Polarizer Research Articles

快速空间测角系统中偏振棱镜消光比的影响

快速空间测角系统中偏振棱镜消光比的影响

Remote audio signals detection using a partial-fiber laser Doppler vibrometer

All-fiber laser Doppler vibrometer (LDV) systems have great potential in the application of remote acoustic detection. However, the system performance is impaired due to the serious intermediate frequency (IF) crosstalk signal, which is caused by the fiber circulator. In this paper, a system adopting a partial-fiber structure is proposed and analyzed. Simulative and experimental analysis indicate that the IF crosstalk signal is mainly caused by the fiber circulator, and it damages demodulation signal. In order to reduce the IF crosstalk signal, a polarization prism is employed to substitute the circulator. Experimental results reveal that the IF crosstalk signal can be eliminated by the partial-fiber LDV effectively. The comprehensible speech signals within the range of 50m can be obtained.

Impact of temperature on sea bass, Dicentrarchus labrax, retina: Fatty acid composition, expression of rhodopsin and enzymes of lipid and melatonin metabolism

Teleost fish are ectothermic vertebrates. Their metabolism, physiology and behavior rely on the external temperature. This study, on the retina of the sea bass Dicentrarchus labrax, reports on the impact of temperature on the fatty acid composition and mRNA abundance of key enzymes of lipid metabolism: fatty acid desaturase-2 (FADS2), fatty acid elongase-5 (ELOVL5), sterol regulatory element-binding protein-1 (SREBP-1), triglyceride lipase and phospholipase A2 (PLA2). We also report on the effects on the photopigment molecule rhodopsin and on enzymes of the melatonin synthesis pathway, namely arylalkylamine N-acetyltransferases 1a and 1b and acetylserotonin methyltransferase. Juvenile fish were placed for 30 days at 18, 23 or 28 °C. At 23 °C, the fatty acid composition of D. labrax retina showed, as generally reported for the retina of other fish species, particularly high amounts of docosahexaenoic (DHA), palmitic and oleic acids. The fatty acids composition was not significantly (P > 0.05) altered between 23 and 28 °C, but did increase at 18 °C compared to 23 and 28 °C. At 18 °C there were noticeable increases in total DHA, ecosapentaenoic, arachidonic, oleic, linoleic, palmitoleic and stearic acids. A negative correlation was found in the abundance of neutral (NL) vs. polar (PL) lipids: 18 °C induced an increase in NL and a decrease in PL, while 28 °C induced higher PL with decreased NL. In NL the changes affected mainly triglycerides. FADS2 and ELOVL5 mRNA abundance decreased from 18° to 28 °C while SREBP-1 and triglyceride lipase mRNA remained stable. Conversely PLA2 mRNA was more abundant at 23 than at 18 and 28 °C. Temperature increased and decreased rhodopsin mRNA abundance, at 28 °C and 18 °C respectively, while there was no effect on mRNA from the melatonin synthesis enzymes. In conclusion the data indicate a temperature induced redistribution of fatty acids among the lipid classes that might affect the physical properties of the plasma membranes as well as functions associated with photoreception or generation of intracellular second messengers. In addition, the results suggest that temperature targets only the proteins and activities of retinal melatonin production. This study opens new lines of investigation related to the role temperature and fatty acids play in fish visual perception. They are relevant in the context of the global warming of seas affecting both the wild and the aquaculture species.

Multispectral subtractive filtering and optical hotspots by dielectric resonators

In this work, we theoretically propose and numerically demonstrate a novel multi-band subtractive filtering platform by utilizing the dielectric resonators. In addition, the plasmon-like hotspots are also observed in this dielectric structure. Multi-band light filtering can be quantitatively adjusted by the polarization state and the classical Malus law is verified in this dielectric structure. These findings lay a foundation for multispectral optical behaviors and hold applications in the nanophotonics.

Suppression of FM-to-AM modulation by polarizing fiber front end for high-power lasers.

