Although optical microscopy is a widely used technique across various multidisciplinary fields for inspecting small-scale objects, surfaces or organisms, it faces a significant limitation: the lateral resolution of optical microscopes is fundamentally constrained by light diffraction. Dielectric micro-spheres, however, offer a promising solution to this issue as they are capable of significantly enhancing lateral resolution through extraordinary phenomena, such as a photonic nanojet.Building upon the potential of dielectric micro-spheres, this paper introduces a novel approach for fabricating 3D micro-devices designed to enhance lateral resolution in optical microscopy. The proposed 3D micro-device comprises a modified coverslip and a micro-sphere, facilitating easy handling and integration into any existing optical microscope. To manufacture the device, two advanced femtosecond laser techniques are employed: femtosecond laser ablation and multi-photon lithography. Femtosecond laser ablation was employed to create a micro-hole in the coverslip, which allows light to be focused through this aperture. Multi-photon lithography was used to fabricate a micro-sphere with a diameter of 20 µm, along with a cantilever that positions the above the processed micro-hole and connect it with the coverslip. In this context, advanced processing strategies for multi-photon lithography to produce a micro-sphere with superior surface roughness and almost perfect geometry (λ/8) from a Zr-based hybrid photoresist are demonstrated. The performance of the micro-device was evaluated using Mirau-type coherence scanning interferometry in conjunction with white light illumination at a central wavelength of 600 nm and a calibration grid (Λ = 0.28 µm, h > 50 nm). Here, the 3D micro-device proved to be capable of enhancing lateral resolution beyond the limits achievable with conventional lenses or microscope objectives when used in air. Simultaneously, it maintained the high axial resolution characteristic of Mirau-type coherence scanning interferometry. The results and optical properties of the micro-sphere were analyzed and further discussed through simulations.
The field-of-view (FOV), depth of field, and resolution of conventional microscopes are constrained by each other; therefore, a zoom function is required. Traditional zoom methods lose real-time performance and have limited information throughput, severely limiting their application, especially in three-dimensional dynamic imaging and large-amount or large-size sample scanning. Here, an adaptive multiscale (AMS) imaging mechanism combining the benefits of liquid lenses and multiscale imaging techniques is proposed to realize the functions of fast zooming, wide working distance (WD) range and large FOV on a self-developed AMS microscope. The design principles were revealed. Moreover, a nonuniform-distortion-correction algorithm and a composite patching algorithm were designed to improve image quality. The continuous tunable magnification range of the AMS microscope is from 9× to 18×, with the corresponding FOV diameters and resolution ranging from 2.31 to 0.98 mm and from 161 to 287 line-pairs/mm, respectively. The extended WD range is 0.8 mm and the zoom response time is 38 ms. Experiments demonstrated the advantages of the proposed microscope in pathological sample scanning, thick-sample imaging, microfluidic process monitoring, and the observation of living microorganisms. The proposed microscope is the first step towards zoom multiscale imaging technology and is expected to be applied in life sciences, medical diagnosis, and industrial detection.
One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s. Here, we present a setup based on a 7 × 7 focus array (rather than 3 × 3 in our previous work) and using a focus velocity of about 1 m/s (rather than 0.5 m/s in our previous work) at the diffraction limit (40×/NA1.4 microscope objective lens). Combined, this advance leads to a ten times increased print speed of about 108 voxels/s. We demonstrate polymer printing of a chiral metamaterial containing more than 1.7 × 1012 voxels as well as millions of printed microparticles for potential pharmaceutical applications. The critical high-quality micro-optical components of the setup, namely a diffractive optical element generating the 7 × 7 beamlets and a 7 × 7 lens array, are manufactured by using a commercial two-photon grayscale 3D laser printer.
Endoscopes are indispensable for minimally invasive optical applications in medicine and production engineering. The smallest lensless endoscopes often use digital optics to compensate the intrinsic distortions of light propagation of multimode or multicore fibers. However, due to the wavelength dependency of the distortion, the approach is restricted to a narrow spectral range, which prevents multispectral imaging modalities. We employ a spatial light modulator with a high stroke above 2
, to generate a hologram which minimizes overall phase distortion for multiple spectral bands. This enables lensless multicore fiber single-shot RGB endoscopy, for the first time in the world. Many applications in advanced manufacturing and biomedicine such as in vivo tissue classification are enabled.
