sharp tips of V-junction are flattened. This approach provides high confinement of electric field distribution of surface plasmon polariton (SPP) mode in the narrow region of the cavity. Consequently, the effective refractive index (neff) of the mode increases and is highly responsive to the ambient medium. The sensitivity analysis of the SPP mode is calculated for six resonator schemes. The results suggest that the NW embedded cavity offers the highest mode sensitivity due to the large shift of effective index when exposed to a slight change in the medium refractive index. Moreover, the device sensitivity of the proposed design is approximated at 2300 nm/RIU which is much higher than the sensitivity of the standard Bow Tie configuration.

Metamaterial absorbers display potential applications in the field of photonics and have been investigated extensively during the last decade. We propose a dual-band resonant metamaterial absorber with right-angle shaped elements (RAEs) in the terahertz range based on numerical simulations. The absorber remains insensitive to a wide range of incidence angles (0° – 70°) by showing a minimum absorbance of ~80% at 70°. Furthermore, the proposed absorber is highly independent on any state of polarization of the incidence electromagnetic wave due to the high absorbance, i.e., greater than 80%, recorded for the considered polarization states. To further comprehend the slight variations in absorbance as a function of change in the angle of incidence, the impedance of the structure has been critically examined. The metamaterial absorber is simple in design, and we provide a possible path of fabrication.

Spectral distortion often occurs in spectral data due to the influence of the bandpass function of the spectrometer. Spectral deconvolution is an effective restoration method to solve this problem. Based on the theory of the maximum posteriori estimation, this paper transforms the spectral deconvolution problem into a multi-parameter optimization problem, and a novel spectral deconvolution method is proposed on the basis of Levenberg-Marquardt algorithm. Furthermore, a spectral adaptive operator is added to the method, which improves the effect of the regularization term. The proposed methods, Richardson-Lucy (R-L) method and Huber-Markov spectroscopic semi-blind deconvolution (HMSBD) method, are employed to deconvolute the white light-emitting diode (LED) spectra with two different color temperatures, respectively. The correction errors, root mean square errors, noise suppression ability, and the computation speed of above methods are compared. The experimental results prove the superiority of the proposed algorithm.

We have demonstrated the realization of a coherent vesicle random lasing (VRL) from the dye doped azobenzene polymer vesicles self-assembled in the tetrahydrofuran-water system, which contains a double-walled structure: a hydrophilic and hydrophobic part. The effect of the dye and azobenzene polymer concentration on the threshold of random laser has been researched. The threshold of random laser decreases with an increase in the concentration of the pyrromethene 597 (PM597) laser and azobenzene polymer. Moreover, the scattering of small size group vesicles is attributed to providing a loop to boost the coherent random laser through the Fourier transform analysis. Due to the vesicles having the similar structure with the cell, the generation of coherent random lasers from vesicles expand random lasers to the biomedicine filed.

The detection mission of gravitational waves in space is that the accuracy of the long-baseline intersatellite laser interferometry on the million-kilometer order needs to reach the order of 8 pm/ Hz . Among all noise sources that affect the interferometry accuracy, tilt-to-length (TTL) coupling noise is the second largest source of noise after shot noise. This paper focuses on studying the contribution of TTL coupling noise of the telescope system in the intersatellite scientific interferometer. By referring to the laser interferometer space antenna (LISA)’s noise budget, TTL coupling noise is required to be within ±25 μm/rad (±300 μrad). Therefore, this paper focuses on studying both the mechanism of TTL coupling noise due to the noise sources of the telescope and the method of suppressing the TTL noise, which can lay a foundation for noise distribution and the development of engineering prototypes in subsequent tasks.

Based on the transverse electro-optic effect of lithium niobate crystal, combined with polarizers and Faraday rotator, this paper presents a collinear closed-loop fiber optic current transformer with spatial non-reciprocity modulation method, and the feasibility of the scheme is verified by both the theoretical and experimental evidences. The detection scheme avoids the limitation of the transition time of the sensing fiber coil on the phase modulation frequency, improves the sensitivity and stability of the system, and reduces the volume and cost of fiber optic current transformer. The sawtooth wave modulation scheme is adopted to realize phase bias modulation and feedback modulation through phase shift of sawtooth wave to achieve closed-loop detection effect, which enhances the signal to noise ratio and simplifies demodulation mode. The experimental results show that the current ratio errors measured at room temperature range from 1% to 120% of rated current meet the requirements of national standard GB/T 20840.8-2007 and reach the accuracy level of 0.2S. The temperature stability of the current transformer is also tested, and the ratio error measured at the rated current does not exceed ±0.2% in the range of –30 ℃ to 50 ℃.

A detailed analysis of the electrical response of In0.3Ga0.7As surface quantum dots (SQDs) coupled to 5-layer buried quantum dots (BQDs) is carried out as a function of ethanol and acetone concentration while temperature-dependent photoluminescence (PL) spectra are also analyzed. The coupling structure is grown by solid source molecular beam epitaxy. Carrier transport from BQDs to SQDs is confirmed by the temperature-dependent PL spectra. The importance of the surface states for the sensing application is once more highlighted. The results show that not only the exposure to the target gas but also the illumination affect the electrical response of the coupling sample strongly. In the ethanol atmosphere and under the illumination, the sheet resistance of the coupling structure decays by 50% while it remains nearly constant for the reference structure with only the 5-layer BQDs but not the SQDs. The strong dependence of the electrical response on the gas concentration makes SQDs very suitable for the development of integrated micrometer-sized gas sensor devices.