The filtering mechanism of a free output coupler mode-locked laser based on large-mode-area photonic-crystal fibre is analysed. A filtering-soliton mode-locked laser with 495 fs pulse width and 21 nJ pulse energy is a...The filtering mechanism of a free output coupler mode-locked laser based on large-mode-area photonic-crystal fibre is analysed. A filtering-soliton mode-locked laser with 495 fs pulse width and 21 nJ pulse energy is achieved. Another novel cavity configuration is established to eliminate the filtering effect. Pulses, each 457 fs in width and 16.5 nJ in energy, are obtained in a soliton-like regime. Pulses, each 387 fs in width and 15.8 nJ in energy, are also generated in a stretched pulse regime and could be dechirped to 119 fs externally to the cavity.展开更多
A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a ...A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.展开更多
The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade ...The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade has resulted in a technology capable of producing a wide variety of features in metallic substrates.Furthermore,the potential for producing similar features in polymeric and ceramic substrates also exists.Recently the potential for utilizing high power focused laser beams to produce surface features using this process has been demonstrated.This paper details the results of recent trials performed with a 200 Yb-fibre laser and a galvanometer driven beam scanner for producing surface features using the Surfi-Sculpt process.A compact,cheap,easily robotically automated,laser Surfi-Sculpt machine,being able to operate at atmospheric pressure may have potential in a range of industry sectors.展开更多
In 2018, the journal High Power Laser Science and Engineering produced a Special Issue on Fibres for High Power Lasers. Nowadays, fibre-based laser sources have found extensive applications both in industry and in sci...In 2018, the journal High Power Laser Science and Engineering produced a Special Issue on Fibres for High Power Lasers. Nowadays, fibre-based laser sources have found extensive applications both in industry and in scientific research. The scope of the special issue was to span the latest developments on the fast developing fibre-based high-power lasers and amplifiers. The topics invited for inclusion were:展开更多
We experimentally demonstrate an all-normal-dispersion Yb-doped mode-locked fibre laser with no intentional spectral filter inserted. Pulses with 1.1 nJ pulse energy at a repetition rate of 20.4 MHz are achieved. A th...We experimentally demonstrate an all-normal-dispersion Yb-doped mode-locked fibre laser with no intentional spectral filter inserted. Pulses with 1.1 nJ pulse energy at a repetition rate of 20.4 MHz are achieved. A theoretical model of the fibre laser is derived, whose coefficients are explicitly dependent on the orientations of the wave plates and the polarizer. Based on the model, stability diagrams of both the mode-locking and the continuous wave regimes of the laser are presented. The influence of group-velocity dispersion （GVD） and cavity length on the stability of mode-locking is also discussed.展开更多
We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power an...We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.展开更多
Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly p...Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS.To obtain a high-performance microwave signal,a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect.Resulting from the technique,homogenous peak power distribution in each burst is ensured.The maximum energy of the laser burst pulse reaches 200μJ with a burst duration of 100 ns at the average power of 10 W,corresponding to a peak power of 4 kW.When the PCSS is illuminated by the burst-mode fibre laser,narrowband microwave generation with tuneable frequency(0.80-1.12 GHz)is obtained with a power up to 300 W.To the best of the authors’knowledge,it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser.The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.展开更多
The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-w...The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-wave pumped WGM fibre laser under two different pump conditions.When the pump beam is strictly along the axial direction of an optical fibre,the lasing emission is transverse electric wave and the electrical vectors at emitting points are along the radial direction of the fibre,which forms a special radial polarization radiation.However,when the pump beam deviates from the axial direction of the fibre,both transverse electric and transverse magnetic waves exist in the lasing emission,which forms a mixed polarization radiation with radial and axial polarized elements.Based on lasing radiation mechanism of evanescent-wave pumped WGM fibre laser,the observed polarization properties are well explained.展开更多
Fibre stress of glass fibre reinforced polymeric copmosites on load is determined by using optical fibre as model fiber and by means of laser interference method. In addition, the origination of fibre stress during mo...Fibre stress of glass fibre reinforced polymeric copmosites on load is determined by using optical fibre as model fiber and by means of laser interference method. In addition, the origination of fibre stress during moulding process of composites and the relation between fiber stress of loaded composites and external stress are examined. The experiments show that fibre stress is related to molecular structure of inter facial materials and structure of inter facial layers. When stress is transferred from matrix to fibre, each inter facial layer has different stress gradient and deformability. This property can be characterized by introducing an inter facial stress transfer coefficient k to the two-phase model.展开更多
基金Project supported by the National Basic Research Program of China (Grant Nos. 2006CB806002 and 2010CB327604)the National High Technology Research and Development Program of China (Grant No. 2007AA03Z447)+3 种基金the National Natural Science Foundation of China (Grant Nos. 60838004 and 60678012)the Foundation for Key Program of Ministry of Education, China(Grant No. 108032)the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 2007B34)the Program for New Century Excellent Talents in University of China (Grant No. NCET-07-0597)
文摘The filtering mechanism of a free output coupler mode-locked laser based on large-mode-area photonic-crystal fibre is analysed. A filtering-soliton mode-locked laser with 495 fs pulse width and 21 nJ pulse energy is achieved. Another novel cavity configuration is established to eliminate the filtering effect. Pulses, each 457 fs in width and 16.5 nJ in energy, are obtained in a soliton-like regime. Pulses, each 387 fs in width and 15.8 nJ in energy, are also generated in a stretched pulse regime and could be dechirped to 119 fs externally to the cavity.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60877037 and 10564005)
文摘A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.