Quartz tuning forks have been recently employed as infrared photodetectors in tunable laser diode spectroscopy because of their high responsivities and fast response time. As for all sensitive elements employed for photodetection, the main drawback is the limited bandwidth of their absorption spectrum. For quartz crystals, the high absorptance for wavelengths above 5 µm guarantees excellent performance in the mid-infrared range, that cannot be easily extended in the visible/near-infrared range because of its transparency from 0.2 to 5 µm. In this work, we report on the development of a laser surface functionalization process to enhance the optical absorption of quartz crystals, named hereafter Black Quartz, in the 1-5 µm spectral range. Black Quartz consists of surface modification of quartz crystal by ultra-fast-pulsed-laser-processing to create localized matrices-like patterns of craters on top. The surface modification decreases the transmittance of quartz in the 1-5 µm range from > 95% down to < 10%, while the transmittance above 5 µm remains unchanged. The Black Quartz process was applied on two quartz-tuning-forks mounted in a tunable laser diode spectroscopy sensor for detecting two water vapor absorption features, one in the near infrared and the other one in the mid-infrared. A comparable responsivity was estimated in detecting both absorption features, confirming the extension of the operation in the near-infrared range. This works represents an important and promising step towards the realization of quartz-based photodetector with high and flat responsivity in the whole infrared spectral range.
Deformable mirrors are essential dynamic wavefront compensation. Among the various types of deformable mirrors with different actuation mechanisms, the unimorph piezoelectric deformable mirror (UPDM) offers distinct advantages owing to its compact size and low cost. The two most critical challenges in UPDM are electrode fabrication and deformation control. This study proposes an integrated electrode fabrication and sensorless feedback control scheme for UPDM, which simplifies the manufacturing process and enhances its performance. The electrode array is created using silkscreen printing combined with flexible printed circuit board technology, integrating electrode fabrication and electrical connection into a single step. The desired mirror deformation is achieved by introducing a closed-loop direct deformation control method based on piezoelectric self-sensing. The feedback mechanism utilizes the local strain-induced charge generated by the piezoelectric plate, effectively addressing the nonlinear behavior of the piezoelectric material. Experimental results confirm the feasibility and effectiveness of the proposed method, with the maximum relative error in the steady state phase remaining below 2%.
Femtosecond 3D-printing offers tantalizing avenues for miniaturization and integration of micro optical systems. Available photoresists, however, restrain their utility in liquid immersion, especially in media with refractive indices larger than n = 1.33, such as glues or biomedical fluids. We present monolithic 3D-printed immersion optics, equipped with compact microfluidic sealing to protect the micro optical device from intrusion of liquid immersion media. We experimentally demonstrate diffraction limited performance in water, silicone-, and immersion oil, for a tailored aspherical-spherical doublet with a numerical aperture of NA = 0.625 and a footprint as small as a single mode optical fiber. Such compact monolithic immersion micro optics yield high potential to advance miniaturization for in situ biomedical sensing and robust coupling between fibers and photonic integrated circuits.
Halide perovskite-based photodiodes are promising for efficient detection across a broad spectral range. Perovskite absorber thin-films have a microcrystalline morphology, characterized by a high density of surface states and defects at inter-grain interfaces. In this work, we used dielectric/ferroelectric poly(vinylidene-fluoride-trifluoroethylene) (P(VDF-TrFE)) to modify the bulk interfaces and electron transport junction in p-i-n perovskite photodiodes. Our complex work demonstrates that interface engineering with P(VDF-TrFE) induces significant Fermi level pinning, reducing from 4.85 eV for intrinsic perovskite to 4.28 eV for the configuration with dielectric interlayers. Modifying the interfaces in the devices resulted in an increase in the key characteristics of photodiodes compared to pristine devices. The integration of P(VDF-TrFE) into the perovskite film didn’t affect the morphology and crystal structure, but significantly changed the charge transport and device performance. IV curve analysis and 2-diode model calculations showed enhanced shunt properties, a decreased non-ideality factor, and reduced saturation dark current. We have shown that the complex introduction of P(VDF-TrFE) into the absorber’s bulk and on its surface is essential to reduce the impact of the trapping processes. For P(VDF-TrFE) containing devices, we increased the specific detectivity from 1011 to ~1012 Jones, expanded the linear dynamic range up to 100 dB, and reduced the equivalent noise power to 10−13 W·Hz−1/2. Reducing non-radiative recombination contributions significantly enhanced device performance, improving rise/fall times from 6.3/10.9 µs to 4.6/6.5 µs, and achieved photo-response dynamics competitive with state-of-the-art analogs. The cut-off frequency (3dB) increased from 64.8 kHz to 74.8 kHz following the introduction of the dielectric. We also demonstrated long-term stabilization of PPD performance under heat-stress. These results provide new insights into the use of organic dielectrics and an improved understanding of trap-states/ion defect compensation for detectors based on perovskite heterostructures.
