A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The charac...A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti：sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.展开更多
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
We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% a...We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.展开更多
A new double-layer grating template is designed to reduce the out-of-band loss as much as 1.8dB when the loss of LPo3 reaches 10.2 dB. Meanwhile, we propose a method to remove the sidelobes in the transmission spectra...A new double-layer grating template is designed to reduce the out-of-band loss as much as 1.8dB when the loss of LPo3 reaches 10.2 dB. Meanwhile, we propose a method to remove the sidelobes in the transmission spectra by the adjustment of the thickness of pressure plates. The plate-thickness-induced shift of resonant wavelength and the attenuation of loss peak intensity when removing sidelobes can be modified by the fibre distance and contact point on the pressure plates.展开更多
The well-known Fraunhofer multi-slit diffraction is described as the multi-slit interference modulated by the singleslit diffraction, namely the multiplication between the single-slit diffraction factor and the multi-...The well-known Fraunhofer multi-slit diffraction is described as the multi-slit interference modulated by the singleslit diffraction, namely the multiplication between the single-slit diffraction factor and the multi-slit interference factor. By considering the simplified argument we show that the multi-slit diffraction of evanescent waves which are in the near-field region also has the interference and diffraction effects, and that this two-fold effect can be expressed as the convolution of the diffraction factor and the interference factor. Our conclusion could be helpful to understand the contribution of evanescent waves to the optical responses of sub-wavelength structures such as slits and grooves.展开更多
We present our measured photoluminescence of the quadrupolar transitions of the yellow series excitons of cuprous oxide at 2K. By tuning the excitation energy in the two-photon quadrupolar absorption scheme of Cu2O, i...We present our measured photoluminescence of the quadrupolar transitions of the yellow series excitons of cuprous oxide at 2K. By tuning the excitation energy in the two-photon quadrupolar absorption scheme of Cu2O, it is found that the band-gap value associated with this optical process can be characterized by a sharp resonance at 2.036eV at cryogenic temperature. This energy value is helpful to guide a proper excitation for creating cold excitonic gas in this crystal.展开更多
We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a comp...We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope effciency of 37.3%. By inserting a type-Ⅰ critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd：YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.展开更多
In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the sol...In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre （PCF） parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.展开更多
We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is...We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is φ6.35×144mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064nm can be obtained with a linear piano-piano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd：YAG ceramic rod as the gain medium.展开更多
Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The exp...Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The experimental results show that multiple filaments are shrunken into a single filament or no filament only by increasing the temperature at the beginning of the filament. This technique offers another degree of freedom of controlling the filamentation and opens a new way for intense monocycle pulse generation through gradient temperature in a noble gas.展开更多
We present a novel cluster-seven-core photonic crystal fiber which possesses high nonlinearity and supports the high-power pumping. Its nonlinearity coefficient and effective mode area are calculated by the full vecto...We present a novel cluster-seven-core photonic crystal fiber which possesses high nonlinearity and supports the high-power pumping. Its nonlinearity coefficient and effective mode area are calculated by the full vector multipole method. Compared with the single core PCF, the cluster-seven-core photonic crystal fiber can support high-power beam transmitting in the core, and simultaneously has high nonlinearity. This kind of photonic crystal fiber can be applied to the photoelectron-device field.展开更多
Using the tunable pump pulses with about lOO fs pulse duration and 1064 nm central wavelength; the polarization-, wavelength- and power-dependent anti-Stokes lines are generated and modulated simultaneously in a polar...Using the tunable pump pulses with about lOO fs pulse duration and 1064 nm central wavelength; the polarization-, wavelength- and power-dependent anti-Stokes lines are generated and modulated simultaneously in a polarization-maintaining photonie crystal fiber （PM-PCF） with two zero-dispersion wavelengths. By accurately controlling the polarization directions, the wavelength and the power of the pump pulse in the fiber anomalous region close to the second zero-dispersion wavelength of the PM-PCF, the output anti-Stokes pulse spectra can be tuned between 563 nm and 603 nm, which is in good agreement with the theoretical simulation. The color conversion of the mode image from yellow to orange is also observed with the different polarization pump pulses. These results can be attributed to the combined interaction between the fiber birefringence （including linear- and nonlinear- birefringence） and dispersion, and are attributed to phase-matching parametric four-wave mixing.展开更多
