小波变换提取放大超短脉冲载波-包络相位的研究

提出了一种新的超短放大脉冲的载波-包络相位还原方法,应用小波变换从超短放大脉冲的光谱拍频干涉中直接提取载波-包络相位. 消除了传统的Fourier变换方法不同宽度的滤波窗口引入不同程度的相位噪声而产生不确定性的影响,得到了更精确的载波-包络相位信息,对于近单周期超短脉冲特性测量具有重要意义. 关键词： 超短脉冲 载波-包络相位 相位还原 小波变换     

Carrier-envelope phase fluctuations of amplified femtosecond pulses: characterization with a simple spatial interference setup

We demonstrate a direct and versatile scheme to determine the carrier-envelope phase fluctuations of tunable ultrashort optical pulses. The spatial interferogram between the high frequency components and the parametrically amplified and frequency doubled low frequency components of an octave broad white light continuum is measured for every single pulse. It directly reveals the carrier-envelope phase fluctuations of the pump pulses from the regenerative amplifier, as well as of the white light and the tunable pulses generated from it. PACS 42.25.Kb; 42.65.Yj; 42.65.Re     

光学元件群延迟的直接测量

提出了一种测量群延迟的新方法,利用白光干涉仪产生的光谱干涉,通过时间频率联合分析直接得出群延迟,减小了传统相位差分方法产生的误差,并通过测量结果减去系统背景,进一步提高了光学元件色散测量的准确度. 该方法适合于具有复杂色散光学元件群延迟和色散的准确测量,也适合于慢光器件群速度延迟的测量. 关键词： 色散测量 白光干涉 时间频率分析 超快激光     

Phase-dependent effects of a few-cycle laser pulse

The Keldysh theory of above-threshold ionization (ATI) is applied to few-cycle laser pulses in order to explore the potential of a recently published new method to measure "carrier-envelope phase difference" phenomena. In this experiment, the carrier-envelope phase difference dependent left-right asymmetry of few-cycle ATI was measured and investigated with a correlation technique. Here, we explore spectral features of the asymmetry, present a theoretical analysis of the experiment, and establish a method to determine the duration of few-cycle pulses whose carrier-envelope phase differences are not controlled.     

Solid-state carrier-envelope phase stabilization via quantum interference control of injected photocurrents

We demonstrate carrier-envelope phase stabilization of a mode-locked Ti:sapphire laser by use of quantum interference control of injected photocurrents in a semiconductor. No harmonic generation is required for this stabilization technique. Instead, interference between coexisting single- and two-photon absorption pathways in the semiconductor provides a phase comparison between different spectral components. The phase comparison, and the detection of the photocurrent that it produces, both occur within a single low-temperature-grown gallium arsenide sample. The carrier-envelope offset beat note fidelity is 30 dB in a 10-kHz resolution bandwidth. The out-of-loop phase-noise level is essentially identical to the best previous measurements with the standard self-referencing technique.     

Single-shot measurement of carrier-envelope phase changes by spectral interferometry

We demonstrated single-shot measurements of spectral interference between a white-light continuum generated in a hollow-fiber and its second harmonic. The interference has information on the carrier-envelope phase of an input pulse to the fiber and the time delay of the blue wing of the continuum. By analyzing the observed spectral interference, we estimated shot-by-shot changes of the carrier-envelope phase. This method is useful for determining the carrier-envelope phase changes of a low-repetition-rate, high-intensity laser.     

空间外差光谱仪干涉图数据处理

空间外差光谱技术是一种新型的超分辨光谱技术。介绍了空间外差光谱仪的基本原理,并针对其特点提出了干涉图数据处理的方法。首先通过一阶差分对干涉图进行去基线处理,然后使用三角函数作为切趾函数对干涉图进行切趾,并对傅里叶变换光谱进行相位校正,最后采用已知双线光源对空间外差光谱仪原理试验装置进行波长定标。文章以Na双线与Hg谱线进行波长定标,得到了波长定标曲线。通过以上的方法对空间外差光谱仪干涉图数据进行处理,能有效地提高干涉图反演光谱的精度。     

Spectrum reconstruction based on the constrained optimal linear inverse methods

The dispersion effect of birefringent material results in spectrally varying Nyquist frequency for the Fourier transform spectrometer based on birefringent prism. Correct spectral information cannot be retrieved from the observed interferogram if the dispersion effect is not appropriately compensated. Some methods, such as nonuniform fast Fourier transforms and compensation method, were proposed to reconstruct the spectrum. In this Letter, an alternative constrained spectrum reconstruction method is suggested for the stationary polarization interference imaging spectrometer (SPIIS) based on the Savart polariscope. In the theoretical model of the interferogram, the noise and the total measurement error are included, and the spectrum reconstruction is performed by using the constrained optimal linear inverse methods. From numerical simulation, it is found that the proposed method is much more effective and robust than the nonconstrained spectrum reconstruction method proposed by Jian, and provides a useful spectrum reconstruction approach for the SPIIS.     

