改善外腔半导体激光器调谐特性的新方法

基于原有的Littman结构外腔半导体激光器,提出采用一种新的光学方法来实现波长调谐。该方法采用了包含一个旋转楔形棱镜的“光杠杆”系统来降低调谐的机械要求,提高波长选择精度。通过选择不同的楔形棱镜顶角和光线入射角,机械要求可以降低1～2个数量级,波长选择精度也得到相同量级的提高。该方法使Littman结构外腔半导体激光器的调谐特性得到极大的改善,并大大降低了震动的敏感性。     

程控宽带连续调谐外腔半导体激光器特性分析

对宽带调谐外腔半导体激光器进行了理论及实验研究,分析了其最大调谐范围和连续调谐条件,为宽带可调谐激光器的设计提供了依据。完成了实用化的程控宽带连续调上腔激光器,该器件调谐范围超过７５ｎｍ,波长重复性精度为１ｎｍ,分辨率为０．０１ｎｍ。     

Defect modes tuning of one-dimensional photonic crystals with lithium niobate and silver material defect

In this paper, a novel PCs defect mode is designed by inserting a Ag/LiNbO₃/Ag sandwich structure into periodically stacked TiO₂/MgF₂ dielectric superlattice. The band gap calculation is conducted using transfer matrix method. An emergence of defect mode around 525 nm is demonstrated. By applying an external voltage on this defect mode, remarkable wavelength tuning can be achieved. At normal incidence, a tuning bandwidth up to 70 nm is obtained by moderate change of external voltage from −250 to 250 V. This feature can be employed to fabricate practical tunable filters in visible region.     

高稳定线性调谐GaAs基波长可调谐共振腔增强型探测器

研制了一种GaAs基波长可调谐共振腔增强型探测器. 采用分子束外延设备生长In_0.25Ga_0.75As/GaAs量子阱作为器件的有源区, 无偏压时器件的响应峰波长在1071 nm,器件在21 V的直流调谐电压下,实现了波长大于23 nm的调谐. 统计结果表明,当调谐电压大于5 V时,调谐电压与响应波长之间具有稳定、精确的对应关系, 且近似线性调谐,同时对器件响应峰的特性进行了理论分析. 关键词： GaAs 共振腔增强型探测器 高稳定 线性调谐     

Theoretical Research on Sensitivity for Resonance Wavelength of Long Period Fiber Grating

In a long period fiber grating(LPFG), the forward-propagating guided mode in the core is coupled to a number of co-propagating lossy cladding modes at resonance wavelengths. Sensitivity of resonance wavelength against temperature, axial strain, and external refractive index is modeled in this paper. Schemes for temperature compensation and enhanced wavelength tuning of LPFG are proposed and analyzed. Experiments show accordant results with simulations. Temperature coefficient of the LPFG compensated by means of axial strain is below 1.8 nm/100℃. For the LPFG with polymer recoating layer, the enhanced tuning range is more than 70 nm.     

Theoretical Research on Sensitivity for Resonance Wavelength of Long Period Fiber Grating

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新型光纤光栅中心波长与带宽独立调谐方法

提出了一种新型光纤光栅中心波长与带宽独立调谐方法，将光纤光栅沿圆柱形弹性梁的轴向成一定角度粘贴于侧面，通过改变梁的扭转角与侧向位移，实现了光纤布拉格光栅中心波长与带宽的准线性独立调谐，实验上获得了8．28nm准无啁啾波长调谐和5．32nm准无中心波长漂移的带宽调谐，实验结果与理论分析一致.     

Dynamic Wavelength Tuning of a Fiber Ring Semiconductor Laser

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准晶非线性光子晶体中二次谐波波长和温度调谐的研究

在八重准周期极化的铌酸锂非线性光子晶体中,通过调节基频光波长实现了多个波长的同时共线准相位匹配倍频,最高转换效率达36%.同时,测量了准晶非线性光子晶体中二次谐波转换效率随晶体温度以及入射波长的变化,结果表明二次谐波在长波处具有更宽的温度以及波长调谐带宽.该项研究对于准周期非线性光子晶体在实际工作中的运用具有重要的指导意义. 关键词： 准周期 非线性光子晶体 温度调谐 波长调谐     

端面反射率的波长特性对外腔半导体激光器调谐范围的影响

端面镀增透膜的激光二极管构成的光栅外腔激光器（ECLD）中,考虑到镀膜端面剩余反射率对波长的依赖关系以后,利用等效腔法导出了该激光器阈值载流子密度随波长变化的解析表达式,以此为出发点,讨论了增透膜反射率极小位置对调谐范围的影响。结果表明,除了增大剩余反射率工和降低剩余反射率能够提高调谐范围这一明显结论这外,在镀膜工艺确定的情况下,即假定剩余反射率带宽和剩余反射率极小值变化不大时,通过控制剩余反射率极小值所对应的波长相对于镀膜前增益峰的偏移量,可进一步拓宽波长调谐范围。     

