Bösel André, Salewski Klaus-Dieter
Institut für Physik, E.-M.-Arndt-Universität Greifwald, Germany.
Appl Opt. 2009 Feb 10;48(5):818-26. doi: 10.1364/ao.48.000818.
We developed a theory that describes fast mode-hop-free tuning of an external cavity diode laser in Littrow configuration with two acousto-optic modulators (AOMs) inside the laser cavity. The theory is based on synchronous shifting of the external cavity modes and the Littrow grating selectivity. It allows calculating the driving signals of both AOMs in order to reach a desired temporal variation of the laser frequency, including particularly fast tuning as well as an arbitrary shape of the tuning function. Furthermore, we present a laser setup for which the needed signals for both AOMs are generated by two direct digital synthesizer circuits. Thereby we were able to verify the theoretical predictions experimentally, achieving, e.g., sinusoidal single-mode tuning of the laser frequency over 40 GHz at a repetition rate of 10 kHz and over 12 GHz at 25 kHz. Finally, the limitations of the theory are discussed.
我们提出了一种理论，该理论描述了在 Littrow 配置的外腔二极管激光器中，利用激光腔内的两个声光调制器（AOM）进行无快速模式跳变调谐的方法。该理论基于外腔模式的同步移位和 Littrow 光栅的选择性。它能够计算两个 AOM 的驱动信号，以实现激光频率所需的时间变化，特别是包括快速调谐以及调谐函数的任意形状。此外，我们展示了一种激光装置，其中两个 AOM 所需的信号由两个直接数字合成器电路生成。通过这种方式，我们能够通过实验验证理论预测，例如，在 10 kHz 的重复频率下实现激光频率超过 40 GHz 的正弦单模调谐，在 25 kHz 时超过 12 GHz。最后，讨论了该理论的局限性。
