Publications by authors named "Tiegen Liu"

105 Publications

Information rates in Kerr nonlinearity limited optical fiber communication systems.

Opt Express 2021 May;29(11):17428-17439

Achievable information rates of optical communication systems are inherently limited by nonlinear distortions due to the Kerr effect occurred in optical fibres. These nonlinear impairments become more significant for communication systems with larger transmission bandwidths, closer channel spacing and higher-order modulation formats. In this paper, the efficacy of nonlinearity compensation techniques, including both digital back-propagation and optical phase conjugation, for enhancing achievable information rates in lumped EDFA- and distributed Raman-amplified fully-loaded C -band systems is investigated considering practical transceiver limitations. The performance of multiple modulation formats, such as dual-polarisation quadrature phase shift keying (DP-QPSK), dual-polarisation 16 -ary quadrature amplitude modulation (DP-16QAM), DP-64QAM and DP-256QAM, has been studied in C -band systems with different transmission distances. It is found that the capabilities of both nonlinearity compensation techniques for enhancing achievable information rates strongly depend on signal modulation formats as well as target transmission distances.
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http://dx.doi.org/10.1364/OE.415753DOI Listing
May 2021

Optical boundary discrimination in spatial posture measurement.

Appl Opt 2021 May;60(13):3797-3800

The measurement of the spatial attitude of the tube sheet is the basis for automated shield assembly. This paper presents an image processing method for measuring the surface grooves of the tube sheet. The measurement process consists of two processes: target detection and target coordinate measurement. The environmental factors that affect the recognition rate are analyzed and effective recognition coefficients are defined to further improve the method's ability to resist interference from external factors.
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http://dx.doi.org/10.1364/AO.421790DOI Listing
May 2021

Applications of liquid crystals in biosensing.

Soft Matter 2021 May 6;17(18):4675-4702. Epub 2021 Apr 6.

School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin, 300072, China.

Liquid crystals (LCs), as a promising branch of highly-sensitive, quick-response, and low-cost materials, are widely applied to the detection of weak external stimuli and have attracted significant attention. Over the past decade, many research groups have been devoted to developing LC-based biosensors due to their self-assembly potential and functional diversity. In this paper, recent investigations on the design and application of LC-based biosensors are reviewed, based on the phenomenon that the orientation of LCs can be directly influenced by the interactions between biomolecules and LC molecules. The sensing principle of LC-based biosensors, as well as their signal detection by probing interfacial interactions, is described to convert, amplify, and quantify the information from targets into optical and electrical parameters. Furthermore, commonly-used LC biosensing targets are introduced, including glucose, proteins, enzymes, nucleic acids, cells, microorganisms, ions, and other micromolecules that are critical to human health. Due to their self-assembly potential, chemical diversity, and high sensitivity, it has been reported that tunable stimuli-responsive LC biosensors show bright perspectives and high superiorities in biological applications. Finally, challenges and future prospects are discussed for the fabrication and application of LC biosensors to both enhance their performance and to realize their promise in the biosensing industry.
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http://dx.doi.org/10.1039/d0sm02088eDOI Listing
May 2021

Integration time optimization and starting angle autocalibration of full Stokes imagers based on a rotating retarder.

Opt Express 2021 Mar;29(6):9494-9512

Full Stokes imaging can be performed with a continuously rotating retarder in front of a fixed polarizer and a standard camera (RRFP) or a division of a focal plane polarization camera (RRDOFP). We determine the optimal number and duration of intensity measurements through a cycle of the retarder for these two types of setups as a function of instrument and noise parameters. We show that this number mainly depends on the type of noise that corrupts the measurements. We also show that with these setups, the starting angle of the retarder need not be known precisely and can be autocalibrated, which facilitates synchronization of the rotating retarder with the camera. We investigate the precision and feasibility domain of this autocalibration and show the RRDOFP setup has more attractive properties compared with RRFP setup. These results are important to optimize and facilitate the operation of polarization imagers based on a rotating retarder.
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http://dx.doi.org/10.1364/OE.418399DOI Listing
March 2021

Design and characteristics of a Maxwell force-driven liquid lens.

