Absorption efficiency of graded-index double-clad fiber lasers or amplifiers is analyzed. As ray optics method is no longer valid for graded-index case, the mode analysis method is used. Calculated results show that a...Absorption efficiency of graded-index double-clad fiber lasers or amplifiers is analyzed. As ray optics method is no longer valid for graded-index case, the mode analysis method is used. Calculated results show that absorption efficiency for a graded-index is higher than that for a step-index in symmetric case. In offset core case, the graded-index can achieve the same absorption efficiency with much smaller offset distance. Absorption efficiencies for different graded-index profiles of the inner cladding are compared.展开更多
We have proposed and demonstrated a double-cladding fiber (DCF) with cladding?mode resonance property for broadband acoustic vibration sensing. Since the fundamental mode in the core waveguide is able to be coupled to...We have proposed and demonstrated a double-cladding fiber (DCF) with cladding?mode resonance property for broadband acoustic vibration sensing. Since the fundamental mode in the core waveguide is able to be coupled to LP05 mode in the tube waveguide once the phase-matching condition is fulfilled, the transmission spectrum can exhibit a dip with a large extinction ratio. An acoustic vibration could induce the wavelength shift of such transmission spectrum, so that the intensity variation at a wavelength near the dip is coded with the information of the acoustic vibration signal. By demodulating the response of intensity variation, the frequency of the applied acoustic vibration signal can be recovered. Such a DCF-based sensor with an intensity modulation could measure the acoustic vibration with a broadband frequency range from 1 Hz to 400 kHz and exhibits the maximum signal-to-noise ratio (SNR) of ?80.79 dB when the vibration frequency is 20 kHz. The obtained results show that the proposed DCF-based acoustic vibration sensor has a potential application in environmental assessment, structural damage detection, and health monitoring.展开更多
A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made largemode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M^2 ≈ 2 and several hundred nano...A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made largemode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M^2 ≈ 2 and several hundred nanoseconds pulse duration are achieved at the repetition rate of 1 - 50 kHz. When the repetition rate is 1 kHz, the pulse energy is 0.93 mJ with the pulse duration of 132 ns. Meanwhile, the profile of laser pulses shows some mode-locking phenomena, the mechanism of the phenomena is discussed.展开更多
A strain-induced birefringence double-clad (DC) fiber Bragg grating (FBG) is proposed and demonstrated. The grating is fabricated in the core of rectangular inner cladding double clad fiber by using phase mask method....A strain-induced birefringence double-clad (DC) fiber Bragg grating (FBG) is proposed and demonstrated. The grating is fabricated in the core of rectangular inner cladding double clad fiber by using phase mask method. By applying lateral strain on the grating, the birefringence is induced. In order to detect the birefringent effect of the grating, we use it as the output mirror of a laser. When lateral strain is applied, the grating becomes birefringent. Therefore, one reflection peak of double-clad fiber Bragg grating becomes two peaks and the laser also lases in two wavelengths. The wavelength spacing of the laser can be tuned from 0 to 0.8 nm. The absolute wavelengths for the two polarizations can be tuned 1.2 and 2.0 nm, respectively.展开更多
Considering the wavelength characteristics of the pump high-power laser diode, a modified Fabry-Perot fiber laser resonator is designed. And a fiber laser with more than 10Watts output, near diffraction-limited and op...Considering the wavelength characteristics of the pump high-power laser diode, a modified Fabry-Perot fiber laser resonator is designed. And a fiber laser with more than 10Watts output, near diffraction-limited and operating in the 1110nm region is developed.展开更多
A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With oneend-pumping...A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With oneend-pumping scheme, pumped by a high-power laser diode with launching power of 280 W, a maximum continuous wave (CW) output of 110 W is obtained with an optical-to-optical efficiency of 40%.展开更多
A large-mode-area neodymium-doped silicate photonic bandgap fiber was theoretically designed and experimen- tMly demonstrated. The relative index step between the high-index rods and the background glass was -0.5%, wh...A large-mode-area neodymium-doped silicate photonic bandgap fiber was theoretically designed and experimen- tMly demonstrated. The relative index step between the high-index rods and the background glass was -0.5%, which is the lowest cladding index difference reported on rare-earth-doped all-solid photonic bandgap fibers to our knowledge. An output power of 3.6 W with a slope efficiency of 31- was obtained for a 100-cm-long fiber.展开更多
Nd<sup>3+</sup> -doped double-clad fiber is a new type of fiber that has large N.A.and large receivingarea compared with single-clad rare-earth-doped fiber.So Nd<sup>3+</sup>-doped double-clad ...Nd<sup>3+</sup> -doped double-clad fiber is a new type of fiber that has large N.A.and large receivingarea compared with single-clad rare-earth-doped fiber.So Nd<sup>3+</sup>-doped double-clad fiberpumped directly by laser-diode arrays can be manufactured into high-power fiber lasers,high-power superfluorescence sources and high-gain fiber amplifiers,and they will be applied展开更多
The absorption characteristics of radially inhomogeneous double-clad fiber (DCF) are investigated firstly with the method of caustic radius, combined with the method of WKBJ. The results are significant for double-cla...The absorption characteristics of radially inhomogeneous double-clad fiber (DCF) are investigated firstly with the method of caustic radius, combined with the method of WKBJ. The results are significant for double-clad optical fiber lasers and amplifiers.展开更多
