近红外S-C-L超宽波带低噪声PbS量子点掺杂光纤放大器

实现了基于PbS量子点掺杂的近红外S-C-L超宽带低噪声光纤放大器(QDFA)。以紫外(UV)固化胶为光纤纤芯本底,以PbS量子点作为增益介质,由973nm单模激光器、隔离器、波分复用器、量子点掺杂光纤等构成全光路结构,在1470~1620nm的宽波带区间实现了对信号光的放大。结果表明:在1550nm波长附近,QDFA的带宽为75nm。当输入信号光功率为-23dBm时,开关增益为16dB~19dB(净增益为12.26dB~15.26dB),噪声系数约为3dB。实验观测到了较明显的激励阈值和增益饱和现象,确定了适用的量子点掺杂浓度与光纤长度之间的线性关系。所实现的QDFA的带宽、C波带增益平坦度、噪声系数等指标优于常规的掺铒光纤放大器(EDFAs),L波带增益平坦度略低于经优化的多光纤EDFAs。     

基于钠铝硼硅酸盐玻璃的近红外宽带PbSe量子点光纤放大器的实验实现

实验实现了基于钠铝硼硅酸盐玻璃的近红外PbSe量子点光纤放大器(QDFA),并在钠铝硼硅酸盐玻璃基底中,通过优化熔融-退火法的热处理条件,制备中心粒径为4.08～5.88 nm的PbSe量子点光纤。该QDFA由量子点光纤、波分复用器、隔离器、抽运源等构成。实验表明:QDFA在1260～1380 nm区间实现了信号光的放大,增益波长区间与量子点的粒径大小有关。当输入信号光功率为-17 dBm时,输出信号光增益为16.4 dB,-3 dB带宽达80 nm。实验观测到明显的激励阈值和增益饱和现象。与常规的掺铒光纤放大器以及少模掺铒光纤放大器相比,本研究的QDFA的激励阈值低、带宽大、噪声小。本研究设计的PbSe-QDFA为扩展光纤通信波段和工业化应用提供了一种新的途径。     

1250～1370nm波带PbSe量子点宽带光纤放大器

实现了一种硒化铅(Pb Se)量子点掺杂的光纤放大器(QDFA)。以直径为4 cm的Pb Se量子点作为光纤增益介质,由量子点掺杂光纤、980 nm单模激光器、波分复用器、隔离器等组成全光传输结构,在1250~1370 nm的宽带区间实现了信号光的放大。实验表明:对于纤芯直径为50μm的多模量子点掺杂光纤,激励阈值为62 m W,-3 d B宽带达120 nm,-1 d B平坦带宽为90 nm,增益可达12 d B。与传统的掺铒光纤放大器相比,QDFA的带宽更宽,增益更平坦,噪声也较低。该QDFA为解决目前密集型光波复用(DWDM)系统对光纤通信放大器日益增长的带宽需求提供了一种新的途径。     

紫外胶固态纤芯PbSe量子点光纤制备及光谱测量

采用粒直径为4.4 nm的Pb Se量子点及紫外(UV)固化胶,制备了掺杂质量浓度为0.1~6.0 mg/m L、不同长度的固态纤芯量子点光纤。通过测量量子点光纤吸收谱,确定了量子点光纤980 nm波长随掺杂浓度和光纤长度变化的吸收截面。测量了量子点光纤的光致荧光(PL)谱,其峰值光强随掺杂浓度和光纤长度变化,存在一个与最大峰值强度对应的掺杂浓度和光纤长度。实验结果有助于对Pb Se量子点光纤放大器和激光器的进一步研究。     

