We demonstrate a 200-MHz all polarization-maintaining, repetition-rate-locked femtosecond fiber laser system with a total electrical power consumption of 11 W. The center wavelength, spectral width, pulse width, and average output power of the laser are 1558.8 nm, 34 nm, 139 fs, and 77.6 mW, respectively. The proposed laser system that integrates all optical components and locking electronics has a volume less than 1.5 L, a mass of 1.3 kg, and a fast locking time of 3 s (from the free running state to the repetition-rate-locked state). Using a hydrogen maser as the frequency reference, after locking, the Allan deviation is 2.8 mHz at a gate time of 1 s. Further, we place the repetition-rate-locked fiber laser system on a homemade shaker table with peak and rms accelerations of 1.97 and 0.7 g, respectively; the experimental results show that the locking state can be maintained robustly with Allan deviation of 2.0 mHz. The highly integrated, robust fiber laser system has potential applications in the areas of ultralow-noise microwave generation and high-precision distance measurement in outdoor environments.
A theoretical model based on rate equations for actively Q-switched Er<sup>3+</sup>-doped ZBLAN fiber laser is built. The operation behaviors and output characteristics of the actively Q-switched fiber laser at 2.8 μm are analyzed. Effects of some important laser parameters, such as pump power levels, reflectivity of the laser output coupler, fiber lengths, Er concentrations, etc., on laser output were investigated. The model and simulating results are useful for design and optimization of actively Q-switched fiber laser at 2.8-μm region.
This paper presents an experimental method to realize the best high-order harmonics generation (HHG) phase matching in the interaction of strong optical field with gas target. By studying the effects of the relative location between gas target source and the Gaussian-shaped driving femtosecond laser field focus on the harmonics yield, conclusions are obtained that the optimum position of gas target for phase matching is always behind the of the focal point of the driving field, with much lower HHG yield before the focus caused by serious harmonics phase mismatch. Meanwhile, with optimum harmonics phase matching, the high-order harmonics field that resulted has the similar Gaussian-shaped spatial distribution characteristics with the driving field, verifying experimentally the commonly used assumptions for attosecond laser pulse based on HHG. This optimization method is also suitable both for other driving field with different spatial distribution of light intensity and other type of target source. The results here have important guiding significance for high harmonic generation and high harmonic isolated attosecond pulse technology.
A fiber chirped-pulse amplification system with pulse energy as high as 105 μJ is achieved at 200-kHz repetition rate using the rod-type photonic crystal fiber. The whole system’s nonlinearity accumulated in the fiber amplification is effectively suppressed, and the compressed pulse duration of 808 fs is obtained. A 500-kHz high-repetition rate KTiOPO4 Pockels cell is also applied to make the ultrafast laser pulse selection for generating pulse trains with controllable pulse number and pulse splitting without changing the pulse energy. The demonstrated pulse selection and splitting method are useful for processing of different materials and parallel processing. The pulse selection efficiency of the Pockels cell is as high as 96%.
We report on the recent progress on high power pulsed 2.8 μm Er<sup>3+</sup>-doped ZBLAN fiber laser through techniques of passively and actively Q-switching in our research group. In passively Q-switched operation, a diode-cladding-pumped mid-infrared passively Q-switched Er<sup>3+</sup>-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) was demonstrated. Stable pulse train was produced at a slope efficient of 17.8% with respect to launched pump power. The maximum average power of 1.01 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 μJ. The maximum peak power was calculated to be 21.9 W. In actively Q-switched operation, a diode-pumped actively Q-switched Er<sup>3+</sup>-doped ZBLAN fiber laser at 2.8 μm with an optical chopper was reported. The maximum laser pulse energy of up to 130 μJ and a pulse width of 127.3 ns at a repetition rate of 10 kHz with an operating wavelength of 2.78 μm was obtained, yielding the maximum peak power of exceeding 1.1 kW.
We demonstrated a compact stable room-temperature multiwavelength erbium doped fiber laser by employing a 45° tilted fiber gratings (TFGs) based all-fiber polarization interference filter. Benefiting from the filter, the channel number, the linewidth, the uniformity and stabilization of the multiwavelength laser were greatly improved. The filter also worked as a polarizing functional device in nonlinear polarization rotation leading to multiwavelength operation. More than 60 wavelengths (within 3dB bandwidth) lasing with a linewidth of 0.03nm and a signal-to-noise ratio of 31dB were obtained. The wavelength spacing was 0.164nm agreeing with the value of the filter and it can be flexibly controlled by adjusting the length of the filter.
