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Resonant electro-optic frequency comb
摘要： High-speed optical telecommunication is enabled by wavelength-division multiplexing, whereby hundreds of individually stabilized lasers encode information within a single-mode optical fibre. Higher bandwidths require higher total optical power, but the power sent into the fibre is limited by optical nonlinearities within the fibre, and energy consumption by the light sources starts to become a substantial cost factor. Optical frequency combs have been suggested to remedy this problem by generating numerous discrete, equidistant laser lines within a monolithic device; however, at present their stability and coherence allow them to operate only within small parameter ranges. Here we show that a broadband frequency comb realized through the electro-optic effect within a high-quality whispering-gallery-mode resonator can operate at low microwave and optical powers. Unlike the usual third-order Kerr nonlinear optical frequency combs, our combs rely on the second-order nonlinear effect, which is much more efficient. Our result uses a fixed microwave signal that is mixed with an optical-pump signal to generate a coherent frequency comb with a precisely determined carrier separation. The resonant enhancement enables us to work with microwave powers that are three orders of magnitude lower than those in commercially available devices. We emphasize the practical relevance of our results to high rates of data communication. To circumvent the limitations imposed by nonlinear effects in optical communication fibres, one has to solve two problems: to provide a compact and fully integrated, yet high-quality and coherent, frequency comb generator; and to calculate nonlinear signal propagation in real time. We report a solution to the first problem.
关键词： optical telecommunication,electro-optic effect,optical frequency combs,wavelength-division multiplexing,whispering-gallery-mode resonator
更新于2025-11-28 14:23:57
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L-band tunable and dual-wavelength mode locked fiber laser with NCF-GIMF based SA
摘要： A hybrid structure of no-core fiber and graded-index multimode fiber (NCF-GIMF) is demonstrated, which can be used as both the saturable absorber (SA) and the wavelength selective element. By employing such a device, an L-band wavelength tunable Er-doped mode-locked laser is realized and stable single solitons of ~1.7ps, with continuously tunable wavelengths from 1574 nm to 1601.1 nm, are generated. Moreover, dual-wavelength mode-locked laser operation at 1575.4 nm and 1603 nm is achieved, with pulse duration of 1.2 ps and 1.7 ps, respectively. The proposed device is simple and compact, and represents an effective approach for tunable and dual-wavelength mode-locked fiber laser operation.
关键词： Laser tuning,Optical fiber devices,Laser mode locking,Fiber-graded index multimode fiber,Fiber nonlinear optics
更新于2025-11-28 14:23:57
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Sub-milliampere-threshold continuous wave operation of GaN-based vertical-cavity surface-emitting laser with lateral optical confinement by curved mirror
摘要： The continuous wave operation of a gallium-nitride-based vertical-cavity surface-emitting laser (GaN-based VCSEL) that uses boron ion implantation for lateral current confinement and a curved mirror for lateral optical confinement was investigated. The threshold current was 0.25 mA (Jth = 3.5 kA cm?2) for a 3 μm diameter current aperture at room temperature and the lasing wavelength was 445.3 nm. This is the lowest threshold current recorded for a GaN-based VCSEL. This result is considered to be a milestone for the further miniaturization of GaN-based VCSELs by the implementation of lateral optical confinement due to the incorporation of a curved mirror.
关键词： continuous wave operation,threshold current,lateral optical confinement,GaN-based VCSEL,curved mirror
更新于2025-11-28 14:23:57
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Study on a high-temperature optical fiber F–P acceleration sensing system based on MEMS
摘要： Vibration measurement at high temperature is of great signi?cance to monitoring the operation of major projects and mechanical equipment. As the temperature resistance of electrical vibration sensors is usually below 600 °C, it cannot meet the requirements of some high-temperature measuring conditions. This paper studies a high-temperature Fabry–Perot (F–P) acceleration sensing system with general single-mode ?ber. A high-temperature sensitive diaphragm is machined based on micro-electromechanical system (MEMS) technology and it is combined with the ?ber microstructure to enable the sensing probe to be packaged under high temperatures. According to the temperature characteristic of the length of the F–P cavity, a signal demodulation system was proposed based on the rapid automatic tracking of the quiescent operation point. The complete optical ?ber F–P acceleration sensing system conducted real-time vibration detection of high temperature casting in the foundry factory. The experimental result indicates that the optical ?ber high-temperature acceleration sensor showed a better vibration response in the working frequency of 100–1000 Hz and the relative error of the frequency measurement is less than 1.56% under normal temperatures and a high temperature of 800 °C.
