Tunable Detector Research Articles

Multi-component Freon gas detection based on infrared tunable Fabry-Perot detector

A multi-component Freon gas sensing system was developed based on the non-dispersive infrared (NDIR) spectroscopy, which had the advantages of simple structure and low cost. This system mainly consisted of a broadband infrared light source, a tunable Fabry-Perot (FP) detector and a small brass absorption cell. In order to improve the utilization rate of infrared light source, the absorption cell was optimized. H1301, R134a and R410A were simultaneously detected through the measurement of gas absorption spectrum. The spectral range of the FP detector was from 8.0 to 10.5 μm, and the entire spectrum was recorded by wavelength scanning. The area of measured absorbance was directly proportional to the concentration of the target gas, which was used to calibrate the sensing system. The temperature and frequency response characteristics of the system were tested. The experimental results showed that the higher the temperature, the lower the responsiveness. In addition, the system had the best signal-to-noise ratio (SNR) at 10 Hz. The minimum detection limits of H1301, R134a and R410A were achieved to be 2.5 ppm, 5.3 ppm and 4.8 ppm, respectively. The cross-interference among the gases was suppressed by using BP neural network.

The development and validation of a stability indicating Rp-UPLC method for the simultaneous estimation of clarithromycin, amoxicillin, and vonoprazan in a physical mixture

A novel technique was developed for simultaneous quantification of clarithromycin (CLA) amoxicillin (AMO), and vonoprazan (VON) in a mixture using the reverse phase ultra-performance liquid chromatography (RP-UPLC) technique and validated as per International Council for Harmonization (ICH) guidelines as there was no literature published for its estimation by UPLC. The method was developed using an acquity UPLC system from waters corporation with Hibar Bis phosphonate C18 column (100 × 2.1 mm, 2 μm) at 35°C and tunable ultra-violet detector (TUV) with detection wavelength at 210 nm, has a run time of below 3 minutes. The mobile phase proportion of 60:40 of 0.1 N monobasic potassium phosphate buffer (pH 3.8) and acetonitrile at a flow velocity of 0.2 ml/ minute was utilized. Linearity was observed for CLA, AMO, and VON between the concentration ranges of 25–150, 25–150, and 1–6 μg/ml, respectively, and R2 was 0.999 for CLA, AMO, and VON. Accuracy and precision were within 2% of the coefficient of variation (RSD) for all drugs. The observed mean percentage recoveries for the CLA, AMO, and VON were determined to be 99.74%, 99.07%, and 99.8%, respectively. The stability of the approach was assessed using degradation studies by exposing it to acid, alkali, oxidizing agent, heat, Ultra Violet (UV) light, and water as per ICH guidelines.

A Tunable Adaptive Detector for Distributed Targets When Signal Mismatch Occurs

Aiming at the problem of detecting a distributed target when signal mismatch occurs, this paper proposes a tunable detector parameterized by an adjustable parameter. By adjusting the parameter, the tunable detector can achieve robust or selective detection of mismatched signals. Moreover, the proposed tunable detector, with a proper tunable parameter, can provide higher detection probability compared with existing detectors in the case of no signal mismatch. In addition, the proposed tunable detector possesses the constant false alarm rate property with the unknown noise covariance matrix.

Quartz-Enhanced Photoacoustic Spectroscopy in the Terahertz Spectral Range

Infrared laser photo-acoustic spectroscopy provides very high sensitivity of a gas sample analysis when high-power tunable laser radiation sources and resonant photo-acoustic detectors (PADs) are used. In the resonant PAD, the acoustic signal generated by absorbed laser radiation in a measurement chamber is amplified proportionally to a Q-factor of the acoustic resonator. But, compact tunable high-power lasers (with power above 100 mW) still are not widely spread in the terahertz spectral range. One of the ways to achieve an acceptable sensitivity of terahertz photo-acoustic spectroscopy is using PADs with a very high Q-factor. The latter can be achieved using PAD with a quartz tuning fork. The current state in this field is presented in the review.