An ultra-short wavelength operation of Tm-doped all fiber laser based on fiber Bragg gratings (FBGs) was developed. A bi-directional pump configuration for the ultra-short wavelength operation was designed and investigated for the first time. the laser yielded 3.15W of continuous-wave output at 1706.75nm with a narrow-linewidth of ~50pm and a maximum slope efficiency of 42.1%. The dependencies of the slope efficiencies and pump threshold of the laser versus the length of active fiber and reflectivity of the output mirror (FBG) were investigated in detail. An experimental comparative study between two Thulium-doped fiber lasers (TDFLs) with two different pumping configuration(forward unidirectional pumping and bidirectional pumping) was presented. It is indisputable that the development of 1.7μm silicate fiber lasers with Watt-level output power open up a number of heart-stirring and tempting application windows.
We demonstrated a passively Q-switched Nd:YAG laser operating at 1.319 μm using a transmission-type single-wall carbon nanotube (SWCNT) as the saturable absorber. This is the first report on using SWCNT as a Q-switcher for 1.319 μm Nd:YAG laser in a side-pumped configuration. A maximum output power of 780 mW was obtained with 1.15-μs pulse duration and 42.7-kHz repetition rate.
A chalcogenide glass was used for an optical Kerr gate to sampling pulse contrast of femtosecond lasers with low repetition rate ( 40 Hz). The dynamic range of this method reached 10<sup>3</sup>, with a scanning range of 150ps and temporal sampling rate of 6.3 fs. The advantage of this method lies in its broad spectrum range including visible and NIR spectral region and easy operation.
High power and widely tunable operation of Tm-doped silica fiber laser around 2 μm has been demonstrated using
volume Bragg grating as the wavelength selection and spectrum narrowing element. The operating wavelength was
continuously tunable from 1930 to 1821 nm, with > 52 W output power over a tuning range of 104 nm and a relatively
narrow spectra width of < 15 pm. Over 60.8 W of diffraction limited (M<sup>2</sup> ~ 1.5) CW output power was generated for 137
W of launched pump power, corresponding to a slope efficiency with respect to launched pump power of 46%. Output
characteristics with a conventional replica diffraction grating for wavelength selection were also investigated as a
comparison with that of using a volume Bragg grating. A maximum output power of 30.6 W at 1963 nm was generated
for 79 W of launched pump power and the lasing wavelength could be tuned over 196 nm from 1859 to 2055 nm at
output power levels in excess of 20 W. The bandwidth of the laser output was ~ 0.8 nm.
A fiber tunable high-power picosecond laser system has been demonstrated. A gain switch semiconductor laser diode was introduced as seed source, and a multi-stage single mode Yb-doped fiber amplifier was combined with a single mode double-clad Yb-doped fiber amplifier and a PCF amplifier to construct the amplification system. High stability and good beam quality pulses with 1MHz tunable repetition rate, 6.8W average power, 90ps pulse duration, and central wavelength tunable from 1053 nm to 1073 nm were generated. The completely fiber-integrated approach has the potential to be scaled to significantly higher average powers.
A robot scanning system consisting of a portable laser 3-D scanner and an industrial robot is demonstrated. In this system, the scanner is precalibrated by the traditional nonlinear two-step approach. In addition, by using a criterion sphere as the calibration object, a new robot tool center point (TCP) calibration approach is proposed for calibrating the relation between the precalibrated laser 3-D scanner and the robot. In this approach, two different translational motions of the robot are first made to determine the rotation part, and then at least three different rotational motions are made to determine the translation part. During the process, the extrinsic camera parameters are not recalibrated for each robot motion, so the calibration errors brought by camera calibration can be decreased. Moreover, the calibration error due to robot positioning error can be decreased by making use of the differences of different robot positions in calculations. An experiment was performed on a portable laser 3-D scanner and an ABB IRB-4400 industrial robot to test the validity of the proposed calibration approach. The experimental results show that this approach is simple and accurate compared to the conventional robot TCP calibration approach.
A self-starting all-solid-state picosecond (ps) laser was demonstrated. Different with a standard cavity design with
semiconductor saturable-absorber mirror (SESAM), self-starting mode-locking was initiated by stretching the length of
arm to reduce the beam spot, which shows the output beam possess higher beam quality than standard one. With a 10%
output coupler, we achieved 1 W output power and 21 ps pulse duration at pump power of 4.5 W. High efficiency and
high beam quality show the merit of the ps-laser.
A passively Q-switched ytterbium-doped double-clad fiber laser with SESAM as a saturable absorber is demonstrated
experimentally. This system showed up to 18.7mW output power, up to 29.4 kHz repetition rate, a maximum pulse
energy of 0.636μJ and a minimum pulse duration of 3.148 μs. The characteristics of pulse were investigated, and the
theoretical analysis agree well with the experimental results.