Opt Express 2021 Mar;29(6):8323-8332

Varifocal lenses (especially large-aperture lenses), which are formed by two immiscible liquids based on electrowetting and dielectrophoretic effects, are usually modulated by an external high-voltage power source, with respect to the volume of the liquid. Hence, a Maxwell force-driven liquid lens with large aperture and low threshold voltage is proposed. With the polarization effect, the accumulated negative charges on the surface of the polyvinyl chloride/dibutyl adipate gel near the anode results in the generation of Maxwell force and deformation with cosine wave. The effect of surface roughness on wettability is linear with the cosine of the contact angle, leading to a sharp reduction in the threshold voltage when the volume of liquid is increased. When the volume of the droplet increases to 80 μl, the threshold voltage is about 10 V. Hence, the aperture of polarization effect-driven liquid lenses can potentially reach the centimeter level. Moreover, when Maxwell force increases, the lens ranges from concave to convex lens, which holds great promise in rich application such as those in light-sheet microscopes and virtual reality systems.
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http://dx.doi.org/10.1364/OE.418630DOI Listing
March 2021

NaYF4:Yb/[email protected]/Cur-CS/OSA Nanoparticles with pH and Photon Responses.

Nanotechnology 2021 Mar 8. Epub 2021 Mar 8.

Tianjin University, Tianjin, Tianjin, CHINA.

Stimulus-triggered drug delivery systems (DDSs) based on lanthanide-doped upconversion nanoparticles (UCNPs) have attracted intensive attention for treating cancers due to the merits of high drug availability, precisely controlled drug release, and low side-effects. However, such DDSs usually exhibit a single stimulus-response, which may limit the efficiency of cancer treatment. To extend response types in a single DDS, we construct NaYF4:Yb/[email protected] doxorubicin (Dox)/curcumin (Cur)-chitosan (CS)/2-Octen-1-ylsuccinic anhydride (OSA) nanoparticles with core-shell structures. Our method is based on the exploration of a synergistic effect of UCNPs and multiple drugs. To be specific, the NaYF4:Yb/Tm is used to convert near-infrared light to visible light, activating Cur photosensitizers to produce singlet oxygen for photodynamic therapy, while CS/OSA responds to a low pH environment to release cancer drugs including Dox and Cur for chemotherapy through breaking a free carboxyl group. The results show that the UCNPs with 40-nm diameter, 23-nm-thick mesoporous SiO2, and 19/1 mol% Yb3+/Tm3+concentrations could continuously release Dox and Cur at a pH value of 6.5 within 6 hours after the excitation of a 980-nm-wavelength laser. Our study provides a promising approach for developing efficient DDSs for cancer treatment.
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http://dx.doi.org/10.1088/1361-6528/abecbaDOI Listing
March 2021

Multi-layer optical fiber surface plasmon resonance biosensor based on a sandwich structure of [email protected] nanoparticles-polydopamine.

Biomed Opt Express 2020 Dec 3;11(12):6840-6851. Epub 2020 Nov 3.

School of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.