Coplanar superconducting resonators with nonlinear kinetic inductance bridge

We present a model and experimental realization of coplanar superconducting resonators terminated by a shunting kinetic inductance bridge made of ultra-thin Al films. The fabrication process that we propose allows us to create very homogeneous films, which makes them suitable for many applications in quantum devices. Due to the specific properties of the films, the resonators exhibit a Duffing oscillator behavior resulting in bifurcations and interactions between different power sources, which was previously observed in similar systems. Moreover, since the nonlinearity of such a system is concentrated at the bridge, while the wave propagates in a linear environment, it is possible to propose a simple model that accurately describes its behavior. We show that, when resonators are operated within a notch-port architecture, our model has a closed-form solution for the transmission coefficient and allows one to accurately extract parameters of the system, including the kinetic inductance of the bridge and its depairing current. Potential applications of such systems include tunable resonators, photon detectors, bifurcation and parametric amplifiers, as well as a measurement device for studying the properties of thin films.

Tunable up-conversion single-photon detector at telecom wavelengths

Abstract Up-conversion single-photon detectors (UCSPD) are based on sum-frequency generation of the telecom band single-photons to near-infrared wavelengths at which efficient and low-noise silicon single-photon detectors are available. Moreover, because of high dynamic range of silicon single-photon detectors, UCSPD is suitable for high-speed quantum communication. UCSPDs reported to date, however, have a very narrow fixed window of detectable wavelengths, severely limiting their applications in wavelength-multiplexed quantum networks. In this work, we report a tunable UCSPD module that covers the complete telecom C band, making it suitable for quantum communication networks based on sharing wavelength-multiplexed entangled photons.

Ferrimagnet based spin Hall detector of subterahertz frequency signals

A concept of a subterahertz (sub-THz) frequency range signals detector based on a ferrimagnet/normal metal (FiM/NM) heterostructure is proposed. An external linearly polarized electromagnetic (EM) wave excites precession in the FiM and spin pumping at the FiM/NM interface. The excited spin current in the NM converts into a direct current via the inverse spin Hall effect. We show that non-zero uncompensation between magnetic spins in FiM gives a non-zero output rectified voltage for both “easy axis” and “easy plane” uniaxial anisotropies. The increase in the uncompensation parameter removes degeneracy from two normal resonance modes and changes the sensitivity to the EM wave. Namely, the sensitivity of the higher mode increases, and the lower mode decreases with increasing the uncompensation parameter. We believe that our results can be helpful for the practical development of sub-THz frequency tunable resonance detector based on the FiM.

Switchable strong coupling between dual hyperbolic phonon polaritons and photons in hybrid structure of metasurfaces and h-BN slab

We propose an all-dielectric hybrid structure combined with hexagonal boron nitride slab and strontium titanate (STO) metasurfaces to excite dual hyperbolic phonon polaritons (HPhPs) and an additional optical (TO) phonon, and achieve their strong coupling with photons. The metasurfaces, supporting tunable guided-mode resonance via adjusting the external temperature, consists of STO two-dimensional grating and STO layer. Thus, the strong coupling can be switched and tuned actively between the dual HPhPs and TO phonon via adjusting the external temperature of metasurfaces. This work has numerous potential applications on multi-channel biosensors, filters and tunable source and detectors.

Quasi Type-1 PLL With Tunable Phase Detector for Unbalanced and Distorted Three-Phase Grid

Out of various moving average filter (MAF)-based phase-locked-loop (PLL), quasi type-1 PLL (QT1-PLL) is widely adopted due to its fast dynamic performance, implementation simplicity, and harmonics rejection abilities. However, the performance of QT1-PLL deteriorates in the presence of an off-nominal frequency unbalanced grid voltage component. Moreover, the sensitivity towards the fundamental frequency negative sequence (FFNS) component is high. Hence, this paper proposes a novel enhanced QT1-PLL solution that is insensitive to unbalance in the grid voltage signal during off-nominal frequency conditions. The proposed adaptive phase detector makes it possible to estimate both the fundamental frequency positive sequence (FFPS) and FFNS components with a high degree of immunity against harmonics. Notably, the pre-loop separation of the FFPS and the FFNS components helps suppress the second harmonic oscillations for improving the parameter estimation accuracy. The loop-filter design of QT1-PLL remains unaffected and requires a proportional gain to estimate the fundamental phase and frequency information. To address the DC offset issue, a modified delayed signal cancellation method is also proposed, which can theoretically eliminate the DC offset for any arbitrary delay length. A small-signal model of the proposed PLL is developed for the sake of stability analysis. Comparative numerical simulation and experimental results are provided with various variants of QT1-PLLs to demonstrate the performance improvement achieved with the proposed technique.

