| 摘要: | 本研究主要係利用矽微製程技術發展一具微型化矽基光學連結架構之元件與模組的相關研究。元件部分的研究可細分為晶片間與晶片內之光子元件開發，晶片間元件包含有：矽45°微反射面製程技術、繞射元件單石整合至矽45°微反射面之新型光學元件開發；晶片內元件是以SOI材料為主要基板，相關的研究包含有：具相位補償微稜鏡之大角度彎曲波導、與分具寬頻或窄頻帶寬的兩種波導濾波器之理論探討。模組部分的研究，則是利用矽微光學平台技術實現一個具微型化之光收發器模組。 在晶片間光學連結之元件研究上，我們發展了一具高深度且高光學品質的矽45°微反射面製程技術，利用KOH與IPA的混合蝕刻溶液，可以在晶向為(100)之矽晶片上，蝕刻深度可達200微米以上，而該深度上的製程誤差小於5%，且表面粗糙度小於20 奈米之45°微反射面，它可以使得光束在矽微光學平台上達到非共平面的偏折。我們接著延伸這個技術，將繞射元件單石化整合至該矽45°微反射面上，它可以使得光束偏折且聚焦於非共平面上的特定位置；此外，橢圓對稱的繞射元件結構有效地消弭該光學系統的離軸像差。該元件實驗的結果顯示，在600微米的工作距離下，可以將一發散的光束偏折90°且同時聚焦，使得收斂後的光點大小僅達15微米，可有效的與單/多模光纖之耦合匹配。 在晶片內光子元件部分，我們發展了彎曲波導與光學濾波器，這些元件均可單石化整合至SOI晶片之脊型光波導架構上，且元件大小僅數微米見方，可以達到光子元件之高密度堆積期待。在彎曲波導部分，我們首次引入一具相位補償之微稜鏡，使得波導的特徵模態波前在彎角處能正確偏折，以抑止輻射損耗的產生。為了達到能自由角度偏折的彎曲波導，在利用BCB材料作為微稜鏡之填充介質下，我們具體驗證10°、 20°、30°、與40°之波導彎曲的效果，其曲率半徑僅達15.4微米，而彎曲損耗最低能達3.43 dB，未來若能進一步改善介面間的反射損耗，還可以有效降低彎曲損耗至1 dB水平。在光學濾波器部分，我們理論探討了一具導波模態共振效應的次波長光柵於SOI平面光波光路上，在矽材與空氣之高折射率反差而對光波的強調制作用下，一個有限寬度的波導模態經由這個光柵結構的作用，就可以達到光學濾波上的收斂，使得穿透光譜的消光比達到14.93 dB，且在0.5 dB的損耗水平下，穿透帶寬可以達到40奈米以上。我們也利用分佈式布拉格反射鏡的濾波器架構，可以設計出半高全寬僅3奈米的穿透譜線，若經由適當的反射鏡層數增加，還可以降低至1奈米以下之帶寬。這兩種波導濾波器可以提供未來具分波多工架構之超高速光連結準備。 最後，我們具體呈現一個具微型化之光收發器模組，利用微機電製程之矽微光學平台技術可單石整合45°微反射面、V型槽、高頻傳輸線、與金錫合金之焊料點等。在這個架構下，可以利用被動對準技術將光電元件與光纖高精度鍵合至該平台上。而由於面射型雷射/光偵測器與光纖之工作距離甚近，僅180微米，無須引入透鏡聚焦就可享有高耦合效率，達到高光學利用率、高精度、且兼具量產可行性之優勢。實驗結果顯示，雷射與多模光纖的耦合效率高於-5.65 dB，多模光纖與光偵測器的耦合效率高於-1.98 dB，1-dB損耗的橫向對位容忍度大於±20微米，且在2.5 Gbps之高速訊號作用下，收/發端均可得到清晰可鑑別的眼圖量測結果。 In this dissertation, the researches focus on the development of the components and modules under a miniaturized silicon-based optical interconnect configuration. The component part can be further divided into two research topics, including inter-chip and intra-chip photonics elements, respectively. The former researches contain the development of the silicon 45° micro-reflectors and a monolithic integration of a diffractive optical element on the silicon 45° micro-reflectors; the latter researches comprise the wide-angle SOI-based waveguide bend combined with a phase-compensated microprism, and two types of SOI-based waveguide filters aiming to narrow and widely-flattened bandwidths, respectively, in spectra response. Regarding the research in module application, a miniaturized optical transceiver module is realized by using silicon optical bench (SiOB) technology. With respect to the researches on the inter-chip optical interconnect components, we first demonstrate a silicon 45° micro-reflector with a deep depth and smooth slant quality. By using the KOH/IPA mixed etchant, the silicon 45° micro-reflector can be fabricated on the common (100) silicon wafers. The etching depth of this 45° slant can be over than 200 μm with the etching depth inaccuracy less than 5% and the slant RMS roughness under 20 nm. Therefore, this 45° slant can act as a great micro- reflector, which makes the light beams propagating on the SiOB deflect to the non-coplanar direction. Then, we further extending this technique to monolithically integrate a diffractive optical element (DOE) lens onto the silicon 45° micro-reflector. This novel optical element can make light beams simultaneously deflect and focus to the specific position in the non-coplanar direction. In addition, this DOE lens with an elliptic-symmetry shape can effectively eliminate the off-axis aberration within