大色散稳定腔长的光纤锁模激光器的锁模特性研究

报道了一种新型的采用大色散腔结构的光纤锁模激光器,它可以有效地克服激光器腔长抖动对锁模的不良影响,同时,实验中发现,该结构对超模噪声也有很好的抑制作用。完成了大色散控制,电光调制器调制的,稳定的光纤锁模激光器实验,得到形状为sech^2的光脉冲输出,脉冲宽度为7.6ps,脉冲带宽积为0．335。     

高信噪比多波长2 μm主动锁模光纤激光器

介绍一种多波长掺铥主动锁模光纤激光器,增益介质为长2 m的掺铥光纤,主动锁模通过铌酸锂强度调制器实现。腔内加入基于双折射的光学滤波器,利用保偏光纤双折射滤波效应在滤除腔内多余超模噪声的同时,还可以实现多波长输出。基频下的锁模脉冲频谱信噪比可达68.48 dB,在稳定的锁模状态下波长信道数最大为5。此外,腔内偏振无关隔离器被替换为偏振相关隔离器后,将锁模脉冲加载数字信号同步调制,测得的眼图光信噪比提高了8.67 dB。测试结果表明,锁模脉冲的时间稳定性得到有效提升。     

利用啁啾脉冲光谱滤波和非线性偏振旋转技术实现高稳定性和开机自启动的全光纤掺Yb~(3+)光纤锁模激光器

建立理论模型,讨论了非线性偏振旋转全光纤锁模激光器的锁模过程、谐波过程以及导致激光器锁模运行难以稳定的影响因素.讨论了采用啁啾脉冲光谱滤波产生脉冲自振幅调制、增加激光器锁模稳定性和自启动能力的机理以及非线性偏振旋转与啁啾脉冲光谱滤波相结合实现锁模的物理过程和脉冲演化过程.研制出全光纤结构的超短脉冲掺Yb~(3+)光纤环形激光器,采用非线性偏振旋转和啁啾脉冲光谱滤波相结合的锁模技术,实现了激光器锁模的开机自启动和高稳定运行.对激光器进行了长期运行稳定性、锁模开机自启动能力、锁模输出参数可重复性监测.锁模脉冲中心波长1052.9 nm,谱宽9.1 nm,脉冲能量4.25 nJ,脉冲宽度17.8 ps.运行期间,各参数波动均小于0.3%.开机自启动能力和可重复性测试显示,激光器可实现一键自启动,启动后各参数可重复精度在0.55%以内.     

被动高阶谐波锁模掺Er3+光纤激光超短光脉冲的产生及其放大

报道了利用光纤的非线性偏振旋转效应产生可饱和吸收体的锁模机制,从掺Er3+光纤环形腔激光器中产生稳定的高阶谐波锁模光脉冲的实验研究结果(限于示波器带宽,实验中最高曾测量到稳定的4076MHz重复频率的谐波锁模光脉冲).实验中发现有三种不同的演化方式产生高阶谐波锁模光脉冲,还观察到在8352MHz谐波锁模光脉冲的光谱中出现孤子光谱边带.四阶谐波锁模(8352MHz重复频率)超短光脉冲经过6m长高掺杂浓度的掺Er3+光纤放大器放大后产生了平均输出功率1388mW,脉宽201fs,中心波长1531μm,单脉冲能 关键词：     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

Er3+-Yb3+共掺杂光纤环型腔被动谐波锁模激光器

 报道了Er³⁺-Yb³⁺共掺杂光纤作为增益介质的环型腔光纤激光器。利用光纤的非线性偏振旋转效应产生可饱和吸收体的锁模机制,通过调整泵浦功率,调节偏振控制器的状态,实现了连续基波锁模和高阶谐波锁模两种稳定的锁模运转状态。其中连续基波锁模重复频率15.89 MHz,中心波长为1.557 nm,光谱宽度为9.9 nm。二阶谐波锁模重复率为31.79 MHz,三阶谐波锁模脉冲重复率为46.99 MHz。观察到了调Q锁模和调Q脉冲序列,给出了各种运转状态的实验结果并对多种锁模机理作了简要的分析。     

多模式输出掺镱光纤激光器的实验研究

实验研究了环行腔掺镱光纤激光器的运行特性.发现在由未完全泵浦的掺镱光纤充当的慢可饱和吸收体与偏振控制器和偏振敏感型隔离器所组成的等效快可饱和吸收体的共同作用下,仔细调节偏振控制器的角度与泵浦功率的大小,掺镱光纤激光器可分别稳定地工作在连续、调Q、调Q锁模和连续锁模多种运转方式.对于不同的运转方式,从原理上给予了一定的解释,并对各种运转方式的工作条件进行了详细研究.由于其具有全光纤结构,且腔内不含任何主动器件,同时有良好的稳定性.     