Theory of Antiferromagnet-Based Detector of Terahertz Frequency Signals

We present a theory of a detector of terahertz-frequency signals based on an antiferromagnetic (AFM) crystal. The conversion of a THz-frequency electromagnetic signal into the DC voltage is realized using the inverse spin Hall effect in an antiferromagnet/heavy metal bilayer. An additional bias DC magnetic field can be used to tune the antiferromagnetic resonance frequency. We show that if a uniaxial AFM is used, the detection of linearly polarized signals is possible only for a non-zero DC magnetic field, while circularly polarized signals can be detected in a zero DC magnetic field. In contrast, a detector based on a biaxial AFM can be used without a bias DC magnetic field for the rectification of both linearly and circularly polarized signals. The sensitivity of a proposed AFM detector can be increased by increasing the magnitude of the bias magnetic field, or by by decreasing the thickness of the AFM layer. We believe that the presented results will be useful for the practical development of tunable, sensitive and portable spintronic detectors of THz-frequency signals based of the antiferromagnetic resonance (AFMR).

A filterless organic photodetector electrically switchable between visible and infrared detection

Wavelength tunable detectors are essential for capturing spectral information within diverse applications such as those related to object recognition and identification. Here, we present a generalizable design for a compact dual-band photodetector based on the integration of two back-to-back organic photodiodes that respond to visible (400–700 nm) and infrared light (700–1,400 nm). The polarity under external bias provides the electronic switch between visible and infrared detection modes. Operating at a low voltage of <1 V, the organic photodetector exhibits a fast response with a −3-dB cutoff frequency of 18 kHz and specific detectivity of 7.8 × 10 9 Jones. The device provides contactless measurements of high temperatures that originated from blackbody radiation and spectroscopic dual-band imaging for object identification. • Bias-switchable photodetection between visible and infrared sensing • Back-to-back diodes designed for tuning spectral ranges • Response speed of 18 kHz and low voltage of <1 V operation Li et al. report an organic dual-band photodetector with a switchable response to visible and IR spectral regions. The rapid response of tens of kHz is enabled by simple voltage control of <1 V. The device is based on back-to-back diodes, a configuration that may be generalizable to other thin-film optoelectronic materials.

Near-field radiative heat transfer between topological insulators via surface plasmon polaritons

SummaryRecently, thanks to its excellent opto-electronic properties, two-dimension topological insulator not only has attracted broad interest in fields such as tunable detectors and nano-electronics but also shall yield more interesting prospect in thermal management, energy conversion, and so on. In this work, the excellent near-filed radiative heat transfer (NFRHT) resulting from monolayer topological insulator (Bi2Se3) is demonstrated. The NFRHT of this system is mainly dominated by the strong coupling effect of the surface plasmon polaritons (SPPs) between two Bi2Se3 sheets. Moreover, the non-monotonic dependence of the Fermi energy of Bi2Se3 on NFRHT is then discovered. It is indicated that the system can provide great thermal adjustability by controlling the Fermi energy, achieving a modulation factor of heat flux as high as 98.94%. Finally, the effect of substrate on the NFRHT is also explored. This work provides a promising pathway for the highly efficient thermal management.

Integrated Nanophotonic Waveguide-Based Devices for IR and Raman Gas Spectroscopy.

On-chip devices for absorption spectroscopy and Raman spectroscopy have been developing rapidly in the last few years, triggered by the growing availability of compact and affordable tunable lasers, detectors, and on-chip spectrometers. Material processing that is compatible with mass production has been proven to be capable of long low-loss waveguides of sophisticated designs, which are indispensable for high-light–analyte interactions. Sensitivity and selectivity have been further improved by the development of sorbent cladding. In this review, we discuss the latest advances and challenges in the field of waveguide-enhanced Raman spectroscopy (WERS) and waveguide infrared absorption spectroscopy (WIRAS). The development of integrated light sources and detectors toward miniaturization will be presented, together with the recent advances on waveguides and cladding to improve sensitivity. The latest reports on gas-sensing applications and main configurations for WERS and WIRAS will be described, and the most relevant figures of merit and limitations of different sensor realizations summarized.

