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     

基于可调谐激光器的局部放电光纤法珀传感器

针对局部放电测量中的光纤法珀传感器,研究了其工作点稳定和提高灵敏度的参数优化方法.通过改变可调谐激光器的波长稳定了传感器的工作点.用激光器波长调谐范围确定腔长,令玻璃薄板的反射率为1,根据单模光纤对高斯光束的耦合特性和多光束干涉原理,通过迭代算法得出光纤端面的最优反射率.基于波长调谐范围1530~1565nm的可调谐激光器,制作了自由光谱范围28nm,腔长43μm,玻璃薄板反射率大于0.97,光纤端面反射率0.52的法珀传感器.经实验测试,法珀腔光损耗为10%,条纹对比度为1.实验结果表明,基于可调谐激光器的传感器工作点稳定,可测试最小局放声压约为1Pa,达到实用要求.     

镀减反射膜后半导体激光器端面反射率谱的测量

比较相同偏置条件下镀减反射膜前后的半导体激光器端面自发辐射谱，测得了端面反射率随波长变化的关系曲线。该方法突破了Ｋａｍｉｎｏｗ法单一波长测量的限制，同时也避免了Ｋａｍｉｎｏｗ法在两端面镀膜后所遇到的调制度过小的问题。实验中确定出了低于８×１０（－５）的第二镀膜端面反射率。     

分布反馈光纤激光器阵列中外腔反馈特性研究

以半导体激光器中的复合腔模型和实测的分布反馈光纤激光器的外腔端面反射率为基础,对不同反射率条件下分布反馈光纤激光器的输出功率进行了仿真,同时搭建了二基元分布反馈光纤激光器阵列实验平台,对仿真结果进行了验证.仿真与实验结果表明:外腔反馈光重新注入分布反馈光纤激光器会增加激光器的输出功率,降低了阵列的输出功率平坦性.并且外腔端面反射率越大,这种平坦性降低的效果越明显.在构建分布反馈光纤激光器阵列时,应考虑外腔反馈对阵列输出功率平坦性造成的影响,尽量选择外腔端面反射率较小的激光器进行组阵.     

反射率小于10-4的1310 nm光电子器件增透膜技术的研究

阐述了电子回旋共振等离子体化学气相沉法淀积半导体器件的端面光学膜的优良特性,介绍了淀积反射率小于１０＾－４的１３１０ｎｍ半导体激光器端面增透膜技术,并对这种技术的优点和两端面淀积增透膜后的激光器特性进行了讨论。     

吸收对垂直腔面发射激光器光学特性的影响

采用光学传输矩阵方法，详细分析了反射镜以及键合界面的吸收对垂直腔面发射激光器光学特性的影响. 结果表明，反射镜以及键合界面的吸收对反射镜和垂直腔面发射激光器的反射率和势透射率有较大影响，而对反射镜中心波长处的反射相移以及垂直腔面发射激光器模式的反射相移和模式位置影响很小. 随着反射镜以及键合界面的吸收增大，反射镜中心波长处的反射率逐渐减小，垂直腔面发射激光器的模式反射率变化则是先急剧减小，达到一个极小值，然后再逐渐增大，而反射镜中心波长处以及垂直腔面发射激光器模式处的势透射率则都是迅速降低的. 此外，将有吸收的键合界面离有源区的距离远一些，有利于提高垂直腔面发射激光器模式处的光输出效率.     

采用新型谐振腔镜的高效可调谐波光器

采用波长变以反射率镜作为可调谐激光器谐振腔的输出镜,大大提高了可调谐激光器的整体运转效率和时间特性参数。     

193 nm氟化物增透膜的特性

 为了研制低损耗、高性能的193 nm氟化物增透膜,研究了基底和不同氟化物材料组合对氟化物增透膜的影响。在熔石英基底上,将挡板法和预镀层技术相结合,采用热舟蒸发方式制备了不同氟化物材料组合增透膜,对增透膜的剩余反射率和光学损耗等光学特性,以及表面粗糙度和应力等特性进行了测量和比较。在分析比较和优化的基础上,设计制备的3层1/4波长规整膜系AlF3/LaF3增透膜在193 nm的剩余反射率低于0.14%,单面镀膜增透膜的透射率为93.85%,增透膜表面均方根粗糙度为0.979 nm,总的损耗约为6％。要得到高性能的193 nm增透膜,应选用超级抛光基底。     

