Author Affiliations
Abstract
1 School of Mechanical and Aerospace Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
2 Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing University of Aeronautics and Astronautics (NUAA), Nanjing 210016, China
3 e-mail: pans@nuaa.edu.cn
We propose and demonstrate an agile X-band signal synthesizer with ultralow phase noise based on all-fiber-photonic techniques for radar applications. It shows phase noise of () at 10 kHz (100 kHz) offset frequency for 10 GHz carrier frequency with integrated RMS timing jitter between 7.6 and 9.1 fs (integration bandwidth: 10 Hz–10 MHz) for frequencies from 9 to 11 GHz. Its frequency switching time is evaluated to be 135 ns with a 135 pHz frequency tuning resolution. In addition, the X-band linear-frequency-modulated signal generated by the proposed synthesizer shows a good pulse compression ratio approximating the theoretical value. In addition to the ultrastable X-band signals, the proposed synthesizer can also provide 0–1 GHz ultralow-jitter clocks for analog-to-digital converters (ADC) and digital-to-analog converters (DAC) in radar systems and ultralow-jitter optical pulse trains for photonic ADC in photonic radar systems. The proposed X-band synthesizer shows great performance in phase stability, switching speed, and modulation capability with robustness and potential low cost, which is enabled by an all-fiber-photonics platform and can be a compelling technology suitable for future X-band radars.
Mode-locked lasers Microwaves Radar Fiber optics Ultrafast technology Photonics Research
2018, 6(1): 01000012
Author Affiliations
Abstract
International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Engineering Technology Research Center for 2D Material Information Function Devices and Systems of Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
An opposite-chirped frequency-domain optical parametric amplification (OC-FOPA) design is demonstrated and numerically verified. This scheme combines both an ultrabroad seeding generation and the subsequent effective amplification in one single optical parametric amplification stage. Based on a slightly asymmetrical 4-f optical system, the spectral contents of both pump and signal waves are spectrally dispersed with opposite spatial chirps, to broaden the initial idler seeding. Via a properly designed fan-out periodically poled LiNbO3 chip, nearly perfect quasi phase matching can be realized across the full spectrum, whereby each individual spectral pair precisely maps to its required grating period. Full-dimensional simulations based on commercial ～110 fs (FWHM) near-infrared (near-IR) lasers at 790 and 1030 nm are quantitatively discussed, and few-cycle mid-IR laser pulses (～60 fs at 3.4 μm) plus a high conversion efficiency exceeding 50% are theoretically predicted. By means of a high-power pump source, the OC-FOPA scheme can be also applied to directly produce high-intensity carrier-envelope-phase-stabilized mid-IR idler pulses.
(190.4970) Parametric oscillators and amplifiers (320.7110) Ultrafast nonlinear optics (320.7160) Ultrafast technology. Photonics Research
2017, 5(6): 06000669
Author Affiliations
Abstract
A systematic series of silicon (Si) wafer with microstructured anti-reflection film is prepared by femtosecond laser pulse. The dependence of the morphology and optical properties of the microstructured Si on the experimental parameters is thoroughly investigated. With the laser pulse duration of 40 fs, central wavelength of 800 nm, repetition rate of 250 kHz, laser pulse power of 300 mW, 250 \mu m/s scanning speed, and 2 \mu m of displacement between the parallel scans in the air, the quasiordered arrays of grain microstructures on the Si wafer up to 800-nm tall and 800-nm diameter at the bottom offered near-unity transmission in the mid-infrared wavelength. An anti-reflection film of approximately 3 \times 3 (mm) is developed on the (211) Si substrate with the optimized parameters, Moreover, up to 30% improvement of the response performance is demonstrated.
310.0310 Thin films 310.1210 Antireflection coatings 310.6628 Subwavelength structures,nanostructures 320.7160 Ultrafast technology Chinese Optics Letters
2013, 11(3): 033101
Author Affiliations
Abstract
We present a numerical study on the evolution of the intense femtosecond pulse propagation in argon by solving the extended nonlinear Schr¨odinger equation which includes the beam diffraction, group velocity dispersion, self focusing, absorption and defocusing due to the electron density, and multiphoton ionization processes. The temporal and spatial profiles and the dynamic picture of the ultrashort pulse propagation in argon under different incident conditions such as initial peak intensity, pressure, beam radius, pulse width, and the focal length are discussed. Because the competition between the self focusing and defocusing effects accompanying with other effects as we mentioned above, we can see the splitting into two or even three peaks of the pulse in the time domain.