This review considers the modern industrial applications of augmented reality headsets. It draws upon a synthesis of information from open sources and press releases of companies, as well as the first-hand experiences of industry representatives. Furthermore, the research incorporates insights from both profile events and in-depth discussions with skilled professionals. A specific focus is placed on the ergonomic characteristics of headsets: image quality, user-friendliness, etc. To provide an objective evaluation of the various headsets, a metric has been proposed which is dependent on the specific application case. This enables a comprehensive comparison of the various devices in terms of their quantitative characteristics, which is of particular importance for the formation of a rapidly developing industry.
Transparent objects are widely used in various fields, leading to increasing demand for methods of measuring them. However, the measurement of such objects has always been challenging owing to the intricate refraction and reflection phenomena they exhibit. Given that traditional contact measurement methods can damage transparent objects, the use of non-destructive measurement techniques, particularly those based on optical principles, is considered preferable. As a result, various non-destructive measurement methods have been developed for transparent objects by leveraging the unique characteristics of light, and a comprehensive review is imperative for exploring these innovative methods and their potential applications. This review accordingly begins by elucidating the necessity of measuring transparent objects and exploring the concept of transparency. Next, an overview of various non-destructive optical measurement techniques spanning macro-, micro-, and general-scale applications is presented, followed by a discussion of their respective advantages and limitations. Finally, the paper concludes by outlining future directions for potential advancements in the field. This review is expected to serve as a valuable resource for newcomers in the field of transparent object measurement and assist researchers seeking to integrate these techniques into interdisciplinary studies.
Light-based additive manufacturing holds great potential in the field of bioprinting due to its exceptional spatial resolution, enabling the reconstruction of intricate tissue structures. However, printing through biological tissues is severely limited due to the strong optical scattering within the tissues. The propagation of light is scrambled to form random speckle patterns, making it impossible to print features at the diffraction-limited size with conventional printing approaches. The poor tissue penetration depth of ultra-violet or blue light, which is commonly used to trigger photopolymerization, further limits the fabrication of high cell-density tissue constructs. Recently, several strategies based on wavefront shaping have been developed to manipulate the light and refocus it inside scattering media to a diffraction-limited spot. In this study, we present a high-resolution additive manufacturing technique using upconversion nanoparticles and a wavefront shaping method that does not require measurement from an invasive detector, i.e., it is a non-invasive technique. Upconversion nanoparticles convert near-infrared light to ultraviolet and visible light. The ultraviolet light serves as a light source for photopolymerization and the visible light as a guide star for digital light shaping. The incident light pattern is manipulated using the feedback information of the guide star to focus light through the tissue. In this way, we experimentally demonstrate that near-infrared light can be non-invasively focused through a strongly scattering medium. By exploiting the optical memory effect, we further demonstrate micro-meter resolution additive manufacturing through highly scattering media such as a 300-μm-thick chicken breast. This study provides a concept of high-resolution additive manufacturing through turbid media with potential application in tissue engineering.
