We demonstrate a stable Q-switched mode-locked erbium-doped fiber laser （EDFL） operating in dark regime based on the nonlinear polarization rotation technique. The EDFL produces a pulse train where the Q-switching e...We demonstrate a stable Q-switched mode-locked erbium-doped fiber laser （EDFL） operating in dark regime based on the nonlinear polarization rotation technique. The EDFL produces a pulse train where the Q-switching envelope is formed by multiple dark pulses. The repetition rate of the Q-switched envelope can be increased from 0.96kHz to 3.26kHz, whereas the pulse width reduces from 211 #s to 86#s. The highest pulse of 479nJ is obtained at the pump power of 55 mW. It is also observed that the dark pulses inside the Q-switching envelope consist of two parts： square and trailing dark pulses. The shortest pulse width of the dark square pulse is obtained at 40.5μs when the pump power is fixed at 145mW. The repetition rate of trailing dark pulses can be increased from 27.62kHz to 50kHz as the pump power increases from 55mW to 145mW.展开更多
A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5th order h...A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5th order harmonic by increasing the pump power with an appropriate polarization controller orientation. The fundamental repetition rate of 2O kHz is obtained at the pump power of 29 m W. The highest pulse energy of 42.6 n3 is obtained at the fundamental repetition rate. The operating frequency of the dark pulse trains shifts to 2nd, 3rd, 4th and 5th harmonic as the pump powers are increased to 34mW, 50mW, 59mW and 137mW, respectively.展开更多
An efficient and low noise short wavelength band erbium-doped fibre amplifier （S-band EDFA） is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500 nm signal as high as 2...An efficient and low noise short wavelength band erbium-doped fibre amplifier （S-band EDFA） is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500 nm signal as high as 26.9 dB, which is 9.6 dB higher than the two-stage single-pass amplifier. The corresponding noise figure obtained is 7.5 dB, which is of the same level as in the single-pass amplifier and more than 2 dB lower than the previously reported double-pass amplifier [IEIOE Electron. Express 2 （2005） 182]. The gain enhancement is due to the double pass-propagation of the test signal in the second stage, which increases the effective erbium-doped fibre （EDF） length. The low noise is attributed to the optical circulator between EDFs, which prevents the backward amplified spontaneous emission from propagating into the input part of the amplifier. The proposed amplifier is expected to play an important role in the development of a practical S-band EDFA.展开更多
Q-switched pulsed laser systems operating in the eye-safe wavelength region （λ〉 1.4 μm） are promis- ing for applications such as light detection and ranging （lidar）, differential absorption lidar, optical commu...Q-switched pulsed laser systems operating in the eye-safe wavelength region （λ〉 1.4 μm） are promis- ing for applications such as light detection and ranging （lidar）, differential absorption lidar, optical communi- cation, sensor and instrumentations. Fiber lasers are particularly attractive for such applications due to the fact that the beam quality can be independent of output power and they can be robustly engineered. There is an increasing interest in Q-switched erbium- doped fiber lasers （EDFLs）, which can be generated by using either active or passive techniques. Com- pared with the actively Q-switched ones, passively Q- switched EDFLs have attracted much attention for their advantages of compactness, low cost, flexibility and simplicity of design. Different kinds of saturable absorbers, such as the transition metal-doped crys- tals and semiconductor quantum-well structures, have been applied to realize Q-switched EDFLs.How- ever, when they are used in the laser cavity, additional alignment devices, such as lens, mirrors or U-bench units, have to be applied. This may increase the in- sertion loss and the complexity of the laser cavity.展开更多
A simple mode-locked erbium-doped fiber laser （EDFL） with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third ...A simple mode-locked erbium-doped fiber laser （EDFL） with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third harmonic pulse repetition rate of 87kHz as the 1480 nm pump power increases from the threshold of 17.5 m W to 34.3mW. The square pulse duration increases from 105 ns to 245ns as the pump power increases within this region. The pulse operation switches to the second operation state as the pump power is varied from 48.2mW to l16.Tm W. The laser operates at a fundamental repetition rate of 29 kHz with a fixed pulse width of 8.5 μs within the pump power region. At a pump power of ll6.TmW, the average output power is 3.84mW, which corresponds to the pulse energy of 131.5 ng. When the pump power continues to increase, the pulse train experiences unstable oscillation before it reaches the third stable operation state within a pump power region of 138.9 m W to 145.0 m W. Within this region, the EDFL produces a fixed pulse width of 2.8 μs and a harmonic pulse repetition rate of 58 kHz.展开更多