The Yb3+-doped double-clad fibers with novel inner cladding have been made by using MCVD process, solution-doping method and optical machining together. The laser power and slope efficiency of the fiber lasers are hig...The Yb3+-doped double-clad fibers with novel inner cladding have been made by using MCVD process, solution-doping method and optical machining together. The laser power and slope efficiency of the fiber lasers are higher than 1.8W and 50% respectively.展开更多
Based on the principle of Fabry-Perot (F-P) interference, a new type of optical fiber curvature sensor is presented,which is fabricated by single-mode fiber(SMF), ceramic tube and double-cladding fiber (DCF). And the ...Based on the principle of Fabry-Perot (F-P) interference, a new type of optical fiber curvature sensor is presented,which is fabricated by single-mode fiber(SMF), ceramic tube and double-cladding fiber (DCF). And the curvature sensing properties are analyzed, and the double-peak method is used to demodulate the cavity length. The experimental results show that the F-P interference spectrum shifts toward long wavelengths with increasing the curvature. And the sensors are placed in different positions on the cantilever to get their different curvature sensitivities. Smaller initial cavity length gives greater sensor sensitivity. The best curvature sensitivity is achieved as 2 554.53 pm/m^(-1) in 0.71—1.18 m^(-1). By demodulating the length of the F-P cavity, the cavity length of sensor 4 is changed by 0.08 mm. Therefore, the sensor has some potential for measure the small displacement.展开更多
This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the...This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the power transfer between the core modes and the cladding modes during thermally-induced refractive index variations is established based on the mode coupling theory. The results of numerical simulations based on actual laser parameters are presented. Experimental measurements were also carried out, the results showed good agreement with the corresponding simulation results.展开更多
Acoustic/ultrasonic sensors are devices that can convert mechanical energy into electrical signals.The Fabry–Perot cavity is processed on the end face of the double-clad fiber by a two-photon three-dimensional lithog...Acoustic/ultrasonic sensors are devices that can convert mechanical energy into electrical signals.The Fabry–Perot cavity is processed on the end face of the double-clad fiber by a two-photon three-dimensional lithography machine.In this study,the outer diameter of the core cladding was 250μm,the diameter of the core was 9μm,and the microcavity sensing unit was only 30μm.It could measure ultrasonic signals with high precision.The characteristics of the proposed ultrasonic sensor were investigated,and its feasibility was proven through experiments.Its design has a small size and can replace a larger ultrasonic detector device for photoacoustic signal detection.The sensor is applicable to the field of biomedical information technology,including medical diagnosis,photoacoustic endoscopy,and photoacoustic imaging.展开更多
Based on propagation-rate equations, the influence of different input pulse durations on the properties of Er^3＋/Yb^3＋ co-doped double-clad fiber amplifier at dynamic equilibrium was analyzed. The change characteris...Based on propagation-rate equations, the influence of different input pulse durations on the properties of Er^3＋/Yb^3＋ co-doped double-clad fiber amplifier at dynamic equilibrium was analyzed. The change characteristic of output power sag with pulse duration and repetition rate was shown. Whether single or multichannel input pulses are amplified, the shorter the input pulse duration is, the smaller the power sags of output pulse will be. At low repetition rate, upper gain values（Gupper） of gain swing are almost the same for different input pulse durations, which tend to the small signal gain, but lower gain value（Glower） of short input pulse is larger than that of long input pulse. At highrepetition rate, lower gain value（Glower） approaches to upper gain value（Glower）.展开更多
Multiple-beam fringes of equal chromatic order interferometry is a powerful technique to extract optical properties over a continuous range of spectrum. In this paper we develop a theory for the spectral shape of the ...Multiple-beam fringes of equal chromatic order interferometry is a powerful technique to extract optical properties over a continuous range of spectrum. In this paper we develop a theory for the spectral shape of the fringes of equal chromatic order (FECO) that are formed across a double-clad fiber. The modified single term Sellmeier dispersion formula is used to construct the refractive index dispersion curves for the liquid, claddings, and core. Expressions for the paraxial optical path length for several rays passing through the fiber and the liquid are developed. The condition of bright fringe is applied to get an analytical expression for the spectral shape of the FECO across a double-clad fiber with an elliptical/circular inner cladding. A potential application of this theory is to determine the dispersion of Kerr constant of the claddings and the core of the fiber. To illustrate the theory and its application, simulation examples are provided and discussed.展开更多
文摘Absorption efficiency of graded-index double-clad fiber lasers or amplifiers is analyzed. As ray optics method is no longer valid for graded-index case, the mode analysis method is used. Calculated results show that absorption efficiency for a graded-index is higher than that for a step-index in symmetric case. In offset core case, the graded-index can achieve the same absorption efficiency with much smaller offset distance. Absorption efficiencies for different graded-index profiles of the inner cladding are compared.
