arXiv subjects

Heping Zeng

Publications and source records attributed to Heping Zeng.

At least 37 records · Page 2Linked to original sources

arXiv2026

High-precision passive stabilization of repetition rate for a mode-locked fiber laser based on optical pulse injection

We have proposed and implemented a novel scheme to obtain high-precision repetition rate stabilization for a polarization-maintaining mode-locked fiber laser. The essential technique lies in the periodic injection of electronically modulated optical pulses into a nonlinear amplifying loop mirror within the laser resonator. Thanks to the nonlinear cross-phase modulation effect, the injected pulses referenced to an external clock serves as a stable and precise timing trigger for an effective intensity modulator. Consequently, synchronous mode-locking can be initiated to output ultrafast pulses with a passively stabilized repetition rate. The capture range of the locking system reaches to a record of 1 mm, which enables a long-term stable operation over 15 hours without the need of temperature stabilization and vibration isolation. Meanwhile, the achieved standard deviation is as low as 100 $μ$Hz with a 1-s sample time, corresponding to a fluctuation instability of 5.0$\times10^{-12}$. Additionally, the repetition rate stabilization performance based on the passive synchronization has been systematically investigated by varying the average power, central wavelength and pulse duration of the optical injection.

physics.optics↗

arXiv2026

High-speed mid-infrared single-photon upconversion spectrometer

Sensitive and fast mid-infrared (MIR) spectroscopy is highly attractive in a variety of applications including astronomical observation, pharmaceutical synthesis, and environmental monitoring. However, the performance of conventional MIR spectrometers has long been hindered by the limited sensitivity of narrow-bandgap detectors and/or the deficient brightness of broadband light sources. Here, we devise and implement an ultra-sensitive and broadband MIR upconversion spectrometer, which integrates a supercontinuum source covering 1.5-4.2 $μ$m based on a silicon nitride nanophotonic waveguide. High-efficiency and low-noise nonlinear frequency upconversion is realized based on coincidence pulsed pumping with spectro-temporal optimization, which enables to leverage silicon detectors for facilitating MIR single-photon spectroscopy at 0.2 photons/nm/pulse. Furthermore, the upconversion-based array spectrometer is manifested with high-speed spectral acquisition rates beyond 200 kHz, which is about ten-fold faster than the state-of-the-art scan rates for FTIR-based spectrometers at a comparable spectral resolution. The achieved features of broadband spectral coverage, single-photon sensitivity, and sub-MHz refreshing rate might open up new possibilities in infrared transient spectral measurements in combustion analysis, high-throughput sorting and reaction tracking, among others.

physics.optics↗

arXiv2026

Mid-infrared single-photon 3D imaging

Active mid-infrared (MIR) imagers capable of retrieving three-dimensional (3D) structure and reflectivity information are highly attractive in a wide range of biomedical and industrial applications. However, the infrared 3D imaging at low-light levels is still challenging due to the deficiency of sensitive and fast MIR sensors. Here we propose and implement a MIR time-of-flight imaging system that operates at single-photon sensitivity and femtosecond timing resolution. Specifically, back-scattered infrared photons from a scene are optically gated by delay-controlled ultrashort pump pulses through nonlinear frequency upconversion. The upconverted images with time stamps are then recorded by a silicon camera to facilitate the 3D reconstruction with high lateral and depth resolutions. Moreover, an effective numerical denoiser based on spatiotemporal correlation allows us to reveal the object profile and reflectivity under photon-starving conditions with a detected flux below 0.05 photons/pixel/second. The presented MIR 3D imager features with high detection sensitivity, precise timing resolution, and wide-field operation, which may open new possibilities in life and material sciences.

physics.optics↗

arXiv2026

Mid-infrared single-pixel imaging at the single-photon level

Single-pixel cameras have recently emerged as promising alternatives to multi-pixel sensors due to reduced costs and superior durability, which are particularly attractive for mid-infrared (MIR) imaging pertinent to applications including industry inspection and biomedical diagnosis. To date, MIR single-pixel photon-sparse imaging has yet been realized, which urgently calls for high-sensitivity optical detectors and high-fidelity spatial modulators. Here, we demonstrate a MIR single-photon computational imaging with a single-element silicon detector. The underlying methodology relies on nonlinear structured detection, where the encoded time-varying pump patterns are optically imprinted onto the MIR object image through sum-frequency generation. Simultaneously, the MIR radiation is spectrally translated into the visible region, thus permitting infrared single-photon upconversion detection. Then, the use of advanced algorithms of compress sensing and deep learning allows us to reconstruct MIR images under sub-Nyquist sampling and photon-starving illumination. The presented paradigm of single-pixel upconversion imaging is featured with single-pixel simplicity, single-photon sensitivity, and room-temperature operation, which would establish a new path for sensitive imaging at longer infrared wavelengths or terahertz frequencies, where high-sensitivity photon counters and high-fidelity spatial modulators are typically hard to access.

