N阶级联拉曼光纤激光器理论模型

考虑拉曼光纤纤芯有效面积随Stokes光波长变化,提出了一种改进的Ⅳ阶级联拉曼光纤激光器理论模型.根据该理论模型,按照拉曼光纤激光器级联阶数N的奇偶性分别推导出了第N阶Stokes光输出功率的解析表达式.通过忽略经输出耦合器反射回拉曼光纤输入端的残余泵浦光功率,计算了5阶级联拉曼光纤激光器的输出特性,并与相关文献上的实验数据进行了比较,结果显示文中的计算结果与实验结果相吻合.文中的理论模型对于设计N阶级联拉曼光纤激光器有一定指导意义.     

Noise characterization of femtosecond fiber Raman soliton lasers

The broadband amplitude noise and phase noise (timing jitter) measured in femtosecond fiber Raman soliton lasers is discussed. For a single-pass compressor using 300 m of either standard single-mode fiber or polarization preserving fiber, white amplitude noise ⩾50 dB above shot noise at 2 mA photocurrent was measured, for frequencies higher than approximately 100 kHz. This is ≈30 dB larger than the amplitude noise observed from fiber grating pulse compressors. The timing jitter increases with pump power, and at 1.6 W pump power, 5.2 ps r.m.s. timing jitter was measured, given ≈2 ps jitter from the Nd:YAG pump. Longer fibers in the single-pass compressor do not affect the amplitude noise, but increase the timing jitter even further. A synchronously pumped ring cavity reduced the timing jitter substantially, but did not significantly improve the amplitude noise     

Spectral modeling of Raman fiber lasers

This letter describes a model of Raman fiber lasers, based on the four-wave mixing interaction between the laser modes. The results predict the laser spectral shape and output power with good accuracy.     

Theoretical gain spectrum of far-infrared Raman lasers

The four-level density matrix theory of the Raman FIR laser is extended to include arbitrary pump and emission field strengths and arbitrary pump frequency offsets from resonance. The results accommodate the full range of spectral variation that is observed when CH₃F Raman FIR lasers are operated at widely differing values of the rotational quantum number J. The extended theory is also useful for optimizing the temperature and pressure of these broadly tunable lasers to achieve maximum spectral coverage     

Raman fiber lasers for optical communication application

We review the principle and characteristics of cascaded Raman fiber lasers in their telecommunication applications. The fundamentals of Raman fiber lasers are described, such as pumping scheme, fiber type and reflectors. We explain simple equations forcw laser operation as well as a possible way to calculate spectral width. We investigate the common issues in the use of Raman fiber lasers: theoretical optimization, control of the linewidth, suppression level of the other Stokes orders and relative intensity noise. Finally the more complex multiple-wavelength Raman fiber lasers are reviewed.     

Stability enhancement for dual-order Raman fiber lasers

A new laser regime for second-order pumping applications is described. Our laser is a dual-output-wavelength Raman fiber laser that generates a low-power first-order-pump line and a high-power second-order-pump line together. We demonstrate how using four-wave mixing combined to Raman gain in the laser cavity permits better stability of the first-order-pump laser line.     

Bandwidth reduction in CW fiber Raman lasers

The oscillation linewidth of CW fiber Raman lasers has been reduced from typical uncontrolled values Of 200 GHz (approximately 0.2 nm for 528 nm radiation) to 9 GHz by employing prisms, gratings, and etalons in various resonator configurations. Further reduction is limited by four-wave mixing and stimulated Brillouin scattering. Although four-wave mixing limits bandwidth reduction, the results demonstrate the use of this nonlinear process for intensity stabilization.     

Theory and design of double-cavity Raman fiber lasers

We introduce the concept of the double-cavity Raman fiber laser (DC-RFL) with three Bragg gratings at the laser wavelength. In such RFLs, the threshold pump power and the conversion efficiency at large pump powers can be designed independently of each other, whereas in ordinary single-cavity RFLs these two optimization criteria collide. The particular behavior of DC-RFLs is interpreted, and a simple technique for the numerical simulation and an analytical relation for the threshold pump power of these devices are presented.     

光纤喇曼激光器及多波长输出的分析

为了优化设计光纤喇曼激光器的各项参数,采用喇曼激光器的基本理论模型模拟分析了用DCF光纤做增益介质的光纤喇曼激光器的输出特性,提供了激光器优化设计的方法;通过改变光纤的长度和输出端面的耦合效率得到最优的激光输出;以及改变泵浦功率时输出激光功率的变化情况;并进一步分析了多波长的光纤激光器,得到四波长输出的光纤激光器。     

Polarization effects in fiber Raman and Brillouin lasers

Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained. Birefringent single-mode fibers are used to demonstrate this gain difference. Threshold powers of 200 mW have been achieved in Raman oscillators.     

Analytic modeling of the P-doped cascaded Raman fiber lasers

An approximate analytic model of the P-doped cascaded Raman fiber lasers had been developed. The threshold pump powers for the first and the second Stokes radiation, output power, slope efficiency, and energy conversion efficiency had been solved and thus the optimization of the lasers could be discussed analytically. A fast numerical simulation of the laser based on the analytic model had also been carried out. Moreover, the comparison between the analytic and numerical solution was made.     