An all-optical fiber multi-layer surface plasmon resonance (SPR) biosensor based on a sandwich structure of [email protected] nanoparticles-polydopamine ([email protected]) was designed for the detection of specific immunoreactions. By optimizing the multi-layer structure and the ratio of MoSe: AuNPs, a sensitivity of 5117.59 nm/RIU has been obtained, which is more than double that of the only Au-filmed optical fiber SPR sensor. A large surface area was produced by integrating the MoSe primitive unit cell and the AuNPs into a hybrid plasmonic nanostructure of [email protected], leading to optical fiber SPR signal amplification. The nanostructure of [email protected] was surrounded by the PDA layer to guarantee the efficient immobilization of the protein molecules on the optical fiber by strong covalent bond. This biosensor achieved a detection limit of 54.05 ng/mL for detecting the goat-anti-rabbit IgG, which demonstrated enhancements of 12.1%, 23.3% and 184.6% in comparison with three reported SPR biosensors decorated with PDA-AuNPs-PDA, PDA and [email protected] nanostructure, respectively. This biosensor achieved favorable selectivity and outstanding sensitivity compared with the reported SPR immuno-sensors, which will provide a miniaturized, rapid-response and label-free optical fiber bio-sensing platform for clinical diagnosis in the future.
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http://dx.doi.org/10.1364/BOE.409535DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7747900PMC
December 2020

GPU-based fast processing for a distributed acoustic sensor using an LFM pulse.

Appl Opt 2020 Dec;59(35):11098-11103

We carried out a fast processing investigation based on a graphics processing unit (GPU) for a distributed acoustic sensor using a linear frequency modulation pulse. The moving window cross-correlation calculations are realized on the GPU, which makes use of parallel computing. We analyzed the effect of the thread number in a block on the GPU streaming multiprocessor utilization efficiency and then compared the acceleration under different calculation scales. By maximizing the streaming multiprocessor utilization efficiency and large calculation scale, a maximum acceleration ratio of 86.01 was obtained.
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http://dx.doi.org/10.1364/AO.412184DOI Listing
December 2020

Three-dimensional spatial reconstruction of coronary arteries based on fusion of intravascular optical coherence tomography and coronary angiography.

J Biophotonics 2021 Mar 6;14(3):e202000370. Epub 2020 Dec 6.

School of Precision Instruments and Opto-Electronics Engineering, Tianjin University, Tianjin, China.

We present a three-dimensional (3D) spatial reconstruction of coronary arteries based on fusion of intravascular optical coherence tomography (IVOCT) and digital subtraction angiography (DSA). Centerline of vessel in DSA images is exacted by multi-scale filtering, adaptive segmentation, morphology thinning and Dijkstra's shortest path algorithm. We apply the cross-correction between lumen shapes of IVOCT and DSA images and match their stenosis positions to realize co-registration. By matching the location and tangent direction of the vessel centerline of DSA images and segmented lumen coordinates of IVOCT along pullback path, 3D spatial models of vessel lumen are reconstructed. Using 1121 distinct positions selected from eight vessels, the correlation coefficient between 3D IVOCT model and DSA image in measuring lumen radius is 0.94% and 97.7% of the positions fall within the limit of agreement by Bland-Altman analysis, which means that the 3D spatial reconstruction IVOCT models and DSA images have high matching level.
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http://dx.doi.org/10.1002/jbio.202000370DOI Listing
March 2021

IPLNet: a neural network for intensity-polarization imaging in low light.

Opt Lett 2020 Nov;45(22):6162-6165

Imaging in low light is significant but challenging in many applications. Adding the polarization information into the imaging system compromises the drawbacks of the conventional intensity imaging to some extent. However, generally speaking, the qualities of intensity images and polarization images cannot be compatible due to the characteristic differences in polarimetric operators. In this Letter, we collected, to the best of our knowledge, the first polarimetric imaging dataset in low light and present a specially designed neural network to enhance the image qualities of intensity and polarization simultaneously. Both indoor and outdoor experiments demonstrate the effectiveness and superiority of this neural network-based solution, which may find important applications for object detection and vision in photon-starved environments.
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http://dx.doi.org/10.1364/OL.409673DOI Listing
November 2020

Optical fiber laser refractometer based on an open microcavity Mach-Zehnder interferometer with an ultra-low detection limit.