Fast f-to-2f interferometer for a direct measurement of the carrier-envelope phase drift of ultrashort amplified laser pulses

We propose a novel method to directly extract the phase from spectral interferograms, without the need for digital signal processing. This method is demonstrated with single-shot measurement and stabilization of the carrier-envelope phase of a 3 kHz amplifier system. Our scheme allows for real-time monitoring of the carrier-envelope drift and an increased loop width for stabilization. We find that in our amplifier laser system fast carrier-envelope phase jitter is mainly inherited from the oscillator stabilization loop but we also find previously unreported indications for a rapid pulse-to-pulse jitter from the amplifier pump laser.     

Rapid and accurate chromatic dispersion measurement of fiber using asymmetric Sagnac interferometer

We propose and experimentally demonstrate an advanced method for chromatic dispersion measurement of fiber. This technique is based on spectral interferometry by using an asymmetric Sagnac loop and broadband optical source. The chromatic dispersion can be directly obtained from the spectral interferogram seen from an optical spectral analyzer. This method is rapid (<1?s), accurate, simple, low cost, and can provide a large dispersion measurement range.     

Spectrally-resolved white-light interferometry as a profilometry tool

Phase-shifting interferometry and white-light interferometry are reliable techniques for surface analysis in which the optical path difference has to be changed by some transducer to evaluate the phase. We present here a different procedure in which optical path modulation is completely avoided. This technique is based on the spectral analysis of white-light interferograms. By means of a spectroscopic device, a non-visible interferogram is split into its monochromatic components and absolute, unambiguous values of the phase are obtained along the spectral axis. Only one interferogram is required to obtain the profile of one-dimensional surfaces with nanometric resolution.     

Coherence three-dimensional imaging spectrometry based on measurement of rotated-hyperbolic volume interferograms

A new interferometric technique to obtain three-dimensional multispectral images of spatially incoherent polychromatic-source distributions is investigated. This technique is based on the measurement of a new type of volume interferogram, herein called the rotated-hyperbolic volume interferogram, which can be obtained by existing interferometer together with a novel aperture synthesis. This paper reports the first demonstration of the method: measurement of a monochromatic point source. The results obtained from this measurement included three-dimensional spatial information and spectral information corresponding to the impulse response function defined over a four-dimensional space. These experimental results confirmed that the imaging characteristics, particularly depth resolution, of the new method are superior to those of previous methods.     

小波变换重建超短脉冲光谱相位的误差分析

分析了噪声对小波变换重建超短脉冲光谱相位的影响. 在理想情况和附加噪声、倍增噪声， 以及干涉条纹采样量化干扰的情况下，分析了小波变换对几种光谱相位的重建精度. 结果显 示，在理想情况和噪声干扰的情况下，小波变换的相位重建精度都在003rad范围以内. 这 说明小波变换是一种精确可信的光谱相位重建方法，具有很强的抗噪声干扰能力. 另外，将 小波变换的轨迹图类比SHG FROG的轨迹图，可以直接定性判断脉冲的啁啾特征. 关键词： 超短脉冲 相位重建 小波变换 噪声     

基于多普勒非对称空间外差光谱技术的多普勒测速仿真

阐述了多普勒非对称空间外差光谱仪用于被动式多普勒测速的基本原理,通过综合考虑干涉条纹对比度和仪器测速灵敏度等关键因素,建立了效率函数,分别针对高斯线型和洛伦兹线型发射谱线,从理论上推导了最优单臂偏置量的选择依据,并以高斯线型目标谱线为例进行了仿真验证.同时,提出了一种基于部分干涉条纹反演多普勒速度的数据处理方法,简化了多谱线目标源的数据处理过程.结合自适应频率跟踪算法对单谱线目标源和多谱线目标源进行了仿真比较,仿真结果表明,在不考虑噪声的情况下,该方法针对多谱线目标源的多普勒测速最大绝对误差在0.004 m/s以内,与针对单谱线目标源的处理精度相当,可以满足实际应用的精度要求.     

