Mid-infrared reconfigurable pulse generators

激光是不可或缺的工具，在许多不同的途径造福我们的社会。激光的实用性来自于它能够发射精确定义波长的光和极其稳定的强度，使其特别适用于需要极高精度的测量，以及通过在海底光缆中使用激光作为数字信息的载体来连接世界。然而，更多的应用将受益于一种新型激光器，它可以同时发射不止一种，而是多种波长的光。该项目的目标就是精确地实现这种激光器。这种激光的输出强度不再是恒定的，而是以相等的时间间隔间隔的一系列短光脉冲。这些脉冲将达到极高的光强度——比单波长激光所能提供的要高得多。这种强烈的脉冲对光谱学家尤其有用，这些科学家努力通过研究物质如何吸收和发射激光来加深我们对物质的理解。短而强的光脉冲可以作为精确的时钟机制来计时材料对激光辐射的响应，可用于化学反应的实时监测以及原子蒸汽、气体分子和半导体晶体的非线性光学响应的研究，直接影响从固体物理学到生物学的学科，在医学研究中具有潜在的应用前景。该项目的主要目标是演示一种新的器件结构——一种中红外环形量子级联激光器，具有集成的有源定向耦合器，由相干外部激光源驱动。通过作用于驱动激光强度及其与环形激光频率的失谐，可以按需重新配置环形激光的状态，范围从亮腔孤子和暗腔孤子，分别代表在激光介质中不加宽传播的超短光脉冲和连续激光背景中的“暗脉冲”，到更复杂的波形，即图灵卷和相位孤子，所有这些都是一体的。全电控装置。从使用商业电磁模式求解器和内部定制激光模拟器的激光谐振器的设计和建模开始，研究人员将根据开发的设计进行纳米级半导体加工。制造设备的特性将基于激光输出的基本发射光谱，以及使用已经存在的光学干涉仪和在项目时间范围内构建的设置进行复杂的时间波形重建。该项目将包括以非线性有源谐振器模式形成为中心的更广泛的数学物理理论研究，并将加深对无源和有源光学谐振器频率梳形成的物理相似性和差异性的理解。从紧凑的芯片级设备实现中红外超短脉冲产生可能是基础科学的变革，它允许探测中红外频率下发生的超快材料过程的时间动力学-从声子到极化子再到复杂有机分子的相互作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Lasers are indispensable tools that benefit our society on many different avenues. Laser utility comes from it being able to emit light of precisely defined wavelength –– and an extremely stable intensity, making it especially suitable for measurements requiring utmost precision and in connecting the world by using laser light as a carrier of digital information in undersea fiber optic cables. More applications, however, would benefit from a new kind of laser, that emits simultaneously not one, but many wavelengths of light. The goal of the project is to realize precisely this kind of laser. The output intensity of such a laser is no longer constant, but is a train of short light pulses, all spaced by equal time intervals. These pulses will attain extremely high optical intensities –– much higher than a single- wavelength laser could provide. Such intense pulses would be especially useful to optical spectroscopists –– scientists who strive to deepen our understanding of matter by studying how it absorbs and emits laser light. Short intense pulses of light can serve as a precise clockwork mechanism to time the response of the material to laser radiation, which can be used for real time monitoring of chemical reactions and for the studies of the nonlinear optical response of atomic vapors, gas molecules and semiconductor crystals, directly impacting disciplines from solid-state physics to biology, with potential applications in the medical research. The primary goal of the project is the demonstration of a new device architecture ¬¬–– a mid-infrared ring quantum cascade laser with an integrated active directional coupler, driven by a coherent external laser source. By acting on the drive laser intensity and its detuning from the ring laser frequency it will be possible to reconfigure the state of the ring laser on-demand, ranging from bright and dark cavity solitons, representing respectively ultrashort pulses of light that propagate without broadening in the laser medium and “dark pulses” in a background of continuous laser light, respectively, to more complex waveforms known as Turing rolls and phase solitons –– all in one, all-electrically controlled device. Starting with the design and modeling of laser resonators using commercial electromagnetic mode solvers and an in-house custom laser simulator the researchers will proceed with nanoscale semiconductor processing according to the developed designs. Characterization of fabricated devices will be based on basic emission spectroscopy of laser output as well as complex temporal waveform reconstruction using already existing optical interferometers and the setups constructed within the timespan of the project. The project will encompass broader theoretical studies in mathematical physics centered around pattern formation in nonlinear active resonators and will deepen the understanding of the similarities and the differences of the physics of frequency comb formation in passive and active optical resonators. Achieving ultrashort pulse generation in the mid-infrared from compact chip-scale devices may be transformative for fundamental science allowing to probe the temporal dynamics of ultrafast material processes occurring at mid-infrared frequencies — from phonons to polaritons to interactions of complex organic molecules.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.