高频调制大功率窄线宽分布反馈光纤激光器

研制了一种窄线宽光纤激光器.在有源相移光栅后加一段掺铒光纤,当用980 nm抽运光注入时,首先形成了分布反馈(DFB)光纤激光器,而残余抽运光将铒纤中铒离子从基态抽运到了激发态,对DFB激光实现了有效放大,实现了对残余抽运光的充分利用,节省了功耗、降低了成本;同时利用温控技术克服了DFB光纤激光器的温度敏感问题;将相移光栅黏贴于片状压电陶瓷(PZT)的表面实现了高频调制.实验研制的激光器的最高调制频率为2 kHz、输出功率为15.6 dBm,线宽为300 kHz. 关键词： 分布反馈光纤激光器 窄线宽 大功率 高频调制     

Frequency tunability and temporal characteristics of a DAMC distributed feedback dye laser

The frequency tunablity characteristics of a simple prism configuration distributed feedback dye laser (DFDL) pumped by a low pressure nitrogen gas laser are described. Tunability is studied as a function of the refractive index of the dye solution and also as a function of the angle of the interfering beams of the pump laser. The tunability range for the dye studied is from 440 to 480 nm with a spectral width of 0·1 Å and the time duration of the DFDL pulses was 50 ps.     

分布反馈式光纤激光器线宽特性及其展宽机理研究

针对分布反馈式光纤激光器(DFB-FL)线宽特性进行了深入研究.通过理论推导和实验验证, 分析了自脉动、相 移光栅、激射窗口宽度以及外界环境扰动等因素对DFB-FL线宽的展宽作用. 进一步提出了压缩DFB-FL线宽的有效方法和途径,给出了自注入锁模方式下对DFB-FL线宽压缩的对比实验结果, 将DFB-FL的线宽从35 kHz压缩到了10 kHz.     

分布式反馈激光器模拟控温检测系统研制

温度对分布式反馈(DFB)激光器的性能指标和工作寿命有着重要影响。针对宽温度范围下的激光器应用,分析了激光器温控系统的研究现状及趋势,给出了温控系统的设计原理,采用线性驱动与PID闭环控制方法,应用模拟器件,研制了一种DFB激光器的模拟控温检测系统,并利用该系统对1550 nm的DFB激光器进行了试验验证。结果表明,系统在−55 ℃～70 ℃的全温度范围下,保持长时间工作（≥2 h）,激光器的工作状态稳定,中心波长未出现漂移。系统的温度控制精度随着工作环境温度的范围不同而有所差异,在室温环境下可达到±0.02 ℃,在全温范围内控制精度在±0.8 ℃以内,跟踪误差小于±0.5 dB。与传统的激光器温控系统相比,本系统工作温度范围宽、控制精度高,且体积小、成本低、简单可靠,对于温度环境要求较为严苛的DFB激光器应用场景,具有重要的工程实践意义。     

880 nm半导体激光主动照明光纤耦合模块

为降低半导体激光主动照明红曝,选择波长880 nm大功率半导体激光器作为新型激光主动照明成像系统光源。根据光纤耦合过程光参数积不变原理,研制出波长880 nm大功率半导体激光器阵列单光纤耦合模块,利用光纤匀光作用使激光光束匀化整圆后用于激光主动照明。首次在波长880 nm大功率半导体激光器上采用阶梯反射镜光束整形方法,使激光光参数积与光纤匹配,激光高效耦合进入纤芯400 μm、数值孔径0.22的光纤。室温条件下光纤耦合模块连续输出功率44.9 W,电光转化效率35%,波长880 nm大功率半导体激光器阵列光纤耦合模块,不仅其红曝小而且对应CMOS图像传感器光谱响应度较高,系统成像质量好。     

Four distributed feedback laser array integrated with multimode-interference and semiconductor optical amplifier

Monolithic integration of four 1.55-μm-range InGaAsP/InP distributed feedback (DFB) lasers using varied ridge width with a 4×1-multimode-interference (MMI) optical combiner and a semiconductor optical amplifier (SOA) is demonstrated. The average output power and the threshold current are 1.8 mW and 35 mA, respectively, when the injection current of the SOA is 100 mA, with a side mode suppression ratio (SMSR) exceeding 40 dB. The four channels have a 1-nm average channel spacing and can operate separately or simultaneously.     

Analysis of tunable picosecond pulse generation from a distributed feedback Ti：sapphire laser

A distributed feedback Ti:sapphire laser (DFTL) pumped by a 532nm Q-switched pulse is proposed for the generation of tunable picosecond pulses. With coupled rate equation model, the temporal characteristics of DFTL are obtained. The numerical solutions show that the DFTL pulse with a 50-ps pulse duration and as much as 3.SmJ pulse energy can be obtained under 40-m J, 5-ns pulse pumping. The dependence of output pulse width on the laser crystal‘s length, pumping pulse duration, and pumping rate is also discussed in detail.     