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arXiv2026

Single-photon time-stretch infrared spectroscopy

Sensitive mid-infrared (MIR) spectroscopy is highly demanded in various fields ranging from industrial inspection, biomedical diagnosis to astronomical observation. However, the detection sensitivity of conventional MIR spectrometers has been severely limited by excessive noises for existing infrared sensors, which hinders widespread use in photon-scarce scenarios. Here, we devise and implement a broadband MIR single-photon time-stretch spectrometer based on high-fidelity spectral upconversion and time-correlated coincidence counting. Specifically, a nanophotonic supercontinuum illumination covering 2.4-4.2 $μ$m is nonlinearly converted to the near-infrared band, where low-loss single-mode fiber and high-performance silicon detector can be leveraged to facilitate dispersive operation and sensitive detection, respectively. The arrival time for the dispersed upconversion photons is precisely registered with a low-timing-jitter photon counter, which enables us to obtain a high spectral resolution about 0.5 cm$^{-1}$ under a low-light-level illumination down to 0.14 photons/nm/pulse. In comparison to previous MIR upconversion spectrometers, the presented time-stretch architecture favors single-pixel simplicity and high-throughput acquisition for the single-photon spectral measurement. The achieved MIR spectroscopic features of broadband spectral coverage, sub-wavenumber resolution, single-photon sensitivity, and room-temperature operation would stimulate immediate applications in material and life sciences.

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arXiv2026

Wide-field mid-infrared hyperspectral imaging beyond video rate

Mid-infrared hyperspectral imaging has become an indispensable tool to spatially resolve chemical information in a wide variety of samples. However, acquiring three-dimensional data cubes is typically time-consuming due to the limited speed of raster scanning or wavelength tuning, which impedes real-time visualization with high spatial definition across broad spectral bands. Here, we devise and implement a high-speed, wide-field mid-infrared hyperspectral imaging system relying on broadband parametric upconversion of high-brightness supercontinuum illumination at the Fourier plane. The upconverted replica is spectrally decomposed by a rapid acousto-optic tunable filter, which records high-definition monochromatic images at a frame rate of 10 kHz based on a megapixel silicon camera. Consequently, the hyperspectral imager allows us to acquire 100 spectral bands over 2600-4085 cm$^{-1}$ in 10 ms, corresponding to a refreshing rate of 100 Hz. Moreover, the angular dependence of phase matching in the image upconversion is leveraged to realize snapshot operation with spatial multiplexing for multiple spectral channels, which may further boost the spectral imaging rate. The high acquisition rate, wide-field operation, and broadband spectral coverage could open new possibilities for high-throughput characterization of transient processes in material and life sciences.

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arXiv2026

Highly-sensitive mid-infrared upconversion detection based on external-cavity pump enhancement

Sensitive mid-infrared (MIR) detection is highly demanded in various applications, ranging from remote sensing, infrared surveillance, environmental monitoring to industrial inspection. Among others, upconversion infrared detectors have recently attracted increasing attention due to the advantageous features of high sensitivity, fast response, and room-temperature operation. However, it remains challenging to realize high-performance passive MIR sensing due to the stringent requirement of high-power continuous-wave pumping. Here, we propose and implement a high-efficiency and low-noise MIR upconversion detection system based on pumping enhancement via a low-loss optical cavity. Specifically, a single-longitudinal-mode pump at 1064 nm is significantly enhanced by a factor of 36, thus allowing for a peak conversion efficiency of up to 22\% at an intra-cavity average power of 55 W. The corresponding noise equivalent power is achieved as low as 0.3 fW/Hz$^{1/2}$, which indicates at least a ten-fold improvement over previous results. Notably, the involved single-frequency pumping would facilitate high-fidelity spectral mapping, which is particularly attractive for high-precision MIR upconversion spectroscopy in photon-starved scenarios.

