Crystal-Based Molecular Modulation for Arbitrary Spatio-Temporal Optical Waveform Synthesis

一种用于亚飞秒脉冲产生和亚周期脉冲整形的技术正在开发中。该技术的本质是在相干叠加态中制备宏观介质。这种制备是通过两个激光脉冲调谐接近分子拉曼共振来完成的。由此产生的分子运动调制输入光以产生宽光谱的离散边带。 宽带相干产生拉曼活性晶体中示出，并证明了在精确和稳定的方式控制光谱相位的拉曼边带的能力。 这是朝向子周期脉冲成形的第一步，其将允许合成其中电场是时间的任意预定函数的波形，而不限于准正弦振荡。其结果是，在光电离和高次谐波产生的电子轨迹的直接和精确的控制将成为可能。此外，还研究了多级拉曼产生中的光轨道角动量相干转移。利用光学涡旋等奇异光束实现超短脉冲的操纵，不仅为超短脉冲的时空工程提供了新的自由度，而且为亚周期脉冲的时空工程开辟了新的可能性，这一研究的广泛影响不仅来自于基础科学领域的重大发现，还来自于新型宽带拉曼光源的各种实际应用。这些应用包括：光学相干断层扫描、超快光谱、精密计量等。此外，分子调制技术可用于在紫外和红外光谱区域产生相干辐射，其中激光源不容易获得。最终，在平版印刷术、化学、生物学和天文学上的应用可能成为现实。 该项目的一个重要部分是研究生和本科生的教育和培训。 该项目为这些学生提供量子光学和激光物理领域的培训，并使他们能够发展高需求的理论和实验技能。

A technique is being developed for sub-femtosecond pulse generation and sub-cycle pulse shaping. The essence of the technique is the preparation of a macroscopic medium in a coherent superposition-state. This preparation is accomplished by two laser pulses tuned close to a molecular Raman resonance. The resultant molecular motion modulates the input light to produce a wide spectrum of discrete sidebands. Broadband coherent generation in Raman-active crystals is shown, and the capability to control spectral phases of the Raman sidebands in a precise and stable manner is demonstrated. This is the first step toward sub-cycle pulse shaping, which will allow synthesis of waveforms where the electric field is an arbitrary predetermined function of time, not limited to quasi-sinusoidal oscillations. As a result, a direct and precise control of electron trajectories in photoionization and high-order harmonic generation will become possible. In addition, coherent transfer of optical orbital angular momentum in multi-order Raman generation is investigated. The use of singular light beams, such as optical vortices, provides a new degree of freedom for ultrashort pulse manipulation, and will open a possibility for spatio-temporal engineering of sub-cycle pulses.The broad impact of this research derives not only from the promised discoveries in fundamental science, but also come from a variety of practical applications of the new broad-band Raman source. These applications are: optical coherence tomography, ultrafast spectroscopy, precision metrology, to name a few. In addition, the technique of molecular modulation can be used to generate coherent radiation in the UV and IR spectral regions, where laser sources are not readily available. Eventually, applications to lithography, chemistry, biology, and astronomy may become practical. An important part of this project is the education and training of graduate and undergraduate students. The project provides these students with training in the field of quantum optics and laser physics and will allow them to develop both theoretical and experimental skills which are in high demand.