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Investigation of narrow band random fiber ring laser based on random phase-shift Bragg grating
摘要： A random ?ber laser based on a 25 mm long random phase-shift ?ber Bragg grating with a ring cavity is experimentally demonstrated in this paper. The random phase-shift grating is fabricated with the beam-scanning method in a single-mode ?ber. The random feedback and light localization are achieved by introducing 20 phase-shift points with random amplitudes along the grating length. A narrow band single-wavelength random ?ber laser with the 3 dB bandwidth of 0.44 pm is realized with a 980 nm laser pumping at 130 mW. The optical signal-to-noise ratio up to 55 dB is obtained at the same pump power. The pump threshold is only 21.8 mW. The number of emitted wavelengths is changeable by adjusting the pump power. The lasing wavelength near 1549.96 nm presents a maximum ?uctuation range of only 1.1 pm over time. With the random grating exposed to water, the mode competition is suppressed and the laser can be operated at more stable single-wavelength mode.
关键词： Laser mode,Ring cavity,Grating,Optical ?ber laser
更新于2025-11-28 14:24:03
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Nanotube mode-locked, wavelength and pulsewidth tunable thulium fiber laser
摘要： Mode-locked oscillators with highly tunable output characteristics are desirable for a range of applications. Here, with a custom-made tunable filter, we demonstrate a carbon nanotube (CNT) mode-locked thulium fiber laser with widely tunable wavelength, spectral bandwidth, and pulse duration. The demonstrated laser’s wavelength tuning range reached 300 nm (from 1733 nm to 2033 nm), which is the widest-ever that was reported for rare-earth ion doped fiber oscillators in the near-infrared. At each wavelength, the pulse duration can be regulated by changing the filter’s bandwidth. For example, at ~1902 nm, the pulse duration can be adjusted from 0.9 ps to 6.4 ps (the corresponding output spectral bandwidth from 4.3 nm to 0.6 nm). Furthermore, we experimentally and numerically study the spectral evolution of the mode-locked laser in presence of a tunable filter, a topic that has not been thoroughly investigated for thulium-doped fiber lasers. The detailed dynamical change of the mode-locked spectra is presented and we observed gradual suppression of the Kelly sidebands as the filter’s bandwidth is reduced. Further, using the polarization-maintaiing (PM) cavity ensures that the laser is stable and the output laser’s polarization extinction ratio is measured to exceed 20 dB.
关键词： thulium fiber laser,spectral bandwidth,polarization-maintaiing cavity,Kelly sidebands,tunable wavelength,pulse duration,Mode-locked oscillators,carbon nanotube
更新于2025-11-28 14:23:57
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Narrow no-gain competition linewidth dual-wavelength laser at 912?nm and 1064 nm
摘要： A narrow linewidth, no-gain competition, 912 nm quasi-three level and 1064 nm four-level dual-wavelength laser is presented for the first time. This system consists of an intra-cavity pumped Nd:YVO4 laser emitting at 1064 nm, using a 912 nm Nd:GdVO4 laser. A Fabry-Perot etalon is used to compress the linewidth located at the common parts of the 912 nm and 1064 nm laser resonators. When the etalon, with an angle of refraction of 15°, was introduced into the cavity, the narrow linewidth dual-wavelength laser was obtained. The corresponding minimum linewidths were 0.284 nm and 0.627 nm.
关键词： intra-cavity pumped,dual-wavelength,narrow linewidth
更新于2025-11-28 14:23:57
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Construction of 879?nm direct intra-cavity pumped dual-wavelength laser operating at 912?nm and 1064?nm
摘要： A dual-wavelength continuous-wave laser with direct intra-cavity pumping using a 879 nm laser diode that utilizes Nd:GdVO4 and Nd:YVO4 crystals, is presented. To the best of our knowledge, this system completely eliminates the gain competition between the 912 nm and 1064 nm transitions for the first time. A theoretical model is introduced to describe this intra-cavity pumped dual-wavelength laser. The lasing threshold of the 912 nm Nd:GdVO4 laser is presented by considering the ground-state reabsorption loss effect. A total output power of 1.33 W at dual-wavelength operation with an absorbed pump power of 7.91 W is experimentally achieved. The individual output power for the 912 nm and 1064 nm emissions were 0.43 W and 0.9 W, respectively. Both wavelengths operate in TEM00 mode with a total slope efficiency > 20%.
关键词： Lasers,Neodymium,Dual-wavelength,Solid-state,Intra-cavity pumped
更新于2025-11-28 14:23:57
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A tunable external cavity laser operating at excited states of bimodal-sized quantum-dot
摘要： In this paper, a tunable external cavity diode laser (ECDL) based on the first excited states of two independent quantum dot (QD) ensemble has been demonstrated. The device exhibits stabilized lasing with high power of 120 mW. We attribute the excellent output characteristics of the QD ECDL to carrier radiation recombination in high energy states, which has higher degeneracy than low energy states and can accommodate more carriers. The linewidth of ECDL is less than 0.2 nm, which is also much narrower than most of QD ECDLs as reported. Preliminary discussion attributes the spectra feature to the lower QD density and independent carrier transitions. The tunable range is 28.9 nm (970.1 ~ 999 nm) and the wavelength shift with the injection current is 0.7 nm/A.
