於空間頻譜分布之雙光學參量振盪器及橘黃光雷射與寬波段波長可調雷射於週期性極化反轉鉭酸鈮之研究

Abstract

本論文之研究包括於空間頻譜分布之雙光學參量振盪器及橘黃光雷射與寬波段波長可調之雷射，其中雙光學參量震盪器及橘黃光雷射是由增益調變週期性極化反轉鉭酸鈮晶體（periodically poled lithium tantalate）所研製，此樣品之設計分為兩部分：雙光學參量部分及上轉換部分，雙光學參量部分包含並聯雙週期（parallel bi-grating）與未極化反轉之空白區（spacer），而上轉換部分則由三週期串聯所組成。由於並聯結構之設計，雙光學參量部分能夠產生於空間上頻譜分布之雙旁波瓣（dual sidelobes）之參量震盪器，其雙旁波瓣各自對應到之信號光與閒置光波長為（980,1164）與（965,1186）奈米。此外，藉由和頻（sum frequency generation）所產生之585 nm黃光雷射，驗證了雙光學參量震盪器之空間模態重疊現象。最後，經由調控未極化反轉之空白區之寬度，雙光參震盪器與三色橘黃光之空間頻譜分布能夠被調變。 本論文之第二項研究為於碟形二維週期性極化反轉鉭酸鈮晶體（2D PPLT）上研製寬波段波長可調之雷射。此碟型樣品成功去除司乃耳定律（Snell’s law）與菲涅耳方程式（the Fresnel equations）於長方形樣品之可旋轉角度之限制。藉由倒晶格向量（reciprocal lattice vector）G1,0，此樣品所產生之信號光波長可於0度到42度之旋轉角度內從787調變至620奈米。由於光譜儀之限制，其所量測到之閒置光波長僅由1648至1680奈米。本實驗所量測之頻譜數據與理論模型之計算結果一致。

This dissertation presents two research topics. The first investigates spatially-spectrally distributed dual optical parametric oscillations (OPOs) and a tricolor yellow-orange laser based on a gain-modulated periodically poled lithium tantalate (PPLT). This PPLT comprised a parallel bi-grating separated by a spacer and was further cascaded with a tri-quasi phase matching (QPM) segment. This configuration enabled simultaneous oscillation of dual OPOs at different sidelobes, with each sidelobe having a (signal, idler) pair at (980, 1164) nm or (965, 1186) nm. Additionally, the sum frequency generated yellow beam at 585 nm, centered between the dual-OPO sidelobes, suggests spatial overlap between the dual OPOs owing to wave continuity. Finally, the experimental spatial-spectral modes of both the dual OPOs and the tricolor yellow-orange beams for different spacer widths confirmed the configurability of the parallel bi-grating structure and the spacer. The second explores a widely wavelength-tunable laser implemented on a disk-shaped two-dimensional (2D) square-lattice patterned PPLT crystal with a periodicity of 8.52 um. This cylindrically polished crystal removed constraints imposed from Snell’s law and the Fresnel equations, and enabled the signal wavelength, associated with G1,0 reciprocal lattice vector, being tunable from 787 nm to 620 nm over an angular interval of [0°, 42°]. However, owing to the limited detection range of the optical spectrum analyzer, the corresponding idler wavelength could only be observed from 1648 nm to 1680 nm. The measured signal and idler spectra are consistent with the theoretical calculation.