Opt Express 2020 Oct;28(21):30570-30585

A fiber laser refractometer based on an open microcavity Mach-Zehnder interferometer (OMZI) is proposed. The open microcavity is constructed by embedding a segment single-mode fiber (SMF) into two multi-mode fiber (MMF) joints with lateral offset for liquid sample, which has the advantages of micro sensing element and easy fabrication. The transmission characteristics of the MMF-assisted OMZI are investigated by simulating and manufacturing the OMZIs with different microcavity lengths and offset distances. By inserting the MMF-assisted OMZI into the erbium-doped fiber ring laser (FRL) cavity, the lasing wavelength can be used to detect the refractive index (RI) change of the medium in the microcavity. Experimental results show a high sensitivity of -2953.444 nm/RIU within the measurement range of 1.33302∼1.33402. More importantly, with the combination of OMZI and FRL, the proposed fiber laser refractometer realizes ultra-low detection limit (DL) and high-quality factor Q, which are two orders of magnitude better than that of previous reports.
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http://dx.doi.org/10.1364/OE.401813DOI Listing
October 2020

High-consistency fiber-optic Fabry-Perot sensor based on MEMS for simultaneous temperature and liquid refractive index measurement.

Appl Opt 2020 Oct;59(30):9353-9358

We proposed a hybrid Fabry-Perot fiber-optic sensor based on the microelectromechanical system (MEMS) technique for measuring temperature and liquid refractive index simultaneously, and we verify the consistency of four sensors in the same batch. The sensor consists of a groove-array structured glass wafer and two silicon wafers, which are connected by double-sided anodic bonding. The three parts form two independent Fabry-Perot cavities for temperature and liquid refractive index sensing, respectively. We randomly selected three sensors in the same batch and conducted temperature and refractive index experiments to establish the sensing equation. The experimental results demonstrate their high consistency with temperature sensitivities of 81.6, 81.8, and 81.4 pm/°C in the range of 10°C to 80°C, and refractive index sensitivities of 1040.11, 1044.24, 1042.91 nm/RIU in the range of 1.333-1.374. The sensors have low cross-sensitivities that are less than 5.86×10 RIU/°C and high precisions of 0.047°C, 2.14×10, respectively. To verify the validity of the sensing equation, we made another sensor in the same batch and got maximum errors of 0.36°C and 7.7×10, respectively.
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http://dx.doi.org/10.1364/AO.401162DOI Listing
October 2020

Data augmentation of optical time series signals for small samples.

Appl Opt 2020 Oct;59(28):8848-8855

It is difficult to obtain a large amount of labeled data, which has become a bottleneck for the application of deep learning to analyze one-dimensional optical time series signals. In order to solve this problem, a deep convolutional generative adversarial network model suitable for augmenting optical time series signals is proposed. Based on the acoustic emission (AE) data set obtained by an optical sensor with a small amount, the model can learn the corresponding data features and apply them to generate new data. The analysis results show that our model can generate stable and diverse AE fragments in epoch 500, and there is no model collapse. All the features between the generated data and the original data are not significantly different at the 0.05 level, which confirms that the method in this paper can generate the optical time series signals effectively.
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http://dx.doi.org/10.1364/AO.404799DOI Listing
October 2020

Electrowetting lens with large aperture and focal length tunability.

Sci Rep 2020 10 1;10(1):16318. Epub 2020 Oct 1.

College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.

The electrowetting lenses has attracted researchers in many fields, such as biology, beam shaping, and drug delivery. Previous research on electrowetting lens has focused on neither expanding the dynamic focal length range nor reducing the wavefront aberration. However, the properties with large numerical aperture and low aberration are also essential properties of lenses, and can promote their application. Therefore, we calculated the meniscus of the lens with different optical apertures, and subsequently, analyzed the relations among the focal length, wavefront aberration, and optical aperture. To expand the focal length range, we designed an electrowetting-based triple-liquid lens with a root-mean-square wavefront aberration error of less than 1/4 waves.
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http://dx.doi.org/10.1038/s41598-020-73260-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7530674PMC
October 2020

Virtual-block-array phase analysis for distributed acoustic sensors with a high signal-to-noise ratio reconstruction waveform.