FM-to-AM modulation is an important effect in the front end of high-power lasers that influences the temporal profile. Various methods have been implemented in standard-fiber and polarization-maintaining (PM)-fiber front ends to suppress the FM-to-AM modulation. To analyze the modulation in the front end, a theoretical model is established and detailed simulations carried out that show that the polarizing (PZ) fiber, whose fast axis has a large loss, can successfully suppress the modulation. Moreover, the stability of the FM-to-AM modulation can be improved, which is important for the front end to obtain a stable output. To verify the model, a PZ fiber front end is constructed experimentally. The FM-to-AM modulation, without any compensation, is less than 4%, whereas that of the PM fiber front end with the same structure is nearly 20%. The stability of the FM-to-AM modulation depth is analyzed experimentally and the peak-to-peak and standard deviation (SD) are 2% and 0.38%, respectively, over 3 h. The experimental results agree with the simulation results and both prove that the PZ fiber front end can successfully suppress the FM-to-AM conversion. The PZ fiber front end is a promising alternative for improving the performance of the front end in high-power laser facilities.

Verification of Malus's Law using a LCD monitor and Digital Photography

An alternative laboratory experiment for verifying Malus's Law, as well as understanding concepts of photometry, polarization and image formation on liquid crystal displays using low cost materials is proposed. The experimental setup could be introduced to any undergraduate curriculum using readily available tools, such as a digital camera, polarizer removed from a cell phone and a LCD laptop screen. A fairly amount of photometric data was collected and analyzed by an astronomical image processing software resulting in a successful verification of Malus's Law.

Partially hollowed ultra-thin dielectric meta-surface for transmission manipulation.

Impressive optical properties are numerically demonstrated in the partially hollowed dielectric meta-surface (p-HDMS), which consists of an air cavity array intercalated in an ultra-thin (~λ/6) high-index dielectric film. Multispectral transmission band-stop response with near-perfect spectral modulation depth is achieved. The spectral slop is up to 80%/nm, indicating the sharp and narrowband transmission behavior. Classical Malus law is confirmed by this sub-wavelength platform. Moreover, the multispectral light propagation manipulation can be perfectly reproduced by using the actual dielectric with absorption loss. In this all-dielectric meta-surface, conduction loss is avoided compared to its metallic plasmonic counterpart. Such configurations can therefore serve as excellent alternatives for plasmonic meta-surfaces and constitute an important step in nanophotonics.

Docking accuracy enhanced by QM-derived protein charges

ABSTRACTEffects of protein polari sation on docking accuracy were investigated using molecular docking programme AutoDock 4 in which topology-specific empirical Gasteiger charges were replaced with Polarised protein-specific charges (PPC) to represent quantum mechanics- polarised protein. Docking was successfully conducted for 50 diverse protein–ligand complexes. The docking with PPC charges shows a decrease in the root-mean-square deviation (RMSD) values of ligands compared to those from the docking with Gasteiger charges. Ligand binding orientations and their key interactions such as hydrogen bonding interactions in X-ray structures were substantially reproduced in complexes docked using PPC scheme with 98% of the RMSDs of the best docking poses less than 2 Å compared to 74% in the docking with Gasteiger charges. Considerable improvements in docking accuracy were observed by simply altering the atomic partial charges in the scoring function, which reflects the importance of protein polarisation in molecular docking. Further research can be carried out to (1) include polarisation of both ligands and proteins to account for polarisation effects within protein and between protein and ligand, and (2) develop a PPC-based scoring function to increase the docking accuracies for protein–ligand complexes from a larger variety of protein families.

Extended Malus law with terahertz metallic metamaterials for sensitive detection with giant tunable quality factor

We study a polarizer-analyzer mounting for the terahertz regime with perfectly conducting metallic polarizers made of a periodic subwavelength pattern. We analytically investigate the influence on the transmission response of the multiple reflections which occur between polarizer and analyzer with a renewed Jones formalism. We demonstrate that this interaction leads to a modified transmission response: the extended Malus' Law. In addition, we show that the transmission response can be controlled by the distance between polarizer and analyzer. For particular set-ups, the mounting exhibits extremely sensitive transmission responses. This interesting feature can be employed for high precision sensing and characterization applications. We specifically propose a general design for measuring electro-optical response of materials in the terahertz domain allowing detection of refractive index variations as small as $10^{-5}$.

