Ultrahigh Spectral Resolution Research Articles

A VIPA spectrograph with ultra-high spectral resolution, ultra-high wavelength calibration accuracy and wide spectral range

Abstract Spectrographs with ultra-high spectral resolution, ultra-high wavelength calibration accuracy, and wide spectral range hold immense potential in broad scientific frontiers, such as precise spectral measurement, femtosecond pulse shaping, and spectral beam combining, etc. In this paper, we have constructed a virtually imaged phased array (VIPA) based spectrograph, leveraging a laser frequency comb for precise wavelength calibration. The calibration methods specifically for the broadband VIPA spectrograph are presented. The spectrograph achieves a resolution exceeding 650,000, a wavelength calibration accuracy better than 0.05 pm, and a remarkable bandwidth of over 110 nm. Spectral measurements are conducted with the spectrograph, and the results validate the performance.

Stray light analysis and suppression of a UV multiple sub-pupil ultra-spectral imager

A multiple sub-pupil ultra-spectral imager system for simultaneous detection of multiple substances is proposed. By employing pupil separation prisms and grating multilevel spectra, the system achieves simultaneous detection of three spectral channels with a single spectrometer and detector, featuring an ultra-high spectral resolution of 0.1 nm. However, due to simultaneous detection of three channels, the system suffers from significant stray light issues. In response to this problem, a UV multiple sub-pupil ultra-spectral imager system optical-machinery model is constructed in this article. The main sources of stray light are determined through theoretical derivation and simulation analysis, and the level of stray light in the system is analyzed using simulation analysis software. A structure for stray light suppression is optimized, and the use of multispectral filters is proposed to suppress stray light generated by spectral crosstalk in the system. The effectiveness of stray light suppression is evaluated based on the energy response of the receiving surface. The analysis results show that after optimization, the level of stray light in the T1 channel is reduced from 1.4% to 0.65‰, in the T2 channel from 3.0‰ to 0.5‰, and in the T3 channel from 0.16‰ to 0.05‰. Therefore, it can be concluded that the proposed method for stray light suppression in the UV multiple sub-pupil ultra-spectral imager system addressed in this article meets the indicator requirements.

Rydberg-Atom Terahertz Heterodyne Receiver with Ultrahigh Spectral Resolution

Abstract Terahertz heterodyne receivers with high sensitivity and spectral resolution are crucial for various applications. Here, we present a room-temperature atomic terahertz heterodyne receiver that achieves ultrahigh sensitivity and frequency resolution. At a signal frequency of 338.7 GHz, we obtain a sensitivity of 2.88 ± 0.09 μV⋅cm−1⋅Hz−1/2 for electric field measurements. The calibrated linear dynamical range spans approximately 89 dB, ranging from −110 dBV/cm to −21 dBV/cm. We demodulate a 400 symbol stream encoded in 4-state phase-shift keying, demonstrating excellent phase detection capability. By scanning the frequency of the local oscillator, we realize a terahertz spectrometer with Hz level frequency resolution. This resolution is more than two orders of magnitude higher than that of existing terahertz spectrometers. The demonstrated terahertz heterodyne receiver holds promising potential for working across the entire terahertz spectrum, significantly advancing its practical applications.

Cathodoluminescence emission and electron energy loss absorption from a 2D transition metal dichalcogenide in van der Waals heterostructures

Nanoscale variations of optical properties in transition metal dichalcogenide (TMD) monolayers can be explored with cathodoluminescence (CL) and electron energy loss spectroscopy (EELS) using electron microscopes. To increase the CL emission intensity from TMD monolayers, the MoSe2 flakes are encapsulated in hexagonal boron nitride (hBN), creating van der Waals (VdW) heterostructures. Until now, the studies have been exclusively focused on scanning transmission electron microscopy (STEM-CL) or scanning electron microscopy (SEM-CL), separately. Here, we present results, using both techniques on the same sample, thereby exploring a large acceleration voltage range. We correlate the CL measurements with STEM-EELS measurements acquired with different energy dispersions, to access both the low-loss region at ultra-high spectral resolution, and the core-loss region. This provides information about the weight of the various absorption phenomena including the direct TMD absorption, the hBN interband transitions, the hBN bulk plasmon, and the core losses of the atoms present in the heterostructure. The S(T)EM-CL measurements from the TMD monolayer only show emission from the A exciton. Combining the STEM-EELS and S(T)EM-CL measurements, we can reconstruct different decay pathways leading to the A exciton CL emission. The comparison with SEM-CL shows that this is also a good technique for TMD heterostructure characterization, where the reduced demands on sample preparation are appealing. To demonstrate the capabilities of SEM-CL imaging, we also measured on a SiO2/Si substrate, quintessential in the sample preparation of two-dimensional materials, which is electron-opaque and can only be measured in SEM-CL. The CL-emitting defects of SiO2 make this substrate challenging to use, but we demonstrate that this background can be suppressed by using lower electron energy.