文摘The functional properties of materials can be enhanced using surface features,for instance;to improve the thermal properties of heat exchangers.The development of the laser Surfi-Sculpt process over the past decade has resulted in a technology capable of producing a wide variety of features in metallic substrates.Furthermore,the potential for producing similar features in polymeric and ceramic substrates also exists.Recently the potential for utilizing high power focused laser beams to produce surface features using this process has been demonstrated.This paper details the results of recent trials performed with a 200 Yb-fibre laser and a galvanometer driven beam scanner for producing surface features using the Surfi-Sculpt process.A compact,cheap,easily robotically automated,laser Surfi-Sculpt machine,being able to operate at atmospheric pressure may have potential in a range of industry sectors.
文摘In 2018, the journal High Power Laser Science and Engineering produced a Special Issue on Fibres for High Power Lasers. Nowadays, fibre-based laser sources have found extensive applications both in industry and in scientific research. The scope of the special issue was to span the latest developments on the fast developing fibre-based high-power lasers and amplifiers. The topics invited for inclusion were:
文摘We experimentally demonstrate an all-normal-dispersion Yb-doped mode-locked fibre laser with no intentional spectral filter inserted. Pulses with 1.1 nJ pulse energy at a repetition rate of 20.4 MHz are achieved. A theoretical model of the fibre laser is derived, whose coefficients are explicitly dependent on the orientations of the wave plates and the polarizer. Based on the model, stability diagrams of both the mode-locking and the continuous wave regimes of the laser are presented. The influence of group-velocity dispersion （GVD） and cavity length on the stability of mode-locking is also discussed.
基金Project supported by the Hebei Natural Science Foundation, China （Grant Nos F2006000183 and 2001241） and the Science Foundation of Hebei Normal University, China （Grant No L2005B05）.
文摘We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.
文摘Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS.To obtain a high-performance microwave signal,a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect.Resulting from the technique,homogenous peak power distribution in each burst is ensured.The maximum energy of the laser burst pulse reaches 200μJ with a burst duration of 100 ns at the average power of 10 W,corresponding to a peak power of 4 kW.When the PCSS is illuminated by the burst-mode fibre laser,narrowband microwave generation with tuneable frequency(0.80-1.12 GHz)is obtained with a power up to 300 W.To the best of the authors’knowledge,it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser.The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.60877037 and 10564005)
文摘The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-wave pumped WGM fibre laser under two different pump conditions.When the pump beam is strictly along the axial direction of an optical fibre,the lasing emission is transverse electric wave and the electrical vectors at emitting points are along the radial direction of the fibre,which forms a special radial polarization radiation.However,when the pump beam deviates from the axial direction of the fibre,both transverse electric and transverse magnetic waves exist in the lasing emission,which forms a mixed polarization radiation with radial and axial polarized elements.Based on lasing radiation mechanism of evanescent-wave pumped WGM fibre laser,the observed polarization properties are well explained.
文摘Fibre stress of glass fibre reinforced polymeric copmosites on load is determined by using optical fibre as model fiber and by means of laser interference method. In addition, the origination of fibre stress during moulding process of composites and the relation between fiber stress of loaded composites and external stress are examined. The experiments show that fibre stress is related to molecular structure of inter facial materials and structure of inter facial layers. When stress is transferred from matrix to fibre, each inter facial layer has different stress gradient and deformability. This property can be characterized by introducing an inter facial stress transfer coefficient k to the two-phase model.