外腔半导体激光器中激光二极管端面反射率的谱特性分析

考虑到端面反射率与波长有关 ,且带宽有限的实验事实 ,以及增益谱随载流子密度变化的因素 ,着重分析了激光二极管 (L D)镀膜端面反射率带宽、极小波长位置参量对光栅外腔激光器 (ECL D)调谐范围的影响。分析表明 ,除了 L D镀膜端面剩余反射率值、外腔反馈效率等因素之外 ,增大反射率带宽、精确控制极小波长位置是进一步挖掘 ECL D调谐范围的有效措施。增大反射率带宽 ,可更有效地提高参考载流子密度 ,延伸长波长端调谐区域 ,抑制 F- P腔影响。在确定的条件下 ,优化后的极小波长位置对应于调谐范围的极大值。理论分析结果较好地解释了实验现象     

Wavelength tuning characteristics of a fabry-perot semiconductor laser with an external short cavity

Wavelength tuning characteristics of a Fabry-Perot semiconductor laser with an external short cavity are analyzed, in which the oscillation wavelength can be changed by slightly altering the external cavity length. Analysis is based on rate equations for an optical power and carrier density. It is shown that the wavelength tuning range is dominated by a change of carrier density through the effect of carrier-induced refractive index change in the active layer of a laser diode. This depends on effective coupling coefficients of the optical field iteratively reflected back to the laser diode by the external mirror, and on reflection coefficients of an anti-reflection coated laser facet and the external mirror which compose the external cavity. The effective coupling coefficient is also derived using the waveguide theory and Kirchhoff ’s theory. Finally, an unstable condition which may limit a stable wavelength tuning range is shown by results of a linear stability analysis of rate equations.     

分布式光纤Bragg光栅波长校准方法

提出了一种利用标准参考光谱进行波长校准的方法。实验中利用由宽带光源和光纤可调谐滤波器组成的可调谐光源分别扫描了参考光谱和传感光栅的光谱。在参考通道,ITU标准参考模块的输出是具有固定波长的梳状光谱。利用高斯拟合算法计算出由标准参考透射谱峰值输出的对应的驱动电压,通过样条插值函数获得了滤波器输出波长与驱动电压的关系。计算光栅反射谱峰值对应的驱动电压,利用上面获得的滤波器输出波长与驱动电压的关系式可以计算出传感光栅的Bragg波长。实验结果表明,在较大的波长范围内实现了对多个传感光栅的波长校准,减小了由滤波器非线性输出造成的测量误差,具有较高的重复性。     

C-band three-port tunable band-pass thin film optical filter with low polarization-sensitivity

According to the oblique incidence characteristics of thin film narrowband filter, the stack of 100 GHz DWDM four cavities angle-tuned thin film filter has been designed and optimized. The two polarization modes’ central wavelengths of the thin film filter can be centered at the same one in oblique incidence, and it has a stable tuning range of 20 nm without the phenomenon of polarization central wavelength separation. Using this kind of angle-tuned thin film filter and the polarization beam-splitters, the tuning range of the angle-tuned thin film filter can be further expanded due to the reason that it can transmit only the s-polarization light. In this paper we also developed a three-port bandpass tunable filter device with new structure, which tuning range can cover the whole C-band and its adjacent channel isolation degree is high. The experiments show that the three-port tunable filter has an effective tuning range of 33 nm, and its adjacent channel isolation degree is more than 35 dB. It has a bright application opportunity for its flexibility and effective performance.     

Multiaccess in all-optical networks with wavelength and code concurrency

A major obstacle in realizing fast packet switching in all-optical networks is the large tuning delays of tunable optical devices. This article proposes a multiaccess scheme for all-optical local area networks that employs both wavelength and code concurrency. In this scheme, several users share a wavelength channel through code multiplexing. The delay performance of hybrid wavelength/code division multiaccess is obtained under a simple, suboptimal access protocol based on cyclic search. Due to the reduction in the number of wavelength channels without an associated reduction in transmission concurrency, hybrid multiaccess is robust against tuning delays. At a given network throughput, the hybrid scheme achieves considerably lower delays than that of Wavelength Division Multiple Access even with a small amount of code concurrency. Conversely, the hybrid network can support a higher load when there is a maximum allowable value for the average packet delay.     