Femtosecond laser pulses can be employed to directly form periodic nanostructures on solid surfaces, including hard materials such as diamond and sapphire, via ablation. Thus, this technique is promising for industrial nanofabrication applications. However, the stable formation of uniform nanostructures is challenging because of their high sensitivity to changes in processing conditions, such as the surface roughness of materials and laser power. Herein, we report a real-time monitoring and control approach for fabricating high-quality nanostructures on glass surfaces. We measured the reflectance and transmittance of a laser-irradiated surface simultaneously and determined their specific values corresponding to the formation of a uniform nanostructure with a period of 200 nm and depth of 1 μm. By utilising these values as feedback signals in a proportional-integral-derivative control system, we adjusted the laser power during irradiation to form a uniform nanostructure. This approach led to a significant reduction in the defect ratio of the nanostructure (~2.4%), which represents a 10-fold reduction compared with uncontrolled processing. Our results demonstrate the potential for the stable and direct fabrication of high-quality nanostructures on solids and offer a valuable method for the quality assurance of nanostructures for various applications.
Mimicking animal skin is an effective strategy for enhancing the performance of artificial skin. Inspired by a chameleon’s iridophore and a spider’s slit organ, a novel photonic-electronic skin (PE-skin) with excellent optical/electrical dual-sensing performance was developed by integrating a photonic crystal (PC) with a conductive MXene/silver nanowire (AgNW) composite into adhesive polydimethylsiloxane. The PC layer containing in-plane-spaced and interplane-packed nanoparticle arrays was fabricated via a fast, facile, combined method of “Marangoni self-assembly”, “plasma etching”, and “adhesive PDMS transfer”. Notably, the PC exhibited a red-shift mechanochromic response through in-plane stretching, which is the first report of sharing the same mechanochromic behavior as a chameleon iridophore. The underlying MXene layer formed slit-organ-like cracks that provided high sensitivity, whereas the AgNWs maintained their conductivity under large strains. The resultant PE-skin exhibited a high mechanochromic sensitivity (2.57 nm %−1) and a high electrical gauge factor of 2600 in a large strain-sensing range (up to 85%). These advantages have been confirmed in the detection of full-range human motions, such as speech recognition, using a deep neural network algorithm. The red-shift stretchable PC demonstrates a new paradigm for artificial chameleon skins, and the bionic PC crack bilayer structure extends the design concept for visually interactive e-skins.
Accelerometers are crucial sensors that measure acceleration resulting from motion or vibration. Compared with their electromechanical counterparts, optical accelerometers are widely regarded as the most promising technology for high-requirement applications. However, compact integration of various optical and mechanical components to create a miniature optomechanical microsystem for acceleration sensing remains a challenge. In this study, we present a miniature optical fiber accelerometer based on a 3D microprinted ferrule-top Fabry–Pérot (FP) microinterferometer. In-situ 3D microprinting technology was developed to directly print a sub-millimeter-scale 3D proof mass/thin-film reflector-integrated FP microinterferometer on the inherently light-coupled end face of a fiber optic ferrule. Experimental results demonstrate that the optical fiber accelerometer has a flat response over a bandwidth of 2 to 3 kHz and its noise equivalent acceleration is 62.45 μg/Hz under 1-g acceleration at 2 kHz. This ultracompact optical fiber interferometric accelerometer offers several distinct advantages, including immunity to electromagnetic interference, remote-sensing capability, and high customizability, making it highly promising for a variety of stringent acceleration-monitoring applications.
In this paper, we experimentally demonstrate a non-volatile switchable infrared stealth metafilm based on high temperature resistant metal Molybdenum (Mo) and phase change material Ge2Sb2Te5(GST). By controlling the phase state of GST, the switch between the infrared stealth and the non-stealth states can be realized. Specifically, when the GST is in the amorphous state, the emissivity of the film in the 3−5 μm and 8−14 μm atmospheric window band is suppressed and can realize infrared stealth, together with a high absorption peak of 94% at 6.08 μm, which enables radiative heat dissipation; While for the crystalline state of the GST, the average emissivity is more than 0.7 in the band of 8−14 μm, and the infrared stealth function cannot be realized. When the background temperature is 100°C, the temperature difference between the two samples reaches as high as 28°C under an infrared thermal imager. Therefore, our proposed metafilm can flexibly regulate the infrared thermal radiation of the target so as to realize the switch between the infrared stealth and non-stealth state. We have fabricated the metafilm on both hard and flexible substrates. Our work holds profound significance for the study of dynamic thermal radiation control and it is set to pave the way for the practical implementation of intelligent infrared stealth technology.