PbS量子点掺杂聚合物宽带光纤放大器

随着人工智能、大数据、云计算、物联网、移动电子等的发展，传统的稀土离子掺杂单芯单模光纤放大器承载的光纤通信系统的传输容量已经逐渐接近香农极限，需要发展新型材料体系，以拓宽光纤通信系统的传输容量。相比于稀土离子，量子点具有较宽的发光带宽、可调波长的发光特性，且量子点的发光性质可以通过多种化学手段调控，在量子点光放大器上显示出了宽带光放大特性，受到学术界和产业界的广泛关注。在该背景下，本文提出将化学合成的PbS/CdS核壳量子点与低损耗聚合物集成，获得量子点掺杂光纤放大器，实现近红外通信波段可调波长、宽带光放大特性。文章研究并揭示了影响固化后的聚合物纤芯连续性的因素和影响机制，提出了降低固化胶前驱体液面附加压力、固化收缩力、聚合物前驱体与光纤内壁的摩擦力，并提高抽真空产生的牵引力以获得连续光纤，在此基础上获得了基于热固化聚二甲基硅氧烷（PDMS）和光固化NOA61、NOA85固化胶的纤芯连续光纤，量子点光纤在1 530～1 630 nm获得了增益带宽达到100 nm以上的开关增益，最高增益达到6.5 dB。本文的研究结果将促进量子点光纤器件和宽带光通信技术的发展。     

较高掺杂浓度下CdSe/ZnS量子点光纤光致荧光光谱

制备了一种较高浓度掺杂的CdSe/ZnS量子点掺杂光纤.测量了不同掺杂浓度和不同光纤长度下的量子点光纤光致荧光光谱,得剑了荧光峰值增益最大时的量子点掺杂浓度和光纤长度.与低浓度掺杂光纤相比,较高掺杂浓度光纤中的荧光峰值光强明显提高.荧光峰值光强随光纤长度的变化在短距离内(L<1 cm)急剧上升,之后缓慢均匀下降.波长473 nm激励光强随光纤}乏度的变化呈指数形式衰减,消光系数为0.26～1.02 cm-1.在给定激励光强和激励波长的条件下,光纤中可达到最大荧光辐射的晕子点总数为一恒量.光纤中的荧光峰值波长存在红移,红移大小约8～15 nm,红移量与掺杂浓度以及光纤长度有关.这些实验结果可为今后量子点光纤放大器的研制提供参考.     

UV胶基底中IV-VI族PbSe纳晶量子点近红外光谱的吸收截面和辐射截面

测量了三种不同直径(4.5,5.0,5.6nm)的IV-VI族PbSe量子点的近红外吸收光谱,给出了吸收峰值波长随量子点直径变化的经验公式。用吸收光谱法,根据Lambert-Beer定律,测量了光谱的吸收截面峰值和吸收系数及其随波长和掺杂浓度的变化,发现吸收截面对掺杂浓度有弱相关性,得到了吸收截面随掺杂浓度变化的指数近似表达式。测量了量子点的荧光辐射谱,由McCumber关系和实测的吸收截面,确定了量子点光谱的辐射截面峰值及随波长的变化。这些光谱截面数据对PbSe量子点掺杂的增益型器件和传感器设计有重要的意义。     

伽马射线辐照增益光纤对光纤放大器低频噪声特性的影响

针对光纤放大器的空间应用,对光纤放大器在辐射环境中的性能变化进行了实验研究。对铒镱共掺光纤放大器的增益光纤进行伽马射线辐射,研究了光纤放大器的输出功率和光谱特性的演化规律,并采用频谱测量法研究了光纤放大器的噪声特性。通过总剂量为50 krad的在线辐照实验发现,光纤放大器输出功率、光谱的中心波长峰值功率以及光噪声都随着辐射剂量的积累而不断降低。采用光噪声模型对辐射后的光纤放大器噪声特性进行分析,与辐射前相比,发现光噪声中的弛豫振荡噪声部分和中频部分的相对强度噪声系数分别增加了1.625×10~(-4)nW·mW~(-2)·Hz-1和3.122×10~(-4)pW·mW~(-2)·Hz~(-1),而光散粒噪声系数分别减小0.900 pW·mW~(-1)·Hz~(-1)和0.035 pW·mW~(-1)·Hz~(-1),对于光纤放大器在太空的实际应用中,需要重视相对强度噪声的抑制。     