Microplastic Analysis in Soil Using Ultra-High-Resolution UV–Vis–NIR Spectroscopy and Chemometric Modeling

The study of microplastics (MPs) in soils is impeded by similarities between plastic and non-plastic particles and the misidentification of MP by current analytical methods such as visual microscopic examination. Soil MPs pose serious ecological and public health risks because of their abundance, persistence, and ubiquity. Thus, reliable identification methods are badly needed for scientific study. One possible solution is UV–Vis–NIR spectroscopy, which has the ability to rapidly identify and quantify concentrations of soil microplastics. In this study, a full-range, field portable spectrometer (350–2500 nm) with ultra-high spectral resolution (1.5 nm, 3.0 nm, and 3.8 nm) identified three types of common plastics: low-density polyethylene (LDPE), polyvinyl chloride (PVC), and polypropylene (PP). Three sets of artificially MP-treated vermiculite soil samples were prepared for model prediction testing and validation: 150 samples for model calibration and 50 samples for model validation. A partial least square regression model using the spectral signatures for quantification of soil and MP mixtures was built with all three plastic polymers. Prediction R2 values of all three polymers showed promising results: polypropylene R2 = 0.943, polyvinyl chloride R2 = 0.983, and polyethylene R2 = 0.957. Our study supports previous work showing that combining ultra-high-resolution UV–Vis–NIR spectrometry with quantitative modeling can improve the accuracy and speed of MP identification and quantification in soil.

Quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy

The extension of dual-comb spectroscopy (DCS) to all wavelengths of light along with its ability to provide ultra-large dynamic range and ultra-high spectral resolution, renders it extremely useful for a diverse array of applications in physics, chemistry, atmospheric science, space science, as well as medical applications. In this work, we report on an innovative technique of quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy (QEMR-PAS), in which the beat frequency response from a dual comb is frequency down-converted into the audio frequency domain. In this way, gas molecules act as an optical-acoustic converter through the photoacoustic effect, generating heterodyne sound waves. Unlike conventional DCS, where the light wave is detected by a wavelength-dependent photoreceiver, QEMR-PAS employs a quartz tuning fork (QTF) as a high-Q sound transducer and works in conjunction with a phase-sensitive detector to extract the resonant sound component from the multiple heterodyne acoustic tones, resulting in a straightforward and low-cost hardware configuration. This novel QEMR-PAS technique enables wavelength-independent DCS detection for gas sensing, providing an unprecedented dynamic range of 63 dB, a remarkable spectral resolution of 43 MHz (or ~0.3 pm), and a prominent noise equivalent absorption of 5.99 × 10-6 cm-1·Hz-1/2.

Multi-Channel Hyperspectral Imaging Spectrometer Design for Ultraviolet Detection in the Atmosphere of Venus

The spectroscopic detection of SO2 and unknown UV absorber substance in the H2SO4 cloud layer of Venus’ atmosphere is currently a focal point in the study of the habitability of Venusian atmospheric clouds. This paper addresses the simultaneous detection requirements of multiple substances in the ultraviolet range of Venus’ atmosphere and proposes a multi-channel hyperspectral imaging system design using pupil separation prisms and grating multilevel spectra. The system achieves a multi-channel design by splitting the entrance pupil of the telescope using prisms. Spectra from different channels are diffracted to the same detector through different orders of the grating. The system features a single spectrometer and detector, enabling simultaneous detection of spectra from different channels. It also boasts advantages such as compact size, ultra-high spectral resolution, and simultaneous multi-channel detection. The system design results indicate that within the working spectral range of three channels, the spectral resolution is better than 0.15 nm, surpassing previous in-orbit or current in-orbit planetary atmospheric detection spectrometers. With a Nyquist frequency of 56 lp/mm, the full-field MTF exceeds 0.7. The system’s smile is less than 0.05 μm, and the keystone is less than 0.04 μm, meeting the requirements for imaging quality.