physics.optics↗

arXiv2026

Mid-Infrared Single-Photon Compressive Spectroscopy

Sensitive mid-infrared (MIR) spectroscopy plays an indispensable role in various photon-starved conditions. However, the detection sensitivity of conventional MIR spectrometers is severely limited by excessive noises of the involved infrared sensors, especially for multi-pixel arrays in parallel spectral acquisition. Here, we devise and implement an ultra-sensitive MIR single-pixel spectrometer, which relies on high-fidelity spectral upconversion and wavelength-encoding compressive measurement. Specifically, a MIR nanophotonic supercontinuum from 3.1 to 3.9 $μ$m is nonlinearly converted to the near-infrared band via synchronous chirped-pulse pumping, which facilitates both the precise spectral mapping and sensitive upconversion detection. The upconverted signal is then spatially dispersed onto a programmable digital micromirror device, before being registered by a single-element silicon detector. Consequently, the spectral information can be deciphered from the correlation between encoded patterns and recorded measurements, which results in a spectral resolution of 0.5 cm$^{-1}$ under an illumination flux down to 0.01 photons/nm/pulse. Moreover, we demonstrate faithful reconstructions at sub-Nyquist sampling rates by using the compressive sensing algorithm, which leads to a 95\% reduction in data acquisition time. The presented single-pixel computational spectrometer features wavelength multiplexing, high throughput, and efficient sampling, which thus paves a new way for sensitive and fast spectroscopic analysis at the single-photon level.

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arXiv2026

High-speed mid-infrared imaging via nonlinear multiplexed detection

High-speed mid-infrared (MIR) videography constitutes an enabling tool to monitor and analyze various dynamics in scientific research and industrial applications, such as combustion diagnostics, explosion reactions, photosynthetic tracking, and thermal surveillance. However, the frame rate of conventional MIR imagers is typically limited by readout electronics and detection sensitivity, especially for large spatial formats with massive pixels. Here, we devise and implement a high-speed MIR upconversion imaging system based on time-multiplexed nonlinear structured pumping. Specifically, the dynamic infrared scene is optically gated by a sequence of spatially periodical pump patterns in a nonlinear crystal, which facilitates both rapid temporal encryption and sensitive upconversion detection. Then, the upconverted frames are superimposed onto a silicon camera within a single exposure, thus resulting in a multiplexed snapshot in the spatial-frequency domain. Finally, the sub-exposure images, corresponding to distinct transient events, can be computationally deciphered and reconstructed by the frequency recognition algorithm based on band-pass filtering and Fourier transform operations. The achieved frame rate is tenfold boosted to 10,000 frames per second without compromising the megapixel spatial format, which allows continuous real-time MIR videography at high speed and high definition. The presented approach could be readily extended to far-infrared or terahertz spectral regions, with an aim of performing high-throughput and high-sensitivity observation of transient phenomena with high temporal complexity.

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arXiv2026

Mid-infrared edge-enhanced imaging via angle-selective nonlinear filtering

Mid-infrared reconfigurable edge-enhanced imaging is highly demanded in sensing and vision fields. Here, we propose a novel scheme for mid-infrared upconversion imaging with high tunability between bright-field and edge-enhanced modalities. The involved engineering of the nonlinear process favors shaping the optical transfer function of the imaging system. Consequently, a nonlinear angle-selective filter can be configured to perform an all-optical Fourier processing of the image, which highly depends on phase-matching parameters. We numerically demonstrate the ability to switch modalities between the bright-field and edge-enhanced imaging by tuning the crystal temperature, and to simultaneously acquire both information by dichromatic illumination. Notably, the achieved reconfigurability is realized without changing the imaging settings, which contrasts to previous instantiations based on pump adaptation. Therefore, the proposed architecture of upconversion imagers would pave a novel way to implement layout-compact and all-optical processing for infrared images.

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arXiv2026

Mid-infrared Fourier ptychographic upconversion imaging

Frequency upconversion technique offers an appealing approach for sensitive mid-infrared (MIR) imaging at room temperature. However, the spatial resolution of the upconversion imager has been notoriously restricted by the limited transverse section of the involved nonlinear crystal at the Fourier plane. Here, we implement a wide-field and high-resolution MIR upconversion imaging system based on elliptical pumping and Fourier ptychography. Specifically, an elliptical pump beam is engineered to accommodate the narrow aperture of chirped-poling crystals, thus facilitating the acquisition of high spatial frequency components in the lateral direction. Such an elliptical passband in the Fourier space is then discretely rotated to generate a sequence of upconversion images, which allows computational recovery of a high-resolution object image through a combination of synthetic aperture and phase retrieval operations. Consequently, an enhanced spatial resolution of 39 $μ$m is achieved within a field of view about 25 mm, which corresponds to a space-bandwidth product of 3.2$\times$10$^5$, over tenfold larger than previously demonstrated values. Moreover, the MIR upconversion imager can operate under a low-light illumination of 1 photon/pulse/pixel. Therefore, the presented paradigm of nonlinear Fourier ptychography paves the way toward high-throughput infrared imaging with massive resolvable elements and single-photon sensitivity, which would stimulate a variety of applications such as industry inspection and biomedical diagnosis.

