Converting the medium infrared field to the visible band is an effective image detection method. We propose a comprehensive theory of image up-conversion under continuous optical pumping, and discuss the relationship between the experimental parameters and imaging field of view, resolution, quantum efficiency, and conversion bandwidth. Theoretical predictions of upconversion imaging results are given based on numerical simulations, which show good agreement with experimental results. In particular, coherent and incoherent light illumination are studied separately and the advantages and disadvantages of their imaging performance are compared and analysed. This work provides a study of the upconversion image detection performance of the system, which is of great value in guiding the design of the detection system and bringing it to practical applications.
We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillato…
We demonstrate the measurement of single-shot spectra of temporally selected micropulses from a mid-infrared (MIR) free-electron laser (FEL) by upconversion. We achieve the upconversion of FEL pulses at 11 μm using externally synchronized Nd:YAG or microchip laser pulses at 1064 nm to produce sum-frequency mixing (SFM) signals at 970 nm, which are detected by a compact CCD spectrometer without an intensifier. Our experimental system is very cost-effective, and allows us to obtain the laser spectra of selected micropulses at any temporal position within a single macropulse from an oscillator-ty…
Coherent interconversion of signals between optical and mechanical domains is enabled by optomechanical interactions. Extreme light-matter coupling produced by confining light to nanoscale mode volumes can then access single mid-infrared (MIR) photon sensitivity. Here we utilise the infrared absorption and Raman activity of molecular vibrations in plasmonic nanocavities to demonstrate frequency upconversion. We convert λ~10 μm incoming light to visible via surface-enhanced Raman scattering (SERS) in doubly-resonant antennas that enhance upconversion by >10^10. We show >200% amplification of th…
Video-rate super-resolution imaging through biological tissue can visualize and track biomolecule interplays and transportations inside cellular organisms. Structured illumination microscopy allows for wide-field super resolution observation of biological samples but is limited by the strong absorption and scattering of light by biological tissues, which degrades its imaging resolution. Here we report a photon upconversion scheme using lanthanide-doped nanoparticles for wide-field super-resolution imaging through the biological transparent window, featured by near-infrared and low-irradiance n…
Upconversion imaging, where mid infrared (IR) photons are converted to visible and near IR photons via a nonlinear crystal and detected on cheap and high-performance Silicon detectors, is an appealing method to address the limitations of thermal sensors which are expensive, often require cooling and suffer from both limited spectral response and limited spatial resolution as well as poor sensitivity. However, phase matching severely limits the spectral bandwidth of this technique therefore requiring serial acquisitions in order to cover a large spectrum. Here, we introduce a novel upconversion…
East China Normal University（华东师范大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）；Shanxi University（山西大学）；Shanghai University（上海大学）
Mid-infrared photon counting and resolving via efficient frequency upconversion
State Key Laboratory of Precision Spectroscopy, East China Normal University（精密光谱科学技术国家重点实验室，华东师范大学）；School of Optical Electrical and Computer Engineering, University of Shanghai for Science and Technology（上海理工大学光学电气与计算机工程学院）；Jinan Institute of Quantum Technology（济南量子技术研究院）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
Upconversion Dual-comb Passive Spectroscopy of Mid-IR Incoherent Light
Department of Electrical, Computer, and Energy Engineering, University of Colorado Boulder（科罗拉多大学博尔德分校电气、计算机和能源工程系）；Department of Physics, University of Colorado Boulder（科罗拉多大学博尔德分校物理系）
We present a system for molecular spectroscopy using a broadband mid-infrared laser with near infrared detection. Difference frequency generation of a Yb:fiber femtosecond laser produced a mid-infrared (MIR) source tunable from 2100-3700 cm^-1 (2.7-4.7 microns) with average power up to 40 mW. The MIR spectrum was upconverted to near-infrared wavelengths for broadband detection using a two-dimensional dispersion imaging technique. Absorption measurements were performed over bandwidths of 240 cm^-1 (7.2 THz) with 0.048 cm^-1 (1.4 GHz) resolution, and absolute frequency scale uncertainty was bett…
