Design and simulation of integrated photonic devices based on tilted Bragg gratings

在传统光学中，仪器是由用于操纵光线的大块部件（镜子、透镜等）制成的。不幸的是，精确地对齐这些组件是非常困难和耗时的，而且这些设备往往又大又重。解决方案是将整个设备集成到单个光学芯片中。光通过所谓的波导在芯片周围传输，波导将光限制在有限数量的光学“状态”中，我们称之为波导的模式。用于处理光信号的组件本身被集成到芯片中。这被称为集成光子学。其中一个元件是布拉格光栅，它由沿波导的材料折射率的周期性调制组成。光栅能够在波导的不同模式之间耦合光，例如在同一波导中向前和向后传播的光之间，就像在特定频率下工作的镜子一样。布拉格光栅还可以在波导和周围材料之间耦合光。一种新开发的制造技术允许我们在这种周期性折射率调制的平面上引入一个倾斜角度。这就产生了一种新的集成光子器件，具有更高的效率，更广泛的设计参数范围和全新的功能。该项目的目的是开发和模拟用于集成光子芯片的基于倾斜布拉格光栅的新器件。我们已经推导出一个方程，量化光通过光栅对周围材料的反射，并设计了一种新的装置，可以在两个波导之间以100%的效率传递光。其他潜在的应用还包括偏振分束器、光束聚焦、光谱分析和量子信息处理。

In traditional optics, instruments are made out of bulk components (mirrors, lenses, etc.) that are used to manipulate light. Unfortunately, it is very difficult and time consuming to align these components precisely and such devices tend to be large and heavy.The solution is to integrate the entire apparatus in a single optical chip. Light is routed around the chip in what are known as waveguides that confine light in a finite number of optical "states", which we call modes of the waveguide. The components that are used to process the light signals are themselves integrated into the chip. This is known as integrated photonics.One such component is the Bragg grating which consists of a periodic modulation of the refractive index of the material along a waveguide. The grating is able to couple light between different modes of the waveguide, for example between forward and backward propagating light in the same waveguide like a mirror operating at a certain frequency. A Bragg grating can also couple light between the waveguide and the surrounding material.A newly developed fabrication technology allows us to introduce a tilt angle to the planes of this periodic refractive index modulation. This gives rise to a new class of integrated photonic devices with higher efficiency, a wider range of design parameters, and completely new functionality.The aim of this project is to develop and simulate new devices based on tilted Bragg gratings for use in integrated photonic chips. We have already derived an equation quantifying the reflection of light by a grating to the surrounding material and have designed a new device that can transfer light between two waveguides with 100% efficiency. Other potential applications are in polarizing beam splitters, beam focusing, spectrometry, and quantum information processing.