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1.
Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numerically. It is found that OPC cannot compensate for pulse waveform distortion due to SS. The initial chirp of pulses and dispersion can counteract SS and improve the compensation performance for the distortion. 相似文献
2.
Anomalous spectral behaviour of diffracted chirped Gaussian pulses in the near field 总被引:1,自引:0,他引:1 下载免费PDF全文
By using the Fourier transform method, analytical expressions for the axial power spectrum and near-field intensity in the spacetime domain of chirped Gaussian pulses diffracted at an aperture are derived, which permit us to study changes in spectral and temporal profiles of the chirped Gaussian pulses both analytically and numerically. Detailed numerical results and physical analysis show that spectral anomalies take place in the neighbourhood of certain critical distances, and the shifting of maximum and splitting of temporal intensity profiles appear. In particular, for ultrashort chirped pulses, there exists also spectral switch. Besides the truncation parameter, the chirp parameter and pulse duration affect the behaviour of spectral switches. 相似文献
3.
Influences of finite gain bandwidth on pulse propagation in parabolic fiber amplifiers with distributed gain profiles 下载免费PDF全文
The evolutions of the pulses propagating in decreasing and increasing gain distributed fiber amplifiers with finite gain bandwidths are investigated by simulations with the nonlinear Schr¨odinger equation. The results show that the parabolic pulse propagations in both the decreasing and the increasing gain amplifiers are restricted by the finite gain bandwidth. For a given input pulse, by choosing a small initial gain coefficient and gain variation rate, the whole gain for the pulse amplification limited by the gain bandwidth may be higher, which is helpful for the enhancement of the output linearly chirped pulse energy. Compared to the decreasing gain distributed fiber amplifier, the increasing gain distributed amplifier may be more conducive to suppress the pulse spectral broadening and increase the critical amplifier length for achieving a larger output linearly chirped pulse energy. 相似文献
4.
We report a highly efficient and high power self-starting femtosecond Cr:forsterite laser pumped by a 1064-nm Yb doped fibre laser. Five chirped mirrors are used to compensate for the intra-cavity group-delay dispersion, and the mode-locking is initiated by a semiconductor saturable absorber mirror (SESAM). Under pump power of 7.9 W, stable femtosecond laser pulses with average power of 760mW are obtained, yielding a pump power slope efficiency of 12.3%. The measured pulse duration and spectral bandwidth (FWHM) are 46 fs and 45 nm; the repetition rate is 82 MHz. 相似文献
5.
Long-Term Stabilization of Carrier-Envelope Phase for Few Cycles Ti:Sapphire Laser Amplifier 下载免费PDF全文
We realize a long-term carrier-envelope phase (CEP) stabilization for a chirped pulse amplified Ti:sapphire laser by locking the oscillator and amplifier independently. Based on the measurement of CEP by employing f-to-2f interference technique between the octave-spanning spectrum which is generated from a rare gas filled hollow fiber, continuous locking time up to 7.2 h with 85 mrad fluctuation is demonstrated. Finely compensating the dispersion by a set of chirped mirrors, quasi-mono cycle pulses as shorter as 3.8 fs are obtained. Further experimental research on high harmonic generation dependence on CEP shown the waveform of laser pulses has been successfully controlled. 相似文献
6.
Relative carrier-envelope phase dependence of resonant propagation of two-colour femtosecond pulses in V-type atomic medium 下载免费PDF全文
Using numerical solution of the full Maxwell--Bloch
equations, which is obtained by the finite-difference time-domain
method and the iterative predictor--corrector method, we investigate
the modulation effect of relative carrier--envelope phase
(hereinafter referred to as the relative phase) on resonant
propagation of two-colour femtosecond ultrashort laser pulses in a
V-type three-level atomic medium. It is found that the pulse
splitting occurs for a smaller value of relative phase; when the
value of relative phase increases to a certain value, only the
variation of pulse shape is present and the pulse splitting does not
occur any more; moreover, when the value of relative phase is
smaller, the pulse group velocity is larger. The relative phase also
has an obvious effect on population and spectral property. Different
population transfers can be realized by adjusting the value of
relative phase. Generally speaking, for the pulses with smaller
areas their spectral strengths and frequency ranges decrease
obviously with the value of relative phase increasing; for the
pulses with larger areas, with value of the relative phase
increasing, their spectral strengths decrease remarkably but the
relative strengths of the higher frequency components increase
significantly, while the spectral frequency range is not varied
evidently. 相似文献
7.
By using the pulse propagation equation in the nonlinear dispersive medium, the effects of second- and third-order group-velocity dispersion on pulse evolution in the stretching, amplification and compressing are studied when chirped pulse am-plification is applied to the pulses of a width <30fs, and the optimum dispersion-compensated conditions among the stretcher, amplifier and compressor are deter-mined. From the standpoint of dispersion compensation and control and the com-pressor adjustment, it is proposed that low-groove-density gratings (≤800 line/mm) are the better choices for stretching and compressing the pulses of a width <30fs in chirped-pulse amplification. It is also shown that, with a proper adjustment of the compressor incident angle and grating separation, an exact null in both second- and third-order dispersions can be achieved without any additional dispersion- compensated elements. 相似文献
8.