Design method for eliminating spectral line tilt in a multiple sub-pupil ultra-spectral imager (MSPUI).

A multiple sub-pupil ultra-spectral imaging system designed with a single spectrometer and detector can simultaneously detect multiple-channel spectra with ultra-high spectral resolution. However, due to using a prism in the system's front end, the nonlinear dispersion introduces spectral line tilt in the imaging spectra. This phenomenon can lead to bias in the final spectral data. To eliminate this issue, we propose a new design by introducing a second prism to correct this spectral tilt in the system. The angle of spectral line tilt generated by the nonlinear dispersion of the first prism is derived. It provides the theoretical basis for characterizing the second complementary prism. Finally, a UV multiple sub-pupil ultra-spectral imaging system is designed. The system employs two pupil separation prisms and one flat panel array to segment the pupil in three channels, each operating within spectral ranges of 180∼210 nm, 275∼305 nm, and 370∼400 nm, respectively. The spectral resolutions in all three channels are better than 0.1 nm. The corrected spectral line tilt is less than 1/3 of a pixel in the two channels with pupil separation prisms. At a Nyquist frequency of 30 lp/mm, the modulation transfer functions of all three channels are greater than 0.7, ensuring imaging quality. The design results indicate that the method proposed in this paper, utilizing complementary prisms, can effectively correct the spectral line tilt caused by the nonlinear dispersion of the pupil separation prisms. This design approach can be a reference for developing multiple sub-pupil ultra-spectral imaging systems.

Nanometer flat blazed x-ray gratings using ion beam figure correction.

With the development of nanometer accuracy stitching interferometry, ion beam figuring (IBF) of x-ray mirrors can now be achieved with unprecedented performance. However, the process of producing x-ray diffraction gratings on these surfaces may degrade the figure quality due to process errors introduced during the ruling of the grating grooves. To address this challenge, we have investigated the post-production correction of gratings using IBF, where stitching interferometry is used to provide in-process feedback. A concern with ion beam correction in this case is that ions will induce enough surface mobility of atoms to cause smoothing of the grating structure and degradation of diffraction efficiency. In this study we found however that it is possible to achieve a nanometer-level planarity of the global grating surface with IBF, while preserving the grating structure. The preservation was so good, that we could not detect a change in the diffraction efficiency after ion beam correction. This is of major importance in achieving ultra-high spectral resolution, and the preservation of brightness for coherent x-ray beams.

First on-sky results of a Fabry–Perot Instrument for Oxygen Searches (FIOS) prototype

Context. The upcoming Extremely Large Telescopes (ELTs) are expected to have a sufficient collecting area required to detect potential biosignature gases such as molecular oxygen, O2, in the atmosphere of terrestrial planets around nearby stars. Aims. One of the most promising detection methods is transmission spectroscopy. To maximize our capability to detect O2 using this method, spectral resolutions R ≥ 300 000 are required to fully resolve the absorption lines in an Earth-like exoplanet atmosphere and disentangle the signal from telluric lines. Methods. Current high-resolution spectrographs typically achieve a spectral resolution of R ~ 100 000. Increasing the resolution in seeing limited observations and/or instruments requires drastically larger optical components, making these instruments even more expensive and hard to fabricate and assemble. Instead, we demonstrate a new approach to high-resolution spectroscopy. We implemented an ultra-high spectral resolution booster to be coupled to a high-resolution spectrograph. The instrument is based on a chained Fabry-Perot array which generates a hyperfine spectral profile. Results. We present on-sky telluric observations with a lab demonstrator. Depending on the configuration, this two-arm prototype reaches a resolution of R = 250 000–350 000. After carefully modeling the prototype’s behavior, we propose a Fabry-Perot Interferometer (FPI) design for an eight-arm array configuration aimed at ELTs capable of exceeding R = 300 000. Conclusions. The novel FPI resolution booster can be plugged in at the front end of an existing R = 100 000 spectrograph to overwrite the spectral profile with a higher resolution for exoplanet atmosphere studies.

Optical spectrum analyzers and typical applications in astronomy and remote sensing.

