A microwave photonic mixer for up and down-conversion with high spurs suppression and image rejection is proposed. Dual parallel in-phase and quadrature (I/Q) modulators and 90-degree electrical hybrid couplers (HCs) are used to realize carrier-suppressed single-sideband (CS-SSB) modulation. The +1/-1st-order sideband of the local oscillator (LO) can be selected by the tunable optical bandpass filter (OBPF) to achieve both up and down-conversion. In the upconversion, a wide upconverted radio frequency (RF) frequency range of 15-37 GHz is achieved. A broad downconverted bandwidth of 8-40 GHz is obtained in the downconversion. Furthermore, a Brillouin-assisted notch filter is used to attenuate the image signal to compensate for the incomplete filtering introduced by the OBPF. In this way, an image rejection ratio (IRR) of more than 60 dB can be obtained when the downconverted intermediate frequency (IF) is 2 GHz. Moreover, the spurs suppression ratio is over 50 dB for both up and downconversion. To the best of our knowledge, this is the highest reported spurs suppression in a microwave photonic mixer.
Ultrashort pulse lasers have the characteristics of narrow output pulse width, high peak power and wide spectrum, and are widely used in precision manufacturing, biomedical, quantum communication, national defense and military. In actual production and life, the wavelength tuning and switching of mode-locked fiber lasers have important applications. In this paper, we demonstrate a wavelength-tunable mode-locked fiber laser, which is a mode-locked ytterbium fiber laser working at 10.84MHz, and achieves wavelength-tuned output in the range of 1017~1029nm by adding tunable devices. This tunable and short pulse all-fiber laser has the advantages of simple structure, easy tuning, and good stability, and has a wide range of application prospects.
As a non-contact three-dimensional measurement method, line structured light measurement is widely used in three-dimensional shape measurement due to its fast speed, high accuracy, and convenient implementation. The line structured light extraction is one of the most important step in the line structured light measurement system. Most traditional algorithms are based on the Hessian matrix or the light intensity distribution of the light strip section to extract the center. In this paper, a novel algorithm based on ridge tracking is proposed to extract the center of the light strip, the approximate direction has been used to estimate the direction of the light strip. Experiments have proved that this algorithm can be applied to the extraction of light strips in a variety of scenes, and has good accuracy and noise resistance.
We demonstrate a low-repetition-rate mode-locked figure-of-9 erbium-doped fiber laser at a center wavelength of 1550 nm by using an all-polarization-maintaining (PM) nonlinear amplifying loop mirror (NALM) configuration. This laser can generate Gaussian-shape noise-like pulses (NLPs) at a repetition rate of 2.15 MHz with a radio-frequency (RF) signal-to-noise ratio of greater than 50 dB and can be self-started mode-locked with a pulse energy of 11.68 nJ. The fluctuation of the average output power in 60 hours is 1.27% root mean square (RMS), which proves its high power stability. To our knowledge, this is the first report of an all-PM NALM erbium-doped fiber laser generating NLPs at the center wavelength of 1550 nm.
The optical frequency comb(OFC) technology is suitable for precise dimensional metrology for its low fractional uncertainty, while coherent optical communication has the advantages of high receiving sensitivity and capacity. To combine the benefits of both technologies, a novel single-polarization 272 Gb/s coherent optical communication scheme employing four wavelengths is proposed and evaluated. By introducing a 100MHz-reption rate home-made mode-lock fiber laser and optical band-pass filters, the 150GHz-bandwidth OFC signal is generated and transmitted with the coherent optical signals. By the demodulation of the real-time coherent optical receiver, the bit-error-rate (BER) results of four wavelengths are obtained. The proposed scheme provides a simple way to achieve wideband communication and the OFC signal transmission, which can be attractive for the application of onboard integration of communication and ranging.
Single and double plasmon induced absorption (PIA) effects have been numerically achieved in a metal-insulator-metal (MIM) waveguides end-coupled with resonators structure. Here, the structure composed of two MIM waveguides and three side-coupled rectangular resonators is proposed to generate double PIA effects. A multimode coupling mechanism derived from the coupled mode theory is established to describe the spectral features, which is greatly agree with the simulation results, may provide a guideline for designing and analyzing the integrated plasmonic devices based on the multiple PIA effects. What’s more, dynamical control of the amplitude and bandwidth of the multiple PIA effects can be achieved by means of filling poly (methy1 methacrylate) or Kerr material in the Fabry-Perot resonators. Compared with previous reports, the multiple PIA effects are analyzed theoretically in a plasmonic waveguides end-coupled with resonators structure, will have practical applications in plasmonic filters, modulators, sensors, switches and fast light in highly integrated plasmonic circuits.
In this article, we propose a novel method using machine learning, especially for artificial neural networks (ANNs) to achieve variability analysis and performance optimization of the plasmonic refractive index sensor (RIS). A Fano resonance (FR) based RIS which consisted of two plasmonic waveguides end-coupled to each other by an asymmetrical square resonator is taken as an illustration to demonstrate the effectiveness of the ANNs. The results reveal that the ANNs can be used in fast and accurate variability analysis because the predicted transmission spectrums and transmittances generated by ANNs are approximate to the actual simulated results. In addition, the ANNs can effectively solve the performance optimization and inverse design problems for the RIS by predicting the structure parameters for RIS accurately. Obviously, our proposed method has potential applications in optical sensing, device design, optical interconnects and so on.