320.2250 Femtosecond phenomena 320.0320 Ultrafast optics 320.7110 Ultrafast nonlinear optics 320.7160 Ultrafast technology Chinese Optics Letters
2012, 10(s2): S23201
Author Affiliations
Abstract
We build a frequency resolved optical gating (FROG) setup based on the second harmonic generation (SHG) FROG to characterize the mid-infrared (MIR) few-cycle laser pulse in single shot basis. Considering the extremely wide bandwidth, we use 20-μm-thick BBO crystal as the nonlinear medium, and correct the spectral response with the frequency summing efficiency. Spatial splitting is adopted to avoid additional material dispersion. In combination with a 4f imaging, this configuration enables the setup to run in single shot. With the central wavelength of 1.8 μm, the measured pulse has a duration of 9.3 fs, which corresponds to about 1.5 cycles.
320.7090 Ultrafast lasers 320.7100 Ultrafast measurements 320.7160 Ultrafast technology 140.7090 Ultrafast lasers Chinese Optics Letters
2012, 10(12): 123202
Author Affiliations
Abstract
An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed.
300.6495 Spectroscopy, teraherz 300.6270 Spectroscopy, far infrared 040.2235 Far infrared or terahertz 320.7160 Ultrafast technology Chinese Optics Letters
2011, 9(11): 110008
Author Affiliations
Abstract
Terrorism has become an international problem in recent years as evidenced by toxins mailed through the post, liquid explosives planted in airplanes, and so on. Clearly, the security screening of packing materials is highly required. We conduct nondestructive and contactless detection of some packing materials used in daily life by terahertz time-domain spectroscopy. The THz time-domain spectra of five typical kinds of packing materials are measured in the frequency range of 0.3–2.5 THz. THz absorption spectra and transmittance are also analyzed.
160.0160 Materials 300.6495 Spectroscopy, teraherz 320.7160 Ultrafast technology Chinese Optics Letters
2011, 9(s1): s10202
1 西安电子科技大学技术物理学院,西安 710071
2 中国科学院西安光学机密机械研究所瞬态光学与光子技术国家重点实验室,西安 710119
以自启动被动锁模掺镱光纤堆积脉冲激光器为种子源，采用非共线相位匹配的方法，进行了光参量啁啾脉冲放大器的实验研究，得到了两级放大总增益为1.1×107，单脉冲能量为11 mJ，能量稳定性小于2％ rms，8 nm的放大谱宽.实验结果表明，采用这种结构的光参量啁啾脉冲放大器，放大增益高，系统稳定、结构紧凑、便于调节，同时通过调节种子源中的堆积器，可以得到不同宽度的放大信号脉冲.
激光放大器 参量振荡器与放大器 超快激光 超快技术 Laser amplifiers Parametric oscillators and amplifiers Ultrafast lasers Ultrafast technology
Author Affiliations
Abstract
1 Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2 Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
Three types of dispersion mirrors are designed and discussed. The first type is the complementary chirpedmirror pair used for providing smooth group delay dispersion (GDD) in the wavelength range of 550-1050 nm. Such mirrors are obtained by shifting the GDD oscillation period. The second type of mirror combines the characteristics of chirped mirrors and Gires-Tournois interferometer mirrors. It provides a high dispersion compensation of about -800-fs2 GDD in the range of 780-830 nm and about -1150-fs2 GDD in the range of 1020-1045 nm. The third type is a protected silver mirror with high reflectivity and low dispersion in the range of 650-1000 nm at 45°.
色散镜 群延迟色散 啁啾镜对 高色散镜 银镜 310.1620 Interference coatings 320.5520 Pulse compression 320.7160 Ultrafast technology Chinese Optics Letters
2010, 8(s1): 18
Author Affiliations
Abstract
Information Optics Laboratory, State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
The transient time-resolved reflectivity of chromium film is studied by femtosecond pump-probe technique with a 70-fs laser. Experimental results show that the reflectivity change increases with the power of the pump laser. The fast decrease of the reflectivity occurs between 0-200 fs which is mainly due to the electron-electron interaction. Subsequencely, the slower recovery of the reflectivity between 200-900 fs is mainly due to the electron-phonon coupling process. The reflectivity after 900 fs rises little to a near-constant value for the thermal equilibrium of the system. The experimental results can be explained properly with numerical simulation of the two-temperature model. It is helpful for understanding of the electron ultrafast dynamics in chromium film.
飞秒激光 泵浦-探测 时间分辨反射率 320.2250 Femtosecond phenomena 320.7160 Ultrafast technology 310.6860 Thin films, optical properties Chinese Optics Letters
2009, 7(7): 07653