Miniaturized VIS-NIR Spectrometers Based on Narrowband and Tunable Transmission Cavity Organic Photodetectors with Ultrahigh Specific Detectivity above 1014 Jones.

Spectroscopic photodetection plays a key role in many emerging applications such as context-aware optical sensing, wearable biometric monitoring, and biomedical imaging. Photodetectors based on organic semiconductors open many new possibilities in this field. However, ease of processing, tailorable optoelectronic properties, and sensitivity for faint light are still significant challenges. Here, the authors report a novel concept for a tunable spectral detector by combining an innovative transmission cavity structure with organic absorbers to yield narrowband organic photodetection in the wavelength range of 400-1100nm, fabricated in a full-vacuum process. Benefiting from this strategy, one of the best performed narrowband organic photodetectors is achieved with a finely wavelength-selective photoresponse (full-width-at-half-maximum of ≈40nm), ultrahigh specific detectivity above 1014 Jones, the maximum response speed of 555kHz, and a large dynamic range up to 168dB. Particularly, an array of transmission cavity organic photodetectors is monolithically integrated on a small substrate to showcase a miniaturized spectrometer application, and a true proof-of-concept transmission spectrum measurement is successfully demonstrated. The excellent performance, the simple device fabrication as well as the possibility of high integration of this new concept challenge state-of-the-art low-noise silicon photodetectors and will mature the spectroscopic photodetection into technological realities.

Tunable and high-performance self-powered ultraviolet detectors using leaf-like nanostructural arrays in ternary tin zinc sulfide system

Recently, self-powered ultraviolet (UV) detectors have received increasing attention for developing the future demands for optoelectronic devices due to their distinguished photoresponse properties. In this study, an emerging type of self-powered UV detectors using the ternary SnxZn1-xS alloy thin films (0.20 ≤ x ≤ 0.40 mol) were fabricated using the solvothermal process. The structural study showed the formation of two distinct phases of ZnS and SnS for the samples with high content Sn2+ ions. According to the ideal crystal-growth mechanism proposed by periodic bond chain theory, a morphological evolution from nanorods to nanoflakes and unique aligned three-dimensional leaf-like nanostructures was achieved by enhancing the Sn2+ content up to the maximum value of 0.40 mol. The optical properties featured the less influence of band tailing on the band gap energy at the high concentration of Sn2+ ions, resulting in the widening of the band gap energy up to 4.56 eV thanks to the Burstein-Moss effect. From the photosensing measurements, the Schottky barrier heights of the devices were found to significantly reduce under UVB exposure as the Sn2+ content increases, confirming a high Ion/Ioff ratio (>103) for the devices. The UV detectors exhibited superior self-powered characteristics under UVB illumination, having high photosensitivity and fast photoswitching response times (τr = 1.9 and τd = 2.6 ms) at zero voltage. Interestingly, the photoresponse performance of UV detectors can be adjusted by varying the content of Sn2+ ions, which signifies that tunable self-powered UV detectors can be designed by varying the Sn2+ concentration in the ternary SnxZn1-xS system.

A Validated Method for Separation and Determination of Codeine Phosphate Hemihydrate Impurities in Bilayer Tablet Dosage Form of Naproxen Sodium and Codeine Phosphate by Using UHPLC

Background: Apranax Plus® is a new bilayer tablet dosage form, which combines two active pharmaceutical ingredients: naproxen sodium and codeine phosphate. Objective: The purpose of this work was to develop an ultra-high-performance liquid chromatography (UHPLC) method for the separation and determination of codeine phosphate hemihydrate impurities in a bilayer tablet dosage form. Methods: The separation and determination of codeine phosphate hemihydrate and its impurities, methylcodeine, morphine, codeine dimer, 10-hydroxycodeine, 14-hydroxycodeine, thebaine and codeinone were achieved by using reversed-phase liquid chromatography with TUV (Tunable UV Detector) and PDA (Photodiode Array Detector) detection by UHPLC. The new proposed method utilized by the Waters Acquity UHPLC® TUV and PDA systems using a UHPLC column Waters Acquity, BEH, C18, 2.1x100 mm, 1.7 μm particle size with a mixture of component A and acetonitrile in a gradient mode at a flow rate of 0.3mL/min, at 25°C with a load of 5μL. The detection for all eluted compounds was carried out at 245nm. Results: The codeine phosphate hemihydrate and peaks of its impurities were adequately obtained, thus proving the stability-indicating power of the method. The developed method was validated as per the ICH guidelines with respect to parameters such as precision, accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ) and robustness. Conclusion: It was verified as being adequate for all the mentioned impurities of codeine phosphate hemihydrate. The described method was found to be useful for routine purity testing and was also found suitable for the analysis of the stability samples of the drug product.