基金the National Key Research and Development Program of China (Grant No. 2016YFF0100600)the National Natural Science Foundation of China (Grant Nos. 61735009 and 61635006).
文摘We have proposed and demonstrated a double-cladding fiber (DCF) with cladding?mode resonance property for broadband acoustic vibration sensing. Since the fundamental mode in the core waveguide is able to be coupled to LP05 mode in the tube waveguide once the phase-matching condition is fulfilled, the transmission spectrum can exhibit a dip with a large extinction ratio. An acoustic vibration could induce the wavelength shift of such transmission spectrum, so that the intensity variation at a wavelength near the dip is coded with the information of the acoustic vibration signal. By demodulating the response of intensity variation, the frequency of the applied acoustic vibration signal can be recovered. Such a DCF-based sensor with an intensity modulation could measure the acoustic vibration with a broadband frequency range from 1 Hz to 400 kHz and exhibits the maximum signal-to-noise ratio (SNR) of ?80.79 dB when the vibration frequency is 20 kHz. The obtained results show that the proposed DCF-based acoustic vibration sensor has a potential application in environmental assessment, structural damage detection, and health monitoring.
基金the National Key Basic Research Project of China.
文摘A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made largemode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M^2 ≈ 2 and several hundred nanoseconds pulse duration are achieved at the repetition rate of 1 - 50 kHz. When the repetition rate is 1 kHz, the pulse energy is 0.93 mJ with the pulse duration of 132 ns. Meanwhile, the profile of laser pulses shows some mode-locking phenomena, the mechanism of the phenomena is discussed.
基金This work was supported by the National Natural Science Foundation of China (No. 60137010) the National '863' Project of China (No. 2003AA312100).
文摘A strain-induced birefringence double-clad (DC) fiber Bragg grating (FBG) is proposed and demonstrated. The grating is fabricated in the core of rectangular inner cladding double clad fiber by using phase mask method. By applying lateral strain on the grating, the birefringence is induced. In order to detect the birefringent effect of the grating, we use it as the output mirror of a laser. When lateral strain is applied, the grating becomes birefringent. Therefore, one reflection peak of double-clad fiber Bragg grating becomes two peaks and the laser also lases in two wavelengths. The wavelength spacing of the laser can be tuned from 0 to 0.8 nm. The absolute wavelengths for the two polarizations can be tuned 1.2 and 2.0 nm, respectively.
文摘Considering the wavelength characteristics of the pump high-power laser diode, a modified Fabry-Perot fiber laser resonator is designed. And a fiber laser with more than 10Watts output, near diffraction-limited and operating in the 1110nm region is developed.
基金This work was supported by the National Natural Sci-ence Foundation of China (No. 60244005)Chinese Academy of Sciences, and Shanghai Science & Technology Foundation (No. 036105034).
文摘A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With oneend-pumping scheme, pumped by a high-power laser diode with launching power of 280 W, a maximum continuous wave (CW) output of 110 W is obtained with an optical-to-optical efficiency of 40%.
基金supported by the Natural Science Foundation of Shanghai(No.17ZR1434000)the China Postdoctoral Science Foundation(No.2016M601653)the National Natural Science Foundation of China(No.61775224)
文摘A large-mode-area neodymium-doped silicate photonic bandgap fiber was theoretically designed and experimen- tMly demonstrated. The relative index step between the high-index rods and the background glass was -0.5%, which is the lowest cladding index difference reported on rare-earth-doped all-solid photonic bandgap fibers to our knowledge. An output power of 3.6 W with a slope efficiency of 31- was obtained for a 100-cm-long fiber.