The multi-pulse operation of the Yb<sup>3+</sup>-doped fiber mode-locked laser with a polarization sensitive isolator and two
polarization controllers is reported. Dual- and triple-pulse of the Yb<sup>3+</sup>-doped fiber mode-locked laser in the normal
dispersion are achieved as the pumping power is increased. The fiber laser can achieve different multi-pulse outputs by
adjusting the polarization controllers or increasing the pump power. The results show that over-driving of the fast
artificial saturable absorber induced the generation of the multi-pulse.
This paper describes characteristics of a short pulse doped rare earth fiber laser and amplifier. We have obtained
very stable pico-second and femto-second laser pulses from fiber laser. An all-fiber laser and amplifier of a
double-clad fiber are researched in detail. The pulse of 177fs at wavelength of ~1.50um has been got from fiber
laser. The energy of single pulse of 153μJ has been obtained after an amplifier of a double-clad fiber at
repetition-rate of 30 KHz.
We report on an experimental investigation into the recording and readout of 3D high-density optical data storage in transparent optical glasses using a femtosecond laser. A compact Ti:sapphire ultrafast laser amplifier as writing laser was developed to output 100mW 2.1ps at 1KHz with 1W pump laser. Laser pulses modulation is realized by modulating two circuits of trigger pulses signal which are used to control laser pulses trapping and switching out from cavity, respectively. A formatted and coded writing was realized in fused silica and doped polymethylmethacrylate(PMMA) bulk. A phase-contrast and a reflection confocal reading system with software are developed for optical readout of multi-layer data bits in parallel.
A high power double-clad ytterbium-doped large-mode-area photonic crystal fibre (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. A Continuous-wave output power of 50 W at ~1.04 μm with a slope efficiency of 76.3% was obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.
In this paper, we discussed different mechanisms which are proved to ensure phase locking in a laser array. We also reported the phase locking in solid-state (crystal) laser array and fiber laser array by using the self-imaging confocal resonator which provides high feedback efficiency, quite insensitive to power variations among the pump beams, simply modal profile and also can achieve phase locking passively. A passive approach is to utilize the process of self-adjustment in lasing frequency to adapt to changes in the optical path lengths. The phase-locked mode is highly stable despite the phase variations in the individual elements caused by thermal and mechanical effects.
With cascade oscillation scheme from level 5I6,to 5I7, to 5I8 in Ho3+: ZBLAN fiber laser, it not only can produce cW 3- and 2- ?m laser beams simultaneously from one oscillator with appropriate pumping source, but also improves the output power and efficiency. In this paper, the operation principles of 3- and 2- ?m cascade Ho3+: ZBLAN fiber laser is analyzed. Both dynamic and steady state rate equations of this laser pumped with1.1-?m band laser are given for the first time. Basic designs of this laser pumped by Ytterbium-doped double clad fiber lasers (YDCFL) are given. Based on the theoretical analysis and designs, numerical computations of the steady state rate equations were performed. The numerical solutions agree well with the experimental results.
Multi-wavelength lasers from near-infrared to deep-ultraviolet range, 532, 266, 830, 415, 208nm, were developed in one all-solid-state laser system for the first time to our knowledge. The laser system was pumped by a diode-Q-YLF laser, a Ti:sapphire laser and the nonlinear SHG crystals LBO and BBO were used to generate different wavelengths. Maximum average powers (repetition rate 1khz) of 1.8W at 266nm, 1.1W at 830nm, 380mW at 415nm, and 39mW at 208nm were obtained when the pumping power was 3.8W. Main characteristics of this system are presented.
This paper presents a Ti-sapphire-based laser amplification system in which the technique of a chirped- pulse- amplification is used. It consists of a laser oscillator, a pulse stretcher, a regenerative amplifier and a pulse compressor. The laser oscillator is a home-made self-mode- locked Ti-sapphire (3 mm long) oscillator. The oscillator pumped by 5 W of cw all line Argon laser can generate Fourier-transform-limited sub-20 fs duration pulses at a 91 MHZ repetition rate, a center wavelength of 800 nm, a FWHM bandwidth of a spectrum of 80 nm. The seed pulses from the oscillator are stretched by a factor of 1000 with a four- pass grating stretcher at first. After stretching, these pulses are seeded into a Ti-sapphire regenerative amplifier pumped by a frequency-doubled Q-switched a Nd:YAG laser at 5 KHZ. We have obtained single-pulse energy of 100 (mu) J, pulse duration of 50 fs at the repetition rate of 5 KHZ.