Few-cycle mid-infrared pulse generation, characterization, and coherent propagation in optically dense media
Few-cycle mid-infrared pulse generation, characterization, and coherent propagation in optically dense media
复制标题
DOI：
10.1063/1.1480464
复制
发表时间：
2002-06-01
影响因子：
1.6
通讯作者：
Scherer, NF
中科院分区：
文献类型：
--
作者：
Gruetzmacher, JA;Scherer, NF
利用单级光参量放大器（OPA）实现了四到五个周期的中红外脉冲的产生。OPA由增益开关Ti：Sapphire再生放大器泵浦，并以白色光连续体的近红外部分作为种子。OPA可在2700至4700 nm范围内连续调谐，并保持使用互相关频率分辨光学门控（XFROG）充分表征的65 fs以下脉冲。这些是在这个大的红外光谱范围内报道的最短的近变换极限脉冲。该装置用于测量超快振动响应，特别是，由O-H振荡器的自由感应衰减（FID）修改的脉冲轮廓。这些脉冲的强度和瞬时相位都是在使用XFROG穿过同位素稀释的水（HDO在D2 O中）的样品后确定的，这代表了XFROG技术在（偶极）分子响应研究中的新应用。即使在光密度为1以下，也可以观察到FID修改脉冲的后沿的明显跳动，并且发现这些特征的细节取决于用于生成FID的场的啁啾。这些结果表明，在选择非线性红外光谱测量的样品条件时应谨慎。(C)2002年美国物理学会。
The generation of four- to five-cycle mid-infrared pulses using a single-stage potassium niobate optical parametric amplifier (OPA) is demonstrated. The OPA is pumped by a gain-switched Ti:Sapphire regenerative amplifier and is seeded with the near-infrared portion of a white light continuum. The OPA is continuously tunable from 2700 to 4700 nm, and maintains sub-65 fs pulses that are fully characterized using cross-correlation frequency-resolved optical gating (XFROG). These are the shortest near-transform-limited pulses reported over this large infrared spectral range. This apparatus is used to measure ultrafast vibrational responses, specifically, pulse profiles modified by the free-induction decay (FID) of O-H oscillators. Both the intensity and instantaneous phase of these pulses are determined after traversing samples of isotopically diluted water (HDO in D2O) using XFROG, representing a new application of the XFROG technique to the study of (dipolar) molecular responses. Pronounced beating of the trailing edges of FID-modified pulses is observed even below optical densities of one, and the details of these features are found to depend on the chirp of the field used to generate the FID. These results indicate that discretion should be used in the selection of sample conditions for nonlinear infrared spectroscopic measurements. (C) 2002 American Institute of Physics.