Scientists are increasingly relying on astronomical and remote sensing technologies to gain deeper insights into the Earth and the universe. In these fields, the optical spectrum analyzer (OSA) or spectrometer plays a pivotal role. This Review offers a comprehensive overview of the fundamental principles, key parameters, and applications of various branches of traditional OSAs, including prisms, gratings, interferometers, tunable filters, and reconstructive spectrometers. We specifically focus on their latest major applications in astronomy and remote sensing. Additionally, we present a mathematical model of the generalized reconstructive spectrometer and provide a summary of its principles pertaining to spectral mapping, reconstruction, and imaging. Despite its limited aperture and étendue, the reconstructive spectrometer holds great potential for future use in astronomy and remote sensing due to its compact size and exceptional ultrahigh spectral resolution.

Ultra-Narrow Bandwidth Microwave Photonic Filter Implemented by Single Longitudinal Mode Parity Time Symmetry Brillouin Fiber Laser.

In this paper, a novel microwave photonic filter (MPF) based on a single longitudinal mode Brillouin laser achieved by parity time (PT) symmetry mode selection is proposed, and its unparalleled ultra-narrow bandwidth as low as to sub-kHz together with simple and agile tuning performance is experimentally verified. The Brillouin fiber laser ring resonator is cascaded with a PT symmetric system to achieve this MPF. Wherein, the Brillouin laser resonator is excited by a 5 km single mode fiber to generate Brillouin gain, and the PT symmetric system is configured with Polarization Beam Splitter (PBS) and polarization controller (PC) to achieve PT symmetry. Thanks to the significant enhancement of the gain difference between the main mode and the edge mode when the polarization state PT symmetry system breaks, a single mode oscillating Brillouin laser is generated. Through the selective amplification of sideband modulated signals by ultra-narrow linewidth Brillouin single mode laser gain, the MPF with ultra-narrow single passband performance is obtained. By simply tuning the central wavelength of the stimulated Brillouin scattering (SBS) pumped laser to adjust the Brillouin oscillation frequency, the gain position of the Brillouin laser can be shifted, thereby achieving flexible tunability. The experimental results indicate that the MPF proposed in this paper achieves a single pass band narrow to 72 Hz and the side mode rejection ratio of more than 18 dB, with a center frequency tuning range of 0-20 GHz in the testing range of vector network analysis, which means that the MPF possesses ultra high spectral resolution and enormous potential application value in the domain of ultra fine microwave spectrum filtering such as radar imaging and electronic countermeasures.

Dispersion Characteristics of the Multi-mode Fiber-fed VIPA Spectrograph

A high-resolution (), multi-mode fiber-fed spectrograph on large telescopes with a reasonable size is desirable in astronomy. In this work, the dispersion characteristics of a multi-mode fiber-fed Virtually Imaged Phased Array (VIPA) spectrograph are studied theoretically and experimentally. A VIPA spectrograph, fed by multi-mode optical fibers with the operating wavelength at 750 ∼ 770 nm, is designed and built in our laboratory. After calibration with a homemade Yb:fiber ring laser frequency comb (with a repetition frequency of 808 MHz), the measured spectral resolution fed by multi-mode fibers with core diameters , 25, 50, and 105 μm is comparable with that of the single-mode fiber, i.e., , with equivalent transmission efficiencies. This verifies experimentally that the spectral resolution is much less affected by the core diameters of the input fibers when compared with that of échelle spectrographs. It is also found that the diffraction envelope of the VIPA spectrograph relies on the coherence of light sources and the width of the point-spread function is inversely proportional to the spatial position on the detector. Since the VIPA spectrograph has no imaging process in the main dispersion direction, the spectral resolution is insensitive to the width of the input slit or the fiber diameter. This makes the VIPA spectrograph a promising instrument to attain an ultra-high spectral resolution () on very large telescopes.