CdS_xSe_(1-x)/ZnS(核/壳)量子点的光谱截面及其掺杂光纤的传光特性

测量了不同组份比例x的CdS_xSe_(1-x)/ZnS(核/壳)量子点的吸收谱和发射谱,确定了量子点的吸收系数、吸收截面和发射截面.量子点吸收截面随粒径的增大而增大、随x的增大而减小.采用紫外固化胶,制备了掺杂浓度为0.1~5mg/mL的CdS_(0.4)Se_(0.6)/ZnS量子点光纤,测量了不同掺杂浓度量子点光纤中473nm泵浦功率的吸收衰减速率.吸收衰减速率和吸收截面弱关联于掺杂浓度.测量了光致荧光光谱强度随光纤长度和量子点浓度的变化.量子点光纤的光致荧光峰值强度随掺杂浓度和光纤长度变化而变化,且存在一个与最大峰值强度对应的饱和掺杂浓度和光纤长度.本文的实验结果有助于进一步构建新型的CdS_xSe_(1-x)/ZnS量子点增益型光电子器件.     

PbSe量子点硅酸盐玻璃光纤的制备及光纤光致荧光光谱特性

对钠硼铝硅酸盐玻璃熔体进行拉丝,再经过退火热处理,制备得到光纤直径80~130μm的PbSe量子点玻璃裸光纤.透射电镜分析发现光纤中PbSe量子点的晶粒尺寸为4.2~5.5nm,掺杂体积比约1%.对量子点光纤的柔性进行了初步测试.以980nm泵浦激光作为激励源,用荧光光谱仪观测了量子点光纤的荧光发射谱.结果表明:合适的量子点光纤的退火条件跟块玻璃不同.当退火温度为500~600℃、热处理时间为5~10h时,观测到量子点光纤有强烈的荧光辐射,峰值波长位于1 300~1 450nm,半高全宽达200~330nm.光纤最佳退火温度为600℃、时间7.5h.本文得到的量子点玻璃光纤可进一步制备成玻璃基底的量子点光纤型增益器件光纤放大器、光纤激光器等.     

The Quantum Theory of Optical Pulses Amplification

The propagation of optical signals in optical fiber amplifier is treated with fully quantum mechanics method in this paper. The micro-Hamiltonian of the system with nonlinear effect is derived by combining spatial mode and temporal mode, and propagation equation of optical pulses in a optical fiber amplifier is derived with dispersion relation. The characteristic parameters such as gain, output power and noise figure of the amplifier are analyzed and their quantum mechanics formulas are obtained.     

Quantum Dot Versus Quantum Well Semiconductor Optical Amplifiers for Subpicosecond Pulse Amplification

The performance of quantum well and quantum dot semiconductor optical amplifiers was theoretically investigated. The effects on subpicosecond pulse propagation due to gain and refractive index dispersion, calculated using a microscopic polarization equation and a reduced wave equation in the linear regime including the background refractive index dispersion, were used in the comparison. In particular, the spectral shift and phase modulation imposed on the pulse were compared. It is shown that quantum dot amplifiers suffer comparable spectral shifts to the quantum well amplifier, strong linear frequency chirp and large pulse broadening. In quantum dot amplifiers with small inhomogeneous broadening, similar pulse break-up is shown as that calculated for the quantum well amplifier. In quantum dot amplifiers with large inhomogeneous broadening, the background refractive index dispersion makes the linear frequency chirp the dominant feature. In the light of our calculations, the advantages and disadvantages of quantum dot and quantum well amplifiers are discussed.     

旋光纤喇曼放大器中ASE噪音模型及仿真计算

通过分析旋光纤喇曼放大器中信号光、抽运光的非线性薛定谔波动方程及放大自发辐射噪音特性,提出一种能同时在旋光纤喇曼放大器中产生预计波形放大自发辐射噪音,又方便计算的方法.根据放大自发辐射噪音时域特性,建立并在波动方程中加入放大自发辐射非高斯噪音模型.在考虑旋光纤双折射的非线性效应同时,通过分步傅里叶法对波动方程求解,计算了旋光纤喇曼放大器中的放大自发辐射噪音,并与实验结果吻合.     