We report an optical vector network analysis (OVNA) based on optical suppressed carrier double-sideband (DSB) modulation and the Pound Drever Hall (PDH) technique. In this novel scheme, the optical carrier suppressed DSB modulation signal propagates through the high Q optical device, and then the double frequency of the driven radio frequency signal is detected, by which the frequency responses of the device can be accurately achieved. Comparing with the common DSB-based OVNA, by biasing the modulator at the minimum transmission point (MITP), the accuracy improvement can be realized since the errors caused by the even-order sidebands are eliminated. Moreover, the high stability of the proposed OVNA can also be achieved by using the PDH technique. In the proof-of-concept experiment, the magnitude and phase responses of the Fabry-Perot (FP) interferometer are realized with high accuracy when the modulation index is small. There is no repeated frequency response even if the test time is up to 30 minutes. The proposed scheme provides a novel strategy for high-accuracy frequency responses measurement, which can be potentially used in high Q optical devices characterization.
We demonstrate a mode-locked all-polarization-maintaining figure-of-8 erbium-doped fiber laser, with a repetition rate of 20.38 MHz. The self-starting fiber laser is based on a structure of nonlinear amplifying loop mirror (NALM). The output pulse duration of this laser can be de-chirped to about 590 fs. Such all-fiber laser with a high repetition rate has the advantages of high stability and self-starting, which leads to many scientific applications.
In this paper, passively mode-locked all polarization-maintaining (PM) dispersion-managed erbium-doped figure-of-9 fiber oscillator based on a nonlinear amplifying loop mirror (NALM) is demonstrated. The figure-of-9 fiber laser can generate 25.7-nm chirped-pulse at a center wavelength of 1550 nm with a repetition of 46.6 MHz, a pulse energy of 0.2 nJ, and a chirped pulse width of 571 fs. The laser output is then amplified by pre-chirped managed nonlinear amplification setup to 5 nJ and further compressed down to 167 fs. Compared to previous studies, the laser presented here has advantages of all-fiber structure, no Kelly sideband and wider bandwidth.
We proposed a mode-locked all-polarization-maintaining erbium-doped fiber laser base on a nonlinear amplifying loop mirror (NALM). The laser can generate 1.6 ps pulses at 1550 nm with the energy of 1 nJ that can be compressed down to 100 fs with the compressor outside the cavity. The repetition rate of the output pulse is 12MHz. Such configuration of laser is easier controlled and self starting long term operation, and is highly desirable for industrial applications, such as micro-machining.
In this paper, we demonstrate an all-normal dispersion (ANDi) femtosecond YDFL. The laser operates around 976 nm via single-clad single-mode core-pumped method, which could enhance the slope efficiency up to 19% compared to that of 14% via double-clad multi-mode pumped method. The pulse repetition rate is 44.3 MHz, and pulse energy is approximately 1 nJ. Through external cavity pulse compression by a pair of gratings, the pulse duration can be compressed to 250 fs, nearly transform-limited.
We propose and demonstrate a multifunction-stabilized photonic link, which is capable of transmitting wideband time signal and stable frequency signal between the central station and the remote end bidirectionally over a single-fiber link. Experimentally, 3.95-GHz frequency signal and pulsed time signal are delivered to the remote end with frequency stability of 3.6×10−16 and time jitter of 0.45 ps at 4000 s average time, respectively. Also, a downlink radio frequency signal is transferred from the remote end back to the central station with suppressed delay variation.
Exploiting the molecular and nano-structure engineering, electroactive polymers (EAPs) with giant electromechanical responses have been developed at Penn State. For the field actuated EAPs, a class of defects modified polar-fluoropolymers have been demonstrated to exhibit a high electrostrictive strain, a high energy conversion efficiency, and high elastic energy density (< 1 J/cm3), which has been commercialized by Akema and commercial actuator products have been developed at Novesentis. This talk will briefly review these results. In contrast, the ionic EAPs such as ionic polymer metal composites whose actuation mechanism is based on the excess ion accumulation/depletion at the electrodes, suffer low actuation strain, elastic energy density, and efficiency. On the other hand, the very low operation voltage, often below 5 volts, of i-EAPs is very attractive, compared with very high operation voltage of the field actuated EAPs. In the past several years, we have been investigating approaches to significantly enhance the electromechanical response of i-EAPs. This talk will present the recent works on a class of nano-structure engineered graphene nano-composites that exhibit a high strain response (< 50% strain) with an exceptionally high elastic energy density < 1.5 J/cm3, induced under low voltage (< 5 V) with a high efficiency. These results point out the potential of EAPs in achieving high performance by exploiting nano-structure engineering and their promise for advanced solid state actuator applications.
ACKNOWLEDGEMENT: The work was supported by NSF under Grant No. CMMI-1130437.
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