Nanolithography with ultra-short laser pulses

光刻是推动基础研究和广泛应用取得进步的关键技术。这通常是在半导体行业和摩尔定律的背景下讨论的：该行业每三年将芯片上的晶体管数量翻两番的能力。为了跟上迅速缩小的晶体管尺寸，人们积极探索替代光刻技术，其中包括原子纳米光刻。与使用单色光束的传统光学光刻不同，原子光刻利用的是原子束，原子束在沉积到固体表面之前受到光场的操纵。在这两种情况下，分辨率都由衍射极限决定，因此也由相应光束的波长决定。虽然光学波长在几百纳米的范围内，但原子物质波的波长是以皮米为单位测量的。因此，使用原子光学来推动纳米光刻的边界并在纳米制造中达到更短的长度尺度是特别有吸引力的。在这里，我提议建立一个利用超短激光脉冲进行原子纳米制造的创新计划。这项计划将有两个主要目标。首先，我们将发展脉冲光场控制原子和分子运动的技术。其次，这项新技术将被用来解决连续波激光源原子光刻的两个主要缺点：1)它只适用于少数选择的原子，2)它固有的对周期性纳米结构的限制。基于原子与高功率飞秒脉冲的非共振相互作用，例如多光子电离，所提出的方法将扩展到甚至复杂的分子。短脉冲的宽光谱带宽和它们在空间上的紧密局部化将使人们能够控制分子分布，而不是目前所证明的周期性调制。这项新的实验技术将架起超快光学、原子物理和纳米科学的桥梁，刺激一个全新的研究方向，并吸引学生进入这个迷人的交叉学科领域。

Lithography is a key technology enabling progress both in fundamental research and in widespread applications. It is usually discussed in the context of the semiconductor industry and Moore's law: the industry's ability to quadruple the number of transistors on a chip every three years. In an effort to keep up with quickly "shrinking" transistor size, alternative lithographic techniques are actively explored, and among them - atom nanolithography. In contrast to conventional optical lithography, which uses monochromatic beam of light, atom lithography utilizes the beam of atoms which is manipulated by optical fields before being deposited on a solid surface. In both cases the resolution is dictated by the diffraction limit, and therefore by wavelength of the corresponding beam. While optical wavelengths are in the range of a few hundred nanometers, the wavelength of a matter wave of atoms is measured in picometers. It is therefore particularly attractive to use atom optics for pushing the boundaries of nanolithography and reaching much shorter length scales in nanofabrication. Here I propose to establish an innovative program on atom nanofabrication with ultra-short laser pulses. This program will have two main objectives. First, we will develop the technology of controlling atomic and molecular motion with pulsed optical fields. And second, the new technique will be applied to tackle two major shortcomings of atom lithography with continuous-wave laser sources: 1) its limited applicability to only a small selection of atoms, and 2) its inherent restriction to only periodic nanostructures. Based on non-resonant interaction of atoms with high-power femtosecond pulses, such as multiphoton ionization, the proposed method will be extended to even complex molecules. Broad spectral bandwidth of short pulses and their tight localization in space will enable control of molecular distribution beyond currently demonstrated periodic modulation. The new experimental technique will bridge ultrafast optics, atomic physics and nanoscience, stimulating a whole new direction of research, and attracting students to this fascinating interdisciplinary field.