Frequency-Modulated Combs Obey a Variational Principle.
Frequency-Modulated Combs Obey a Variational Principle.
复制标题
调频梳遵循变分原理。
DOI：
10.1103/physrevlett.122.253901
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发表时间：
2019
影响因子：
8.6
通讯作者：
F. Capasso
中科院分区：
文献类型：
--
作者：
M. Piccardo;P. Chevalier;B. Schwarz;D. Kazakov;Yongrui Wang;A. Belyanin;F. Capasso
激光动力学包含了物理学许多领域中可能遇到的普遍现象，如分叉和混沌、模式竞争、共振非线性和振荡器的同步或锁定。当多模激光器发生锁定过程时，产生光频梳，它是由具有固定相位关系的等距离模组成的光谱。用控制腔内场的基本激光方程来描述自启动频率梳的形成，一般来说，并不能让人理解激光器是如何改变其模式的。我们的发现是，在一类特殊的激光器中，输出是频率调制的强度调制小或可忽略不计，一个大大简化的描述自锁存在。我们表明，在量子级联激光器的固态代表，这些激光器的特点是由超短载波弛豫时间的频率梳形成服从一个简单的变分原理，这是假设超过50年前，并依赖于激光输出功率的最大化。这一原则的故障的条件也通过实验确定，许多不同类型的激光器，如染料，二极管和其他级联激光器的行为脱落光。这一发现表明，调频梳的形成是由物理系统解决的优化问题的一个优雅的例子。
Laser dynamics encompasses universal phenomena that can be encountered in many areas of physics, such as bifurcation and chaos, mode competition, resonant nonlinearities, and synchronization-or locking-of oscillators. When a locking process occurs in a multimode laser, an optical frequency comb is produced, which is an optical spectrum consisting of equidistant modes with a fixed phase relationship. Describing the formation of self-starting frequency combs in terms of fundamental laser equations governing the field inside the cavity does not allow one, in general, to grasp how the laser synchronizes its modes. Our finding is that, in a particular class of lasers where the output is frequency modulated with small or negligible intensity modulation, a greatly simplified description of self-locking exists. We show that in quantum cascade lasers-solid-state representatives of these lasers characterized by an ultrashort carrier relaxation time-the frequency comb formation obeys a simple variational principle, which was postulated over 50 years ago and relies on the maximization of the laser output power. The conditions for the breakdown of this principle are also experimentally identified, shedding light on the behavior of many different types of lasers, such as dye, diode, and other cascade lasers. This discovery reveals that the formation of frequency-modulated combs is an elegant example of an optimization problem solved by a physical system.