Dispersion Analysis and Compensation of Collinear Optical Parametric Chirped Pulse Amplification Systems 下载免费PDF全文
In an optical parametric chirped pulse amplification (OPCPA) laser system, residual phase dispersion should be compensated as much as possible to shorten the amplified pulses and improve the pulse contrast ratio. Expressions of orders of the induced phases in collinear optical parametric amplification (OPA) processes are presented at the central signal wavelength to depict a c/ear physics picture and to simplify the design of phase compensation. As examples, we simulate two OPCPA systems to compensate for the phases up to the partial fourth-order terms, and obtain flat phase spectra of 200-nm bandwidth at 1064nm and 90-nm at 800nm. 相似文献
9.
Accurate determination of the absolute phase and temporal-pulse phase of few-cycle laser pulses 下载免费PDF全文
A Fourier analysis method is used to accurately determine not
only the absolute phase but also the temporal-pulse phase of an
isolated few-cycle (chirped) laser pulse. This method is
independent of the pulse shape and can fully characterize the
light wave even though only a few samples per optical cycle are
available. It paves the way for investigating the absolute
phase-dependent extreme nonlinear optics, and the evolutions of
the absolute phase and the temporal-pulse phase of few-cycle
laser pulses. 相似文献
10.
Development of the spectrum of gamma-ray burst pulses influenced by the intrinsic spectral evolution and the curvature effect 下载免费PDF全文
The spectral evolution of gamma-ray burst pulses assumed to arise from
the emission of fireballs is explored. It is found that due to the
curvature effect, the integrated flux is well related to peak energy
by a power law in the decaying phase of pulses, where the index is
about 3, which does not depend on intrinsic emission and the Lorentz
factor. The spectra of pulses in the decaying phase are slightly
different from each other when different intrinsic spectral
evolution patterns are considered, indicating that it is dominated
by the curvature effect. In the rising phase, the integrated flux
keeps increasing whilst the peak energy remains unchanged when the
intrinsic emission bears an unchanged spectrum. Within this phase,
the flux decreases with the increase of the peak energy for a
hard-to-soft intrinsic spectrum, and for a soft-to-hard-to-soft
intrinsic spectrum, the flux generally increases with the increase
of the peak energy. An intrinsic soft-to-hard-to-soft spectral
evolution within a co-moving pulse would give rise to a pulse-like
evolutionary curve for the peak energy. 相似文献
11.
12.
Ultraviolet pulses with a duration of 7 fs are efficiently generated by frequency doubling the output of a noncollinear optical parametric amplifier. The ultraviolet pulses are tunable between 275 to 335 nm. The acceptance bandwidth of the doubling crystal is increased by a factor of 80 through high-order achromatic phase matching. The chirp of the visible pulses and the dispersion introduced along the beam path are compensated partially before and partially after the doubling crystal. For the design of the dispersion management, we investigate the second harmonic generation of pulses with mixed orders of chirp and explicitly discuss the transfer of the spectral phase in frequency doubling. A simple analytic theory is derived that correctly describes frequently observed spectral narrowing effects. We find that chirped SHG avoids spectral narrowing and allows for precompression of dispersion encountered in the ultraviolet beam path. We apply chirped SHG to generate 18.7 fs ultraviolet pulses in an extremely simple setup. PACS 42.65.Re; 42.65.Ky; 42.65.Yj 相似文献
13.
We report a study of the scaling and limits to pulse energy in an all-normal-dispersion femtosecond fiber laser. Theoretical calculations show that operation at large normal cavity dispersion is possible in the presence of large nonlinear phase shifts, owing to strong pulse shaping by spectral filtering of the chirped pulse in the laser. Stable pulses are possible with energies of tens of nanojoules. Experimental results from Yb-doped fiber lasers agree with the trends of numerical simulations. Stable and self-starting pulses are generated with energies above 20 nJ, and these can be dechirped to <200 fs duration. Femtosecond pulses with peak powers near 100 kW are thus available from this simple and practical design. 相似文献
14.
利用三五阶非线性效应下的扩展非线性薛定谔方程,在忽略光纤色散的情况下,计算模拟了以二阶情形为例的啁啾超高斯光脉冲的啁啾和频谱。结果表明,脉冲无预啁啾时,正五阶非线性增大啁啾量,负五阶非线性在减小啁啾量的同时还改变啁啾曲线的形状。当预啁啾与五阶非线性系数同(异)号时,总啁啾增加(减小)。随着超高斯脉冲阶次的增大,总啁啾量增大,脉冲中心附近无啁啾的范围变宽,整个有啁啾的范围变小,总啁啾中预啁啾所占比重增大。脉冲无预啁啾时,正负五阶非线性分别可以增大和减小频谱展宽。预啁啾若增强非线性所致啁啾,则可能使频谱峰值结构加强,谱峰数目增多。当超高斯光脉冲的阶次或最大非线性相移增大时,在某些宽大的频谱峰上还可能出现许多精细谱峰。 相似文献
15.