We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength l...We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW.展开更多
The straight channel optical waveguide coated with the SnO_(2) nanoparticle is studied as an all-optical humidity sensor.The proposed sensor shows that the transmission loss of the waveguide increases with increasing ...The straight channel optical waveguide coated with the SnO_(2) nanoparticle is studied as an all-optical humidity sensor.The proposed sensor shows that the transmission loss of the waveguide increases with increasing relative humidity(RH)from 56%to 90%with very good repeatability.The sensitivity to changes in relative humidity is~2 dB/%RH.The response time of the humidity sensor is 2.5 s,and the recovery time is 3.5 s.The response to humidity can be divided into 3 different regions,which are correlated to the degree of water adsorption in the SnO_(2) nanoparticle layer.Compared with the previous all-optical humidity sensor based on SnO_(2),the proposed sensor exhibits more rapid response,simpler fabrication process,and higher sensitivity.The proposed sensor has a potential application in the long distance,remote agriculture,and biological humidity sensing.展开更多
The pre-treatment of few-mode fibers (FMFs) has been successfully done with CO2 laser The wavelength difference, AA between the two resonant wavelengths in the few-mode fiber Bragg grating (FMFBG) varies with temperat...The pre-treatment of few-mode fibers (FMFs) has been successfully done with CO2 laser The wavelength difference, AA between the two resonant wavelengths in the few-mode fiber Bragg grating (FMFBG) varies with temperature increment during the annealing process. The results show that the treated fibers with lower stresses have lower thermal sensitivity in △λ than that of non-treated fiber. However, the treated fibers produce FMFBGs with better thermal durability and regeneration ratio. It is conceived that the presence of those stresses in the pristine fiber is responsible for the high thermal sensitivity in △λ. The thennal relaxation of stresses and structural rearrangement during the thennal annealing process are responsible for the degradation of the strength and resilience of the regenerated grating.展开更多
A non-adiabatic microfiber coupler is fabricated by flame brushing technique and then theoretically and experimentally analyzed.The effective length of the microfiber coupler is determined by simulation,and a low-nois...A non-adiabatic microfiber coupler is fabricated by flame brushing technique and then theoretically and experimentally analyzed.The effective length of the microfiber coupler is determined by simulation,and a low-noise laser is demonstrated using various lengths of erbium-doped fiber（EDF） when incorporated in a laser setup.At 18.6-mW input pump power,the maximum output power of 20 μW and the lowest lasing threshold of 3.8 mW are obtained with a 90-cm-long EDF.展开更多
A new and easy-to-fabricate strain sensor has been developed,based on fiber Bragg grating(FBG)technology embedded into a thermoplastic polyurethane filament using a 3-dimensional(3D)printer.Taking advantage of the fle...A new and easy-to-fabricate strain sensor has been developed,based on fiber Bragg grating(FBG)technology embedded into a thermoplastic polyurethane filament using a 3-dimensional(3D)printer.Taking advantage of the flexibility and elastic properties of the thermoplastic polyurethane material,the embedding of the FBG provides durable protection with enhanced flexibility and sensitivity,as compared to the use of a bare FBG.Results of an evaluation of its performance have shown that the FBG sensors embedded in this way can be applied effectively in the measurement of strain,with an average wavelength responsivity of 0.0135 nm/cm of displacement for tensile strain and -0.0142 nm/cm for compressive strain,both showing a linearity value of up to 99%.Furthermore,such an embedded FBG-based strain sensor has a sensitivity of~1.74 times greater than that of a bare FBG used for strain measurement and is well protected and suitable for in-the-field use.It is also observed that the thermoplastic polyurethane based(TPU-based)FBG strain sensor carries a sensitivity value of~2.05 times higher than that of the polylactic acid based(PLA-based)FBG strain sensor proving that TPU material can be made as the material of choice as a“sensing”pad for the FBG.展开更多