基于类噪声方波脉冲的掺铒光纤激光器

搭建了长腔"8"字型掺铒光纤激光器,并对产生的谐波锁模方波脉冲进行了实验研究.结果表明,该脉冲具有光滑的宽带光谱,示波器上显示为方波脉冲,但自相关迹证实其为类噪声脉冲,即为类噪声方波脉冲;通过调节偏振控制器和泵浦功率等激光器腔内参量,获得了高达5阶的谐波锁模类噪声方波脉冲;该类噪声方波脉冲并非可以无限增大脉冲能量,而是在一定条件下产生脉冲分裂,出现谐波锁模方波脉冲现象.     

一种新型主动锁模光纤激光器腔长稳定技术研究

提出了一种全新的主动锁模光纤激光器的腔长稳定方案,通过波长的变化检测腔长的漂移,使用波长锁定器得到偏移误差信号补偿腔长变化.实验得到了脉宽为7.6 ps的近变换极限锁模脉冲,其超模抑制比达到60 dB,并且在近2 h的工作时间内工作稳定,波长漂移小于0.01 nm.与已有的方案相比较,不但输出脉冲质量高、并可长时间稳定工作,而且由于采用了低成本的稳定方案,更易于实现.     

基于非线性偏振旋转效应的多波长掺铥锁模光纤激光器

运用非线性偏振旋转效应实现了一种掺铥锁模多波长光纤激光器.采用环形腔结构,以1 565nm半导体光源为泵浦源,3m长掺铥光纤为增益介质.利用非线性偏振旋转效应进行滤波.当泵浦功率在800mW时,通过调节光纤偏振控制器,激光器出现了被动锁模状态的脉冲输出,脉冲重复频率为3.178MHz,脉冲宽度为617ps.进一步增加泵浦功率,激光器进入多波长输出的工作状态.调节偏振控制器在室温下得到1~5个稳定的波长激光输出,边摸抑制比为40~60dB.     

Ultralow noise and supermode suppression in an actively mode-locked external-cavity semiconductor diode ring laser

We report what is to our knowledge the lowest phase and amplitude noise characteristics achieved to date in a 10-GHz pulse train produced by the active harmonic mode locking of an external-cavity semiconductor diode laser. Supermode noise has also been suppressed below -140 dBc/Hz by use of a high-finesse fiber Fabry-Perot etalon as an intracavity filter. Novel noise sideband measurements that extend to the Nyquist offset frequency suggest a significant advantage in using harmonic (rather than fundamental) mode locking to produce ultralow-noise pulse trains, owing to the relationship between the noise roll-off frequency and the fundamental cavity frequency.     

Spectral polarimetry with a differential group delay bias

We show that the addition of a polarization controller and bias differential group delay to a spectral polarimeter increases the amount of polarization information that can be extracted from a Stokes spectrum measurement. We use this biased spectral polarimetry on 40-Gbit/s signals to measure the polarization mode dispersion of the optical fiber through which they propagate. Our measurements do not require any control of the polarization at the fiber input. Averaging measurements from several settings of the polarization controller yields improved accuracy, and, after data rejection is applied, both the accuracy and the number of valid data points is increased when using several measurements.     

光纤1/f热噪声的实验研究

光纤热噪声是限制光纤传感、测量系统性能的最终因素.但是低频区域呈1/f谱特性的光纤热噪声的形成机制迄今仍然存在争论.实验研究了光纤1/f热噪声水平与光纤内杂质离子浓度和光纤施加张力的关系,验证了这类热噪声来源于光纤内部的机械耗散引起的长度自发抖动,符合热机械噪声的理论假设.     