East China Normal University（华东师范大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）；Shanxi University（山西大学）；Jinan Institute of Quantum Technology（济南量子技术研究院）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
The emerging optical multiplexing within nanoscale shows super-capacity in encoding information by using the time-domain fingerprints from uniform nanoparticles. However, the optical diffraction limit compromises the decoding throughput and accuracy of the nanoparticles during wide-field imaging. This, in turn, challenges the quality of nanoparticles to afford the modulated excitation condition, and further to retain the multiplexed optical fingerprints for super-resolution multiplexing. Here we report a tailor-made time-domain super-resolution method with the lifetime-engineered upconversion …
We demonstrate a photon-sensitive, three-dimensional camera by active near-infrared illumination and fast time-of-flight gating. It uses pico-second pump pulses to selectively up-convert the backscattered photons according to their spatiotemporal modes via sum-frequency generation in a \c{hi}2 nonlinear crystal, which are then detected by electron-multiplying CCD with photon sensitive detection. As such, it achieves sub-millimeter depth resolution, exceptional noise suppression, and high detection sensitivity. Our results show that it can accurately reconstruct the surface profiles of occluded…
We present a scheme for estimating the noise-equivalent temperature difference (NETD) of frequency upconversion detectors (UCDs) that detect mid-infrared (MIR) light. In particular, this letter investigates the frequency upconversion of a periodically polarized crystal based on lithium niobate, where a mid-infrared conversion bandwidth of 220 nm can be achieved in a single poled period by a special design. Experimentally for a temperature target with a central wavelength of 7.89 μm in mid-infrared radiation, we estimated the NETD of the device to be 56 mK. Meanwhile, a direct measurement of th…
Spatial polarization independent (SPI) parametric conversion is the basis of many optical applications, such as SPI frequency interface for communication channels carried by vector modes and upconversion detection for polarization-resolved imaging. However, realizing such conversion remains a challenge. In this proof-of-principle work, we demonstrated SPI parametric upconversion using a polarization Sagnac nonlinear interferometer based on type-II second-harmonic generation (SHG). Our results show that the vector (including both polarization and intensity) profile and associated SOC state of t…
We devise a new detection technique for mid-infrared multi-heterodyne spectroscopy. As an experimental implementation, mid-infrared light interrogates a gas sample in the 3-$μ$m region of the fundamental CH, OH, NH stretch in molecules and detection is performed in the near-infrared telecommunication region. Spectra showing 18000 resolved comb lines of 100-MHz spacing are recorded at a sensitivity close to the shot-noise limit. The demonstration adds to the unique advantages of dual-comb spectroscopy, such as potential very high resolution, negligible instrumental line width, and direct calibr…
As a novel technique for infrared detection, frequency upconversion has been successfully deployed in many applications. However, investigations into the noise properties of upconversion detectors (UCDs) have also received considerable attention. In this letter, we present a new noise source - second harmonic generation (SHG)-induced spontaneous parametric downconversion (SPDC) - experimentally and theoretically shown to exist in short-wavelength-pumped UCDs. We investigate the noise properties of two UCDs based on single-pass 1064 nm-pumped periodically poled LiNbO$_{3}$ bulk crystals. One UC…
Wavelength stability of free-electron lasers (FELs) is one of the important parameters for various applications. In this paper we describe two different methods to diagnose the wavelength stability of a mid-infrared (MIR) FEL. The first one is based on autocorrelation which is usually used to measure the pulse duration, and the second one is based on frequency upconversion through sum-frequency mixing (SFM).
Mid-infrared snapshot spectral imaging via nonlinear radial dispersion
East China Normal University（华东师范大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）；Shanxi University（山西大学）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Guangyang Bay Laboratory
We report on Mid-infrared (MIR) OCT at 4 $μ$m based on collinear sum-frequency upconversion and promote the A-scan scan rate to 3 kHz. We demonstrate the increased imaging speed for two spectral realizations, one providing an axial resolution of 8.6 $μ$m, and one providing a record axial resolution of 5.8 $μ$m. Image performance is evaluated by sub-surface micro-mapping of a plastic glove and real-time monitoring of CO$_2$ in parallel with OCT imaging.