关键词： tunable external cavity laser,bimodal-sized,quantum-dot,excited states
更新于2025-11-28 14:23:57
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Fast and simple interrogation of extrinsic Fabry–Perot interferometer sensor based on dual-wavelength intensity ratio
摘要： A fast and simple demodulation method for the variation of Fabry-Perot (FP) cavity length is proposed and demonstrated. Taking advantages of differentially detecting optical power intensities of dual-wavelength, a reliable linear correlation between the variation of FP cavity length and differential intensity ratio of dual-wavelength can be obtained. Besides, an extrinsic Fabry-Perot interferometer (EFPI) sensor with a length of 196.8 um was used to demonstrate performance of the method, and the time for each experimental operation is within 100 ms by the demodulation method and an integrable tunable laser assembly (ITLA). The demodulation resolution of 0.726 nm was achieved for the change of cavity length in a strain sensing experiment. By selecting two wavelengths at different positions in the system, the linear ranges of FP cavity length variation are 180 nm, 150 nm, and 130 nm responding to the sensitivities of -0.01099 nm-1, -0.01485 nm-1, and -0.02253 nm-1, respectively. It shows a high flexibility between the linear range and the sensitivity. Consequently, the different requirements of the EFPI sensor system can be easily fulfilled through appropriate selections of two different wavelengths. Moreover, the advantages of simplicity, fast speed, low cost can be fully revealed in the demodulation of large-scale production EFPI sensors.
关键词： Fabry-Perot cavity,Fiber sensors,Dual-wavelength.
更新于2025-11-28 14:23:57
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Metasurface for Constructing a Stable High- <i>Q</i> Plano-Planar Open Cavity
摘要： Traditional open cavities are constructed by planar or concave mirrors. A Fabry–Pérot (FP) cavity is convenient to integrate and fabricate, but highly sensitive to the parallelism of the end mirrors. In contrast, a concave cavity is more stable and possesses a lower leaky rate, but the curved geometry brings inconvenience. Here, it is suggested that a planar meta-cavity can simultaneously possess the advantages of both of the above open cavities by using a metasurface to create a planar meta-mirror that mimics the behavior of a concave mirror. For demonstration, a microwave meta-cavity is constructed, whose meta-mirror consists of subwavelength ceramic blocks on a metal substrate. Compared to an FP cavity, the meta-cavity is more robust against the alignment error of the end mirrors, and 15-fold enhancement of the quality factor is observed numerically. Experimental results are in good agreement with the simulated results. The suggested method may be extended to work in high frequency ranges. This work would support the planarization and miniaturization of an open cavity and may also increase the functionality.
关键词： open cavities,cavity stability,high quality factor,metasurfaces
更新于2025-09-23 15:23:52
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Design of a high-gain wideband antenna using double-layer metasurface
摘要： A wideband antenna is studied in this paper using a multi-layer metasurface structure and implementing a periodic array for enhancing the gain. The performance of the multilayer antenna is improved by using a sub-wavelength Fabry-Perot cavity (FPC). The feeding and main radiation patches of the microstrip antenna are placed separately on two substrates, which are stacked on top of each other without an air-gap in between. Two other substrates are placed within an optimized distance on top of the microstrip antenna. This structure, which has a double-sided periodic array configuration, includes a capacitive artificial impedance surface (AIS) on one side, and an inductive partially reflective surface (PRS) on the other side of the substrates. Making use of this configuration increases the gain up to 18 dBi and widens the frequency bandwidth. Moreover, measurement results indicate a frequency range from 10.8 GHz to 15 GHz with an S11 less than ?10 dB.
关键词： Fabry-Perot cavity,microstrip antenna,artificial impedance surface,partially reflective surface,metasurface
更新于2025-09-23 15:23:52
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Quantum Dialogue Based on Entanglement Swapping and Hadamard Operation via Cavity QED
摘要： A quantum dialogue scheme based on entanglement swapping and Hadamard operation via cavity QED is proposed, which effectively uses the evolution law of atom in cavity QED. The proposed scheme uses Bell states and GHZ states as quantum resource and only needs single-atom measurements. The proposed scheme is secure against active attacks from an eavesdropper and can transmit 4 secret bits per round communication.
关键词： Entanglement swapping,Hadamard operation,Quantum dialogue,Cavity QED
更新于2025-09-23 15:23:52
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Design of high gain, broadband resonant cavity antenna with meta-material inspired superstrate
摘要： A broadband high gain planar meta-material based Resonant Cavity Antenna (RCA) operating at C-band is proposed. The RCA is modeled using simple ray tracing method. The unit cell metamaterial consists of Artificial Magnetic Conductor (AMC) and square patch laminated on either side of a lossy commercial dielectric material of dielectric constant 4.4 & thickness 1.6mm, is used as the superstrate to design RCA. Square patch is the capacitive type and that AMC as inductive. Effects of the reflection phase of the substrate decide the high gain of the antenna. A cylindrical dielectric resonator antenna (CDRA) is embedded into the cavity as a feed. The proposed antenna achieves 22.4dBi gain with 2 layers of 4x4 array superstrate with a bandwidth of around 5.1GHz. The full-wave analysis is performed to extract the impedance matching, radiation pattern & gain of the composite RCA. A prototype antenna is fabricated and tested for verification of experimental results which was found to be well correlated. It also shows that the proposed RCA achieves -10dB impedance bandwidth of 72.72% ranging from 4 to 9.1GHz with a high gain around 22.4dBi.
关键词： Cylindrical Dielectric Resonator Antenna (CDRA),Metamaterials (MTM),Resonant Cavity Antenna (RCA)
更新于2025-09-23 15:23:52