关键词： Optical ?ber F–P,High-temperature,Acceleration sensor,Tunable laser source,MEMS
更新于2025-11-28 14:23:57
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Fiber laser based on a fiber Bragg grating and its application in high-temperature sensing
摘要： A fiber laser based on an FBG fabricated by femtosecond laser and a Sagnac loop as cavity mirrors is demonstrated. The fiber laser can work stably as a temperature sensor at 1000 ℃ after the FBG was annealed at 1100 ℃. The wavelength of the fiber laser had a quadratic dependence on temperature from room temperature to 1000 ℃. The temperature–wavelength had a good linear relationship from 300 ℃ to 1000 ℃. Its sensing sensitivity was about 15.9 pm/℃.
关键词： Optical fiber lasers,Fiber Bragg gratings,High temperature sensors
更新于2025-11-28 14:23:57
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Analysis of optical injection on red and blue laser diodes for high bit-rate visible light communication
摘要： In this work, self-injection and external-injection in ～450 nm InGaN/GaN blue and ～650 nm InGaP/AlGaInP red diode lasers are investigated. A distinct locking characteristic is observed in the self-injection case with small 19 cm cavity length, demonstrating enhanced ～2.34 and ～2.07 GHz 3-dB bandwidths, corresponding to a factor of ～1.4 and ～1.1 improvement, and reduced ～60 and ～80 pm spectral linewidths, for the blue and the red lasers, respectively. Moreover, this short external cavity self-injection locked system exhibited superior performance by a factor of 1.1–1.3 compared to the long cavity (26 cm) configuration. Conversely, the external optical injection exhibited weak locking signature with improved linewidths by a factor of ～1.6–2.8 and reaching as small as ～70 and ～87 pm for the blue laser, respectively, while almost doubling in the peak powers. Later, on–off keying modulation technique based data transmission rates of up to 3.5 and 4.5 Gb/s are demonstrated on free-running blue and red laser diodes, respectively, employing an in-house laser diode mount based system. Moreover, owing to the bandwidth limitation of the optically injected systems, successful transmission of up to 2 Gb/s is demonstrated with better performance compared to the respective free-running cases, in particular, the external-optically injected system demonstrated more than double improvement in the bit-error-rate.
关键词： Visible light communication,Semiconductor laser diodes,External optical injection,Self-injection locking
更新于2025-11-28 14:23:57
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An optical fiber strain sensor by using of taper based TCF structure
摘要： We propose an optical fiber strain sensor consisting of a spliced twin-core fiber (TCF). The sensor structure has two fiber tapers, which are weak taper and T-shaped taper. The taper waist of T-shaped taper is about half-size of the weak taper, but the length of the T-shaped taper is also about half-length of the weak taper. In the sensing structure, core mode and cladding modes of the TCF are excited simultaneously. Two tapered regions around the splicing interfaces can play the roles of splitting and combining the modes in the fiber. In experiment, the proposed device has good quality interferometric spectra, and the highest extinction ratio of 20 dB is achieved. When the stress increases from 0 με to 841.5 με, different wavelength sensitivities of 3.31 pm/με and 6.11 pm/με are achieved. Different intensity sensitivities of 7.5 × 10?3 dB/με and 9.9 × 10?3 dB/με are also achieved, respectively. The sensor has shown good test stability and low temperature sensitivity, which is good for precise strain measurement in practical applications.