A passive mode-locked diode-pumped self-frequency-doubling Yb:YAB laser with a low modulation depth semiconductor saturable absorber mirror operating at 374 MHz is demonstrated. The measured pulse duration is 1.98 ps ...A passive mode-locked diode-pumped self-frequency-doubling Yb:YAB laser with a low modulation depth semiconductor saturable absorber mirror operating at 374 MHz is demonstrated. The measured pulse duration is 1.98 ps at the wavelength of 1044 nm. The maximum average power reaches 45 mW.展开更多
A Galerkin's method-based numerical procedure is extended to obtain the modal field distribution of multicore photonic crystal fibers for the first time to our knowledge, which can reveal how the air hole size inf...A Galerkin's method-based numerical procedure is extended to obtain the modal field distribution of multicore photonic crystal fibers for the first time to our knowledge, which can reveal how the air hole size influences the mode coupling and how the coupling strength varies with wavelength. These results will be helpful in the future design of multicore photonic crystal fibers with proper guidance properties.展开更多
When femtosecond laser pulses interfere with chirped femtosecond laser pulses in As2S3 fiber, a chirped fiber grating is formed. An analytical expression is given to describe the chirped grating, and its Bragg reflect...When femtosecond laser pulses interfere with chirped femtosecond laser pulses in As2S3 fiber, a chirped fiber grating is formed. An analytical expression is given to describe the chirped grating, and its Bragg reflectivity is calculated. Because of the high photosensitive effect of As2S3 material, the chirped fiber grating has a wide Bragg reflective spectrum and high reflectivity by choosing proper parameters. This indicates that the chirped fiber grating can be used as a stretcher in the femtosecond chirped pulse amplification (CPA) system.展开更多
The Ti:sapphire oscillator is used to realize structural change in an organic glass (polymethyl -methacrylate (PMMA)). Single pulse fluence threshold of PMMA and the relation of the breakdown threshold with different ...The Ti:sapphire oscillator is used to realize structural change in an organic glass (polymethyl -methacrylate (PMMA)). Single pulse fluence threshold of PMMA and the relation of the breakdown threshold with different numerical aperture objectives are determined using a formula deduced from an existent equation. Three-dimensional dots in the organic glass is performed at the same time.展开更多
Ablation process of 1-kHz femtosecond lasers （pulse duration of 148 fs, wavelength of 775 nm） of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the ...Ablation process of 1-kHz femtosecond lasers （pulse duration of 148 fs, wavelength of 775 nm） of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D^2 of the ablated craters and the laser fluence Ф0. From the plot of the accumulated laser fluence NCth（N） and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.展开更多
Lines are induced on the surface of a photosensitive （FOTURAN） glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scann...Lines are induced on the surface of a photosensitive （FOTURAN） glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scanning electron microscope （SEM） and optical microscope （OM）. It is observed that three distinct morphologies of lines are produced depending on the scanning velocity. Lines written in low velocity level （40 - 100 μm/s） and high velocity level （1000 - 1800 μm/s） are uniform and regular, while those written in moderate velocity level （150 - 600 μm/s） are rough. The influence of scanning velocity is explained based on different pulses overlapping or cumulative dose of laser exposure in irradiated area. Fabrication of shallow groove on the surface is also demonstrated.展开更多
Stable mode-locking in a diode-pumped Yb:YAG laser was obtained with a very fast semiconductor sat-urable absorber mirror (SESAM). The pulse width was measured to be 4 ps at the central wavelength of 1047 nm. The aver...Stable mode-locking in a diode-pumped Yb:YAG laser was obtained with a very fast semiconductor sat-urable absorber mirror (SESAM). The pulse width was measured to be 4 ps at the central wavelength of 1047 nm. The average power was 200 mW and the repetition rate was 200 MHz.展开更多
Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diame...Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diameters of the dots ablated in the organic polymers are influenced by the laser fluence and the number of laser pulses. It is observed that heat is diffused in a threadlike manner in all directions around the central focus region.Explanations of the observed phenomena are presented. A one-dimensional waveguide is also ablated in the organic polymers.展开更多
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB806002)the National High Technology Research and Development Program of China (Grant No. 2007AA03Z447)+3 种基金National Natural Science Foundation of China (Grant Nos. 60678012 and 60838004)the Foundation for Key Program of Ministry of Education, China (Grant No. 108032)FANEDD(Grant No. 2007B34)NCET (Grant No. NCET-07-0597)
文摘A Kerr-lens mode-locked Ti：sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti：sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.