Metallic carbon nanotube quantum dots with broken symmetries as a platform for tunable terahertz detection

Generating and detecting radiation in the technologically relevant range of the so-called terahertz gap (0.1–10 THz) is challenging because of a lack of efficient sources and detectors. Quantum dots in carbon nanotubes have shown great potential to build sensitive terahertz detectors, usually based on photon-assisted tunneling. A recently reported mechanism combining resonant quantum dot transitions and tunneling barrier asymmetries results in a narrow linewidth photocurrent response with a large signal-to-noise ratio under weak THz radiation. That device was sensitive to one frequency, corresponding to transitions between equidistant quantized states. In this work we show, using numerical simulations together with scanning tunneling spectroscopy studies of a defect-induced metallic zigzag single-walled carbon nanotube quantum dot, that breaking simultaneously various symmetries in metallic nanotube quantum dots of arbitrary chirality strongly relaxes the selection rules in the electric dipole approximation and removes energy degeneracies. This leads to a richer set of allowed optical transitions spanning frequencies from 1 THz to several tens of THz, for a ∼10 nm quantum dot. Based on these findings, we propose a terahertz detector device based on a metallic single-walled carbon nanotube quantum dot defined by artificial defects. Depending on its length and contacts transparency, the operating regimes range from a high-resolution gate-tunable terahertz sensor to a broadband terahertz detector. Our calculations indicate that the device is largely unaffected by temperatures up to 100 K, making carbon nanotube quantum dots with broken symmetries a promising platform to design tunable terahertz detectors that could operate at liquid nitrogen temperatures.

A tunable detector for distributed targets when signal mismatch occurs

Aiming at the problem of distributed target detection when there is signal mismatch, this paper proposes a tunable detector, which is characterised by a tunable parameter. The proposed detector can realise the flexible detection of mismatch signals by adjusting the tunable parameter, and hence the directivity (robustness or selectivity to mismatched signals) of the tunable detector can be smoothly adjusted. In addition, the tunable detector can obtain approximately the same detection performance as the corresponding generalised likelihood ratio test in the absence of signal mismatch. The proposed tunable detector also possesses the constant false alarm rate property. Numerical examples illustrate the effectiveness of the proposed detector.

A two‐stage tunable detector with enhanced rejection capabilities

This paper focuses on the method of an adaptive detector which works against Gaussian background with unknown parameters, such as covariance matrix. The authors design a tunable detector for point-like targets by mixing the Kelly's generalized likelihood ratio test and the enhanced Rao test. The analytical expression of the false alarm probability and detection probability of the proposed detector are derived. The performances of the new scheme are assessed, and analysed in comparison with its natural counterparts. The results show that it can provide enhanced rejection capabilities of mismatched signals, at the price of a limited detection loss for matched signals.

Development and Validation of a Novel Analytical Method for the Determination of Dissolution Rate of Acetylsalicylic Acid in Enteric-Coated Tablet Dosage Form by Liquid Chromatography

Objective: The aim of this study is to determine the applicability of UV detection method by the sensitive, simply, precise, specific, and low-cost High-Performance Liquid Chromatography (UHPLC) for acetylsalicylic acid in presence of its degradation product. Methods: Method development and determination of dissolution rate for acetylsalicylic acid, were achieved by using reversed-phase liquid chromatography with PDA (Photodiode Array Detector) and TUV (Tunable UV Detector) detection by HCLASS-UHPLC. The new proposed method utilized by the Waters Acquity UHPLC® TUV and PDA systems using a UHPLC column Waters Acquity, BEH, C18, 2.1mm x 50mm, 1.7μm particle size with a mixture of heptane-1-sulphonic acid sodium salt solution which was prepared in acetonitrile: deionized water (15%: 85% v/v) in isocritic mode at a flow rate of 0.5ml/ min, at 25°C with a load of 5μL. The detection for all eluted compounds was carried out at 280nm.