physics.optics↗

arXiv2026

High-resolution mid-infrared single-photon upconversion ranging

Single-photon laser ranging has widespread applications in remote sensing and target recognition. However, highly-sensitive light detection and ranging (LiDAR) has long been restricted in visible or near-infrared bands. An appealing quest is to extend the operation wavelength into the mid-infrared (MIR) region, which calls for an infrared photon counting system at high detection sensitivity and precise temporal resolution. Here, we devise and demonstrate a MIR upconversion LiDAR based on nonlinear asynchronous optical sampling. Specifically, the infrared probe is interrogated in a nonlinear crystal by a train of pump pulses at a slightly different repetition rate, which favors for a temporal optical scanning at a picosecond timing resolution and a kilohertz refreshing rate over $\sim$50 ns. Moreover, the cross-correlation upconversion trace is temporally stretched by a factor of 2$\times$10$^4$, which can thus be recorded by a low-bandwidth silicon detector. In combination with time-correlated photon-counting technique, the achieved effective resolution is about two orders of magnitude better than the timing jitter of the detector itself, which facilitates a ranging precision of 4 $μ$m under a low detected flux of 8$\times$10$^{-5}$ photons per pulse. The presented MIR time-of-flight range finder is featured with single-photon sensitivity and high positioning resolution, which would be particularly useful in infrared sensing and imaging in photon-starved scenarios.

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arXiv2026

Widely tunable mid-infrared fiber-feedback optical parametric oscillator

Synchronously pumped optical parametric oscillators (OPOs) provide uniquely versatile platforms to generate ultrafast mid-infrared pulses within a spectral range beyond the access of conventional mode-locked lasers. However, conventional OPO sources based on bulk crystals have been plagued by complex optical alignment and large physical footprint. Here, we devise and implement two OPO variants based on a polarization-maintaining fiber-feedback cavity, which allow to robustly deliver sub-picosecond MIR pulses without the need of active stabilization. The first one integrates an erbium-doped fiber into the OPO cavity as the additional gain medium, which significantly reduces the pump threshold and allows stable optical pulse formation within a spectral range of 1553-1586 nm. The second one adopts a chirped poling nonlinear crystal in a passive-fiber cavity to further extend the operation spectral coverage, which facilitates broad tuning ranges of 1350-1768 nm and 2450-4450 nm for the signal and idler bands, respectively. Therefore, the presented mid-infrared OPO source is featured with high compactness, robust operation, and wide tunability, which would be attractive for subsequent applications such as infrared photonics, biomedical examination, and molecular spectroscopy.

physics.optics↗

arXiv2026

Mid-infrared single-photon computational temporal ghost imaging

The capture of transient optical waveforms is critical to reveal dynamical phenomena in various fields. However, fast and sensitive mid-infrared (MIR) measurements are typically limited by processing bandwidth and detection sensitivity of conventional infrared detectors. Here, we propose and implement a computational temporal ghost imaging system, which favors high-speed and high-sensitivity characterization of MIR temporal objects. The core process relies on high-fidelity nonlinear optical transduction for facilitating both the programmable structured illumination and frequency upconversion detection based on the high-performance near-infrared light modulator and detector, respectively. Consequently, the correlation between the recorded integral upconversion intensity and the designated encoding patterns allows one to reconstruct the MIR profiles with a temporal resolution of 80 ps, well beyond the intrinsic bandwidth or timing jitter of the involved detectors. Moreover, a record-high detection sensitivity is manifested by recovering single-photon MIR waveforms with an incident flux below 0.1 photon/bit. Additionally, faithful reconstructions at sub-Nyquist sampling rates are demonstrated using the compressive sensing algorithm, which can reduce the data acquisition time by over 90\%. The presented paradigm features high timing precision, single-photon sensitivity, and efficient data sampling, which could be extended into far-infrared or terahertz regions to address pressing demands in fast and sensitive sensing.

physics.optics↗

arXiv2026

Infrared Single-Pixel Hyperspectral Imaging via Spatial-Temporal Multiplexing

Near-infrared (NIR) hyperspectral imaging is widely used to reveal morphological and chemical information. However, conventional spectral imagers usually rely on costly focal plane arrays and suffer from data redundancy and inefficiencies in spatial-spectral data acquisition. Here, we devise and implement a single-pixel NIR hyperspectral imaging system based on high-fidelity spectrum-to-time mapping and high-precision spatial-encoding compressive measurements. The system employs a single-mode telecommunication fiber for temporal dispersion and a programmable spatial light modulator to impose structured spatial patterns, with all signals detected by a single InGaAs photodetector. By correlating temporally stretched waveforms with spatial encodings, we reconstruct 64$\times$64 spatially resolved hyperspectral datacubes spanning 50 spectral bands over the 1550-1600 nm range. Furthermore, real-time monitoring of dynamic liquid injection is demonstrated at a datacube refreshing rate of 12 Hz under sub-Nyquist sampling. The presented architecture features single-pixel simplicity, high optical throughput, and efficient data acquisition, which would pave a novel way for NIR spectral imaging in biomedical diagnostics and material characterization.