260 frames-per-second 648x488 resolution division-of-focal-plane polarimeter with structural dynamics and tracking applications.

We have designed an image sensor that can capture the first three Stokes parameters at 648 by 488 spatial resolution at 260 frames per second. The sensor consists of a CCD image sensor monolithically integrated with pixel pitch-matched aluminum nanowire polarization filters. The sensor demonstrates a Malus law response over all pixels, and has a relatively uniform diattenuation over the visible spectrum. We demonstrate two potential applications for the sensor. The first uses circular polarization in transmission mode to observe high-speed stress failure in polycarbonate. The second uses polarization in reflected mode to track high speed automobile traffic.

Monochromatic filter with multiple manipulation approaches by the layered all-dielectric patch array

Monochromatic filtering with ultra-narrowband and high spectral contrast is desirable for wide applications in display, image, and other optoelectronics. However, owing to the inherent omhic losses in the metallic materials, a broadband spectrum with a low Q-factor down to 10 inevitably limits the device performance. Herein, we for the first time theoretically propose and demonstrate an ultra-narrowband color-filtering platform based on the layered all-dielectric meta-material (LADM), which consists of a triple-layer high/low/high-index dielectrics cavity structure. Owing to the lossless dielectric materials used, sharp resonances with the bandwidth down to sub-10 nm are observed in the sub-wavelength LADM-based filters. A spectral Q-factor of 361.6 is achieved, which is orders of magnitude larger than that of the plasmonic resonators. Moreover, for the other significant factor for evaluation of filtering performance, the spectral contrast reaches 94.5%. These optical properties are the main results of the excitation of the resonant modes in the LADMs. Furthermore, polarization-manipulated light filtering is realized in this LADM. The classical Malus law is also confirmed in the reflective spectrum by tuning the polarization state. More interestingly and importantly, the filtering phenomenon shows novel features of the wavelength-independent and tunable resonant intensity for the reflective spectrum when the LADM-based filter is illuminated under an oblique state. High scalability of the sharp reflective spectrum is obtained by tuning the structural parameters. A single-wavelength reflective filtering window is also achieved in the visible frequencies. These features hold promise for the LADM-based filter with wide applications in color engineering, displaying, imaging, etc.

Research of time fiducial laser and probe laser of velocity interferometer system for any reflector for Shenguang-III laser facility

Time fiducial laser is an important timing marker for different diagnostic instruments in high energy density physics experiments. The probe laser in velocity interferometer system for any reflector (VISAR) is also vital for precise shock wave diagnosis in inertial confinement fusion (ICF) research. Here, time fiducial laser and VISAR probe laser are generated from one source in SG-III laser facility. After generated from a 1064 nm DFB laser, the laser is modulated by an amplitude modulator driven by a 10 GS/s arbitrary waveform generator. Using time division multiplexing technology, the ten-pulse time fiducial laser and the 20 ns pulse width VISAR probe laser are split by a 12 multiplexer and then the time fiducial and VISAR pulses will be selected individually by acoustic-optic modulators. Using this technology, the cost for the system can be reduced. The technologies adopted in the system also include pulse polarization stabilization, high stable Nd: YAG amplification, high precision thermally controlled frequency conversion, fiber coupling, and energy transmission. The fiber laser system is connected to the Nd: YAG rod amplifier stage with polarizing (PZ) fibers to maintain the polarization state. The output laser of Nd: YAG amplification stage is coupled with different kinds of energy transfer fibers to propagate enough energy and maintain the pulse shape for the time fiducial and VISAR probe laser. The input and output fibers are all coupled to the rod amplifiers with high precision and being easy to plug and play for users. Since the time fiducial and imaging VISAR laser system is far from the front end room and located in the target area, the system also uses an arbitrary waveform generator (AWG) to generate the shaped ten-pulse time fiducial laser and 20 ns VISAR laser. This AWG and the other three AWGs used for the main laser pulse of SG-III laser facility will be all synchronized by 10 GHz clock inputs, realizing the smaller than 7 ps (RMS) jitter between the main laser pulse, time fiducial laser and VISAR pulse. After amplification and frequency conversion, the time fiducial laser finally generates 12 beam 2 and 4-beam 3 laserbeams, providing important reference marks for different detectors in the ICF experiments and making it convenient for the analysis of multiple diagnostic data. The VISAR laser pulse is also amplified by the Nd: YAG amplifiers and frequency-converted to 532 nm green light by a thermally controlled LBO crystal, with output energy larger than 20 mJ. Finally, the 532 nm VISAR probe laser beam is coupled with a 1-mm core diameter fused silica optical fiber, and then propagates 30 meters to the imaging VISAR system. The VISAR probe laser has been used in many high energy density physics experiments. The shock wave loading and slowdown processes are measured. Function for measuring velocity history of shock wave front movement in different kinds of materials can be also added to the SG-III laser facility.