A universal method of micro-patterning thin quantum dot films is highly desired by industry to enable the integration of quantum dot materials with optoelectronic devices. Many of the methods reported so far, including specially engineered photoresist or ink-jet printing, are either of poor yield, resolution limited, difficult to scale for mass production, overly expensive, or sacrificing some optical quality of the quantum dots. In our previous work, we presented a dry photolithographic lift-off method for pixelization of solution-processed materials and demonstrated its application in patterning perovskite quantum dot pixels, 10 µm in diameter, to construct a static micro-display. This report presents further development of this method and demonstrates high-resolution patterning (~1 µm diameter), full-scale processing on a 100 mm wafer, and multi-color integration of two different varieties of quantum dots. Perovskite and cadmium-selenide quantum dots were adopted for the experimentation, but the method can be applied to other types of solution-processed materials. We also demonstrate the viability of this method for constructing high-resolution micro-arrays of quantum dot color-convertors by fabricating patterned films directly on top of a blue gallium-nitride LED substrate. The green perovskite quantum dots used for fabrication were synthesized via the room-temperature ligand-assisted reprecipitation method developed by our research group, yielding a photoluminescent quantum yield of 93.6% and full-width half-maximum emission linewidth less than 20 nm. Our results demonstrate the viability of this method for use in scalable manufacturing of high-resolution micro-displays paving the way for improved optoelectronic applications.
Complex field modulation (CFM) has found a plethora of applications in physics, biomedicine, and instrumentation. Among existing methods, superpixel-based CFM has been increasingly featured because of its advantages in high modulation accuracy and its compatibility with high-speed spatial light modulators (SLMs). Nonetheless, the mainstream approach based on binary-amplitude modulation confronts limitations in optical efficiency and dynamic range. To surmount these challenges, we develop binary phase-engraved (BiPE) superpixel-based CFM and implement it using the phase light modulator (PLM)—a new micro-electromechanical system-based SLM undergoing development by Texas Instruments in recent years. Using BiPE superpixels, we demonstrate high-accuracy spatial amplitude and phase modulation at up to 1.44 kHz. To showcase its broad utility, we apply BiPE superpixel-based CFM to beam shaping, high-speed projection, and augmented-reality display.
Advancements in additive manufacturing (AM) are revolutionizing 3D part production, making 3D printing crucial for creating optical devices like lenses and waveguides. This study employs vat photopolymerization (VPP) to fabricate adaptive 4D printed smart Fresnel lenses with photochromic properties using digital light processing (DLP). These lenses are fabricated with precise optical performance and geometric dimensions. Photochromic powders enable dynamic color changes upon UV exposure. The lenses were optically evaluated in both inactive and active states, demonstrating excellent UV and blue light blocking when inactive. Upon UV activation, the lenses darken and absorb parts of the visible light spectrum, with the degree of absorption and color change dependent on the photochromic material and its concentration. The lenses show minimal focal length errors, maintaining high precision and UV responsiveness even at low concentrations. This research highlights the lenses’ precision, UV responsiveness, blue light filtering capabilities, and stability after multiple UV exposure cycles. These findings underscore the potential of 4D printing in developing smart optical devices tailored for applications that demand dynamic light modulation and UV filtering, highlighting a combination of innovative manufacturing techniques and functional optics.
Quantum dots, semiconductor crystals with nanometer-scale dimensions, exhibit adjustable chemical, electrical, and optical characteristics owing to the quantum confinement effect. However, achieving high-quality quantum dots necessitates simultaneous attainment of crystalline integrity within their cores, uniformity in size and shape, as well as effective surface passivation with charge transport functionality—challenges persist regardless of the chosen method. Here, we introduce a novel approach for synthesizing quantum-dot/perovskite heterocrystals: the Colloidal Quantum Dot-Oriented Attachment to Perovskite Single Crystal (CQD-OA-PSC) method. This method involves optimizing quantum dot growth through chemical colloidal synthesis methods, followed by their oriented attachment onto macroscopic perovskite single crystals with impeccable lattice alignment. Consequently, the CQD-OA-PSC method amalgamates the strengths of wet chemical colloidal synthesis methods and solution-based epitaxial growth, offering precise control over quantum dot size, morphology, and structure while leveraging charge transport functionality conferred by the matrix crystal. High-resolution transmission electron microscopy confirms matched lattice orientations between the perovskite matrix and quantum dots. This approach promises to yield high-quality quantum dots perovskite heterocrystals with controlled size, morphology, and optoelectronic properties, thereby holding significant potential for advancing the development of efficient optoelectronic devices.