文摘Nd<sup>3+</sup> -doped double-clad fiber is a new type of fiber that has large N.A.and large receivingarea compared with single-clad rare-earth-doped fiber.So Nd<sup>3+</sup>-doped double-clad fiberpumped directly by laser-diode arrays can be manufactured into high-power fiber lasers,high-power superfluorescence sources and high-gain fiber amplifiers,and they will be applied
基金This work was supported by the National Science Foundation of China (60277025)
文摘The absorption characteristics of radially inhomogeneous double-clad fiber (DCF) are investigated firstly with the method of caustic radius, combined with the method of WKBJ. The results are significant for double-clad optical fiber lasers and amplifiers.
文摘The Yb3+-doped double-clad fibers with novel inner cladding have been made by using MCVD process, solution-doping method and optical machining together. The laser power and slope efficiency of the fiber lasers are higher than 1.8W and 50% respectively.
基金supported by the National Natural Science Foundation of China(Nos.61575170 and 61605168)the State Scholarship Fund of China(No.201708130199)+1 种基金the Key Basic Research Program of Hebei Province(No.17961701D)"Xin Rui Gong Cheng" Talent Project of Yanshan University
文摘Based on the principle of Fabry-Perot (F-P) interference, a new type of optical fiber curvature sensor is presented,which is fabricated by single-mode fiber(SMF), ceramic tube and double-cladding fiber (DCF). And the curvature sensing properties are analyzed, and the double-peak method is used to demodulate the cavity length. The experimental results show that the F-P interference spectrum shifts toward long wavelengths with increasing the curvature. And the sensors are placed in different positions on the cantilever to get their different curvature sensitivities. Smaller initial cavity length gives greater sensor sensitivity. The best curvature sensitivity is achieved as 2 554.53 pm/m^(-1) in 0.71—1.18 m^(-1). By demodulating the length of the F-P cavity, the cavity length of sensor 4 is changed by 0.08 mm. Therefore, the sensor has some potential for measure the small displacement.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61307057 and 61675114)
文摘This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the power transfer between the core modes and the cladding modes during thermally-induced refractive index variations is established based on the mode coupling theory. The results of numerical simulations based on actual laser parameters are presented. Experimental measurements were also carried out, the results showed good agreement with the corresponding simulation results.
基金This work was supported in part by the Natural Science Foundation of Guangdong Province,No.2020A1515010958Key Project of Shenzhen Science and Technology Plan,No.JCYJ20200109113808048.
文摘Acoustic/ultrasonic sensors are devices that can convert mechanical energy into electrical signals.The Fabry–Perot cavity is processed on the end face of the double-clad fiber by a two-photon three-dimensional lithography machine.In this study,the outer diameter of the core cladding was 250μm,the diameter of the core was 9μm,and the microcavity sensing unit was only 30μm.It could measure ultrasonic signals with high precision.The characteristics of the proposed ultrasonic sensor were investigated,and its feasibility was proven through experiments.Its design has a small size and can replace a larger ultrasonic detector device for photoacoustic signal detection.The sensor is applicable to the field of biomedical information technology,including medical diagnosis,photoacoustic endoscopy,and photoacoustic imaging.
文摘Based on propagation-rate equations, the influence of different input pulse durations on the properties of Er^3＋/Yb^3＋ co-doped double-clad fiber amplifier at dynamic equilibrium was analyzed. The change characteristic of output power sag with pulse duration and repetition rate was shown. Whether single or multichannel input pulses are amplified, the shorter the input pulse duration is, the smaller the power sags of output pulse will be. At low repetition rate, upper gain values（Gupper） of gain swing are almost the same for different input pulse durations, which tend to the small signal gain, but lower gain value（Glower） of short input pulse is larger than that of long input pulse. At highrepetition rate, lower gain value（Glower） approaches to upper gain value（Glower）.
文摘Multiple-beam fringes of equal chromatic order interferometry is a powerful technique to extract optical properties over a continuous range of spectrum. In this paper we develop a theory for the spectral shape of the fringes of equal chromatic order (FECO) that are formed across a double-clad fiber. The modified single term Sellmeier dispersion formula is used to construct the refractive index dispersion curves for the liquid, claddings, and core. Expressions for the paraxial optical path length for several rays passing through the fiber and the liquid are developed. The condition of bright fringe is applied to get an analytical expression for the spectral shape of the FECO across a double-clad fiber with an elliptical/circular inner cladding. A potential application of this theory is to determine the dispersion of Kerr constant of the claddings and the core of the fiber. To illustrate the theory and its application, simulation examples are provided and discussed.