Nonlinearity Correction of Fourier Transform Spectrometer in Solar Observation Using Simulated Annealing

A Fourier transform spectrometer (FTS) has been used to observe solar activities due to its ultra-high spectral resolution. However, the FTS in-band spectra are usually distorted and some artifacts appear in out-of-band regions due to nonlinear effects. Therefore, the FTS nonlinear problem must be corrected. In this study, we proposed a novel method to correct the nonlinear effects using simulated annealing. We simulated several nonlinear spectra to evaluate the performance of our method. The calculated quadratic coefficients are extremely close to the given values, demonstrating that the method is effective and accurate. The proposed method is further used to correct the blackbody and solar spectra with nonlinearity obtained by Bruker IFS-125HR installed at the Huairou Solar Observing Station, which is a pathfinder for the accurate infrared magnetic field measurements of the Sun project. To the blackbody spectra, the nonlinearity in low- and high-frequency regions are corrected by 89.09% and 60.84%. The nonlinear correction of the solar spectra in the low- and high-frequency regions have reached 65.34% and 81.04%, respectively. These results prove that our method can correct the nonlinear problem to improve the data accuracy.

Stratospheric Temperature Observations by Narrow Bands Ultra-High Spectral Resolution Sounder from Nadir-Viewing Satellites

Accurate stratospheric temperature observations are crucial for weather forecasts and climate change studies. This paper discusses a precise measurement method for the stratospheric temperature profile using narrow bands with ultra-high spectral resolution from nadir-viewing satellites. First, the CO2 absorption band around 15 μm is selected as the major sounding source by the calculation and analysis of the temperature Jacobian and the atmospheric molecular spectra. Next, the influence of spectral resolution, spectral range and instrumental noise on the sounding capability is analyzed, and the sounding feasibility of the single spectral band and multiple spectral bands is discussed under the condition that the spaceborne long-wave infrared space heterodyne spectrometer (SHS) is selected as suggested sounder onboard the satellite. Finally, the optimal joint-sounding scheme of narrow bands is proposed. The temperature retrieval and validation show that the joint-sounding of two discontinuous narrow bands can realize the high precision measurement of the stratospheric temperature profile for the given spectral resolution, spectral range, and instrumental noise. When the sounder adopts two narrow bands (the regions of 666.87–676.44 cm−1 and 683.58–693.15 cm−1) and a spectral resolution of 0.03 cm−1, the retrieval accuracy (RMSE) is about 0.9 K over a pressure range of 200 to 0.7 hPa (11.5–50 km). This study will provide technical preparation for high-precision and low-cost satellite sounder design for stratospheric temperature observations.

Sine-Cosine Techniques for Detecting Fast Optical Frequency Variations With Ultra-High Resolution

We introduce the concept of sine-cosine optical frequency detection (OFD) for measuring fast optical frequency variations with the ultra-high spectral resolution for applications requiring rapidly tunable or low frequency-jitter lasers, including coherent detection based distributed sensing and communication systems and tunable diode laser spectroscopy (TDLS) systems, for which conventional spectral measurement techniques cannot meet the speed and spectral resolution requirements. The concept relies on representing the frequency-dependent differential phase of the laser light passing through two different optical paths as sine and cosine functions to calculate the optical frequency, similar to the sine-cosine encoder concept commonly used for obtaining the rotation information of a motor, which can simultaneously achieve both high spectral resolution and wide frequency range without mutual constraints. We present multiple schemes, some are seemingly very different, for implementing the concept and demonstrate that all frequency-related parameters of a tunable light source, including frequency tuning rate, nonlinearity, ripple, range, duty cycle, repeatability, and power swing can be precisely characterized. In addition, the frequency jitter of a fixed narrow line-width laser can also be accurately measured. Ultra-fast optical frequency sweep with a rate in excess of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> nm/s and a resolution down to MHz is demonstrated with a differential delay of only 0.8 mm, suggesting that the concept is feasible to be implemented with photonic integrated circuit (PIC). Our work is attractive for applications such as coherent distributed sensing (OCT, OFDR and FMCW lidar), coherent detection, FBG sensing interrogation and TDLS, especially considering that some schemes can be integrated on PIC chips.

Анализ изменений природно-антропогенной трансформации береговой линии Азербайджанского сектора Каспийского моря

The aim of the research was to analyze changes in natural and anthropogenic transformations of the coastal territory of the Caspian Sea. For this, the possibility of using images with a spatial resolution of up to 10 m, obtained by superimposing channels with ultra-high spectral resolution (20 m and 60 m) was studied to obtain the maximum amount of information about the surface.Climate change, sea level rise significantly change the physical condition of the coastal area. During the active transregression and then regression, the coastal territory has changed over the past 50 years. The flooded coastal area (more than 540 sq. km) is an alluvial plain of marine origin. Space monitoring research is relevant for the sustainable development of the coastal territory and environmental protection of these regions. The article presents the results of using different-time space data and images of remote sensing of the Earth obtained by different survey systems. The results of the research can contribute to improving the development of coastal ecosystem engineering, as well as socio-ecological research based on a systematic approach.