ZnO nanomaterials have become appealing for next-generation micro/nanodevices owing to their remarkable functionality and outstanding performance. However, in-situ, one-step, patterned synthesis of ZnO nanomaterials with small grain sizes and high specific surface areas remains challenging. While breakthroughs in laser-based synthesis techniques have enabled simultaneous growth and patterning of these materials, device integration restrictions owing to pre-prepared laser-absorbing layers remain a severe issue. Herein, we report a single-step femtosecond laser direct writing (FsLDW) method for fabricating ZnO nanomaterial micropatterns with a minimum linewidth of less than 1 μm without requiring laser-absorbing layers. Furthermore, utilizing the grain-size modulation effect of glycerol, we successfully reduced the grain size and addressed the challenges of discontinuity and non-uniform product formation during FsLDW. Using this technique, we successfully fabricated a series of micro-photodetectors with exceptional performance, a switching ratio of 105, and a responsivity of 102 A/W. Notably, the devices exhibited an ultralow dark current of less than 10 pA, more than one order of magnitude lower than the dark current of ZnO photodetectors under the same bias voltage—crucial for enhancing the signal-to-noise ratio and reducing the power consumption of photodetectors. The proposed method could be extended to preparing other metal-oxide nanomaterials and devices, thus providing new opportunities for developing customized, miniaturized, and integrated functional devices.
Melanoma, a highly malignant and complex form of cancer, has increased in global incidence, with a growing number of new cases annually. Active targeting strategies, such as leveraging the α-melanocyte-stimulating hormone (αMSH) and its interaction with the melanocortin 1 receptor (MC1R) overexpressed in melanoma cells, enhance the concentration of therapeutic agents at tumor sites. For instance, targeted delivery of plasmonic light-sensitive agents and precise hyperthermia management provide an effective, minimally invasive treatment for tumors. In this work, we present a comparative study on targeted photothermal therapy (PTT) using plasmonic gold nanorods (Au NRs) as a robust and safe nanotool to reveal how key treatment parameters affect therapy outcomes. Using an animal model (B16-F10) of melanoma tumors, we compare the targeting abilities of Au NRs modified with two different MC1R agonists, either closely mimicking the αMSH sequence or providing a superior functionalization extent of Au NRs (4.5% (w/w) versus 1.8% (w/w)), revealing 1.6 times better intratumoral localization. Following theoretical and experimental assessments of the heating capabilities of the developed Au NRs under laser irradiation in either the femtosecond (FS)- or nanosecond (NS)- pulsed regime, we perform targeted PTT employing two types of peptide-modified Au NRs and compare therapeutic outcomes revealing the most appropriate PTT conditions. Our investigation reveals greater heat release from Au NRs under irradiation with FS laser, due to the relaxation rates of the electron and phonon temperatures dissipating in the surrounding, which correlates with a more pronounced 17.6 times inhibition of tumor growth when using FS-pulsed regime.
We experimentally demonstrate ultrafast laser-writing wide-gamut structural colors on TiAlN thin film that is coated on TiN substrate via laser-induced surface oxidation. The experiments involve thorough control over laser parameters, including powers, scanning speeds and pulse durations, to investigate the interplay between these variables and the resulting structural colors. Surface characterization techniques, such as scanning electron microscopy, energy-dispersive x-ray spectroscopy and atomic force microscopy, are employed to analyze the properties of laser-induced oxide layers and their chromatic responses. Our findings indicate that while laser powers and scanning speeds are critical in determining the irradiated dose and the subsequent coloring effects, the pulse duration exerts a distinct influence, particularly at low laser powers as well as slow scanning speeds. Longer pulse durations are found to produce a more significant coloring change despite exhibiting lower oxygen content. This is attributed to the increased surface roughness and deeper oxidation layer achieved with prolonged pulses. We propose two oxidation mechanisms – photo-oxidation and thermal-oxidation – to elucidate the influence of pulse duration on laser coloring effects. These findings not only refine existing paradigms in laser-induced surface coloration but also stimulate further exploration of structural colors’ multifaceted applications across diverse technological contexts.
