Optical interconnect (OI)技術在下一個世代的目標是達到56Gbps的data rate，為了達到此目標vertical-cavity surface-emitting laser (VCSEL)的3dB頻寬必須達到30GHz以上，不僅在常溫特性要好且在85℃的3dB頻寬也不能掉太多。在論文裡會探討940nm VCSEL的元件設計，藉由鋅擴散以及成長一層current spreading使元件電阻接近50歐姆，使元件與外部驅動電路有良好的阻抗匹配，並且探討水氧化掏離的技術對VCSEL的特性有什麼影響。首先，在相同水氧孔徑(~6µm)下比較有掏離以及沒有掏離的元件特性，結果顯示有氧化掏離的元件在室溫可達到30GHz，在85℃為24GHz，而沒有進行氧化掏離的元件在室溫下只能達到26GHz，且85℃為21GHz，所以透過氧化掏離可以有效提升VCSEL的3dB頻寬並且改善高溫特性。 同時在論文中也會做不同水氧孔徑(5~6µm & 3~4µm)以及和其他實驗團隊的980nm VCSEL做比較。其他實驗團隊的980nm VCSEL透過優化VCSEL共振腔內的光子壽命，使元件可以在室溫達到26.6GHz，在85℃為24.5GHz，有良好的高溫特性。而在相同的水氧孔徑下(~5µm)，我們透過水氧掏離以及鋅擴散製程，使我們的VCSELs在室溫下的3dB頻率可以達到31GHz，在85℃則可達到29GHz，同樣有非常良好的高溫特性。接著是我們團隊改變氧化孔徑的實驗，結果顯示縮小水氧孔徑後的元件(3~4µm) 3dB頻寬雖然沒有提高，但是仍有較高的調變效率以及較好的傳輸速率(>50Gbps)。 ;High-speed, high-efficiency, and low power consumption vertical-cavity surface-emitting lasers (VCSELs) that operate at a wavelength of 850nm or around 1000nm have lately attracted a lot of attention due to their suitability for applications in optical interconnects (OIs). To further enhance the modulation speed of VCSELs is one of the most important ways to meet the required data rate (56 Gbit/sec) for next generation OIs. Recently, the 850 nm VCSEL with a 30 GHz E-O bandwidth has been demonstrated, which can satisfy the >50 Gbit/sec on-off keying (OOK) transmission over OM4 multi-mode fiber (MMF). However, when the ambient temperature (T) reaches 85℃, the pre-emphasis driving circuit is usually necessary to be integrated with VCSEL to compensate the high-T induced speed degradation. To increase the detuning wavelength (~20 nm) in 850 nm VCSEL, or shift the lasing wavelength of VCSEL to 980 nm are both promising way to improve the high-T performance of VCSEL. Recently, by optimizing the photon lifetime inside the 980 nm VCSEL cavity, an almost invariable 3-dB E-O bandwidth as high as around 26 GHz and 50 Gbit/sec transmission data rate from RT to 85℃ operations can be achieved. In this work, we demonstrate a novel 940 nm VCSEL for the application of shortwave wavelength division multiplexing (SWDM) over MMF with state-of-the-art dynamic performances. By use of Zn-diffusion and oxide-relief apertures, such device can have a nearly 50Ω differential resistance, which usually matches very well with the external driving circuit, and achieve a 30 and 26 GHz 3-dB E-O bandwidth under RT and 85℃ operations, respectively.
