Kulishov Mykola, Kress Bernard, Slavík Radan
HTA Photomask, 1605 Remuda Lane, San Jose, CA. 95112, USA.
Opt Express. 2013 Apr 22;21(8):9473-83. doi: 10.1364/OE.21.009473.
We explore a new class of Distributed Feedback (DFB) and Distributed Bragg Reflector (DBR) structures that employ the recently-developed concept of Parity-Time (PT) symmetry in optics. The approach is based on using so-called unidirectional Bragg gratings that are non diffractive (transparent) when illuminated from one side and diffracting (Bragg reflection) when illuminated from the other side, thus providing a uni-directional Bragg functionality. Such unusual property is achieved through diffraction through a grating having periodic variations in both, phase and amplitude. DFB and DBR structures traditionally consist of a gain medium and reflector(s) made via periodic variation of the (gain media) refractive index in the direction of propagation. As such structures are produced in a gain material. It becomes just possible to add periodic amplitude modulation in order to produce the unidirectional Bragg functionality. We propose here new and unique DFB and DBR structures by concatenating two such unidirectional Bragg gratings with their nonreflective ends oriented outwards the cavity. We analyze the transmission and reflection properties of these new structures through a transfer matrix approach. One of the unique characteristics of the structure is that it inherently supports only one lasing mode.
我们探索了一类新型的分布反馈（DFB）和分布布拉格反射器（DBR）结构，它们采用了光学中最近发展起来的奇偶时间（PT）对称概念。该方法基于使用所谓的单向布拉格光栅，当从一侧照射时它是非衍射的（透明的），而从另一侧照射时则是衍射的（布拉格反射），从而提供单向布拉格功能。这种不寻常的特性是通过在相位和幅度上都具有周期性变化的光栅进行衍射来实现的。传统的DFB和DBR结构由增益介质和通过在传播方向上（增益介质）折射率的周期性变化制成的反射器组成。由于这种结构是在增益材料中产生的，所以刚好可以添加周期性幅度调制以产生单向布拉格功能。我们在此提出通过将两个这样的单向布拉格光栅的非反射端向外定向到腔外而串联起来的新型独特DFB和DBR结构。我们通过传输矩阵方法分析这些新结构的透射和反射特性。该结构的独特特性之一是它本质上仅支持一种激光模式。