In this study, a ray tracing model based on the law of reflection in vector form was developed to obtain the design parameters of multipass cells (MPC) with dense spot patterns. Four MPCs with distinct patterns were obtained using an established mathematical model. An MPC with a four-concentric-circle pattern exhibited the longest optical path length (OPL) of approximately 38 m and an optimal ratio of optical path length to volume (RLV) of 13.8 cm-2. A light-induced thermoelastic spectroscopy (LITES)-based methane (CH4) sensor was constructed for the first time using the developed optimal MPC and Raman fiber amplifier (RFA). A novel trapezoidal-tip quartz tuning fork (QTF) was used as the detector to further improve the sensing performance. The CH4-LITES sensor exhibited an excellent linear response to optical power and CH4 concentration. The minimum detection limit (MDL) of the CH4-LITES sensor reached 322 ppb when the output optical power of the RFA was 350 mW. The Allan deviation of the system indicated that the MDL decreased to 59.5 ppb when the average time was increased to 100 s.
Femtosecond laser fabrication technology has been applied to photonic-lantern mode (de)multiplexers owing to its 3D fabrication capability. Current photonic-lantern mode (de)multiplexer designs based on femtosecond laser fabrication technology mostly follow a fibre-type photonic lantern design, which uses trajectory-symmetry structures with non-uniform waveguides for selective mode excitation. However, non-uniform waveguides can lead to inconsistent waveguide transmission and coupling losses. Trajectory-symmetry designs are inefficient for selective-mode excitation. Therefore, we optimised the design using trajectory asymmetry with uniform waveguides and fabricated superior ultrafast laser-inscribed photonic-lantern mode (de)multiplexers. Consistent waveguide transmission and coupling losses (0.1 dB/cm and 0.2 dB/facet, respectively) at 1550 nm were obtained on uniform single-mode waveguides. Based on the trajectory-asymmetry design for photonic-lantern mode (de)multiplexers, efficient mode excitation (
,
, and
) with average insertion losses as low as 1 dB at 1550 nm was achieved, with mode-dependent losses of less than 0.3 dB. The photonic-lantern design was polarisation-insensitive, and the polarisation-determined losses were less than 0.2 dB. Along with polarisation multiplexing realised by fibre-type polarisation beam splitters, six signal channels (
,
,
,
,
, and
), each carrying 42 Gaud/s quadrature phase-shift keying signals, were transmitted through a few-mode fibre for optical transmission. The average insertion loss of the system is less than 5 dB, while its maximum crosstalk with the few-mode fibre is less than −12 dB, leading to a 4-dB power penalty. The findings of this study pave the way for the practical application of 3D integrated photonic chips in high-capacity optical transmission systems.
Lunar sample return missions are crucial for researching the composition and origin of the Moon. In recent decades, several lunar sample return missions have been conducted, yielding abundant and valuable lunar samples. As the latest development in lunar sample returns, the Chang’e-6 mission aimed to implement lunar farside sampling. The shorter time available for sampling requires higher sampling efficiency. In this study, the main factors in the sampling site selection and sampling process are introduced and a vision-based sampling implementation is designed for the Chang’e-6 mission to significantly simplify manual operation while maintaining high sampling quality. By sufficiently leveraging the point cloud data reconstructed from the binocular camera images, autonomous terrain analysis and sample point selection are achieved. A 6D pose estimation pipeline based on point cloud registration provides a robust method for sampler pose measurement, replacing the previous manual fine-tuning process and achieving better accuracy. Owing to the well-analyzed sample points and accurate fine-tuning, the proposed approach demonstrates high accuracy in controlling the scooping depth, while significantly reducing the time cost of the sampling implementation, effectively supporting the Chang’e-6 lunar sample mission.
ISSN 2689-9620 EISSN 2831-4093
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2021, 2(3): 350-369. doi: 10.37188/lam.2021.024
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2023, 4(4): 519-542. doi: 10.37188/lam.2023.031
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2021, 2(3): 313-332. doi: 10.37188/lam.2021.020
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2021, 2(4): 446-459. doi: 10.37188/lam.2021.028
