本文選題：體布拉格光柵 + 角選擇濾波　； 參考：《蘇州大學(xué)》2016年博士論文

【摘要】：激光光束控制是高功率激光研究的關(guān)鍵技術(shù)之一。在高功率激光裝置中,灰塵、鏡面上的加工瑕疵以及光學(xué)材料自身的不均勻都會在光束中引入振幅或相位調(diào)制,降低光束質(zhì)量。空間濾波器是提高光束質(zhì)量、實現(xiàn)光束控制的主要方法之一。傳統(tǒng)針孔空間濾波器由于其聚焦原理會衍生出其他一些問題,包括等離子體堵孔效應(yīng)、空氣擊穿等,因此要求針孔濾波器具有龐大的體積和較高的環(huán)境真空度等。記錄在光熱敏折射率玻璃中的體布拉格光柵由于其具有較高的衍射效率和優(yōu)秀的布拉格選擇特性而被廣泛應(yīng)用在近場角選擇空間濾波領(lǐng)域。角選擇空間濾波能夠在非聚焦的光束近場實現(xiàn)高質(zhì)量的空間濾波,提高光束強度分布的均勻性。角選擇空間濾波器在實際激光裝置中應(yīng)用存在兩個問題：一是角選擇空間濾波器會使光束發(fā)生偏轉(zhuǎn),難以實現(xiàn)即插即用；二是受體布拉格光柵光譜選擇性的制約,角選擇空間濾波器難以實現(xiàn)對大帶寬(數(shù)十納米)光束的濾波。針對上述問題,本論文提出一種可實現(xiàn)即插即用的寬帶角選擇濾波方案,能夠?qū)捀咧翑?shù)十納米的光束實現(xiàn)高質(zhì)量的空間濾波,為寬帶激光的光束近場質(zhì)量控制提供了一個新的思路。本論文取得的主要研究結(jié)果如下：(1)分析了體布拉格光柵的衍射特性。研究了體布拉格光柵的角響應(yīng)帶寬與光譜響應(yīng)帶寬的關(guān)系,二者共同影響體布拉格光柵的衍射效率；提出同時增大體布拉格光柵的厚度和周期,可以在保證角響應(yīng)帶寬不變時獲得更大的光譜響應(yīng)帶寬；分析了基于體布拉格光柵的角選擇濾波適用范圍,并指出對于一定范圍內(nèi)的任意波長都存在一個入射角度使得體布拉格柵的衍射效率最大。(2)首次提出了一種基于體布拉格光柵的寬帶角選擇空間濾波技術(shù)。利用面光柵的色散能力與體布拉格光柵的角度選擇能力,在保證角響應(yīng)帶寬的同時將光譜響應(yīng)帶寬提高至數(shù)十納米；基于矢量分析給出了光柵組合的匹配條件。研究結(jié)果表明,在可見光至近紅外波段,各個波長成分均可被光柵組合高效衍射,實現(xiàn)良好的寬帶角選擇空間濾波。(3)研究了寬帶光束經(jīng)寬帶角選擇空間濾波器的衍射特性。采用傅里葉方法與耦合波理論,分析了寬帶角選擇空間濾波器對有限口徑寬帶光束的空間濾波效果。模擬結(jié)果表明,寬帶角選擇空間濾波器能夠?qū)⒐馐械闹懈哳l調(diào)制濾除,且理論設(shè)計時只需要考慮體布拉格光柵的角響應(yīng)帶寬。分析了面-體光柵失配對寬帶角選擇空間濾波器的輸出特性的影響。研究結(jié)果對于寬帶角選擇空間濾波器的實際應(yīng)用具有重要參考價值。(4)開展了寬帶角選擇空間濾波器的原理驗證實驗研究。結(jié)果表明：光柵組合的輸出光束光譜帶寬可達到65 nm,當面-體光柵周期失配量較小時可以通過旋轉(zhuǎn)體布拉格光柵補償輸出光束帶寬；在空域和頻域分析了寬帶角選擇空間濾波器的濾波能力,目標光束中1mm-1以上的特征空間頻率被完全濾除,提高了目標光束近場分布特性。本論文所取得的成果為寬帶角選擇空間濾波技術(shù)奠定了基礎(chǔ),為拓展體布拉格光柵在高功率激光領(lǐng)域的應(yīng)用提供了一定的參考。
[Abstract]:Laser beam control is one of the key technologies in high power laser research. In high power laser devices, the dust, the defects on the mirror surface and the inhomogeneous of the optical material will introduce the amplitude or phase modulation in the beam to reduce the beam quality. The spatial filter is the main method to improve the beam quality and realize the beam control. Firstly, the traditional pinhole space filter will derive other problems due to its focusing principle, including the plasma plugging effect, air breakdown and so on. Therefore, the pinhole filter is required to have a large volume and a higher environmental vacuum. The volume Prague grating in the light thermal refractive index glass is recorded because of its high diffraction efficiency. The rate and excellent selection characteristics of Prague are widely used in the field of near field angular selection space filtering. Angular selection spatial filtering can achieve high quality spatial filtering in the near field of non focused beam, and improve the uniformity of the intensity distribution of the beam. There are two problems in the application of angular selection space filter in the actual laser device: one is the angle. The selection of spatial filters will make the beam deflect, and it is difficult to achieve plug and play. Two is the restriction of the spectral selectivity of the receptor Prague grating. The angular selection space filter is difficult to realize the filtering of large bandwidth (tens of nanometers). High quality spatial filtering for beams with high bandwidth to dozens of nanometers provides a new idea for the near field quality control of wide-band