- 标题
- 摘要
- 关键词
- 实验方案
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A High-Resolution 220-GHz Ultra-Wideband Fully Integrated ISAR Imaging System
摘要： In this paper, an ultra-wideband fully integrated imaging radar at sub-terahertz (sub-THz) frequencies is presented, which demonstrates a fine lateral resolution without using any focal lens/mirror. We have achieved a lateral resolution of 2 mm for an object at 23-cm distance as well as a range resolution of 2.7 mm. To achieve the decent range resolution, in a frequency modulation continuous wave radar configuration, a state-of-the-art chirp bandwidth (BW) of 62.4 GHz at a center frequency of 221.1 GHz is generated and efficiently radiated. We have presented a design technique for the optimal design of the passive embedding around the core transistor to maximize the tuning BW of the voltage controlled oscillator. At the receiver side, to maximize the intermediate frequency level, a subharmonic mixer is utilized, which is designed for the lowest conversion loss. Finally, to obtain the fine lateral resolution, we have implemented near-field beamforming algorithm based on the inverse synthetic aperture radar (ISAR) systems. The synthesized beamwidth is less than 0.5°; hence, high-resolution images are reconstructed. The system is fabricated in a 55-nm BiCMOS process. To the best of our knowledge, this is the first imaging radar at THz/sub-THz frequencies, which utilizes ISAR to achieve a high lateral resolution while the radar system is fully integrated.
关键词： ultra-wideband,Frequency modulation continuous wave (FMCW),remote sensing,THz,radar,sub-terahertz (sub-THz),oscillator,inverse synthetic aperture radar (ISAR),plane wave
更新于2025-09-23 15:21:21
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[IEEE 2019 24th Microoptics Conference (MOC) - Toyama, Japan (2019.11.17-2019.11.20)] 2019 24th Microoptics Conference (MOC) - Light-Induced Self-Written Optical Waveguide Fabrication by Near Infrared Continuous Wave Laser Light with Microwatt Power
摘要： We have successfully demonstrated light-induced self-written (LISW) waveguides at a wavelength of 1070 nm and 1310 nm, respectively. Microwatt level photopolymerization threshold value was obtained at both wavelengths. The results show a promising approach for optical interconnection in silicon photonics.
关键词： Photopolymerization,Continuous Wave (CW) laser,Silicon photonics,Near Infrared (NIR),Light-induced self-written (LISW) waveguides
更新于2025-09-23 15:21:01
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Continuous-wave operation of a 1.3 <i>??</i> m wavelength npn AlGaInAs/InP transistor laser up to 90 ?°C
摘要： A transistor laser (TL) is a device that operates at a high-speed with multiple functions such as output control with low wavelength shift and signal mixing. By adopting a high heat dissipation structure with a high-speed compatible wide electrode pad and thick Au plating in TLs, improvement of temperature performance in 1.3 μm wavelength npn AlGaInAs/InP TL was demonstrated. As a result, continuous-wave operation of a 1.3 μm TL up to 90 °C was achieved. The thermal resistance was estimated to be 25 K W?1, based on the spectrum behavior, which is at least four times lower than the previously observed value.
关键词： transistor laser,AlGaInAs/InP,continuous-wave operation,thermal resistance,high heat dissipation structure
更新于2025-09-23 15:21:01
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Continuous-wave dual-wavelength operation of the in-band diode-pumped Nd:GdVO4/Nd:YVO4 composite laser with controllable spectral power ratio
摘要： Controllable continuous-wave dual-wavelength laser operation of a Nd:GdVO4/Nd:YVO4 composite crystal at 1063 and 1064 nm was demonstrated using in-band diode pumping around 912 nm. The spectral power ratio of the two laser wavelengths could be adjusted simply by controlling the pump wavelength of the laser diode via temperature. The laser produced the maximum total output power of 4.48 W. The maximum slope and optical-to-optical efficiency with respect to the absorbed pump power were 43.8% and 38.8%, respectively.