小型多功能CO2激光器

研制了一种小型多功能CO2激光器。该激光器可以单脉冲、重频或连续方式输出,并可实现输出脉冲频率的编码及波长调谐。激光器谐振腔采用光栅一级振荡,零级输出的工作方式,分别利用声光调Q技术和脉冲放电技术实现了百ns至亚ms量级的脉冲激光输出。详细介绍了该激光器中基于光学角反射器原理设计的光栅调谐定向输出装置,并对其进行了理论计算和论证,实现了不同波长激光的定向、定位输出,获得调谐激光输出谱线超过60条,谱线分辨率优于0.01μm。激光器脉冲重复频率1Hz～10KHz连续可调,输出波长调谐范围9.2μm～10.8μm,激光器连续输出最大功率8W,重复频率1KHz时最小激光脉宽180ns,峰值功率4062W。该激光器在激光与物质相互作用科学领域,特别是激光对物质作用与破坏机理的研究方面具有重要的应用价值。     

宽范围可调谐内腔液晶垂直腔面发射激光器设计与研究

为增加可调谐激光器的波长调谐范围,提高系统的可靠性和稳定性,基于液晶的电控双折射特性,设计了一种中心波长为852 nm的内腔液晶可调谐垂直腔面发射激光器结构。分析了该结构获得宽范围波长调谐和单偏振稳定输出的物理原理,利用传输矩阵法进一步计算整个器件下不同液晶层厚度所对应的反射谱,得出不同液晶厚度和折射率下激光器的激射波长。结果表明,液晶可调谐激光器单偏振波长调谐范围达到31 nm,调谐效率大于10 nm/V。     

Continuous Wavelength Sweep of External Cavity 630 nm Laser Diode without Antireflection Coating on Output Facet

We developed a simple method of continuous wavelength sweep using a commercial laser diode (LD) without antireflection (AR) coating. A 630 nm AlGalnP LD was installed in a Littrow-type external cavity. In this cavity, the LD has the same effect as an etalon, and its free spectral range can be controlled easily by the LD drive current. By scanning the grating angle of the external cavity and LD drive current simultaneously, we obtained single-mode oscillation and continuous wavelength sweep of over 22 GHz without mode hopping. This technique is simple and inexpensive because it does not need AR coating on its output facet, and does not use a servo system which requires apparatuses such as a lock-in amplifier and local oscillator.     

785nm便携式光栅外腔可调谐半导体激光器的研制和输出特性

针对移频激发拉曼光谱测试系统的小型化需求,在Littrow结构中,采用商用的785nm大功率激光二极管作为增益器件,构建了一款便携式光栅外腔可调谐半导体激光器。该激光器通过采用一种新型的波长调谐方法,即以改变半导体增益器件相对于准直透镜的水平位置来实现波长的连续调谐,实现了尺寸为140mm×65mm×50mm的小型化结构设计。相比于传统的旋转衍射光栅改变光线在光栅上的入射角来实现波长调谐的方式,该方法有效地缩减了增益器件的平移距离,从而有利于便携式外腔激光器波长的快速宽带调谐。实验结果表明,该激光器具有较宽的波长调谐范围,在340~900mA注入电流下均可实现10nm以上的波长调谐,尤其在900mA大注入电流下,其波长调谐覆盖779.40~791.07nm,调谐范围可达11.67nm,且激射线宽小于0.2nm,单波长输出功率最高可达280mW,放大的自发辐射抑制比大于25dB,呈现出较优异的输出性能,满足移频激发拉曼光谱检测系统对光源的基本要求。此外,该激光器可采用一微型压电陶瓷驱动器来实现波长的电动调谐,实验获得了1.35nm的波长调谐范围,证实了所制785nm便携式光栅外腔可调谐半导体激光器适合作为便携式移频激发拉曼光谱检测系统的光源用于减除原始拉曼光谱中的荧光背景。     

Wavelength Tuning of Long-Period Fiber Gratings by Fabrication Using a Tilted Amplitude Mask

We propose a method of tuning resonant wavelengths in the fabrication process of a long-period fiber grating using an amplitude mask tilted relative to the fiber. We irradiated a hydrogenated single-mode fiber with a KrF excimer laser through a tilted amplitude mask with a grating period of 460 Μm. Growth of resonant loss peaks in transmission spectra was measured for various tilt angles. A tuning range up to 329 nm was obtained by tilting up to 45°. The measured results agreed with numerical simulation. It was shown that using only an amplitude mask it is possible to fabricate a long-period fiber grating having resonance at any wavelength throughout the range of 1.2-1.6 Μm. A method to determine the tilt angle for a designed wavelength is discussed.