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Supported by the National Basic Research Programme of China under Grant No 2006CB806000, the National Natural Science Foundation of China under Grant Nos 60490280 and 60578007, NSFC-JSPS International Cooperation Programme under Grant No 60611140297, the Tianjin Natural Science Foundation under Grant No 07JCYBJC15500.
文摘We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.
文摘A new double-layer grating template is designed to reduce the out-of-band loss as much as 1.8dB when the loss of LPo3 reaches 10.2 dB. Meanwhile, we propose a method to remove the sidelobes in the transmission spectra by the adjustment of the thickness of pressure plates. The plate-thickness-induced shift of resonant wavelength and the attenuation of loss peak intensity when removing sidelobes can be modified by the fibre distance and contact point on the pressure plates.
文摘The well-known Fraunhofer multi-slit diffraction is described as the multi-slit interference modulated by the singleslit diffraction, namely the multiplication between the single-slit diffraction factor and the multi-slit interference factor. By considering the simplified argument we show that the multi-slit diffraction of evanescent waves which are in the near-field region also has the interference and diffraction effects, and that this two-fold effect can be expressed as the convolution of the diffraction factor and the interference factor. Our conclusion could be helpful to understand the contribution of evanescent waves to the optical responses of sub-wavelength structures such as slits and grooves.
文摘We present our measured photoluminescence of the quadrupolar transitions of the yellow series excitons of cuprous oxide at 2K. By tuning the excitation energy in the two-photon quadrupolar absorption scheme of Cu2O, it is found that the band-gap value associated with this optical process can be characterized by a sharp resonance at 2.036eV at cryogenic temperature. This energy value is helpful to guide a proper excitation for creating cold excitonic gas in this crystal.
文摘We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope effciency of 37.3%. By inserting a type-Ⅰ critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd：YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.
文摘In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre （PCF） parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.
文摘We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is φ6.35×144mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064nm can be obtained with a linear piano-piano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd：YAG ceramic rod as the gain medium.
基金Supported by the Major Project of the National Natural Science Foundation of China under Grant No 60490280, the National Natural Science Foundation of China under Grant No 60578007, the National Basle Research Programme of China under Grant No 2006CB806000.
文摘Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The experimental results show that multiple filaments are shrunken into a single filament or no filament only by increasing the temperature at the beginning of the filament. This technique offers another degree of freedom of controlling the filamentation and opens a new way for intense monocycle pulse generation through gradient temperature in a noble gas.
基金Supported by the National Basic Research Program of China under Grant Nos 2006CB806002 and 2010CB327604, and the National Natural Science Foundation of China under Grant Nos 60678012 and 60838004, and the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant Nos 20070056083 and 20070056073.
文摘We present a novel cluster-seven-core photonic crystal fiber which possesses high nonlinearity and supports the high-power pumping. Its nonlinearity coefficient and effective mode area are calculated by the full vector multipole method. Compared with the single core PCF, the cluster-seven-core photonic crystal fiber can support high-power beam transmitting in the core, and simultaneously has high nonlinearity. This kind of photonic crystal fiber can be applied to the photoelectron-device field.
文摘Using the tunable pump pulses with about lOO fs pulse duration and 1064 nm central wavelength; the polarization-, wavelength- and power-dependent anti-Stokes lines are generated and modulated simultaneously in a polarization-maintaining photonie crystal fiber （PM-PCF） with two zero-dispersion wavelengths. By accurately controlling the polarization directions, the wavelength and the power of the pump pulse in the fiber anomalous region close to the second zero-dispersion wavelength of the PM-PCF, the output anti-Stokes pulse spectra can be tuned between 563 nm and 603 nm, which is in good agreement with the theoretical simulation. The color conversion of the mode image from yellow to orange is also observed with the different polarization pump pulses. These results can be attributed to the combined interaction between the fiber birefringence （including linear- and nonlinear- birefringence） and dispersion, and are attributed to phase-matching parametric four-wave mixing.
基金work was supported by the National Key Basic Research Special Foundation of China (No. G1999075201-2)the National Natural Science Foundation of China (No. 69978007, 60178008).
