High-power Ultrashort Pulses Research Articles

High peak power and sub-picosecond Fourier-limited pulse generation from passively mode-locked monolithic two-section gain-guided tapered InGaAs quantum-dot lasers

We report on the development of a new generation of high-power ultrashort pulse quantum-dot lasers with tapered gain section. Two device designs are proposed and fabricated, with different total lengths and absorber-to-gain-section length-ratios. These designs have been informed by numerical simulations of the dynamic mode-locking regimes and their dependence on the structural parameters. One device design demonstrated a record-high peak power of 17.7 W with 1.26 ps pulse width and a second design enabled the generation of a Fourier-limited 672 fs pulse width with a peak power of 3.8 W. A maximum output average power of 288 mW with 28.7 pJ pulse energy was also attained. In addition, the integrated timing jitter of 2.6 ps and far-field patterns are demonstrated.

振幅调制连续光产生高功率超短脉冲串的研究

振幅调制连续光产生高功率超短脉冲串的研究

All-fiber design of hybrid Er-doped laser/Yb-doped amplifier system for high-power ultrashort pulse generation

We propose a design of an all-fiber laser system that combines the most advanced Er:fiber laser in the telecommunication range and an efficient Yb-doped amplifier for generation of high-power ultrashort pulses. The system is based on nonlinear wavelength conversion of 1.56 μm ultrashort Er:fiber laser pulses to the 1 μm range in a short pigtail of dispersion-shifted silica fiber with subsequent amplification in the Yb-doped fiber amplifier. Pulses with a duration as short as 85 fs and averaged power of 200 mW are demonstrated.

Growth and spectroscopic properties of Yb:Lu 1.5Y 1.5Al 5O 12 mixed crystal

Yb 3+-doped (Lu 0.5Y 0.5) 3Al 5O 12 (Yb:LuYAG) single crystal has been grown by the Czochralski method. The segregation coefficient of Yb 3+ was studied by the inductively coupled plasma atomic emission spectrometry (ICP-AES) method. The crystal structure has been determined by X-ray diffraction analysis. The absorption and emission spectra and fluorescence lifetime of Yb:LuYAG crystal were measured at room temperature. The spectroscopic parameters of Yb:LuYAG crystal were compared with those of Yb:YAG and Yb:LuAG crystals with the same doping level. The results indicate that Yb:LuYAG crystals are potential candidates for high-power ultrashort pulse lasers.

Ultrafast Manipulation of Self‐Assembled Form Birefringence in Glass

Ultrashort pulse lasers have allowed probing of molecular dynamics in real time on the femtosecond time scale, with exotic behavior ranging from alignment of molecules and clusters, structural deformation, phase transitions on solid, and electron localization in magnetic materials. A recent progress in high power ultrashort pulse lasers has opened new frontiers in physics and technology of light-matter interactions from X-ray generation, nuclear fusion, laser surgery, integrated and fiber optics, optical data storage, to 3D micro- and nano-structuring. An intriguing phenomenon that currently attracts a lot of interest is the self-assembly of periodic nanostructures in the direction perpendicular to the light polarization. Uniaxial birefringence observed after femtosecond laser irradiation of silica glass has been explained by induced nanogratings and referred as self-assembled form birefringence. Self organization process has been interpreted in terms of the interference of electron plasma waves resulting in electron concentration modulation, followed by freezing of the interference pattern by structural change in glass. However, the mechanism including dynamics of self-organized nanostructures formation is still not fully understood. Recently, a double-pulse pump-probe configuration was used to enhance ablation in fused silica and silicon. In similar experiments molecular ensembles with an oriented angular momentum were produced. Here, we describe the ultrafast writing dynamics of form birefringence produced by self-organized nanogratings in double pulse experiments. Rewritable five-dimensional (5D) optical data storage using self-assembled form birefringence was demonstrated.

高功率超短脉冲在增益介质中的传输特性

Taking the group velocity dispersion,Kerr nonlinear effects,gain saturation and gain spectrum of gain medium into account,a equation describing the propagation of optical pulse in the medium is derived.The propagation state of a high power linear chirped pulse in the gain medium is simulated numerically using Split-step Fourier transform method,and the influence of gain dispersion on the profile and power spectrum of optical pulse is discussed emphatically.The results show that when propagating and amplified in the gain medium,the high power super-Gaussian optical pulse's shape becomes sharp,peak moves to pulse front edge,the spectral peak moves to lower frequency,and the asymmetric oscillation structure is formed in spectral edge.When the gain dispersion of medium increases,the spectrum width of optical pulse becomes narrow,and its peak power decreases.As a result,the gain dispersion will cause loss of the broadband spectrum pulse.