Design Study of Broadband and Ultrahigh-Resolution Imaging Spectrometer Using Snapshot Multimode Interference in Fiber Bundles

Imaging spectrometry plays a significant role in various scientific realms. Although imaging spectrometers based on different schemes have been proposed, the pursuit of compact and high-performance devices is still ongoing. A compact broadband and ultrahigh-resolution imaging spectrometer (CBURIS) is presented, which comprises a microlens array, multiple fiber bundles, a microscope, and a two-dimensional detector array. The principle of the device is to spatially sample and integrate the field information via the front microlens array and then further process with the fiber bundles and imaging system based on the multimode interference theory. From both the theoretical and numerical analysis, this CBURIS design is a superior concept that not only achieves a 0.17° spatial resolution and ultrahigh spectral resolution (resolving power exceeds 2.58 × 106 at 1.55 µm) from the visible to mid-infrared region but also has the advantages of snapshot measurement, thermal stability, and a compact footprint compared with most existing imaging spectrometers.

HiRISE - High-Resolution Imaging and Spectroscopy Explorer - Ultrahigh resolution, interferometric and external occulting coronagraphic science

Recent solar physics missions have shown the definite role of waves and magnetic fields deep in the inner corona, at the chromosphere-corona interface, where dramatic and physically dominant changes occur. HiRISE (High Resolution Imaging and Spectroscopy Explorer), the ambitious new generation ultra-high resolution, interferometric, and coronagraphic, solar physics mission, proposed in response to the ESA Voyage 2050 Call, would address these issues and provide the best-ever and most complete solar observatory, capable of ultra-high spatial, spectral, and temporal resolution observations of the solar atmosphere, from the photosphere to the corona, and of new insights of the solar interior from the core to the photosphere. HiRISE, at the L1 Lagrangian point, would provide meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, magnetic fields measurements, and ambitious and comprehensive coronagraphy by a remote external occulter (two satellites formation flying 375 m apart, with a coronagraph on a chaser satellite). This major and state-of-the-art payload would allow us to characterize temperatures, densities, and velocities in the solar upper chromosphere, transition zone, and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, and, direct coronal magnetic field measurement, thus providing a unique set of tools to understand the structure and onset of coronal heating. HiRISE’s objectives are natural complements to the Parker Solar Probe and Solar Orbiter-type missions. We present the science case for HiRISE which will address: i) the fine structure of the chromosphere-corona interface by 2D spectroscopy in FUV at very high resolution; ii) coronal heating roots in the inner corona by ambitious externally-occulted coronagraphy; iii) resolved and global helioseismology thanks to continuity and stability of observing at the L1 Lagrange point; and iv) solar variability and space climate with, in addition, a global comprehensive view of UV variability.

An Enhanced Photonic-Assisted Sampling Approach for Spectrum-Sparse Signal by Compressed Sensing

Spectrum-sparse signals are vital for wideband radars and wireless communication applications. A high-speed analog-to-digital converter (ADC) with the capacities of tens of gigahertz sampling rates is often required to acquire these signals. In this work, an enhanced photonic-assisted sampling approach with the combination of the photonic-assisted time-interleaved ADC and compressed sensing techniques is presented, which enables the measured signal to be reconstructed through very few samples by utilizing the sparsity of the spectrum-spare signal. An ultrahigh spectral resolution Fourier dictionary is introduced to suppress the spectrum leakage and obtain the actual sparse expression of the spectrum-sparse signals. Moreover, a layered tracking orthogonal matching pursuit signal recovery algorithm is employed to reduce computational complexity and enhance processing speed. The performance of the proposed approach has been investigated via simulations and laboratory experiments by varying the applied spectrum-sparse signals over 100 times. The experimental result demonstrated that the proposed approach can capture the blind-frequency spectrum-sparse signal at the equivalent sampling rate of 1 GS/s by utilizing four parallel ADCs with a sampling rate of 50 MS/s. It is proven that the proposed approach achieves ~5 times higher equivalent sampling rate than the conventional PTIADC at the same sampling rate. This work provides a useful method for the acquisition of spectrum sparse signals in practical applications.