自高轉換效率之側向入射薄膜式兆赫波發射器

Edge-Coupled Membrane Terahertz Photonic Transmitters with High Conversion Efficiency

田名峻(M. C. Tien)

《光學工程》 85期 (2004/03) Pp. 66-70

https://doi.org/10.30011/OE.200403.0007

摘要

光電轉換式兆赫波發射器其有許多的優點，例如可以在室溫下操作、發射出的兆赫波波長具有可調性、以及容易和其他半導體元件作整合（例如半導體雷射、放大器…）。一個良好的兆赫波發射器可以促進兆赫波科技的應用，在本論文中，我們提出並展示了一種側向入射薄膜式兆赫波發射器，它是由金屬－半導體－金屬行波式光偵測器和由共平面波導饋入之開槽天線所組成。藉由使用高速光偵測器以及薄膜式的結構，兆赫波發射器可以達到高轉換效率的目標，其設計方法以及模擬結果在本論文中亦會討論。
我們使用一個在時間上其有調制信號的光脈衝來激發兆赫波發射器，並且使用熱輻射偵測器來偵測由兆赫波發射器所輻射出來之兆赫波功率大小。在頻率為645 GHz的激發下，我們的兆赫波發射器展示了極高的光電轉換效率(0.11%)，有這麼高的光電轉換效率，兆赫波發射器可以輕易的和側向發射、低功率之半導體雷射做結合，形成一個體積小且緊密的兆赫波發射源。
在本論文中，我們也研究了兆赫波發射器在波長為800奈米的雷射光激發下，表現出來的飽和行為。其結果和之前由本實驗室其他成員利用光電取樣平台以及激發探測法所量得的結果一致，這些結果幫助我們找出兆赫波發射器之最佳的操作模式以及更進一步改善其轉換效率。

關鍵字

兆赫波 ； 毫米波 ； 次毫米波 ； 行波式光偵測器 ； 光混波器 ； 低溫成長砷化鎵

並列摘要

A terahertz photonic transmitter is a kind of terahertz emitter with a lot of advantages such as room-temperature operation, tunable output wavelength, compactness, and ease of integrating with other devices (such as semiconductor lasers, amplifiers...). A suitable THz source can promote the development of the followed THz technology and applications. In this thesis, we proposed and demonstrated an edge-coupled membrane THz photonic transmitter composed of metal-semiconductor-metal traveling-wave photodetectors (MSM-TWPD) and coplanar waveguide (CPW) fed slot antennas. By using a high-speed photodetector and a membrane structure, the photonic transmitter with high conversion efficiency can be achieved. The detailed design method and simulation of the photonic transmitters are also introduced in this thesis.
We used a broad optical pulse with a temporal modulation inside the pulse envelope to excite the photonic transmitter and a liquid-helium-cooled bolometer to detect the radiation power from the photonic transmitter. A record-high light-THz external conversion efficiency (1.1×10^(-3)) has been demonstrated at 645 GHz. With such a high-conversion-efficiency photonic transmitter, it can be combined with an edge-emitting low power laser diode and will be a compact THz source.
The saturation behaviors of the photonic transmitter were also studied under 800 nm wavelength excitations. The results are consistent with the previous E-O sampling and pump-probe measurement results completed by other members of our research group. These results give guidance to find the optimized operation of photonic transmitters and further to improve the conversion efficiency.

並列關鍵字

Terahertz ； millimeter wave ； sub-millimeter wave ； traveling-wave photodetectors ； photomixer ； LT-GaAs