High-speed, high-resolution, and large-scanning-range three-dimensional optical measurement system using a wavelength-tunable orthogonally polarized ultrashort twin pulse source

A high-speed, high-resolution, and large-scanning-range three-dimensional measurement system was demonstrated using an electronically controlled wavelength-tunable orthogonally polarized high-power ultrashort twin pulse source and an all-fiber interferometer. Thanks to the high peak power, the ultrashort optical pulses propagated along a fiber while maintaining the pulse shape by means of the soliton effect, allowing us to demonstrate high-speed, high-resolution, and large-scanning-range measurement. First, the interference was analyzed by numerical calculations and then the measurement system was demonstrated experimentally. A longitudinal scanning range of about 25 mm, a longitudinal resolution of 33 μm, and a scanning speed of 1000 points/s were achieved without moving parts. For a measurement distance of 0.5 m, a sensitivity of 60 dB was obtained. Clear three-dimensional images of a 100 yen Japanese coin and metal samples were obtained using this system.

Ultrafast high power Yb:KLuW regenerative amplifier

We report on an high power ultra-short pulse regenerative Yb:KLuW amplifier based on the thin disk concept. A maximum pulse energy of 571 microJ was extracted at a repetition rate of 20 kHz. Compression of the output pulses resulted in a pulse duration of 197 fs assuming a deconvolution factor of 2.16. At a repetition rate of 125 kHz a maximum average power of 17.9 W was measured in front of the compressor.

Generation of 045-138 μm visible to near-infrared widely broadened supercontinuum using Er-doped ultrashort-pulse fiber laser system

Visible to near-infrared, widely broadened supercontinuum generation is demonstrated using an ultrashort-pulse fiber laser system. A 229 mW, 83 fs high-power ultrashort pulse was generated at 1550 nm in an Er-doped fiber-chirped pulse amplification system. An almost pedestal-free 107 fs second-harmonic pulse was generated at 780 nm using periodically poled LiNbO3. A 0.45-1.38 μm widely broadened supercontinuum was generated in a highly nonlinear photonic crystal fiber. In terms of spectral flatness, the total modulation bandwidth was within 14 dB. All of the fiber devices were fusion spliced so that the system showed good stability. The effect of a pulse-trapping phenomenon in the supercontinuum generation process was discussed from experimental considerations.

Energy Squeeze of Ultrashort Light Pulse by Kerr Nonlinear Photonic Crystals

Self-phase modulation can efficiently shape the spectrum of an optical pulse propagating along an optical material with Kerr nonlinearity. In this work we show that a one-dimensional Kerr nonlinear photonic crystal can impose anomalous spectrum modulation to a high-power ultrashort light pulse. The spectrum component at the photonic band gap edge can be one order of magnitude enhanced in addition to the ordinary spectrum broadening due to self-phase modulation. The enhancement is strictly pinned at the band gap edge by changing the sample length, the intensity or central wavelength of the incident pulse. The phenomenon is attributed to band gap induced enhancement of light-matter interaction.

Compositional Dependence of g-Factor and Damping Constant of GdFeCo Amorphous Alloy Films

Time-domain magnetization dynamics of sputtered GdFeCo (30 nm) amorphous alloy films was measured by pump-probe method using high-power ultra-short pulse fiber laser. The effective g-factor g eff and effective damping constant alphaeff of the GdFeCo films were estimated by using a numerical calculation of Landau-Lifshitz-Gilbert equation. The precessional frequency took a maximum near the magnetization compensation composition C M of the GdFeCo, while the estimated g eff and alphaeff increased around the angular momentum compensation composition C A. The compositional dependences of g eff and alphaeff were roughly described by a mean-field model. The g eff and alphaeff were also estimated from the ferromagnetic resonance (FMR) spectra, and the data from the FMR spectra agreed well with those from the pump-probe measurement except for the composition near C M. The FMR method was unable to excite the magnetization near C M because of the small net magnetization.

Parametric transformation and spectral shaping of supercontinuum by high-intensity femtosecond laser pulses

The cascaded nonlinear-optical transformation of high-power ultrashort light pulses in an ionizing gas medium involving supercontinuum generation, followed by a frequency conversion of this radiation in the field of femtosecond laser pulses with an intensity of 1014–1015 W/cm2 has been demonstrated. Parametric four-wave mixing is shown to allow a highly efficient spectral transformation and shaping of supercontinuum radiation. The maximum efficiency of a parametric frequency conversion of femtosecond laser pulses in an ionizing gas medium achieved under the conditions of our experiments is estimated as 1%.