Opt Express 2020 Aug;28(17):24577-24585

A virtual-block-array phase analysis method is proposed for the fiber-optic distributed acoustic sensor. The sensing fiber is divided into a serial of discrete virtual blocks according to the pulse spatial length. The phase variation caused by acoustic events is obtained by combining the operation of the temporal differential process between traces and local spatial average in virtual blocks. The linear frequency-modulated probe pulse produces phase compensation effects at the event location. High signal-to-noise ratio (SNR) measurement is verified by simulation and experiment. The reconstructed waveform of 1.5 kHz sinusoidal signal showed a root mean square error of 0.0359 and an SNR of 47.28 dB.
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http://dx.doi.org/10.1364/OE.395281DOI Listing
August 2020

Impact of Equalization-Enhanced Phase Noise on Digital Nonlinearity Compensation in High-Capacity Optical Communication Systems.

Sensors (Basel) 2020 Jul 26;20(15). Epub 2020 Jul 26.

Key Laboratory of Opto-Electronic Information Technical Science of Ministry of Education, School of Precision Instruments and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China.

Equalization-enhanced phase noise (EEPN) can severely degrade the performance of long-haul optical fiber transmission systems. In this paper, the impact of EEPN in Nyquist-spaced dual-polarization quadrature phase shift keying (DP-QPSK), dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM), and DP-64QAM optical transmission systems is investigated considering the use of electrical dispersion compensation (EDC) and multi-channel digital backpropagation (MC-DBP). Our results demonstrate that full-field DBP (FF-DBP) is more susceptible to EEPN compared to single-channel and partial-bandwidth DBP. EEPN-induced distortions become more significant with the increase of the local oscillator (LO) laser linewidth, and this results in degradations in bit-error-rates (BERs), achievable information rates (AIRs), and AIR-distance products in optical communication systems. Transmission systems using higher-order modulation formats can enhance information rates and spectral efficiencies, but will be more seriously degraded by EEPN. It is found that degradations on AIRs, for the investigated FF-DBP schemes, in the DP-QPSK, the DP-16QAM, and the DP-64QAM systems are 0.07 Tbit/s, 0.11 Tbit/s, and 0.57 Tbit/s, respectively, due to the EEPN with an LO laser linewidth of 1 MHz. It is also seen that the selection of a higher-quality LO laser can significantly reduce the bandwidth requirement and the computational complexity in the MC-DBP.
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http://dx.doi.org/10.3390/s20154149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7436092PMC
July 2020

Refractometric Sensitivity Enhancement of Weakly Tilted Fiber Bragg Grating Integrated with Black Phosphorus.

Nanomaterials (Basel) 2020 Jul 21;10(7). Epub 2020 Jul 21.

School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China.

The sensitivity enhancement of the weakly tilted fiber Bragg grating (WTFBG) integrated with black phosphorus (BP) was investigated via numerical simulations and experimental demonstrations. BP nanosheets were deposited twice on the cylindrical WTFBG surface using the in situ layer-by-layer (i-LbL) deposition technique. The resonance intensity of the deepest cladding mode located around 1552 nm of WTFBG had a 9.2 dB decrease after the BP deposition process. This allows for the application of the intensity-modulated refractive index (RI) sensor. The sensing platform was implemented on the use of the BP integrated with WTFBG (BP-WTFBG). The refractometric sensing was achieved with the sensitivity enhancement of the resonance intensity modulation of the deepest cladding mode for the BP-WTFBG. The sensitivities were 137.6 dB/RIU and 75.6 dB/RIU in the RI region of 1.33-1.35 and 1.35-1.38, respectively. This platform shows great potential applications for biochemical sensing because of its highly sensitive RI sensing ability around the biochemical sensing window.
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http://dx.doi.org/10.3390/nano10071423DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407606PMC
July 2020

Graphene-based dual-mode modulators.