Letters: Interpretation of Colours Seen Between Crossed Polarizers

Letters: Interpretation of Colours Seen Between Crossed Polarizers

Acousto-optic modulator of depolarized laser radiation on the paratellurite crystal

An original acousto-optic modulator of depolarized laser radiation is based on a paratellurite crystal in the regime of anisotropic diffraction by a slow acoustic wave. Two acoustic waves with different frequencies are simultaneously excited in a single acousto-optic cell. Two diffraction orders of orthogonal polarizations at the exit from the cell are diffracted in opposite sides relative to the zero order. A polarization prism that is placed immediately behind the cell transforms the diffraction orders into a single output depolarized beam. The total efficiency is 96%.

Polarization-adjusting ultra-narrow multi-band color filtering by dielectric metamaterials

Ultra-narrow multi-band filter (UMF) is with significant applications in the light propagation manipulation, such as the notch filtering and color generation. The widely studied plasmonic resonant systems are usually with broadband spectral response due to the large ohmic loss of the electron oscillations. Herein, we propose and demonstrate a novel polarization-controllable sharp multispectral filtering scheme by a lossless dielectric resonator-based metamaterial. Triple-band with the minimal bandwidth down to 4 nm and the corresponding spectral slope up to 84%/nm is achieved. The particle resonances of the top cylinders and the cavity modes by the bottom optical cavity and their coupling effects contribute to the subtractive light transmission filtering. Further study confirms the feasibility for adjusting the transmittance by controlling the polarization state. Classical Malus law is also verified in this filtering platform. The observed optical properties can be highly tuned by the structural parameters. These features hold the proposed filtering platform with wide applications in the optoelectronics, such as the color filters and displayers.

UV-Inscribed optical fiber gratings in Mid-IR range and their laser applications

We have UV-inscribed fiber Bragg gratings (FBGs), long-period gratings (LPGs), and tilted fiber gratings (TFGs) into mid-IR 2μm range using three common optical fiber grating fabrication techniques (two-beam holographic, phase mask, and point-by-point). The fabricated FBGs have been evaluated for thermal and strain response. It has been revealed that the FBG devices with responses in mid-IR range are much more sensitive to temperature than that in near-IR range. To explore the unique cladding mode coupling function, we have investigated the thermal and refractive index sensitivities of LPGs and identified that the coupled cladding modes in mid-IR range are also much more sensitive to temperature and surrounding medium refractive index change. The 45° tilted fiber gratings (45°-TFGs) as polarizing devices in mid-IR have been investigated for their polarization extinction characteristics. As efficient reflection filters and in-cavity polarizers, the mid-IR FBGs and 45°-TFGs have been employed in fiber laser cavity to realize multi-wavelength 2 μm Tm-doped CW and mode locked fiber lasers, respectively.