关键词： in-band diode pumping,Nd:GdVO4/Nd:YVO4 composite crystal,dual-wavelength laser,spectral power ratio,continuous-wave operation
更新于2025-09-23 15:21:01
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New high-power 1.1-??m light source: diode-pumped continuous-wave and passively Q-switched Nd:LuYAG mixed crystal lasers
摘要： 1.1-μm laser operation has been rarely investigated in laser materials other than Nd:YAG. In this report, using a diode end pumping geometry for providing a compact, low-threshold and high-efficiency system, continuous-wave and passively Q-switched Nd:LuYAG mixed crystal lasers at 1.1 μm were demonstrated, for the first time to our knowledge. In continuous-wave mode, a maximum output power up to 6.04 W was achieved at 1112.9 nm, 1116.64 nm and 1122.65 nm with a slope efficiency of 41.8%. Wavelength tuning was obtained from 1112.05 nm to 1123.17 nm discontinuously, which has never been demonstrated in Nd:YAG lasers. Moreover, using a Cr4+:YAG saturable absorber, stable passively Q-switched laser operation was also attained with a maximum average output power up to 1.71 W. The shortest pulse width was about 37.3 ns at repetition rate of about 21.52 kHz. The maximum pulse energy was about 79.3 μJ, which is believed to be the highest pulse energy that has ever been achieved in diode-end-pumped Nd3+ lasers at this specific 1.1 μm emission band.
关键词： 1.1 μm lasers,passive Q-switching,continuous-wave,Nd:LuYAG mixed crystal
更新于2025-09-23 15:19:57
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Femtosecond laser-induced non-thermal welding for a single Cu nanowire glucose sensor
摘要： Copper nanowires (CuNWs) are a key building block to facilitate carrier conduction across a broad range of nanodevices. For integration into nanoscale devices, manipulation and welding of these nanowires need to be overcome. Based on high energy density laser processing investigation, we report on innovative welding of single CuNWs to a silver film using a tightly focused laser beam combined with manipulation of CuNWs through the dielectrophoresis (DEP) method. Two types of lasers, femtosecond (FS) and continuous-wave (CW), were employed to analyze, improve, and control Cu-NW melting characteristics under high energy density irradiation. The FS laser welding of CuNWs resulted in a metallic joint with a low contact resistance suitable for functional electronic nanodevices. Computational simulations using the 1-D heat diffusion equation and finite difference method (FDM) were performed to gain an insight into metal–laser interactions for high performance welded contact development. Simulation studies on lasers established contrasting melting behavior of metal under laser irradiation. The device feasibility of CuNW based welded contacts was evaluated in terms of the electrical performance of a glucose sensor. It was possible to sense glucose concentration down to 10?6 M, demonstrating a path towards integration of CuNWs into wearable, flexible nanoelectronic devices.
关键词： glucose sensor,femtosecond laser,Copper nanowires,laser welding,dielectrophoresis,nanoelectronics,continuous-wave laser
更新于2025-09-23 15:19:57
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Laser-based surface pre-treatment for metal-plastic hybrids using a new process strategy
摘要： In order to join metal-plastic hybrid parts so as to achieve lightweight constructions, innovative joining technologies are essential. For this, thermal joining is a promising approach due to the absence of any joining agent. The joint strength can be increased by surface pre-treatment of the metal with continuous wave laser radiation. Large joining areas, however, are challenging in terms of productivity, efficiency and geometrical flexibility when beam trajectories, which can be easily combined with on-the-fly processing. More precisely, a load direction, and causes lower thermal distortion of the metal sheet than using conventional processing of large areas. In this context, the resulting topography of the metal was analyzed circularly oscillating laser focal spot is geometrically independent of every possible in-plane with respect to the surface roughness and a design criterion was mathematically derived and experimentally validated. Additionally, the joint strength was compared to the strength using conventional beam trajectories. A more promising approach is the use of continuous with a carbon-fiber-reinforced thermoset. The laser-based pre-treatment using the circularly oscillating laser focal spot led to a similar joint strength, while being more productive when resulting from conventional beam trajectories. For verification, steel substrates were joined combined with on-the-fly processing, compared to conventional structuring trajectories.