Opt Express 2020 Jun;28(12):18456-18471

Mode-division multiplexing (MDM) has attracted broad attention as it could effectively boost up transmission capability by utilizing optical modes as a spatial dimension in optical interconnects. In such a technique, different data channels are usually modulated to the respective carriers over different spatial modes by using individual parallel electro-optic modulators. Each modulated channel is then multiplexed to a multi-mode waveguide. However, the method inevitably suffers from a high cost, large device footprint and high insertion loss. Here, we design intensity and phase dual-mode modulators, enabling simultaneous modulations over two channels via a graphene-on-silicon waveguide. Our method is based on the exploration of co-planar interactions between structured graphene nanoribbons (GNs) and spatial modes in a silicon waveguide. Specifically, the zeroth-order transverse electric (TE) and first-order transverse electric (TE) modes are modulated separately and simultaneously by applying independent driving electrodes to different GNs in an identical modulator. Our study is expected to open an avenue to develop high-density MDM photonics integrated circuits for tera-scale optical interconnects.
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http://dx.doi.org/10.1364/OE.394409DOI Listing
June 2020

Optimal tradeoff between precision and sampling rate in DoFP imaging polarimeters.

Opt Lett 2019 Dec;44(24):5900-5903

A linear division-of-focal-plane camera combined with a controllable polarization modulator constitutes a versatile full-Stokes imager with four possible sampling rate modes, depending on the number of acquisitions. Considering several polarization modulator architectures, we determine the parameter settings that minimize estimation variance in each sampling rate mode, so that precision, sampling rate, and acquisition time can be optimally and dynamically balanced to implement the imaging solution best adapted to a given application.
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http://dx.doi.org/10.1364/OL.44.005900DOI Listing
December 2019

Learning-based denoising for polarimetric images.

Opt Express 2020 May;28(11):16309-16321

Based on measuring the polarimetric parameters which contain specific physical information, polarimetric imaging has been widely applied to various fields. However, in practice, the noise during image acquisition could lead to the output of noisy polarimetric images. In this paper, we propose, for the first time to our knowledge, a learning-based method for polarimetric image denoising. This method is based on the residual dense network and can significantly suppress the noise in polarimetric images. The experimental results show that the proposed method has an evident performance on the noise suppression and outperforms other existing methods. Especially for the images of the degree of polarization and the angle of polarization, which are quite sensitive to the noise, the proposed learning-based method can well reconstruct the details flooded in strong noise.
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http://dx.doi.org/10.1364/OE.391017DOI Listing
May 2020

Wall-thickness-controlled microbubble fabrication for WGM-based application.

Appl Opt 2020 Jun;59(16):5052-5057

We present a wall-thickness-controlled microbubble fabrication model for whispering-gallery-mode (WGM)-based application. The process of fabricating the model is divided into three sequenced steps: geometry size change of the microcapillary during drawing, expanding the process under internal injection air pressure, and microcapillary waist swell into a microbubble. Experiments were carried out to verify the effectiveness of the model. Experiment results show that wall thickness can reach 1.28 µm-1.46 µm at different injection pressure ranges of 50 kPa. The expected wall thickness of the microbubble can be achieved by changing injection pressure while keeping the diameter, which helps to prepare the required microbubble for practical application.
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http://dx.doi.org/10.1364/AO.391545DOI Listing
June 2020

Temperature compensation of optical alternating magnetic field sensor via a novel method for on-line measuring.