文摘A passive mode-locked diode-pumped self-frequency-doubling Yb:YAB laser with a low modulation depth semiconductor saturable absorber mirror operating at 374 MHz is demonstrated. The measured pulse duration is 1.98 ps at the wavelength of 1044 nm. The maximum average power reaches 45 mW.
基金This work was supported by the National Natural Science Foundation of China under Grant NO. 60278003 and the National Key Basic Research Special Foundation of China under Grant No.G1999075201,
文摘A Galerkin's method-based numerical procedure is extended to obtain the modal field distribution of multicore photonic crystal fibers for the first time to our knowledge, which can reveal how the air hole size influences the mode coupling and how the coupling strength varies with wavelength. These results will be helpful in the future design of multicore photonic crystal fibers with proper guidance properties.
基金The authors acknowledge the support of the National Key Basic Research Special Foundation of China (No. G1999075201-2)the National Natural Science Foundation of China (No. 60178007)the Science Foundation of China for Post Ph. D (2002032163).
文摘When femtosecond laser pulses interfere with chirped femtosecond laser pulses in As2S3 fiber, a chirped fiber grating is formed. An analytical expression is given to describe the chirped grating, and its Bragg reflectivity is calculated. Because of the high photosensitive effect of As2S3 material, the chirped fiber grating has a wide Bragg reflective spectrum and high reflectivity by choosing proper parameters. This indicates that the chirped fiber grating can be used as a stretcher in the femtosecond chirped pulse amplification (CPA) system.
基金This work was supported by the National Key Basic Research Special Foundation (NKBRSF) (Grant No. G1999075201) the National Natural Science Foundation of China (Grant No. 60278003).
文摘The Ti:sapphire oscillator is used to realize structural change in an organic glass (polymethyl -methacrylate (PMMA)). Single pulse fluence threshold of PMMA and the relation of the breakdown threshold with different numerical aperture objectives are determined using a formula deduced from an existent equation. Three-dimensional dots in the organic glass is performed at the same time.
基金This work was supported by the Key Grant Project of the Ministry of Education of China (No. 10410)the Science and Technology Development Project Fund of Tianjin (No. 043103911)the Specialized Research Fund for the Doctoral Program of Higher Education (No.2003056021), and the Postdoctoral Science Foundation in China.
文摘Ablation process of 1-kHz femtosecond lasers （pulse duration of 148 fs, wavelength of 775 nm） of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D^2 of the ablated craters and the laser fluence Ф0. From the plot of the accumulated laser fluence NCth（N） and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.
基金This work was supported by the Key Grant Project of the Ministry of Education,P.R.China(No.10410)the Science and Technology Development Project of Tianjin City (No.043103911)the National Natural Science Fundation of China(No.60608004)
文摘Lines are induced on the surface of a photosensitive （FOTURAN） glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scanning electron microscope （SEM） and optical microscope （OM）. It is observed that three distinct morphologies of lines are produced depending on the scanning velocity. Lines written in low velocity level （40 - 100 μm/s） and high velocity level （1000 - 1800 μm/s） are uniform and regular, while those written in moderate velocity level （150 - 600 μm/s） are rough. The influence of scanning velocity is explained based on different pulses overlapping or cumulative dose of laser exposure in irradiated area. Fabrication of shallow groove on the surface is also demonstrated.
基金This work was supported by the National Key Basic Research Special Foundation of China (No. G1999075201-2) the National Natural Science Foundation of China (No. 69978016, 60178008) the Foundation of the Optoelectronic United Center of Tianjin, the Na
文摘Stable mode-locking in a diode-pumped Yb:YAG laser was obtained with a very fast semiconductor sat-urable absorber mirror (SESAM). The pulse width was measured to be 4 ps at the central wavelength of 1047 nm. The average power was 200 mW and the repetition rate was 200 MHz.
基金This work was supported by the National Key Basic Research Special。Foundation(NKBRSF)(NO.G1999075201) and the National Natural Science Founda-tion of China (No. 60278003).
文摘Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diameters of the dots ablated in the organic polymers are influenced by the laser fluence and the number of laser pulses. It is observed that heat is diffused in a threadlike manner in all directions around the central focus region.Explanations of the observed phenomena are presented. A one-dimensional waveguide is also ablated in the organic polymers.