Numerical calculation of the linewidth of Raman fiber lasers due to spontaneous Raman scattering

We calculate the spectral width of the Stokes output of Raman fiber lasers determined by spontaneous Raman scattering. The conventional model with zero bandwidths of the pump and Stokes lines is extended so that it describes a frequency-resolved Stokes band driven by the pump wave through both stimulated and spontaneous Raman scattering. To solve the boundary value problem for the Stokes spectra, a semi-analytic method is developed which reduces the spectrally resolved problem to an equivalent conventional model based on effective mirror reflectivities. The Stokes spectra are given in closed form in terms of the mirror reflection spectra. Spontaneous Raman scattering perceptibly broadens the RFL output spectra for pump powers around the lasing threshold.     

Theoretical model of optical fiber secure communication system with chaotic multiple-quantum-well lasers

Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchroniza- tion system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55 μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55 μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communica- tions at wavelength 1.55 μm     

可调谐Yb光纤激光器LBO倍频特性理论研究

针对大信号高斯光束聚焦情况,对平面波耦合波方程进行了改进;利用改进后的耦合波方程,分析了LBO晶体对掺Yb光纤激光整个发射光谱的腔外倍频特性。结果显示,利用温度调谐,LBO晶体可以在掺Yb光纤的整个发射光谱内达到非临界相位匹配;随着基频光波长的增加,倍频效率会有小幅度下降,可接收角有小幅度增长,可接收温度宽度和可接收线宽有较大幅度加宽。结果表明,采取非临界相位匹配,并选用较长的基频光波,易于得到理想的倍频效果。     

1064 nm波段泵浦掺铥光纤激光器的理论研究

文章对1064 nm波段泵浦掺铥光纤激光器进行理论分析,以获得到对实际研究有用的结论.先从理论分析计算了1064 nm泵浦掺铥光纤激光器的粒子速率方程和传输方程,并在传输方程中考虑了泵浦光和激光本征吸收影响.利用matlab软件理论模拟不同长度光纤的正反向泵浦光和激光在光纤中的分布.模拟讨论了输出功率与最佳光纤长度的关系,以及激光本征吸收系数和掺铥离子浓度对输出功率的影响.最佳光纤长度时的激光输出功率最高.考虑激光本征吸收是合理的,较小的本征吸收有较高的最大的输出功率.存在一个最佳的掺杂离子浓度使得输出功率最大.     

多点抽运双包层光纤激光器理论及数值分析

大功率双包层光纤激光器采用分布式多点抽运有利于功率扩展和输出特性的优化.采用数值模拟的方法分别计算了正向多点抽运和反向多点抽运,得出了不同抽运光反射限制和不同的光纤长度条件下抽运点数与输出功率的关系,以及不同抽运点数和不同抽运光反射限制下的光纤最佳长度,并进一步得出,多点抽运时,通过在双包层光纤内包层写入光栅的方法对抽运光进行反射限制可以大大改善光纤激光器的输出特性.这些结论对多点抽运双包层光纤激光器的结构优化具有指导意义.     

Theoretical analyses on short-term stability of semiconductor fiber ring lasers

Detailed analyses of the short-term stability of the semiconductor fiber ring laser (SFRL) are presented. Analysis with rate equations shows that the relaxation oscillation effect does not exist in the SFRL. With a frequency-domain model, the mode competition in the SFRL is shown to be suppressed by the gain saturation effect of the semiconductor optical amplifier. Thus the observed good short-term stability of SFRL is theoretically explained. The analyses are verified in experiments.     

Raman oscillation with intracavity sum-frequency generation

We use a plane-wave analysis to examine a Raman oscillator containing an intracavity sum-frequency interaction that frequency sums the circulating first-order Stokes radiation with the pump radiation. We find that there is an optimum ratio between the nonlinear coupling in the Raman medium and the nonlinear coupling in the sum-frequency generator. We also find that higher order Stokes radiation should be suppressed with the optimum choice of nonlinear coupling in the sum-frequency interaction. Numerical integration of the equations containing transverse effects predicts a time-averaged power-conversion efficiency of 61.4% for conversion of 532- to 273.5-nm radiation using a CW mode-locked frequency-doubled Nd:YAG laser with Ba(NO₂) ₃ for the Raman material and CsLiB₆O₁₀ (CLBO) for the sum-frequency material     

Modeling of multiwavelength Raman fiber lasers using a new and fast algorithm

We describe a numerical model for a multiwavelength Raman fiber laser. It uses an original algorithm which makes the model robust and fast. We show a comparison between simulated and measured Raman laser output powers, characterized by their slope efficiency and their threshold.     

中红外ZBLAN光纤拉曼激光器的理论分析与设计

根据ZBALN光纤拉曼激光器的结构,理论分析了中红外ZBLAN光纤级联拉曼激光器运行方式并建立了泵浦光和斯托克斯光的非线性耦合方程组.基于该方程组,对用高功率掺铥光纤激光器泵浦ZBLAN光纤产生拉曼频移时泵浦光和斯托克斯光在光纤中的演化过程进行了仿真.为了提高激光器性能,对光纤长度、输出耦合器反射率、泵浦功率等激光器参...