We experimentally demonstrate the application of MoSe2 thin film as a nonlinear medium and stabilizer to generate a multi-wavelength erbium-doped fiber laser. The cooperation of a photonic crystal fiber and a polari- ...We experimentally demonstrate the application of MoSe2 thin film as a nonlinear medium and stabilizer to generate a multi-wavelength erbium-doped fiber laser. The cooperation of a photonic crystal fiber and a polari- zation-dependent isolator induces unstable multi-wavelength oscillations based on the nonlinear polarization rotation effect. A MoSe2 thin film is further incorporated into the cavity to achieve a stable multi-wavelength. The laser generates 7 lasings with a constant spacing of 0.47 nm at a pump power of 250 roW. The nmlti- wavelength erbium-doped fiber laser is stable with power fluctuations of less than 5 dB over 30 min.展开更多
An abrupt change in optical transmission characteristic of a graphene oxide(GO)coated optical planar waveguide was observed.This observation was based on the peculiar characteristics of the graphene oxide film,namely ...An abrupt change in optical transmission characteristic of a graphene oxide(GO)coated optical planar waveguide was observed.This observation was based on the peculiar characteristics of the graphene oxide film,namely its high transverse-electric polarized light propagation loss,highly selective permeability of water,and change in optical propagation characteristic in the presence of water.The as-fabricated GO-coated optical waveguide showed a large polarization dependent loss of~32 dB in the C-band optical fiber communication window(1550 nm).The response of the proposed sensor was first tested by using water.When a drop of water was applied onto the GO coating,the large polarization dependent loss was fully suppressed almost instantaneously.This effect was reversible as the polarization dependent loss was restored after complete water evaporation from the GO coating.All-optical measurement of water content in alcohol was then demonstrated by using the GO-coated optical waveguide.By analyzing the drying profile of the water-alcohol mixture,water content in the range of 0.2 volume%-100 volume%could be measured.These measurements were carried out by using solution volume of 1.0μL only.The all-optical sensing nature of the proposed sensor has potential applications in in-situ monitoring of water content in alcohol.展开更多
We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controll...We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.展开更多
基金Supported by the Fund from University of Malaya under Grant No RU007/2015LRGS(2015)/NGOD/UM/KPTMOSTI under Grant No SF014-2014
文摘We demonstrate a stable Q-switched mode-locked erbium-doped fiber laser （EDFL） operating in dark regime based on the nonlinear polarization rotation technique. The EDFL produces a pulse train where the Q-switching envelope is formed by multiple dark pulses. The repetition rate of the Q-switched envelope can be increased from 0.96kHz to 3.26kHz, whereas the pulse width reduces from 211 #s to 86#s. The highest pulse of 479nJ is obtained at the pump power of 55 mW. It is also observed that the dark pulses inside the Q-switching envelope consist of two parts： square and trailing dark pulses. The shortest pulse width of the dark square pulse is obtained at 40.5μs when the pump power is fixed at 145mW. The repetition rate of trailing dark pulses can be increased from 27.62kHz to 50kHz as the pump power increases from 55mW to 145mW.
文摘A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5th order harmonic by increasing the pump power with an appropriate polarization controller orientation. The fundamental repetition rate of 2O kHz is obtained at the pump power of 29 m W. The highest pulse energy of 42.6 n3 is obtained at the fundamental repetition rate. The operating frequency of the dark pulse trains shifts to 2nd, 3rd, 4th and 5th harmonic as the pump powers are increased to 34mW, 50mW, 59mW and 137mW, respectively.
文摘An efficient and low noise short wavelength band erbium-doped fibre amplifier （S-band EDFA） is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500 nm signal as high as 26.9 dB, which is 9.6 dB higher than the two-stage single-pass amplifier. The corresponding noise figure obtained is 7.5 dB, which is of the same level as in the single-pass amplifier and more than 2 dB lower than the previously reported double-pass amplifier [IEIOE Electron. Express 2 （2005） 182]. The gain enhancement is due to the double pass-propagation of the test signal in the second stage, which increases the effective erbium-doped fibre （EDF） length. The low noise is attributed to the optical circulator between EDFs, which prevents the backward amplified spontaneous emission from propagating into the input part of the amplifier. The proposed amplifier is expected to play an important role in the development of a practical S-band EDFA.