An investigation of quantum-chaotic signals generation using a fiber ring resonator and an add/drop multiplexer

We successfully generate the double security using a fiber ring resonator incorporating an add/drop device, whereas the quantum-chaotic encoding of light in a single fiber ring resonator is constructed. In the experiment, the nonlinear Kerr effects in the fiber ring resonator induced the chaotic wave form within the fiber ring resonator, which could be used to scramble or encode into the original signals. The laser input power used was 15 mW, with a fiber ring radius of 50 cm. We found that the double security can be formed, where the randomly polarized photons could be controlled by using the polarization controller and observed.     

Impact of interstitial air holes on a wide-bandwidth rejection filter made from a photonic crystal fiber

We have investigated the spectral properties of a band rejection filter made with a long-period fiber grating written in photonic crystal fiber that has interstitial air holes. Experiments showed that only one mode was coupled strongly to the fundamental core mode over a 600 nm spectral range. The central wavelength of the filter could be tuned over that range without being appreciably affected by any other mode. By using the multipole method, we found that the interstitial air holes of the photonic crystal fiber played a critical role in limiting the number of modes that could strongly interact with the fundamental mode and in obtaining well-separated resonance peaks. Excellent agreement between theory and experiment was obtained.     

Arbitrarily switchable multi-wavelength Yb-doped fiber lasers with phase-shifted long-period fiber grating

An arbitrarily switchable multi-wavelength Yb-doped fiber laser (YDFL) based on a phase-shifted long-period fiber grating (PS-LPFG) is proposed and demonstrated. The PS-LPFG, which was fabricated by a CO₂ laser under asymmetric exposure, acts as a spectral filter with anisotropic transmission spectrum at different states of polarization. The capability of arbitrary wavelength switching can be attributed to the combination of the polarization-dependent loss (PDL) of the PS-LPFG and the nonlinear polarization rotation (NPR) effect. The method suggests a new possibility to achieve even more wavelengths output with an all-fiber format, arbitrarily switchable and tunable capability in the Yb-doped fiber laser system in a simple, stable and well controlled manner.     

Erbium-ytterbium co-doped multi-wavelength double-clad fiber laser around 1612 nm

We report an erbium-ytterbium (Er/Yb) co-doped multi-wavelength laser operation around 1612 nm. The fiber laser was constructed in a figure-of-eight configuration and using a piece of polarization-maintaining (PM) Er/Yb double clad fiber as the gain medium. The oscillation laser lines around 1612 nm could be controlled by carefully adjusting the polarization controllers in the cavity, which might result in single line, dual line or triple line fiber laser operation. The line space was measured about 3.3 nm (±0.2 nm) which was believed to be strongly dependent on the length of the PM Er/Yb co-doped double-clad fiber.     

全光纤密集型波分复用器

分析了全光纤Ｍａｃｈ－Ｚｅｈｎｄｅｒ结构的功率谱特性，并利用自行设计的耦合器拉锥设备，研制成功最小波长复用间隔为０．４５ｎｍ的密集型波分复用器。该类器件具有附加损耗低，偏振不灵敏和较好的温度及机械稳定性等特点。     

S波段光纤拉曼放大器中级联受激布里渊散射串扰的实验研究

研究了光纤激光器前向抽运的S波段分布式光纤拉曼放大器中级联的受激布里渊散射(SBS)串扰现象。用窄光谱带宽(<100MHz)的可调谐激光二极管作为信号源,通过S波段分布式光纤拉曼放大器,当被放大的信号功率超过单模光纤受激布里渊散射的阈值时,出现了前向受激布里渊散射,这是传导声波布里渊散射在光纤放大器中放大的现象。随着拉曼放大器抽运功率的提高,在斯托克斯区,出现了两阶受激布里渊散射线,在实验中观测到偶数阶的受激布里渊散射谱线功率大于奇数阶的布里渊一瑞利散射线。当进一步增加拉曼放大器的抽运功率,出现了前向级联的多阶受激布里渊散射现象,拉曼放大器的增益下降,被放大的信号功率转换为受激布里渊散射,噪声变大。受激布里渊散射的串扰破坏了拉曼放大器的特性,使拉曼放大器无法在密集波分复用光纤传输系统中使用,因此需要严格地控制入纤的信号功率和放大器的抽运功率。在实验中还观测到在光纤拉曼放大器中被放大的信号光和受激布里渊散射线两侧的伴线。