| 摘要: | 高速、高亮度的垂直共振腔面射型雷射(VCSEL)陣列可以作為有效率的光無線通訊光源，也是實現下一世代無線通訊網路(例如:6G、衛星通訊)非常關鍵的技術，然而傳統的高功率、高亮度及(類)單模的VCSEL通常存在高相對雜訊強度(RIN noise)和空間電洞不足(spatial hole burning)效應而嚴重限制了高速資料傳輸的表現。
在本論文中，會利用特殊的VCSEL陣列結構來改善最大單模(SM)輸出功率、亮度、相對雜訊強度及調變速度，與傳統VCSEL陣列不同，我們在各個Mesa間加入波導互相連結並且於晶片背面電鍍銅基板，加入這兩種特殊結構能夠得到更高的輸出功率、更窄的發散角、更低的RIN noise(-130 vs. -140 dB)及更平坦的頻率響應，也使Data rate為12.5Gbit/s的眼圖能有更小的jitters(4.5 vs. 5.9 ps)及更小的RIN noise，我們所製作的7x7陣列可達到約100mW的最大單模功率，發散角1/e^2為8°、半高寬(FWHM)為5°，單極化輸出(10dB正交極化抑制比)，且在Data rate為12.5Gbit/s時有清晰的眼圖傳輸。
我們設計的VCSEL陣列有這些顯著的靜態與動態特性，主要因素為使用波導結構及電鍍銅基板造成的應力導致單模輸出時的光子密度被稀釋，使得VCSEL陣列達到單極化並且增加了基模的選擇性，進而降低了RIN noise和提高了輸出亮度。
;High-speed and high-brightness vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as an efficient light source for optical wireless communication (OWC), plays a crucial role in the next generation wireless communication network e.g, 6G and satellite communications. However, the traditional high-power, high-brightness, and (quasi-) single-mode (SM) VCSEL usually suffers the problems of high relative intensity noise (RIN) and spatial hole burning effect, which seriously limit their performances in high-speed data transmission. In this work, a novel VCSEL array structure is demonstrated to fundamentally overcome the trade-off among the maximum SM output power, brightness, RIN, and modulation speed. Compared with the traditional VCSEL arrays, which have several independent VCSEL cavities in parallel, the novel array structure demonstrated here has additional passive optical waveguides connecting the neighboring VCSEL unit and an extra electroplated cooper substrate integrated with the backside of our chip. As compared to the reference array without cooper substrate and connected waveguides, the demonstrated array exhibits higher (quasi-) SM output power, narrower divergence angle (higher brightness), a lower RIN (-130 vs. -140 dB), and a flatter E-O response. This is turn leads to smaller jitters (4.5 vs. 5.9 ps) and less intensity noise in the measured 12.5 Gbit/sec eye-patterns. The demonstrated 7x7 array exhibits around 100mW maximum SM output power with 1/e^2 divergence angle as norrow as 8°(FWHM:5°), single polarized output (10dB polarization suppression ratio), and clear eye-opening under 12.5 Gbit/sec modulation. These remarkable static/dynamic performances in our array are due to the dilution of photon density in the SM output pattern by the extended passive waveguide and the external strain induced by the electroplating cooper substrate. It leads to the single polarized lasing mode and the increase of fundamental mode selectivity, which reduces the RIN and enhances the brightness of output beam, respectively. |
