本文關(guān)鍵詞： 窄線寬 單縱模 瑞利散射 布里淵散射 拉錐光纖　出處：《哈爾濱工業(yè)大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：窄線寬(kHz量級(jí))激光器由于其超長(zhǎng)的相干長(zhǎng)度和極低的相位噪聲,在密集波分復(fù)用DWDM、光學(xué)傳感、光學(xué)探測(cè)和微波光子學(xué)等領(lǐng)域具有很大的前景。單縱模窄線寬光纖激光器其輸出激光中只包含一個(gè)縱模形式,因此激光輸出線寬即為單縱模線寬。利用光纖中的瑞利散射效應(yīng)實(shí)現(xiàn)的單縱模窄線寬激光線寬可窄至-810 nm,比窄線寬DFB激光器的線寬甚至可以窄兩個(gè)數(shù)量級(jí),比目前光通信中應(yīng)用的信號(hào)光源線寬甚至窄5個(gè)數(shù)量級(jí)。該論文的研究?jī)?nèi)容即為基于高受激布里淵閾值拉錐光纖中瑞利散射的單縱模窄線寬光纖激光器。主要工作如下:從理論出發(fā),調(diào)研了光纖中布里淵散射和瑞利散射的理論基礎(chǔ),重點(diǎn)描述了光纖瑞利散射線寬壓窄的機(jī)理。實(shí)驗(yàn)測(cè)量了一定長(zhǎng)度單模光纖的受激布里淵閾值,來(lái)驗(yàn)證理論計(jì)算值。介紹了幾種行之有效的抑制光纖中受激布里淵的方法,并根據(jù)布里淵散射產(chǎn)生的機(jī)理及影響布里淵散射的因素,確定出本論文將要采用的抑制光纖中受激布里淵散射的方法:拉制纖芯直徑周期分布變化的拉錐光纖以改變聲模場(chǎng)從而抑制受激布里淵的產(chǎn)生。介紹了幾種常用的窄線寬激光的線寬測(cè)量方法,著重介紹本論文將要采用的延時(shí)頻移自外差法,并進(jìn)行了公式推導(dǎo),計(jì)算出測(cè)量指定量級(jí)激光線寬所需的延時(shí)光纖的最短理論長(zhǎng)度。最后對(duì)特定激光線寬采用不同長(zhǎng)度延時(shí)光纖進(jìn)行自外差法測(cè)量,對(duì)比不同長(zhǎng)度延時(shí)光纖對(duì)測(cè)量結(jié)果的影響,當(dāng)延時(shí)光纖的長(zhǎng)度小于激光的相干長(zhǎng)度時(shí),由延時(shí)自外差法測(cè)得的功率譜存在邊帶波紋,測(cè)量誤差較大。隨著延時(shí)光纖長(zhǎng)度增長(zhǎng),測(cè)得的功率譜向洛倫茲線型收斂,測(cè)得的激光線寬也逐漸收斂于激光實(shí)際線寬。利用拉制的高受激布里淵閾值的拉錐光纖作為分布反饋介質(zhì),進(jìn)行了環(huán)形腔光纖激光器的實(shí)驗(yàn)。文中詳細(xì)介紹了拉錐光纖的拉制過(guò)程,最終拉制出長(zhǎng)150 m,每隔5 m一段錐區(qū)共30段錐區(qū),每個(gè)錐區(qū)長(zhǎng)度約2 cm,束腰直徑約80m的高受激布里淵閾值光纖,經(jīng)測(cè)量該拉錐光纖的損耗僅1 dB,受激布里淵閾值提高了近10 dB。經(jīng)微調(diào)腔內(nèi)損耗和泵浦功率,該激光器穩(wěn)定輸出了3 dB線寬25 kHz的單縱模激光。后又對(duì)環(huán)形腔進(jìn)行改進(jìn),引入自注入反饋機(jī)制來(lái)進(jìn)一步壓縮線寬并穩(wěn)定縱模輸出,經(jīng)調(diào)節(jié)自注入反饋的功率,輸出最窄3 dB線寬至13.5 kHz的單縱模激光,且縱模十分穩(wěn)定,邊模抑制比達(dá)52 dB,輸出功率在6 mW以上。
[Abstract]:Because of its ultra-long coherent length and extremely low phase noise, the laser is used in dense wavelength division multiplexing (DWDMs) for optical sensing. Optical detection and microwave photonics have great prospects. Single longitudinal mode narrow linewidth fiber laser has only one longitudinal mode in its output laser. Therefore, the laser output linewidth is the single longitudinal mode linewidth, which can be reduced to -810 nm by the Rayleigh scattering effect in the fiber, and even two orders of magnitude smaller than that of the narrower linewidth DFB laser. The linewidth of signal source is even 5 orders of magnitude narrower than that used in optical communication at present. The research content of this paper is the Rayleigh scattering single longitudinal mode narrow linewidth fiber laser based on high stimulated Brillouin threshold in tapered fiber. Do the following: starting from the theory, The theoretical basis of Brillouin scattering and Rayleigh scattering in optical fiber is investigated, and the mechanism of narrow linewidth of Rayleigh scattering is described. The stimulated Brillouin threshold of a certain length single-mode fiber is experimentally measured. Several effective methods for suppressing stimulated Brillouin scattering in optical fiber are introduced. According to the mechanism of Brillouin scattering and the factors affecting Brillouin scattering, The method of restraining stimulated Brillouin scattering in fiber is determined in this paper. The tapered fiber with periodic distribution of core diameter is drawn to change the sound mode field and restrain the generation of stimulated Brillouin. Several kinds of commonly used methods are introduced. A method for measuring the linewidth of a narrow linewidth laser based on, This paper mainly introduces the method of time-delay frequency shift self-heterodyne which will be used in this paper, and deduces the formula. The shortest theoretical length of the delay fiber needed to measure the laser linewidth of a given order of magnitude is calculated. Finally, the self-heterodyne method is used to measure the length of the specific laser line width by using the different length delay fiber, and the effect of the different length of the delay fiber on the measurement results is compared. When the length of the delayed fiber is smaller than the coherent length of the laser, the power spectrum measured by the time-delay self-heterodyne method has sideband ripple and the measurement error is large. With the increase of the length of the delayed fiber, the measured power spectrum converges to the Lorentz line. The measured laser linewidth gradually converges to the actual laser linewidth. The tapered fiber with high stimulated Brillouin threshold is used as the distributed feedback medium. The experiment of ring cavity fiber laser is carried out. The drawing process of tapered fiber is introduced in detail. Finally, 150 m long conical region with 30 cones every 5 m interval is produced. The length of each cone is about 2 cm and the beam waist diameter is about 80 m. The loss of the tapered fiber is only 1 dB, and the stimulated Brillouin threshold is increased by nearly 10 dB. The single longitudinal mode laser with 3 dB linewidth of 25 kHz is output stably, and then the ring cavity is improved. The self-injection feedback mechanism is introduced to further compress the linewidth and stabilize the longitudinal mode output, and the power of self-injection feedback is adjusted. The single longitudinal mode laser with the narrowest linewidth of 3 dB up to 13.5 kHz is output, and the longitudinal mode is very stable. The edge mode suppresses Prida 52 dB and the output power is above 6 MW.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN248

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本文編號(hào)：1496847