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Spectral responsivity calibration of a polarization remote sensor based on a supercontinuum laser and monochromator
摘要： Relative spectral responsivity is a basic parameter for detecting and evaluating the in-band response non-consistency of the channel polarization remote sensor (CPRS) in laboratory calibration. In this paper, a spectrally resolved calibration facility was assembled for the calibration of relative spectral responsivity by using novel supercontinuum laser and monochromator (SLM). Taking three polarization channels of 490 nm, 670 nm and 910 nm as examples, the relative spectral responsivity of the CPRS was obtained from two calibration sources, respectively – the SLM and the monochromatic light from SLM steered into integrating sphere. Before measuring the relative spectral responsivity of the CPRS, the degree of linear polarization (DOLP) and the polarization orientation angle of two calibration sources were acquired by the spectral polarization analyser (SPOLA). The test result indicates that the output light of the latter calibration source has less the DOLP and smaller range of variation in the polarization orientation angle. In the experiment of measuring the relative spectral responsivity, while using monochromator as calibration source, the in-band response non-consistency of the three channels were 0.91%, 4.25% and 1.06%, respectively. Correspondingly, while using monochromatic light steered into integrating sphere, there were 0.15%, 0.47% and 0.57%, respectively. It can be concluded that SLM equipped integrating sphere sharply decreased the impact from the polarization characteristic of the source and could be e?ectively applied in the relative spectral responsivity calibration of CPRS.
关键词： spectral responsivity,integrating sphere,monochromator,supercontinuum laser,polarization remote sensor
更新于2025-09-19 17:13:59
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Simultaneous Measurements of Light Hydrocarbons Using Supercontinuum Laser Absorption Spectroscopy
摘要： Simultaneous measurements of light hydrocarbon species based on near-infrared (near-IR) supercontinuum laser absorption spectroscopy (SCLAS) are demonstrated. SCLAS is a broadband absorption diagnostic technique that provides significant advantages over existing absorption diagnostic techniques. Coupled with a fast spectrum analysis strategy, accurate measurements of multiple hydrocarbon concentrations can be made concurrently. Methane (CH4), acetylene (C2H2), ethylene (C2H4), and their mixtures were probed near ambient temperature and pressure conditions. Light hydrocarbons are found in many fuel and energy applications, and a sensor that can accurately and simultaneously probe multiple species’ concentrations and temperature would greatly enhance measurement versatility. Absorption spectra of the three hydrocarbon species were measured between 1.5 and 1.7 μm in this study. These spectra can be very convoluted, where broad absorption features interfere with neighboring features, be it from the same or different species. Species concentrations and temperatures were resolved using a spectrum analysis strategy based on linear regression. Experimental results showed good agreement with test conditions even in the presence of significant spectral overlap.
关键词： supercontinuum laser absorption spectroscopy,light hydrocarbons,spectrum analysis strategy,simultaneous measurements,near-infrared
更新于2025-09-19 17:13:59
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On the application of a supercontinuum white light laser for simultaneous measurements of temperature and velocity fields using thermochromic liquid crystals
摘要： Simultaneous velocity and temperature measurements using thermochromic liquid crystals (TLC) as tracer particles are discussed, with regard to measuring range, uncertainty and spatial resolution. For the first time, a supercontinuum laser is used to illuminate these particles, which shall later be used for the characterization of the momentum and heat transfer in Rayleigh-Bénard cells with high aspect ratio using particle image velocimetry (PIV) and particle image thermometry (PIT). Light scattered from the TLCs is analyzed by spectrometer measurements, revealing its general scattering characteristics depending on the angle between the light sheet plane and the viewing axis. It is shown that white light sources with continuous spectral characteristic and a slightly higher fraction of light in the red wavelength range perform well, thereby the supercontinuum white light laser can be used, even though it has a cut-in wavelength of about 475 nm. The numerical aperture of the detection optics and chromatic aberrations of the laser light significantly affect the temperature sensitivity and dynamic range of the color of the TLCs. This may cause an effective temperature sensitivity range of about one-tenth of their nominal range, particularly at large angles between light sheet plane and viewing axis, as usually applied in PIV. A simultaneous velocity and temperature measurement in a Rayleigh-Bénard cell experimentally validates that the use of the supercontinuum laser allows for reliable simultaneous PIV and PIT measurements with high spatial resolution of less than 500 μm in out-of-plane direction, on condition that an appropriate two-dimensional calibration is applied.
关键词： Thermochromic liquid crystals,Supercontinuum laser,Rayleigh-Bénard convection,Particle image thermometry,Particle image velocimetry
更新于2025-09-16 10:30:52
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Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source
摘要： Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 mm path length) and compared with the conventional FT-IR (130 mm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.
关键词： Mid-infrared spectroscopy,mid-IR,supercontinuum laser source,Fourier transform infrared spectroscopy,FT-IR
更新于2025-09-16 10:30:52
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Optical Transition Edge Sensors: Wavelength Dependence of System Detection Efficiency
摘要： Optical transition edge sensors (TESs) which can resolve an energy of a single photon have proven desirable in quantum information and biology. TESs can provide spectra ranging from near-infrared to visible regions, and have the potential to reveal new phenomena in biology. To obtain reliable spectra, wavelength dependence of the system detection ef?ciency should be calibrated. The dependence is due to a cavity structure of the detector, consisting of an anti-re?ection coating and a mirror. We will present a calibration using a supercontinuum laser and acousto-optic tunable ?lters (AOTF).
关键词： system detection ef?ciency,superconducting detector,supercontinuum laser,Single photon detection,transition edge sensor
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Hyperspectral LiDAR with Eight Channels Covering from VIS to SWIR
摘要： Hyperspectral LiDAR (HSL) possesses the advantages of the LiDAR and the hyperspectral detection, and detects ranging and spectrum information synchronously, by one HSL system. The data fusion is also avoided. At present, the spectrum range of reported HSLs usually covers only 500 nm-1000 nm (from visual (VIS) to near infrared (NIR) band). However, there is requirement to extend the spectrum range to short wave infrared (SWIR) band, which often contains more useful spectral information. In this paper, a HSL covering the spectrum from VIS to SWIR is reported. In the HSL, the echoes are divided into two sections and are detected by the different optoelectronic devices, of which the spectral response ranges are respectively compatible to the corresponding echoes. The HSL detection experiment in the laboratory was carried out. The waveforms of the echoes were analyzed, and the spectra of different targets were measured by the HSL. The experiment results demonstrate the capability of the prototyped HSL that obtaining the ranging information and the spectrum information of the targets in VIS-SWIR bands synchronously.
关键词： remote sensing,SWIR,supercontinuum laser,hyperspectral LiDAR
更新于2025-09-09 09:28:46