Nâng cao hệ số phẩm chất của bộ lọc phổ cộng hưởng Fano vùng khả kiến dựa trên sự giao thoa các mode dẫn sóng lệch pha trong phiến tinh thể quang tử 2D=Design calculation and simulation of the Fano-like guided-mode resonances in the visible spectrum range based on the interference of the two in-plane waves

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Thông tin xuất bản: Tạp chí Phát triển Khoa học & Công nghệ: Khoa học Tự nhiên, 2018

Mô tả vật lý: tr.136

Bộ sưu tập: Báo, Tạp chí

ID: 636585

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Bài báo trình bày các kết quả nghiên cứu đạt được về thiết kế, tính toán và mô phỏng bộ lọc phổ cộng hưởng Fano vùng khả kiến dựa trên sự giao thoa của các mode dẫn sóng lệch pha trong phiến tinh thể quang tử hai chiều (PhC-2D). Việc giảm độ bán rộng phổ để tăng hệ số phẩm chất của bộ lọc cộng hưởng dẫn sóng của phiến PhC-2D bằng việc thêm vào giữa mỗi ô đơn vị một phần tử dạng hình trụ tròn hoặc hình trụ chữ nhật mà không thay đổi kích thước ô đơn vị ban đầu. Trong mỗi ô đơn vị của phiến PhC-2D có hai phần tử có hình dạng, kích thước khác nhau nhưng có cùng chỉ số chiết suất, nên tồn tại hai mode dẫn sóng tương ứng. Cả hai mode dẫn sóng trong phiến PhC-2D đều có tính chất là kết hợp với sóng tới từ môi trường ngoài và lệch pha nhau nên biên độ giao thoa tổng sẽ giảm và do vậy độ bán rộng phổ cộng hưởng sẽ bị thu hẹp và hệ số phẩm chất Q của bộ lọc cộng hưởng sẽ được tăng cường. Phương pháp đạo hàm hữu hạn trong miền thời gian (FDTD) được sử dụng để tính toán các phổ phản xạ và mô phỏng các tính chất và đặc trưng quang học của bộ lọc cộng hưởng dẫn sóng. Phổ cộng hưởng dẫn sóng thu được có dạng Fano được làm khớp với mô hình lý thuyết để xác định chính xác các tham số của phổ cộng hưởng: bước sóng cộng hưởng, hệ số phẩm chất, và hệ số bất đối xứng của phổ. Các kết quả thu được cho thấy phổ phản xạ, tính chất và đặc trưng quang học của cộng hưởng dẫn sóng dạng Fano phụ thuộc vào cách chọn hình dạng và các tham số hình học của phần tử được thêm vào phiến PhC-2D. Kết quả này rất có ý nghĩa và là nền tảng cho nghiên cứu các linh kiện “quang học trong không gian” hiệu suất cao.This paper presented the design, calculation and simulation of the Fano-like guided-mode resonances (GMRs) in the visible spectrum range based on the interference of the two in-plane waves oscillate towards the opposite directions with a phase difference in two-dimensional photonic crystal slabs (2D-PhCs). Narrowing linewidth or enhancing Q-factor of the GMR in 2D-PhC slab was based on the innovative PhC lattice, which was formed by introducing an additional cylinder or rectangular in each unit cell to enhance the light confinement in the waveguide slab. As such the induced Fano-like GMRs’ Q-factor was significantly increased about two orders of magnitude compared to the traditional PhC without additional cylinder or rectangular. The Finite-Difference Time-Domain (FDTD) method was used to determine the reflection spectra and simulated optical characteristics of the GMRs. The simulated spectra had Fano forms and were fitted to the theoretical model to determine precisely the resonant characteristics such as Q-factor and asymmetric factor (q-factor). The results showed that the resonant spectrum, optical properties, and characteristics influenced the shape and size of the addition elements. As a result, the innovative 2D-PhC slab excited Fano-like GMRs in this work would find fascinating applications in efficient free-space optic devices.

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