this optical system. Under the 600-μm working distance, the experimental results reveal that a diverged light beam can be deflected to the non-coplanar direction and focused with a spot size of only 15 μm, which would facilitate the single-/multi-mode fiber coupling issues. Regarding the intra-chip photonics components, the waveguide bends and waveguide filters are developed in this research topic. These components can be monolithically integrated onto the SOI-based rib waveguide platform. In addition, the sizes of these components are only a couple of micrometer squares, which can fit the high-density integration expectation for the intra-chip photonics. For the wide-angle waveguide bend, a phase-compensated microprism is introduced into the SOI rib waveguides in order to correctly tilt the wavefront of the waveguide eigen-mode and effectively suppress the radiation loss. The bending angles with 10°, 20°, 30°, and 40° cases are demonstrated to examine the effects of the arbitrary optical paths. Under filling the BCB material to the microprism area, the compact bending radius and bending loss are only 15.4 μm and 3.43 dB, respectively. After improving the interface Fresnel losses in the next design, the bending losses could be effectively suppressed to only 1 dB. For the waveguide filters, we theoretically investigate a silicon sub-wavelength grating, possessing the guided-mode resonance (GMR) effects, on the SOI rib waveguide. Based on the design of a strongly-modulated effect, a finite-sized waveguide mode passing this grating can converge with an extinction ratio of 14.93 dB in optical spectral response. In addition, the transmissive flattened bandwidth can be available to over 40 nm in 0.5-dB degradation. We also apply the distributed Bragg reflectors (DBR) grating to design a 3-nm narrow bandwidth in full width at half maximum (FWHM). Less than the bandwidth with 1-nm FWHM could be expected by properly increasing the DBR layers. Both mentioned waveguide filters can serve the future requirements of the ultra-high-speed optical interconnects by introducing the wavelength-division multiplexing (WDM) approaches. Finally, compact and passive-alignment 4-channel ? 2.5-Gbps optical interconnect modules including transmitting and receiving parts are developed based on the SiOBs of 5 ? 5 mm2. A silicon-based 45° micro-reflector and V-groove arrays are fabricated on the SiOB using anisotropic wet etching. Moreover, 2.5-GHz high-frequency transmission lines with 4 channels, and bonding pads with Au-Sn eutectic solder are also deposited on the SiOB using evaporating. The vertical-cavity surface-emitting laser (VCSEL) array and photo-detector (PD) array are flip-chip assembled on the intended positions. The multi-mode fiber (MMF) ribbons are passively aligned and mounted onto the V-groove arrays using UV curing. Without the assistance of additional optics, the coupling efficiencies of VCSEL-to-MMF in the transmitting part and MMF-to-PD in the receiving part can be as high as -5.65 and -1.98 dB, respectively, under an optical path of 180 μm. The 1-dB coupling tolerance of greater than ±20 μm is achieved for both transmitting and receiving parts. Eye patterns of both parts are demonstrated using 15-bit PRBS at 2.5 Gbps. |