文摘Q-switched pulsed laser systems operating in the eye-safe wavelength region （λ〉 1.4 μm） are promis- ing for applications such as light detection and ranging （lidar）, differential absorption lidar, optical communi- cation, sensor and instrumentations. Fiber lasers are particularly attractive for such applications due to the fact that the beam quality can be independent of output power and they can be robustly engineered. There is an increasing interest in Q-switched erbium- doped fiber lasers （EDFLs）, which can be generated by using either active or passive techniques. Com- pared with the actively Q-switched ones, passively Q- switched EDFLs have attracted much attention for their advantages of compactness, low cost, flexibility and simplicity of design. Different kinds of saturable absorbers, such as the transition metal-doped crys- tals and semiconductor quantum-well structures, have been applied to realize Q-switched EDFLs.How- ever, when they are used in the laser cavity, additional alignment devices, such as lens, mirrors or U-bench units, have to be applied. This may increase the in- sertion loss and the complexity of the laser cavity.
文摘A simple mode-locked erbium-doped fiber laser （EDFL） with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third harmonic pulse repetition rate of 87kHz as the 1480 nm pump power increases from the threshold of 17.5 m W to 34.3mW. The square pulse duration increases from 105 ns to 245ns as the pump power increases within this region. The pulse operation switches to the second operation state as the pump power is varied from 48.2mW to l16.Tm W. The laser operates at a fundamental repetition rate of 29 kHz with a fixed pulse width of 8.5 μs within the pump power region. At a pump power of ll6.TmW, the average output power is 3.84mW, which corresponds to the pulse energy of 131.5 ng. When the pump power continues to increase, the pulse train experiences unstable oscillation before it reaches the third stable operation state within a pump power region of 138.9 m W to 145.0 m W. Within this region, the EDFL produces a fixed pulse width of 2.8 μs and a harmonic pulse repetition rate of 58 kHz.
文摘We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW.
基金supported by the Ministry of Research,Technology&Higher Education of Indonesia with PMDSU scholarship fundingthe Malaysia Ministry of Higher Education(MOHE)(LRGS(2015)/NGOD/UM/KPT)。
文摘The straight channel optical waveguide coated with the SnO_(2) nanoparticle is studied as an all-optical humidity sensor.The proposed sensor shows that the transmission loss of the waveguide increases with increasing relative humidity(RH)from 56%to 90%with very good repeatability.The sensitivity to changes in relative humidity is~2 dB/%RH.The response time of the humidity sensor is 2.5 s,and the recovery time is 3.5 s.The response to humidity can be divided into 3 different regions,which are correlated to the degree of water adsorption in the SnO_(2) nanoparticle layer.Compared with the previous all-optical humidity sensor based on SnO_(2),the proposed sensor exhibits more rapid response,simpler fabrication process,and higher sensitivity.The proposed sensor has a potential application in the long distance,remote agriculture,and biological humidity sensing.
文摘The pre-treatment of few-mode fibers (FMFs) has been successfully done with CO2 laser The wavelength difference, AA between the two resonant wavelengths in the few-mode fiber Bragg grating (FMFBG) varies with temperature increment during the annealing process. The results show that the treated fibers with lower stresses have lower thermal sensitivity in △λ than that of non-treated fiber. However, the treated fibers produce FMFBGs with better thermal durability and regeneration ratio. It is conceived that the presence of those stresses in the pristine fiber is responsible for the high thermal sensitivity in △λ. The thennal relaxation of stresses and structural rearrangement during the thennal annealing process are responsible for the degradation of the strength and resilience of the regenerated grating.