关键词： surface pre-treatment,continuous wave laser radiation,metal-plastic hybrids,thermal joining
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Study of nonlinear optical refractive index in thin films formed by bloom gelatin and organic materials : (Indigo carmine dye and phenol red Ph indicator)
摘要： The presence of phase noise (PN) severely deteriorates the sensitivity and range of frequency-modulated continuous wave radar systems. Thus, characterization and continuous monitoring of the PN is indispensable, and its estimation is often employed directly on chip. Although many contributions investigate methods for PN estimation, almost all of them consider a continuous-wave (CW) input signal. Differently, in this paper, we aim to estimate the PN from a linear frequency modulated continuous wave (FMCW) signal. For that, we propose two methods utilizing a so-called artificial on-chip target and further digital signal processing. These methods are evaluated in real-time and are the first-known solutions to determine PN estimates during the operation of an FMCW radar transceiver. We prove our methods with both simulation and measurement results from a hardware prototype. Further, we present techniques to efficiently realize the concepts in digital hardware. Finally, we compare and trade off the proposed methods against computational complexity and performance. The novel techniques may be applied to arbitrary input frequencies and bandwidths, and do not require a reference-clock input.
关键词： Delay lines,millimeter-wave radar,phase noise (PN),(FMCW),estimation,monolithic microwave integrated circuits,frequency-modulated continuous wave
更新于2025-09-19 17:13:59
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - All-Dielectric Metasurfaces for Reflection and Transmission-Mode Color Filter Arrays
摘要： A major drawback of frequency modulated continuous-wave (FMCW) radar systems is the permanent leakage from the transmit into the receive path. Besides leakage within the radar device itself, signal reflections from a fixed object in front of the antennas additionally introduce so-called short-range (SR) leakage. It causes a strong degradation of detection sensitivity due to the unavoidable phase noise of the transmit oscillator. In this work, we introduce an artificial on-chip target (OCT) to mitigate the SR leakage. The OCT consists of a delay line whose time delay is significantly smaller than the round-trip delay time of the SR leakage. This is motivated by the fact that in integrated circuits for automotive radar applications operating at 77 GHz delay lines in the range of only a few picoseconds can be realized with a reasonable amount of circuitry. Despite this constraint, we show that the proposed method achieves almost perfect cancelation of the SR leakage. The concept is based on the cross-correlation properties of the residual phase noise in the intermediate frequency (IF) domain. Further, the effectiveness of the proposed method is verified in an FMCW radar system simulation. It almost perfectly shows that a gain in sensitivity of approximately 6 dB is achieved, compensating for the performance degradation caused by the SR leakage. The novel leakage cancelation concept is carried out mainly in the digital domain enabling high flexibility and adaptivity.
关键词： Digital signal processing,frequency modulated continuous-wave (FMCW) radar,leakage cancelation,phase noise,reflected power canceler
更新于2025-09-19 17:13:59
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Room-temperature continuous-wave operation of green vertical-cavity surface-emitting lasers with a curved mirror fabricated on {20a??21} semi-polar GaN
摘要： We demonstrate a room-temperature continuous-wave operation of green vertical-cavity surface-emitting laser with a 20-μm-long cavity possessing a dielectric curved mirror formed over a {20?21} semi-polar Gallium Nitride substrate. The emission wavelength and the threshold current were 515 nm and 1.8 mA, respectively. We also confirmed that white light is generated by overlaying three prime colors of light, i.e. red, blue and green, emitted only from vertical-cavity surface-emitting lasers.
关键词： curved mirror,green emission,continuous-wave operation,semi-polar GaN,vertical-cavity surface-emitting laser
更新于2025-09-19 17:13:59