Back-side-coated chirped mirrors with ultra-smooth broadband dispersion characteristics 总被引:1,自引:0,他引:1
N. Matuschek L. Gallmann D.H. Sutter G. Steinmeyer U. Keller 《Applied physics. B, Lasers and optics》2000,71(4):509-522
We demonstrate a new technique for the design of chirped mirrors with extremely smooth dispersion characteristics over an
extended ultra-broadband wavelength range. Our approach suppresses spectral dispersion oscillations, which can lead to unwanted
strong spectral modulations and limit the bandwidth of mode-locked laser pulses. Dispersion oscillations are significantly
reduced by coating the chirped mirror structure on the back side of a substrate, providing ideal impedance matching between
coating and ambient medium. An anti-reflection coating may be added on the front side of the substrate, geometrically separated
from the chirped mirror. The chirped mirror structure and the anti-reflection coating are non-interfering and can be independently
designed and optimized. The separation of both coating sections provides a much better solution for the impedance-matching
problems than previous approaches to chirped mirror design. We show by a theoretical analysis and numerical simulations that
minimum dispersion oscillations are achieved if the index of the substrate is identical to the index of one of the coating
materials and if double-chirping is used for the chirped mirror structure. Based on this analysis, we design a mirror that
supports a bandwidth of 220 THz with group delay dispersion oscillations of about 2 fs2 (rms), an order-of magnitude improvement compared to previous designs of similar bandwidth. In a first experimental demonstration
of back-side-coated (BASIC) mirrors, we achieve nearly transform-limited and virtually unchirped pulses of 5.8 fs duration
from a Kerr-lens mode-locked Ti:sapphire laser. BASIC mirrors are particularly suited for higher-order dispersion compensation
schemes. They support the extremely broad spectra of few-cycle pulses and promise to provide clean pulse shapes in this regime.
Received: 19 April 2000 / Published online: 6 September 2000 相似文献
16.
17.
提出一种利用周期性抛物线调制信号对光脉冲进行相位调制以获得周期性线性啁啾脉冲的方法, 并对其进行了数值模拟与实验研究. 数值模拟结果表明: 增益饱和效应、群速度色散以及同步误差对啁啾脉冲的时间-光谱特性影响较大; 自相位调制对啁啾脉冲的影响较小. 实验获得了0.52 nm带宽的周期性线性啁啾脉冲, 与模拟结果符合较好. 实验结果同时表明装置中存在较大的偏振模色散, 导致幅频效应较大, 后续的研究中需加入对此的考虑. 模拟及实验研究表明: 直接相位调制是一种新型的可方便地获得周期性线性啁啾脉冲的方法, 其在光谱色散平滑中具有潜在应用.
关键词:
直接相位调制
周期性线性啁啾脉冲
幅频效应 相似文献
18.
19.
Gan Gao Yijie Shen Decai Deng Yuan Meng Linlu He Mali Gong Haitao Zhang 《Optical Review》2018,25(5):598-607
A new method is proposed to systematically measure the phase-intensity information of chirped pulses that is based on the chirp-coefficient bisection iteration (CBI) concept. Through the CBI procedure with measured spectrum and temporal intensity profiles (or intensity autocorrelations), spectral and temporal amplitude–phase information can be rapidly retrieved. We experimentally verified that our method has high precision for nanosecond- and picosecond-level pulses and low precision for femtosecond-level pulses. Our proposed method does not require a sophisticated setup and has the advantage of accurate determination of temporal and spectral chirp coefficients with various orders. It also has lower cost, simple operation, in particular covers a wider measurement range than the main current methods. Moreover, the retrieved waveforms can reveal both the pulse shape and the actual intensity with spectral and temporal chirped coefficients of various orders, which can be directly used in various pulse propagation analyses such as chirped pulse amplification. 相似文献
20.
A.P. Kovács K. Osvay G. Kurdi M. Görbe J. Klebniczki Z. Bor 《Applied physics. B, Lasers and optics》2005,80(2):165-170
The frequency dependence of the group delay of both a pulse stretcher and a stretcher–compressor system of a chirped pulse amplification laser is determined with a two-dimensional extension of a spectral interferometric method called the stationary phase point method. The 800-nm, 15-fs probe pulse from a Ti:S oscillator propagates through the stretcher or the stretcher–compressor system. The reference pulse is one of the subsequent oscillator pulses but passes the system and interferes with the probe pulse; hence, a Mach–Zehnder-type interferometer is formed. The shape of the spectrally resolved interference fringes is peculiar to the amount and sign of the relative dispersion properties of the pulses. Group-delay dispersion is obtained from the observation of the position of the stationary phase point in spectrally resolved interferograms at different time delays. This simple method allows for an almost complete and fast alignment of the stretcher–compressor system from scratch until the final adjustments. PACS 42.65.Re 相似文献