超短脉冲分布反馈染料激光器稳定工作条件分析

利用耦合波理论,分析了一种作为KrF准分子激光MOPA系统的振荡源-亚皮秒超短脉冲分布反馈染料激光器（DFDL）的输出模式,指出实际的分布反馈染料激光器工作在单纵模状态是周期性增益调制的必然结果。数值模拟结果表明,DFDL输出光谱出现多条谱线的精细结构或调制现象,这是由多个顺序相干脉冲产生的。可以利用这种光谱调制现象来控制激光器的泵浦强度,获得稳定的单脉冲。光谱测量结果表明,在2倍泵浦阈值左右DFDL能够获得稳定的单模单脉冲输出。     

Single‐mode distributed feedback laser operation with no dependence on the morphology of the gain medium

Organic distributed feedback (DFB) lasers can be useful photonic tools for biological applications where the roles of organic materials are important, because highly coherent single mode emission with broad tuning range can be obtained. However, the formulaic structures of organic lasers, and the uses of gain media as resonators themselves, are not suitable for inducing laser emission from irregular shaped gain media, such as dye‐staining cells and tissues. Here, we report a reusable photonic template comprising an exceedingly thin and discrete titanium dioxide (TiO₂) layer on a one‐dimensional (1D) quartz grating to induce single mode DFB lasing from a variety of states of optical gain media. Using the same template, the external gain media of optically thick and thin casted film, liquid, and a free‐standing thick film reveal single mode lasing with reliable performance. Numerical simulations demonstrate that the 25‐nm thick TiO₂ disconnected grating lines support a spatially confined DFB mode in the vertical direction, even under no index difference between superstrate and substrate. Additionally, not using the typical waveguide gain layer promises high sensitivity and detection limit in refractometric sensing. These results suggest that the photonic structure may serve as a versatile sensing platform for bioapplications.     

分布式反馈激光器动态扫描光纤布拉格光栅波长解调系统

通过对该系统采集到的法布里-珀罗(F-P)标准具透射谱和光纤布拉格光栅(FBG)传感器反射谱进行寻峰算法以及拟合算法的研究,采用C语言编程和LabVIEW编程相结合的方式,实现了FBG波长信号的解调。其中,由于系统采集到的F-P透射谱和FBG反射谱线时域信号数据都由离散点构成, 且在3 dB带宽内均符合高斯曲线分布,采用高斯拟合对采集到的信号数据进行寻峰处理,提高系统精度;又由于分布式反馈(DFB)激光器的波长扫描存在着一定的非线性,采用二项式拟合对DFB激光器的波长扫描曲线进行拟合,以降低其非线性导致的误差。另外,设置一路标准FBG传感通道用于波长校准。实验研究表明该系统稳定性良好,波长测量范围为1 550.012~1 554.812 nm,分辨力为1 pm,精度为10 pm,验证了该系统可用于FBG波长信号检测的可行性。     

分布反馈激光特性的实验研究

研究了以脉冲YAG倍频激光泵浦Rh6G染料,产生分布反馈激光振荡的辐射光谱、转换效率、时间过程以及可调谐特性;发现在大于泵浦阈值下的分布反馈激光输出的多谱线结构与双脉冲辐射现象,以及分布反馈激光脉冲变窄的自开关效应.作为详细的实验观察和分析.     

稳定波长反馈引起的失谐对自由电子激光的影响

利用修改的一维非定态程序,基于美国杰弗逊实验室（JLab）Demo自由电子激光装置的参数,对高功率自由电子激光振荡器稳定波长的反馈系统进行了数值模拟。电子微脉冲为高斯型分布,每个纵向网格中取16个模拟宏电子,不考虑电子束的能散度。结果表明：当无反馈时,腔内光功率和波长都可以在一定范围内稳定;加入反馈后,由于电子束能量的变化所引起的等效失谐对整个系统有着重要的影响,甚至可能导致电子和光场失去相互作用,从而使得装置不能工作。提出应该在光场达到饱和以后再启动稳定波长反馈系统。模拟结果证明,该实施方案是合理有效的,可以避免其对FEL运行的严重影响。     

基于聚合物支撑形貌液晶/聚合物光栅的低阈值分布反馈式激光器

利用低光强曝光进行全息液晶/聚合物光栅(HPDLC)的制备,获得了内部无液晶微滴具有聚合物支撑形貌的低散射透射光栅结构.分别研究了染料PM567,DCM,DCJTI的放大的自发辐射(ASE)阈值及相对出射光强等性质,得到三种染料中DCJIT的ASE阈值最低,相对出射光强最高,表明DCJTI更适于制备低阈值、高转化效率激光器.分别采用这三种染料制备基于聚合物支撑形貌光栅的分布反馈式激光器,通过改变光栅周期得到不同出射波长的激光.其中,以DCJTI为工作物质,得到中心波长为648 nm,阈值为0.65μJ/pulse,转化效率为1.6%,线宽为0.3 nm的高性能激光.与国内外同类激光器相比,在阈值、转化效率、线宽三个方面均有不同程度的提高.     