Pulse breaking recovery in fiber lasers

Pulse breaking recovery is numerically demonstrated in dispersion-managed fiber lasers designed for generating high peak power ultrashort optical pulses. It is shown that due to the cavity boundary condition, local pulse breaking can be absorbed by the pulse propagation in erbium-doped fiber with normal dispersion. Consequently, high peak power transform-limited pulses beyond the gain-bandwidth limitation could be generated.

Two-level model of a superradiant laser with distributed feedback

Numerical one-dimensional simulation of the superradiance phenomenon in a sample of a two-level medium with cw pumping under the conditions of resonant Bragg backscattering of counterpropagating waves has been performed. A range of parameters is determined in which a superradiant laser generating a chaotic sequence of ultrashort high-power pulses can be implemented, and the properties of these pulses are studied.

Dynamics of self-similar light pulses of limiting pulse width and energy in a fiber laser

We investigate dynamics of the formation of high-power ultrashort self-similar light pulses (similaritons) in a fiber laser in the regime of positive dispersion. The physical factors limiting the energy and the pulse width of such pulses are revealed. We specify regimes where a laser system based on an ytterbium-doped fiber can generate self-similar pulses with an energy of about 80 nJ compressible to a pulse width of about 150 fs through extracavity linear chirp compensation.

高平均功率超短脉冲激光光纤放大研究进展

高平均功率超短脉冲激光光纤放大研究进展

Passively mode-locked single-polarization microstructure fiber laser

The generation of high-power and stable ultra-short pulses from a passively mode-locked purely normal dispersion fiber laser is reported using the unique combination of a photonic crystal fiber featuring single-polarization, single-mode, and low nonlinearity with a high modulation depth semiconductor saturable absorber mirror. The environmentally-stable, self-starting fiber laser generates 1.6 W of average power at a repetition rate of 63 MHz, corresponding to a pulse energy of 25 nJ. The emitted pulses are positively chirped with a pulse duration of 3.7 ps. They are compressible down to a near transform-limited duration of 750 fs. Numerical simulations are in good agreement with the experimental results.

Control of surface modes in low loss hollow-core photonic bandgap fibers

We report on the fabrication and characterization of hollow-core photonic bandgap fibers that do not suffer from surface mode coupling within the photonic bandgap of the cladding. This enables low attenuation over the full spectral width of the bandgap--we measured a minimum loss of 15 dB/km and less than 50 dB/km over 300 nm for a fiber operating at 1550 nm. As a result of the increased bandwidth, the fiber has reduced dispersion and dispersion slope--by a factor of almost 2 compared to previous fibers. These features are important for several applications in high-power ultrashort pulse compression and delivery. Realizing these advances has been possible due to development of a modified fabrication process which makes the production of low-loss hollow-core fibers both simpler and quicker than previously.

Generation of high-power ultrashort electromagnetic pulses on the basis of effects of superradiance of electron bunches

One of the promising methods for generation of ultrashort electromagnetic pulses (with duration of about ten periods of high-frequency oscillations) is radiation from spatially localized electron ensembles (bunches), which can be considered a classical analog of Dicke superradiance known in quantum electronics. In classical electronics, superradiance can be related to various mechanisms of stimulated radiation. Until now, cyclotron, undulator, and Cerenkov (in the case of interaction with both copropagating and counterpropagating waves) superradiance of electron bunches as well as superradiance during stimulated scattering of a pump wave have been studied theoretically and experimentally. As a result of these studies based on high-current RADAN and SINUS accelerators and their modifications, a new class of oscillators producing pulsed electromagnetic radiation has been created. They have such unique characteristics as pulses of high peak power (up to 1 GW and 3 GW in the millimeter-and centimeter-wave ranges, respectively) and ultrashort duration (from 300 ps to 1 ns, respectively). In this case, regimes with a peak radiation power exceeding the electron-beam power are experimentally realized. Regimes with high (kilohertz) pulse repetition rate and high average power (up to 2.5 kW) are obtained.

Microstructure optical fibers for a new generation of fiber-optic sources and converters of light pulses

Breakthroughs in microstructure-fiber technologies are pushing the development of a new class of fiber-optic frequency converters, broadband light sources, and short-pulse lasers. The frequency profile of dispersion and the spatial profile of electromagnetic field distribution in waveguide modes of microstructure fibers can be tailored by modifying the core and cladding design on a micro- and nanoscale, suggesting ways of creating novel fiber-optic devices providing the highly efficient spectral and temporal transformation of laser pulses with pulse widths ranging from dozens of nanoseconds to a few optical cycles (several femtoseconds) within a broad range of peak powers from hundreds of watts to several gigawatts. In new fiber lasers, microstructure fibers provide a precise balance of dispersion within a broad spectral range, allowing the creation of compact all-fiber sources of high-power ultrashort light pulses.