An integrated circuit subsystem of quantum dot semiconductor optical amplifier coupled with electro-absorption modulator and its application in wavelength conversion

A multi-section circuit model of quantum dot semiconductor optical amplifier is proposed by employing the standard rate equations. Using this model, gain spectra, saturation property, and occupation probability of quantum dot semiconductor optical amplifier are analyzed by PSPICE simulation. An integrated circuit subsystem of quantum dot semiconductor optical amplifier cascaded with electro-absorption modulator is also derived to investigate the patterning effect reduction in wavelength conversion.     

Fundamentals of optical amplifiers

The minimum noise figure of linear phase-insensitive amplifiers is 3 dB, according to the constraint of the uncertainty principle. Laser amplifiers, parametric amplifiers and Raman amplifiers obey the general quantum limit in an ideal case. A degenerate parametric amplifier is a phase-sensitive linear amplifier, and thus is a noiseless amplifier with a noise figure of 0 dB. The noise figure degradation in a practical amplifier and the signal-to-noise ratio design of an optical amplifier system are presented. Several other amplifier characteristics, such as signal gain, frequency bandwidth and saturation output power, are also discussed.     

Noise figure and gain temperature dependent of praseodymium-doped fiber amplifier by using rate equations

A theoretical study of the temperature dependent noise effects of praseodymium-doped fiber amplifiers (PEDFAs) has been examined. The Pr³⁺-doped ZBLAN fiber amplifier pumped at 1017 nm and Pr³⁺-doped GeGa-sulfied fiber amplifier pumped at 1028 nm are chosen. The temperature-dependent rate and propagation equation related to four-level system consideration which is based on the population difference among amplification levels has been used. The population difference depends on pump and signal powers, Boltzman factor K_B, cross-sections, noise figure (NF) and Pr³⁺ concentration. The numerical results obtained over the temperature range from −20 °C to + 60 °C are used to present an analytical expression for the signal gain and noise figure effects in PDFAs length and noise figure with input pump power. The amplified spontaneous emission (ASE) has been taken into account.     

PbS quantum dot fiber amplifier based on a tapered SMF fiber

A PbS quantum dot coated (QD-coated) tapered fiber amplifier with a broad bandwidth is theoretically demonstrated. The QD layer is coated on the surface of a tapered fiber and is excited by the evanescent wave of a pump. An optical gain of 10.5 dB, with a 160-nm broad bandwidth of at 1530-nm center wavelength, is achieved. The gain efficiency is over 4 dB/cm. This QD-tapered fiber amplifier has a concentration control of the QDs, a lower insertion loss, and shows good suppression of amplified spontaneous emission (ASE), while its structure is also quite simple. Therefore, the proposed fiber amplifier has great potential in fiber-optic communication systems.     

Measurement of the photon statistics and the noise figure of a fiber-optic parametric amplifier

We report measurement of the noise statistics of spontaneous parametric fluorescence in a fiber parametric amplifier with single-mode, single-photon resolution. We employ optical homodyne tomography for this purpose, which also provides a self-calibrating measurement of the noise figure of the amplifier. The measured photon statistics agree with quantum-mechanical predictions, and the amplifier's noise figure is found to be almost quantum limited.     

Modeling of gain and phase dynamics in quantum dot amplifiers

By means of an electron hole rate equation model we explain the phase dynamics of a quantum dot semiconductor optical amplifier and the appearance of different decay times observed in pump and probe experiments. The ultrafast hole relaxation leads to a first ultrafast recovery of the gain, followed by electron relaxation and, in the nanosecond timescale, radiative and non-radiative recombinations. The phase dynamics is slower and is affected by thermal redistribution of carriers within the dot. We explain the ultrafast response of quantum dot amplifiers as an effect of hole escape and recombination without the need to assume Auger processes.     

A Multi-Section Quantum-Dot Semiconductor Optical Amplifier for Ultrabroad-Band Gain-Flattened Low-Noise Amplification

We propose an ultrabroad-band 1R regenerator utilizing a multi-section quantum-dot semiconductor optical amplifier.Due to the reduced electron states, quantum dot is beneficial in broadening the gain spectrum and lowering the noise figure. Combining this with a multi-section structure drastically improves the gain equality among the different bound states, leading to an increase in the maximum output power and an improvement of the noise figure.