分布式反馈激光器动态扫描光纤布拉格光栅波长解调系统

通过对该系统采集到的法布里-珀罗(F-P)标准具透射谱和光纤布拉格光栅(FBG)传感器反射谱进行寻峰算法以及拟合算法的研究,采用C语言编程和LabVIEW编程相结合的方式,实现了FBG波长信号的解调。其中,由于系统采集到的F-P透射谱和FBG反射谱线时域信号数据都由离散点构成,且在3dB带宽内均符合高斯曲线分布,采用高斯拟合对采集到的信号数据进行寻峰处理,提高系统精度;又由于分布式反馈(DFB)激光器的波长扫描存在着一定的非线性,采用二项式拟合对DFB激光器的波长扫描曲线进行拟合,以降低其非线性导致的误差。另外,设置一路标准FBG传感通道用于波长校准。实验研究表明该系统稳定性良好,波长测量范围为1 550.012~1 554.812nm,分辨力为1pm,精度为±10pm,验证了该系统可用于FBG波长信号检测的可行性。     

高功率二极管列阵泵浦固体激光泵浦耦合优化设计

高功率二极管阵列泵浦固体激光系统的核心在于泵浦耦合技术,泵浦耦合直接决定了系统的成本、增益能力、增益均匀性、泵浦引发动态波前畸变和泵浦引发动态光束漂移等关键问题。通过对用于高功率二极管列阵泵浦固体激光系统泵浦耦合优化设计的3维光线追迹方法的研究,从二极管发光远场属性出发,建立其理论计算模型,对高功率激光二极管阵列端面泵浦大口径放大器的一种新型耦合方式——二极管列阵拟球面排列、空心镀银导管耦合进行了优化设计,并开展了泵浦耦合效率、泵浦场均匀性、泵浦场传输性等实验研究,实现了72%耦合效率、5 mm内80%传输效率的均匀平顶泵浦耦合场输出,理论计算与实验结果符合较好。     

Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency

A 7.8-$\mu $m surface emitting second-order distributed feedback quantum cascade laser (DFB QCL) structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet--Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22{\%} and a low threshold gain of 10~cm$^{ - 1}$. Using a {$\pi $} phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained.     

High‐power random distributed feedback fiber laser: From science to application

A fiber laser based on random distributed feedback has attracted increasing attention in recent years, as it has become an important photonic device and has found wide applications in fiber communications or sensing. In this article, recent advances in high‐power random distributed feedback fiber laser are reviewed, including the theoretical analyses, experimental approaches, discussion on the practical applications and outlook. It is found that a random distributed feedback fiber laser can not only act as an information photonics device, but also has the feasibility for high‐efficiency/high‐power generation, which makes it competitive with conventional high‐power laser sources. In addition, high‐power random distributed feedback fiber laser has been successfully applied for midinfrared lasing, frequency doubling to the visible and high‐quality imaging. It is believed that the high‐power random distributed feedback fiber laser could become a promising light source with simple and economic configurations.

     

Study on a broad-area laser diode with external cavity feedback

The external cavity feedback of a broad-area laser diode is investigated. In Fourier optic methods, the inserted prism in an external cavity can be interpreted as a spatial filter in the Fourier plane of the laser diode. The transverse mode can be selected by changing the position of the filter. As the result of a self-consistency theoretical analysis, the output beam of the external cavity has a single-lobed far-field profile. It agrees well with the experiment result. The beam times-diffraction-limit-factor M² is measured to be 1.16.     

高功率二极管列阵泵浦固体激光泵浦耦合优化设计

 高功率二极管阵列泵浦固体激光系统的核心在于泵浦耦合技术,泵浦耦合直接决定了系统的成本、增益能力、增益均匀性、泵浦引发动态波前畸变和泵浦引发动态光束漂移等关键问题。通过对用于高功率二极管列阵泵浦固体激光系统泵浦耦合优化设计的3维光线追迹方法的研究,从二极管发光远场属性出发,建立其理论计算模型,对高功率激光二极管阵列端面泵浦大口径放大器的一种新型耦合方式——二极管列阵拟球面排列、空心镀银导管耦合进行了优化设计,并开展了泵浦耦合效率、泵浦场均匀性、泵浦场传输性等实验研究,实现了72%耦合效率、5 mm内80%传输效率的均匀平顶泵浦耦合场输出,理论计算与实验结果符合较好。     

The combined effect of temperature of operation and external optical feedback on the turn-on time delay of semiconductor laser diodes

In this paper, the combined effect of temperature of operation (T) and external optical feedback (EOF) on the turn-on time delay (t_on) of semiconductor laser (SLD) is investigated theoretically. General and exact analytical model of t_on in term nonradiative (A), radiative (B) and Auger (C) recombination coefficients, carrier density, injection current (I_inj) and T is derived for the first time. In addition, EOF parameters, i.e. external reflectivity (r_ext) and phase of reflected light (?) is also included. The combined effect of T and EOF on t_on is calculated according to its effect on threshold carrier density (N_th). We show that when SLD operates under the effect of coherent (incoherent) EOF, t_on decreases (increases) as r_ext increases due to decreasing (increasing) of N_th at coherent (incoherent) EOF. Moreover, t_on increases as T increases due to increasing of N_th. Moreover, we identified in operable regions of SLD where the latter fails to operate due to very long t_on.