Research On Near And Infrared Ultrafast Laser

Near-mid infrared ultrafast lasers have shown increasingly important applications in scientific research,industrial fabrication,defense and medical treatment.So it is very significant to accelerate the study of laser technology ahout this waveband.For the purpose above,this paper focuses on the experimental study of high power near-infrared femtosecond fiber lasers and mid-infrared femtosecond all solid-state mode-locked lasers.The main research contents include the following parts: 1.Based on the nonlinear polarization rotation mode-locking mechanism,the experiment of ultrafast Yb-doped fiber laser was studied.Firstly,by using dispersion management mechanism,a stabilized dispersion-managed soliton is generated in stretched-pulse platform.With the repetition rate more than 250 MHz,the average power of the output pulses is 128 mW.The full width at half maximum(FWHM)of the laser spectrum is 64 nm,with the measured chirped pulse duration of 5.8 ps(theoretical limit pulse width is about 25 fs).In the same type of experimental equipment,self-similar mode-locked picosecond fiber laser was realized by dispersion management.The average output power was 34 m W at a repetition rate of 49 MHz.The measured chired pulse width was 4.4 ps(theoretical limit pulse width 57 fs)with FWHM of the spectrum of 18 nm at a center wavelength of 1035 nm.2.Based on the SESAM mode–locking mechanism,the experiment of mode-locked Yb-doped fiber laser was studied.The stable SESAM mode-locked laser is obtained by using the fiber Bragg grating as an end mirror and for intracavity dispersion compensation.The laser average output power is 2.4 mW at a repetition rate of 25.3 MHz.The measured chired pulse duration is 3.6 ps at a center wavelength is 1030 nm.3.Based on the self-built high repetition rate fiber laser as above,we carried out the fiber laser amplifier experiment by using chirped pulse amplification technique.After being broadened to 20 picosecond by ordinary single-mode fiber,the power of seed pulses was amplified to 16.4W through two stages of power amplication.After the PBS and a pair of diffraction gratings,4.3 W S-polarized femtosecond pulses is obtained.The final output pulse duration is 175 fs.4.By using the self-built high repetition rate femtosecond fiber amplifier,we carried out the experimental study on the supercontinuum generation based on the photonic crystal fiber.The femtosecond pulse was coupled into the photonic crystal fiber through a lens,and the spectral broadening is observed under different input power.Under the input power of 6 W,nearly 810 nm wide spectrum was obtained,and the spectrum covered the range of 650-1467 nm.5.Based on the Kerr lens mode-locking mechanism,we carried out the research on the mid-infrared wavelength mode-locked laser of polycrystalline chromium-doped zinc chalcogenide crystal.Firstly,a 1645 nm narrow linewidth laser with S-polarization was obtained by pumping a single Er:YAG laser oscillator with a commercially available erbium-doped fiber laser at a wavelength of 1532 nm.Then,the obtained laser was used to pump the polycrystalline Cr: ZnS crystal,a continuous output power of 212 mW was obtained at 5.12 W pump power.Limited by the lens coating range,the wavelength could be tuned between 2213 nm-2498 nm.At the stability edge of the cavity,a Kerr lens mode-locked output with a center wavelength of 2347 nm,an average power of 80 mW and a pulse width of 125 fs was obtained.Due to the special nonlinear properties of the polycrystalline Cr: ZnS material,it is easy to achieve quasi-phase matching.Therefore,we observed second to fourth harmonics at the same time of the Kerr lens mode locking.The corresponding output wavelengths were 1164 nm,783 nm and 586 nm,respectively.