Characterisation of ferroelectric poly(vinylidene fluoride–trifluoroethylene) film prepared by Langmuir‐Blodgett deposition

Ferroelectric polymer is a flexible memory material that is insensitive to environmental variations and lends itself to research in emerging optoelectronic applications. Using Langmuir-Blodgett (LB) deposition technology, the thickness of a ferroelectric film can be controlled in the nanometre range, offering a pathway to molecular electronics. In this reported work, ultrathin ferroelectric polymer films were fabricated through LB deposition technology and characterised by observing the surface morphology, crystallinity and polarisation–voltage relationships. Unlike previously reported ferroelectric LB films, this work has shown a maximum remanent polarisation (PR) of 6 μC/cm2 at 35 nm, which is compatible with the thick film prepared by the spin-coating method. In addition, the polarisation stability in terms of depolarisation was investigated, which showed that the engineering of the interface between the ferroelectric LB film and the substrate is an important, deterministic factor for reliable memory applications with high signal-to-noise ratios.

Analysis of the polarization characteristics of wheat and maize crops using land-based remote-sensing measurements

The paper presents analysis of a study of the polarized component of the reflectance factor (Rq) and the degree of polarization (P) of wheat and maize crops depending on the wavelength. Registration of polarization characteristics was carried out in the field from the elevated work platform at heights of 10 to 18 m in June and July. Measurements were performed using a double-beam spectrophotometer with a polarized light filter attachment, within the spectral range from 400 to 820-nm. The viewing angle was no greater than 20 degree with respect to the nadir. The reflection spectra of wheat and maize crops obtained using a polarizer adjusted to transmit the maximum and minimum amounts of light (R(max) and R(min)) were studied. Based on these reflection spectra polarization characteristics, which. differ in the visible and infrared spectral region, were determined and analyzed.

High saturated fat diet alters the lipid composition of triacylglycerol and polar lipids in the femur of dam and offspring rats.

Previous work has shown that dietary lipids alter femur lipid composition. Specifically, we have shown that exposure to high saturated fatty acid (SFA) diets in utero, during suckling, or post-weaning alters femur total lipid composition, resulting in higher percent bone mass in males and females and bone mineral density (BMD) in female offspring with no effect on bone mineral outcomes in dams. Comparatively, high n-3 polyunsaturated fatty acid (PUFA) diets increase femur polar (PL) lipid n-3 content, which has been associated with increased bone mineral content and strength. However, the extent that PL or triacylglycerol (TAG) lipids change with high SFA diets is unknown. The current investigation examined the influence of a high SFA diet (20 % lard by weight) on femur PL and TAG lipid composition in 5-month old female Wistar rats (fed high SFA diet from age 28 days onwards; dams) and their 19-day old offspring (exposed to high SFA in utero and during suckling; pups). High SFA exposure resulted in increased monounsaturates and decreased n-3 and n-6 PUFA in the TAG fraction in both dams and pups, and higher SFA and n-6:n-3 ratio in dams only. The PL fraction showed decreased n-6 PUFA in both dams and pups. The magnitude of the diet-mediated responses, specifically TAG 18:1 and PL n-6 PUFA, may have contributed to the previously reported altered BMD, which was supported with correlation analysis. Future research should investigate the relationship of diet-induced changes in bone lipids on bone structure, as quantified through micro-computed tomography.

A Research on Improving the Precision of Rotating-Wave Plate Polarization Measurement

The device errors of a rotating-wave-plate-based polarization measurement system can be mainly categorized as the angle error of the polarization prism, the fast axis angle error of wave-plate and the retardation error. By applying Fourier analysis to solve Stokes vectors, we obtain the formulas to calculate the three errors mentioned above, using linear 0° and 45° polarized light to illuminate the system for the error solving. We analyze the measurement errors of the degree of polarization, the polarization purity and the intensity of polarization state, under certain simulation conditions. The results show that after the calibration, the measurement accuracy is improved. Finally, we analyze the effects of the angle error of the linear polarized light used for calibration to the measurement of the three parameters.