physics.optics↗

arXiv2026

Wide-field mid-infrared cavity-enhanced upconversion imaging

Mid-infrared (MIR) spectral imaging enables precise target identification and analysis by capturing rich chemical fingerprints, which calls for high-sensitivity broadband MIR imagers at room temperature. Here, we devise and implement a continuous-wave pumping MIR upconversion imaging system based on external-cavity enhancement, which favors a large field of view, a low cavity loss, and a high spectral resolution. The involved optical cavity is constructed in an integrated fashion by utilizing one crystal facet as a cavity mirror, which allows a 43-fold power enhancement for the single-longitudinal-mode pump at 1064 nm. In combination with the chirped-poled crystal design, high-fidelity and wide-field spectral imaging mapping is permitted to facilitate an acceptance angle up to 28.5$^\circ$ over a spectral coverage of 2.5--5 $μ$m. Moreover, a thermal locking approach is used to stabilize the cavity at the high-power operation, eliminating active feedback and ensuring long-term stability. A proof-of-principle demonstration is presented to showcase real-time observation of CO$_{2}$ gas injection dynamics. The implemented MIR upconversion imager features wide-field operation, high detection sensitivity, and compact footprint, which would benefit subsequent applications including environment monitoring, gas leakage inspection, and medical diagnostics.

physics.optics↗

arXiv2026

Mid-infrared single-pixel imaging via two-photon optical encoding

Mid-infrared (MIR) imaging offers powerful capabilities for label-free chemical analysis, yet its practical deployment remains hindered by the high cost and cryogenic complexity of conventional cameras. Two-photon absorption (TPA) provides a promising route to room-temperature MIR detection, but existing TPA imagers based on raster scanning or array detectors are constrained by slow acquisition speed or limited detection sensitivity. Here we present a scanning-free MIR single-pixel imaging approach based on non-degenerate TPA in a silicon detector. The involved spatial encoding is realized by a near-infrared structured pump with a resolution of 7 $μ$m, thus allowing high-fidelity MIR optical modulation through the phase-matching-free nonlinear interaction. Consequently, the spatially modulated TPA response is intrinsically integrated in the single-element photodetector, which favors computational reconstruction of the impinging MIR image by correlating measured intensities and predetermined patterns. Notably, the use of advanced algorithms of compressed sensing and deep learning facilitate image recovery under sub-Nyquist sampling with a compression ratio of 10\% and photon-starved illumination with an incident light flux of 0.5 pJ/pulse. Furthermore, a multispectral imaging over 2.5-3.8 $μ$m is manifested for chemical discrimination of plastic films. The presented architecture would offer a broadband and sensitive alternative for MIR imaging in various fields ranging from biomedical diagnostics to material inspection.

physics.optics↗

arXiv2026

Mid-infrared nonlinear pinhole imaging

Pinhole imaging is the most primitive and simplest lensless imaging paradigm, capable of transcending the physical limitations of conventional lens optics. This modality is particularly attractive for accessing a virtually infinite depth of focus or operating at extreme wavelengths. Here, we devise and implement a mid-infrared (MIR) pinhole imaging system at 3.07 $μ$m based on nonlinear spatial filtering. Instead of using a physical aperture, the involved pinhole is optically formed by a near-infrared pump at 1.03 $μ$m within a nonlinear crystal, which allows flexible and precise control over the effective aperture size to optimize imaging performance. Meanwhile, the MIR rays passing through the nonlinear pinhole are spectrally upconverted to facilitate sensitive imaging via a silicon camera. Consequently, the implemented upconversion pinhole imaging enables a large depth of field over 35 cm, beyond the reach of typical lens-based upconversion imagers. Furthermore, depth-resolving imaging across a large depth range is demonstrated in both the reflection and transmission modes based on time-of-flight and trigonometric techniques, respectively. The achieved capabilities -- featuring large operation depth, wide field of view, and flexible adaptability to various illumination conditions -- highlight the potential of the presented MIR imaging architecture for expansive scene detection and motion-aware applications in industrial inspection and night vision.

physics.optics↗