外差式偏振干涉成像光谱技术研究

提出了一种新型的基于Savart偏光镜的外差式偏振干涉成像光谱技术,该技术在偏振干涉成像光谱仪中引入一对平行偏振光栅对,使其得到的干涉图频率与波数相关,具有了波数外差的特点,降低了干涉图频率,从而可利用较少的采样点数实现很高的光谱分辨率.对外差式偏振干涉成像光谱技术的基本原理进行了研究,详细分析了系统光程差、干涉图表达式、光谱分辨率以及光谱复原方法等.最后给出了外差式偏振干涉成像光谱仪的设计实例并进行了计算机仿真模拟,所复原的光谱与输入光谱曲线相符合,验证了方案的正确性.外差式偏振干涉成像光谱仪具有结构紧凑、光通量高、稳定性强、光谱分辨率高的特点,尤其适合超小型高稳定性、高探测灵敏度的高光谱探测应用.     

Time-domain surface profile imaging via a hyperspectral Fourier transform spectrometer

We describe a method for time-domain surface profile measurements via white-light reflection spectroscopy using a hyperspectral Fourier transform spectrometer (HS-FTS). This technique measures the frequency of the spectral modulation of reflected light from a multilayer optical surface and reports the spatially resolved optical thickness. Owing to the Fourier relationship, the Fourier transform spectrometer manifests this spectral modulation as temporal satellites in interferogram space. We show that measurement of the positions of these satellites can be used to reconstruct the optical thickness profile over a surface using the HS-FTS.     

Double-beam fourier spectroscopy with interferometric background compensation

A double-beam multiplex spectrometer is described which is specially suited for measuring small variations in absorptivity or reflectivity, or narrow spectral lines, against a strong and varying background. By a modification of the conventional Fourier spectrometer, the interferogram beam and the radiation normally going back to the source — the anti-interferogram beam — are combined in the sensitive area of a single detector. If a sample and a reference standard are placed in the interferogram and the anti-interferogram paths respectively, the Fourier transform of the interferogram of the combined intensity directly yields the difference between the spectra of the sample and the reference standard with the optical cancellation of the common features. The advantages and possible applications of this technique are discussed.     

自参考光谱相干法的小波变换相位重建

将小波变换法引入光谱相位相干电场重建法的相位重建，从光谱干涉条纹的小波变换中直接 读取条纹相位，消除了传统傅里叶方法滤波过程中产生的相位噪声. 这种方法将有利于超宽 带、单周期超短脉冲的产生，更适用于超短脉冲的评价. 关键词： 超短脉冲 相位重建 小波变换     

All-optical stabilization of carrier-envelope phase by use of difference frequency generation with seeded amplification of colored conical emission

We stabilized the carrier-envelope phase of pulses emitted by a femtosecond regenerative amplifier through difference frequency generation between pump and seeded amplification of colored conical emission. Seeded amplification of colored conical emission was induced by modulational instability in the second harmonic generation with a supercontinuum injected and amplified. As a consequence, it inherited the origin phase of the pump pulse. After difference frequency with the pump pulses, the generated tunable idler pulses were carrier-envelope phase stabilized, which was verified with a simple and robust spectral interference setup. PACS 42.65.Re; 42.65.Yj; 42.25.Kb     

空间调制傅里叶变换光谱仪分束器色散特性研究

在基于多级微反射镜的傅里叶变换光谱仪中,由于分束器的色散特性, 不同波长的干涉图具有不同的横向偏移量,其在横向空间会发生混叠. 同时,不同波长的干涉图还具有不同的光程差偏移量,使其在纵向空间也会发生混叠. 根据几何光学原理,干涉图的横向混叠会减小干涉图元的有效面积. 计算表明,本研究中干涉图元的横向混叠面积为总面积的3.4%, 通过数据处理扣除混叠部分可以消除横向混叠的影响. 干涉图的纵向混叠会产生一个附加的相位延迟,削弱谱线的强度. 经分析,附加相位延迟与分束器和补偿板之间的厚度差成正比. 本文给出了发生对比度反转时分束器与补偿板厚度差的极限值, 并利用解线性方程组的方法对纵向混叠的干涉图进行了校正, 反演出的光谱与理想光谱的标准偏差仅为1.76×10^-14.