Opt Express 2020 Apr;28(9):13682-13693

The variation of environment temperature is a crucial problem for optical magnetic field sensors based on the magneto-optical crystal. In this paper, we propose a novel temperature compensation method for optical alternating magnetic field measuring by analyzing the demodulation principle and establishing the temperature compensation model, which can implement the functions of temperature compensation and on-line measuring simultaneously. Both the temperature and the alternating magnetic field flux density can be obtained only by adding two magnet rings on the magnetic field sensor. The experimental phenomenon agrees well with the temperature characteristics of the magneto-optical crystal and the theoretical compensation model. The experimental results demonstrate that this sensor has excellent stability whose max relative fluctuation is only 0.7402% in the range of 0-4 mT under a constant temperature. In the temperature compensation experiment of 0 °C, 20 °C and 40 °C, the sensor shows strong temperature robustness that the max absolute and relative errors are 0.07 mT and 3.50%, respectively. Meanwhile, compensation efficiency reaches 83.968%, which can effectively avoid temperature crosstalk to a large extent. Additionally, it has a better compensation performance whose max absolute and relative errors are 0.15 mT and 1.66% in the broader range of 0-16 mT when the actual temperature is accurately known.
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http://dx.doi.org/10.1364/OE.388407DOI Listing
April 2020

All optic-fiber coupled plasmon waveguide resonance sensor using ZrS based dielectric layer.

Opt Express 2020 Apr;28(8):11280-11289

We developed an all optic-fiber coupled plasmon waveguide resonance (CPWR) sensor using a zirconium disulfide (ZrS) based dielectric layer. The dielectric constants of ZrS were obtained using first-principles calculations. The theoretical model of the proposed sensor was established based on the transfer matrix method, leading to the optimization of the parameters in the sensor. The sensor was fabricated by depositing a gold layer of 35 nm on the fiber core and immobilizing the ZrS layer on the gold layer via physical adsorption method. An experimental setup was implemented for measuring the refractive index. The sensor with two cycles showed the best performance, with a sensitivity of higher than 8000 nm/RIU.
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http://dx.doi.org/10.1364/OE.389279DOI Listing
April 2020

Theory of autocalibration feasibility and precision in full Stokes polarization imagers.

Opt Express 2020 May;28(10):15268-15283

We propose a general theory of simultaneous estimation of Stokes vector and instrumental autocalibration of polarization imagers. This theory is applicable to any polarization imager defined by its measurement matrix. We illustrate it on the example of retardance autocalibration in a large class of polarization imagers based on rotating retarders and polarimeters. We show that although all these architectures can yield optimal estimation precision of the Stokes vector if they are properly configured, they do not have the same autocalibration capacity and have to be specifically optimized for that purpose. These results are important to determine the best compromise between autocalibration capacity and polarimetric precision in practical applications.
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http://dx.doi.org/10.1364/OE.390882DOI Listing
May 2020

Gap-matching algorithm with the impCEEMDAN in scanning white-light interference microscopy.

Opt Express 2020 May;28(10):15101-15111

Coherence scanning interferometry (CSI) is a common optical measurement method for measuring three-dimensional surface profiles. However, batwings and ghost steps are common obstacles in CSI. In this paper, we proposed a gap-matching algorithm with the improved complete ensemble empirical mode decomposition with adaptive noise (impCEEMDAN) to solve the above two obstacles without any priori knowledge of the surface geometry from the tested sample. A micro-component with 500 nm and 1200 nm step heights and a 10 µm standard step of were used as test samples to evaluate the accuracy of the proposed method. Simulations and experimental results show that this approach can effectively suppress the batwings effect and eliminate the ghost steps. Experiments also confirm that the approach has good accuracy and repeatability.
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http://dx.doi.org/10.1364/OE.391587DOI Listing
May 2020

Cryogen adaptive and integrated differential pressure sensor for level sensing based on an optical Fabry-Perot interferometer.