关键词： Twin-core fiber,Fiber design and fabrication,Fiber optical sensor
更新于2025-11-28 14:23:57
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High-Power Continuous-Wave and Acousto-Optical Q-Switched Ho:(Sc <sub/>0.5</sub> Y <sub/>0.5</sub> ) <sub/>2</sub> SiO <sub/>5</sub> Laser Pumped by Laser Diode
摘要： We experimentally investigate the continuous-wave (cw) and acousto-optical (AO) Q-switched performance of a diode-pumped Ho:(Sc0.5Y0.5)2SiO5 (Ho:SYSO) laser. A fiber-coupled laser diode at 1.91 ??m is employed as the pump source. The cw Ho:SYSO laser produces 13.0 W output power at 2097.9 nm and 56.0% slope efficiency with respect to the absorbed pump power. In the AO Q-switched regime, at a pulse repetition frequency of 5 kHz, the Ho:SYSO laser yields 2.1 mJ pulse energy and 21 ns pulse width, resulting in a calculated peak power of 100 kW. In addition, at the maximum output level, the beam quality factor of the Q-switched Ho:SYSO laser is measured to be about 1.6.
关键词： Laser Diode Pumped,Continuous-Wave,Acousto-Optical Q-Switched,High-Power,Ho:(Sc0.5Y0.5)2SiO5 Laser
更新于2025-11-28 14:23:57
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Active ring resonance cavity assisted single-mode all-optical microwave oscillator
摘要： A pure optical microwave oscillator with single mode oscillation is proposed and demonstrated. This system has no any electrical microwave devices as well as electro-optic (E/O) and opto-electronic (O/E) conversion. The oscillation frequency is chosen by Brillouin-selective sideband amplification, and the optical envelope detection and feedback modulation are implemented by a semiconductor optical amplifier (SOA). As a high-Q tunable optical comb filter, an active ring resonance cavity (ARRC) is employed to select one oscillation mode within the Brillouin gain region, and consequently a single mode oscillation signal can be generated. In the experiment, a single mode photonic microwave signal with frequency of 10.83 GHz and side-mode suppression ratio of 48 dB is obtained. The measured phase noise is ?88 dBc/Hz@10 kHz. In addition, the tunability is also demonstrated by adjusting the wavelength of the light source.
关键词： Microwave photonics,SBS,All-optical microwave oscillator
更新于2025-11-28 14:23:57
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Ultrasensitive tantalum oxide nano-coated long-period gratings for detection of various biological targets
摘要： In this work we discussed a label-free biosensing application of long-period gratings (LPGs) optimized in refractive index (RI) sensitivity by deposition of thin tantalum oxide (TaOx) overlays. Comparing to other thin film and materials already applied for maximizing the RI sensitivity, TaOx offers good chemical and mechanical stability during its surface functionalization and other biosensing experiments. It was shown theoretically and experimentally that when RI of the overlay is as high as 2 in IR spectral range, for obtaining LPGs ultrasensitive to RI, the overlay’s thickness must be determined with subnanometer precision. In this experiment the TaOx overlays were deposited using Atomic Layer Deposition method that allowed for achieving overlays with exceptionally well-defined thickness and optical properties. The TaOx nano-coated LPGs show RI sensitivity determined for a single resonance exceeding 11,500 nm/RIU in RI range nD=1.335-1.345 RIU, as expected for label-free biosensing applications. Capability for detection of various in size biological targets, i.e., proteins (avidin) and bacteria (Escherichia coli), with TaOx-coated LPGs was verified using biotin and bacteriophage adhesin as recognition elements, respectively. It has been shown that functionalization process, as well as type of recognition elements and target analyte must be taken into consideration when the LPG sensitivity is optimized. In this work optimized approach made possible detection of small in size biological targets such as proteins with sensitivity reaching 10.21 nm/log(ng/ml).
关键词： protein detection,label-free biosensing,optical fiber sensor,tantalum oxide,bacteria detection,long-period grating,atomic layer deposition
更新于2025-11-28 14:23:57