laser beams. The main results obtained in this paper are as follows: (1) the diffraction characteristics of the body Prague grating are analyzed. The angular response bandwidth and spectral response bandwidth of the body Prague grating are studied. The relationship between the two factors affects the diffraction efficiency of the body Prague grating. The thickness and period of the volume of the body Prague grating can be increased at the same time. The larger spectral response bandwidth can be obtained when the angular response bandwidth is kept constant, and the application range of the angular selection filter based on the body of the body Prague grating is analyzed, and the arbitrary range is pointed out. The diffraction efficiency of the appropriate Prague gate is the largest in wavelength. (2) a broadband angle selection spatial filtering technique based on body Prague grating is proposed for the first time. Using the dispersion ability of the surface grating and the angle selection of the body of the body of the Prague grating, the spectral response bandwidth is increased to the bandwidth of the angular response while increasing the spectral response bandwidth. The matching conditions of the grating combination are given based on the vector analysis. The results show that, in the visible to near infrared wavelengths, all the wavelengths can be diffracted by the grating combination efficiently to achieve a good wideband angular selection spatial filtering. (3) the diffraction characteristics of the wideband beam through the wide band angle selection space filter are studied. The spatial filtering effect of the wide-band angular selection space filter to the limited aperture wideband beam is analyzed with the coupled wave theory and the coupled wave theory. The simulation results show that the wide-band angle selection spatial filter can filter the medium and high frequency modulation in the beam, and the theoretical design only needs to consider the angular response bandwidth of the body Prague grating. The effect of grating mismatch on the output characteristics of wide-band angular selection spatial filter. The results are of important reference value for the practical application of wide-band angular selection space filters. (4) the experimental research on the principle verification of wide-band angle selection spatial filter is carried out. The results show that the spectral bandwidth of the output beam of the grating combination can reach 65 nm, The bandwidth of the output beam can be compensated by the rotating body Prague grating. The filtering capability of the wideband angle selection spatial filter is analyzed in the airspace and frequency domain. The characteristic spatial frequency above the 1mm-1 in the target beam is completely filtered out and the near-field distribution characteristics of the target beam are improved. The results laid the foundation for the wideband angle selective spatial filtering technology, and provided a reference for expanding the application of the volume Prague grating in the high-power laser field.

【學(xué)位授予單位】：蘇州大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TN24

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