Appl Opt 2020 Mar;59(8):2457-2461

In this paper, we introduce a cryogen-adaptive sensor based on a micro-electromechanical system (MEMS) for level measurement of cryogenic fluids. The sensor is fabricated by an optical fiber inserted in a glass ferrule and an integrated Fabry-Perot (FP) chip using the MEMS technique. We carried a liquid nitrogen level measurement experiment to verify the performance of the sensor and a low coherent interference system is used to transform the liquid level to absolute phase. The measuring range is 24 cm and can be expanded more widely. The experimental results show that the sensor has a good monotonic linear response (coefficient determination ${{\rm R}^2} \gt {0.998}$R>0.998), and the measurement error is less than ${ \pm 5}\;{\rm mm}$±5mm in liquid nitrogen. The excellent cryogenic temperature performance from $ - {260}^\circ {\rm C}$-260C to $ - {100}^\circ {\rm C}$-100C also is demonstrated, which shows the potential application in level measurement of various cryogenic liquids.
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http://dx.doi.org/10.1364/AO.384293DOI Listing
March 2020

Liquid Lens with Large Focal Length Tunability Fabricated in a Polyvinyl Chloride/Dibutyl Phthalate Gel Tube.

Langmuir 2020 Feb 5;36(6):1430-1436. Epub 2020 Feb 5.

School of Engineering and Digital Arts , University of Kent , Canterbury , Kent CT2 7NT , U. K.

Usually, an adaptive liquid lens only has a positive focal length, which severely limits its application in imaging and other fields. Therefore, a liquid lens consisting of polyvinyl chloride/dibutyl phthalate (PVC/DBP) gel, glycerol solution, and a glass substrate is proposed to extend the dynamic focal length range. A spherical tube is formed by the PVC/DBP gel under the effect of hydrostatic and surface tensions, which is used to restrict the glycerol solution. The PVC/DBP gel does not deform under the effect of an electric field, so the tangent line at the three-phase junction changes with the change of contact angle, which leads to an enlargement of the dynamic focal length range. At different voltage values, the proposed lens can be configured to work in three different schemes, namely, converging light, nondeflecting light, and diverging light. Here, the proposed lens has high imaging quality; the resolution is better than 114 lp/mm. A lens with a reconfigurable focal length holds great promise in diverse applications such as fluorescence detection, beam shaping, and adaptive optics.
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http://dx.doi.org/10.1021/acs.langmuir.9b03585DOI Listing
February 2020

Measurement of cloud particles in a cloud chamber based on interference technology.

Appl Opt 2019 Nov;58(32):8757-8764

Based on interference technology, a cloud particle measurement system is designed. The scattering angle of the system is selected as 90°. The iterative mean filter algorithm is modified, and the system testing using laboratory measurement is completed. The measurement of the spectral distribution of warm cloud particles in a cloud chamber is realized. Similar particle-sized distributions are observed under different pressures, and the particle size is mainly distributed in the range of 5 to 50 µm. The peak appears at particle sizes of 20 to 30 µm. This system features potential applications in cloud microphysics research.
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http://dx.doi.org/10.1364/AO.58.008757DOI Listing
November 2019

Precision of retardance autocalibration in full-Stokes division-of-focal-plane imaging polarimeters: publisher's note.

Opt Lett 2019 Dec;44(23):5759

This publisher's note contains corrections to Opt. Lett.44, 5410 (2019)OPLEDP0146-959210.1364/OL.44.005410.
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http://dx.doi.org/10.1364/OL.44.005759DOI Listing
December 2019

Precision of retardance autocalibration in full-Stokes division-of-focal-plane imaging polarimeters.

Opt Lett 2019 Nov;44(22):5410-5413

We investigate the validity domain and precision of retardance autocalibration in full-Stokes imaging polarimeters based on a linear division-of-focal-plane polarization camera. We demonstrate that the level of precision of autocalibration in these systems gets worse as the degree of linear polarization of input Stokes vector approaches zero. Autocalibration is impossible when the input is purely circular or totally unpolarized. In all other cases, reaching a given level of precision requires a higher signal-to-noise ratio as the input gets closer to circular or unpolarized.
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http://dx.doi.org/10.1364/OL.44.005410DOI Listing
November 2019