基金supported by the University of Malaya Research Grant Scheme under Grant No.PG139-2012B
文摘A non-adiabatic microfiber coupler is fabricated by flame brushing technique and then theoretically and experimentally analyzed.The effective length of the microfiber coupler is determined by simulation,and a low-noise laser is demonstrated using various lengths of erbium-doped fiber（EDF） when incorporated in a laser setup.At 18.6-mW input pump power,the maximum output power of 20 μW and the lowest lasing threshold of 3.8 mW are obtained with a 90-cm-long EDF.
基金financially supported by a Newton Fund Impact Scheme under the Newton-Ungku Omar Fund Partnership(Grant No.IF022-2020)funded by the UK Department for Business,Energy and Industrial Strategy and Malaysian Industry-Government Group for High Technology(MIGHT)and delivered by the British Council and MIGHT+1 种基金the support from University of Malaya(Grant Nos.RK021-2019 and TOP100PRC)the support from the Royal Academy of Engineering.
文摘A new and easy-to-fabricate strain sensor has been developed,based on fiber Bragg grating(FBG)technology embedded into a thermoplastic polyurethane filament using a 3-dimensional(3D)printer.Taking advantage of the flexibility and elastic properties of the thermoplastic polyurethane material,the embedding of the FBG provides durable protection with enhanced flexibility and sensitivity,as compared to the use of a bare FBG.Results of an evaluation of its performance have shown that the FBG sensors embedded in this way can be applied effectively in the measurement of strain,with an average wavelength responsivity of 0.0135 nm/cm of displacement for tensile strain and -0.0142 nm/cm for compressive strain,both showing a linearity value of up to 99%.Furthermore,such an embedded FBG-based strain sensor has a sensitivity of~1.74 times greater than that of a bare FBG used for strain measurement and is well protected and suitable for in-the-field use.It is also observed that the thermoplastic polyurethane based(TPU-based)FBG strain sensor carries a sensitivity value of~2.05 times higher than that of the polylactic acid based(PLA-based)FBG strain sensor proving that TPU material can be made as the material of choice as a“sensing”pad for the FBG.
基金funding from the University of Malaya through Grant Nos. RU007/2015 and LRGS(2015)/NGOD/UM/KPT
文摘We experimentally demonstrate the application of MoSe2 thin film as a nonlinear medium and stabilizer to generate a multi-wavelength erbium-doped fiber laser. The cooperation of a photonic crystal fiber and a polari- zation-dependent isolator induces unstable multi-wavelength oscillations based on the nonlinear polarization rotation effect. A MoSe2 thin film is further incorporated into the cavity to achieve a stable multi-wavelength. The laser generates 7 lasings with a constant spacing of 0.47 nm at a pump power of 250 roW. The nmlti- wavelength erbium-doped fiber laser is stable with power fluctuations of less than 5 dB over 30 min.
基金This research work is jointly supported by the Ministry of Education Fundamental Research Grant Scheme(Grant No.FRGS/1/2018/STG02/HWUM/02/2)University of Malaya Research grant(Grant No.RU013-2019)the Asian Office of Aerospace Research and Development(AOARD)Grant(Grant No.16IOA017).
文摘An abrupt change in optical transmission characteristic of a graphene oxide(GO)coated optical planar waveguide was observed.This observation was based on the peculiar characteristics of the graphene oxide film,namely its high transverse-electric polarized light propagation loss,highly selective permeability of water,and change in optical propagation characteristic in the presence of water.The as-fabricated GO-coated optical waveguide showed a large polarization dependent loss of~32 dB in the C-band optical fiber communication window(1550 nm).The response of the proposed sensor was first tested by using water.When a drop of water was applied onto the GO coating,the large polarization dependent loss was fully suppressed almost instantaneously.This effect was reversible as the polarization dependent loss was restored after complete water evaporation from the GO coating.All-optical measurement of water content in alcohol was then demonstrated by using the GO-coated optical waveguide.By analyzing the drying profile of the water-alcohol mixture,water content in the range of 0.2 volume%-100 volume%could be measured.These measurements were carried out by using solution volume of 1.0μL only.The all-optical sensing nature of the proposed sensor has potential applications in in-situ monitoring of water content in alcohol.
基金supported by the University of Malaya under the PPP grant scheme(No.PG139-2012B)
文摘We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.
