| 摘要: | \par 實驗結果顯示，在性能表現方面，在最佳工作點下，本元件可提供約 $19~\mathrm{dB}$ 的功率增益，傳統定義下的 $3~\mathrm{dB}$ 增益寬度約為 $24.1~\mathrm{MHz}$。然而，增益頻譜與系統雜訊溫度皆隨頻率改變，單以 $3~\mathrm{dB}$ 頻寬未必足以反映實際可用頻帶。本論文因此改以訊噪比提升 $\eta(f)=\mathrm{SNR}_{\mathrm{on}}/\mathrm{SNR}_{\mathrm{off}}$ 並設定門檻 $\eta_{\mathrm{th}}=4$（對應系統雜訊溫度至少壓低為原本的四分之一）定義有效工作頻寬，得到本元件的有效頻帶約為 $\Delta f_{\mathrm{eff}}\approx 120~\mathrm{MHz}$，顯示其在實際讀出應用中具有明顯寬於 $3~\mathrm{dB}$ 頻寬的可用頻帶。值得一提的是，在此由 $\eta$ 所定義的有效工作頻帶內，實際量測增益大致維持在 $12\text{–}19~\mathrm{dB}$ 之間，顯示在整段可用頻帶中放大器皆能提供足以壓制後級雜訊的放大量。系統訊噪比提升最高可達 $6$ 倍，飽和功率為 $-128~\mathrm{dBm}$。大部分指標已達應用需求，惟飽和功率仍有提升空間，未來將以提升飽和功率作為優化重點，進一步強化其於超導量子系統讀出的應用潛力；但本研究已足以展現黃光微影於大規模超導放大器元件製造的可行性與優勢。;This thesis presents the development and experimental demonstration of a lumped-element Josephson parametric amplifier (LJPA) fabricated using optical lithography (OL). A three-route, phase-based comparison framework is established, including (i) HFSS full-wave simulation, (ii) circuit parameter extraction via Q3D combined with ADS circuit modeling, and (iii) cryogenic S-parameter measurements. All three are compared on a common $S_{11}$ phase–frequency baseline.
\par The study focuses not only on comparing data but also on treating the discrepancies among the three routes as meaningful results, which provide guidance for model refinement and system-level optimization. The thesis covers device design, process optimization, experimental setups, and performance analysis including gain, effective operating bandwidth, SNR improvement, and saturation power, along with a performance comparison to electron-beam lithography (EBL) counterparts.
\par Experimentally, the OL-fabricated device achieves a maximum gain of about $19$\,dB. The conventional $3$\,dB gain bandwidth is $24.1$\,MHz; however, both the gain spectrum and the system noise temperature vary with frequency, so a single $3$\,dB number does not fully capture the practically usable band. In this work, the effective operating bandwidth is therefore defined as the contiguous frequency range where the system SNR improvement $\eta(f)=\mathrm{SNR}_{\mathrm{on}}(f)/\mathrm{SNR}_{\mathrm{off}}(f)$ remains above~4, yielding an effective bandwidth of about $120$\,MHz. Within this $\eta$-defined band, the measured power gain $G(f)$ typically lies in the range of roughly $12$–$19$\,dB, and the amplifier provides up to $6\times$ system SNR improvement; the $1$\,dB compression point is about $-128$\,dBm at the optimal operating point. Most metrics meet practical readout requirements, while the saturation power remains the main target for further improvement. The device thus offers competitive gain and SNR at substantially reduced fabrication cost, indicating a favorable cost–performance trade-off. Overall, our results establish OL as a viable, scalable, and cost-effective route for large-scale LJPA implementation. |