Pulse-to-pulse spectral phase characterization of mid-infrared pulses at megahertz rates
The University of Tokyo（东京大学）；Polytechnique Montréal（蒙特利尔理工大学）；University of New Mexico（新墨西哥大学）；RIKEN Center for Advanced Photonics, RIKEN（理化学研究所先进光子中心）
Mid-infrared single-pixel imaging at the single-photon level
East China Normal University（华东师范大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）；Shanxi University（山西大学）；Jinan Institute of Quantum Technology（济南量子技术研究院）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
Frequency upconversion is a cornerstone of electromagnetic signal processing, analysis and detection. It is used to transfer energy and information from one frequency domain to another where transmission, modulation or detection is technically easier or more efficient. Optomechanical transduction is emerging as a flexible approach to coherent frequency upconversion; it has been successfully demonstrated for conversion from radio- and microwaves (kHz to GHz) to optical fields. Nevertheless, optomechanical transduction of multi-THz and mid-infrared signals remains an open challenge. Here, we uti…
Direct detection of single photons at wavelengths beyond 2 microns under ambient conditions remains an outstanding technological challenge. One promising approach is frequency upconversion into the visible (VIS) or near-infrared (NIR) domain, where single photon detectors are readily available. Here, we propose a nanoscale solution based on a molecular optomechanical platform to up-convert photons from the far and mid-infrared (covering part of the THz gap) into the VIS-NIR domain. We perform a detailed analysis of its outgoing noise spectral density and conversion efficiency with a full quant…
We present the vertically illuminated Si compatible mid-infrared photodetectors based on graphene that forms negative-index metamaterial. The coupling into a 2D layer at the angles near normal to the surface is negligible without the help of a metamaterial. We propose a low loss metamaterial, the dielectric structure with the nano/microholes through 2D materials that supports a resonance and enhances quantum efficiency in a wide range of incident angles.
Ultrasensitive infrared-to-visible artificial vision via self-evolving projection guided by single-pixel detection
School of Physics, Beihang University（北京航空航天大学物理学院）；School of Instrumentation and Optoelectronics Engineering, Beihang University（北京航空航天大学仪器科学与光电工程学院）；Hangzhou International Innovation Institute, Beihang University（北京航空航天大学杭州国际创新研究院）
Spectral imaging and detection of mid-infrared (mid-IR) wavelengths are emerging as an enabling technology of great technical and scientific interest; primarily because important chemical compounds display unique and strong mid-IR spectral fingerprints revealing valuable chemical information. While modern Quantum cascade lasers have evolved as ideal coherent mid-IR excitation sources, simple, low noise, room temperature detectors and imaging systems still lag behind. We address this need presenting a novel, field-deployable, upconversion system for sensitive, 2-D, mid-IR spectral imaging. Meas…
The potential for improving the penetration depth of optical coherence tomography systems by using increasingly longer wavelength light sources has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at 4 micron central wavelength with an axi…
State Key Laboratory of Precision Spectroscopy, East China Normal University（精密光谱学国家重点实验室，华东师范大学）；Chongqing Key Laboratory of Precision Optics, Chongqing Institute of East China Normal University（精密光学重庆市重点实验室，华东理工大学重庆研究院）；Collaborative Innovation Center of Extreme Optics, Shanxi University（极端光学协同创新中心，山西大学）；Chongqing Institute for Brain and Intelligence, Guangyang Bay Laboratory（脑与智能重庆研究院，广阳湾实验室）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Jinan Institute of Quantum Technology（济南量子技术研究院）
Mid-Infrared Single-Photon Edge Enhanced Imaging based on Nonlinear Vortex Filtering
East China Normal University（华东师范大学）；University of Shanghai for Science and Technology（上海理工大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）
The advancement of technologies for the precise interrogation of molecules offers exciting possibilities for new studies in the realms of precision spectroscopy and quantum technologies. Experiments in these domains often address molecular vibrations in the mid-infrared (MIR) spectral region, thus generating the need for spectrally pure and accurate MIR laser sources. Quantum-cascade lasers (QCLs) have emerged as flexible sources of coherent radiation available over a wide range of MIR frequencies. Here, we demonstrate a robust approach for the simultaneous linewidth narrowing, frequency stabi…