采用新型谐振腔镜的高效可调谐激光器

采用波长变反射率镜作为可调谐激光器谐振腔的输出镜, 大大提高了可调谐激光器的整体运转效率和时间特性参数     

双波长工作的光纤光栅外腔半导体激光器

本文利用多波长光纤布拉格光栅与端面镀有增透膜的半导体激光器管芯耦合形成外腔激光器。研究了不同光纤光栅布拉格波长间隔下,器件的工作性能。当光纤光栅波长间隔不同于管芯的FP腔模式间隔时,不能得到稳定的多波长输出。通过调整光纤栅的各个布拉格波长间隔,使之和半导体激光器FP模式间距相同时,得到了输出稳定的双波长激光。     

1.55 μm偏振无关半导体光放大器腔面减反膜的研制

设计并制作了1.55 μm偏振无关半导体光放大器腔面TiO2/SiO2多层减反膜, 工艺过程中设计并使用了反射率实时监控装置, 得到了低于5×10－4的腔面剩余反射率. 器件测试结果表明, 管芯在250 mA电流下仍处于未激射状态, 表明减反膜有效抑制了芯片的激射. 半导体光放大器的自发辐射（ASE）谱波动在0.4 dB以下, 3 dB带宽大于52 nm, 半导体光放大器小信号增益近27 dB, 在1520~1580 nm波长范围内偏振灵敏度小于0.5 dB.     

Experimental Study on Semiconductor Optical Amplifiers with Angled Facets

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中红外光参变振荡器在高反射率测量中的应用

根据光腔衰荡光谱技术(CRDS)原理,使用中红外光参变振荡器(OPO)为光源建立了直腔与折叠腔相结合的中红外波段3.6 μm 反射率测量实验装置,用于研究中红外波段的高反射膜反射率,测试精度为10-4。使用直型衰荡光腔测试了三对不同薄膜材料设计镀制的高反射腔镜的反射率,并选择了一对腔镜用于实验装置中。采用该装置精确测试了不同薄膜材料镀制的高反射膜的反射率,包括YbF3/ZnS,YbF3 /ZnSe多层膜,以及由银加保护膜镀制的反射镜。研究表明,中红外波段介质膜的反射率可达到R>0.9990,其中由YbF3/ZnSe镀制在硅基底上的多层介质膜3.6 μm反射率可达到99.96％。     

Tunable Bragg gratings for fiber lasers

A tuning method of a fiber Bragg grating by the bending compression-tension is considered. With this method, a relative tuning range of the resonance wavelength of the grating of about 5% has been obtained. The changes in the shape of the spectrum and in the grating reflectivity during the tuning process are studied. The reflectivity of the fiber Bragg grating has been found to considerably increase with increasing degree of compression. It is shown that such an increase is caused by compression-induced changes in the refractive index modulation amplitude in the grating. The fiber Bragg grating developed has been applied for tuning the radiation wavelength of an ytterbium fiber laser. The tuning range of the laser has been found to be 45 nm around the central wavelength 1080 nm.     

Axial mode tuning of a single frequency Yb:YAG thin disk laser

We describe an arrangement for an Yb:YAG thin disk laser, which enables narrow bandwidth operation in single-frequency mode at freely selectable wavelengths within the broad tuning range of the laser. This is facilitated by a combination of a double-stage birefringent filter and an etalon inside the laser cavity. We investigate the wavelength selection characteristics of the single elements as well as their combination. A simple procedure is implemented for a computer-based automation of wavelength tuning. The reflectivity of the partially reflecting resonator mirror is optimised, and the laser pump power is adapted for best tuning performance. Single-frequency emission is achieved in a frequency range of 9.75 THz (wavelength range 1020 nm to 1055 nm). Each axial laser mode in this range can be selected individually. The axial mode separation of 0.47 GHz corresponds to wavelength steps of 1.7 pm at 1030 nm. PACS 42.55.Xi; 42.60.Fc; 42.60.Lh     

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.     

Spectral properties of edge-emitting semiconductor laser subject to optical feedback from extremely short external cavity

We experimentally and theoretically study the impact of optical feedback from an extremely short external cavity (tens of μm) on the spectral behavior of edge emitting lasers (EELs). We are able to investigate a broad range of external cavity lengths and feedback strengths, by using a nanometer precision movable mirror attached to a fiber facet. A discrete modulation of the wavelength of operation is observed and its amplitude depends on the external cavity length and the external mirror reflectivity. We show that it is possible to optimize the tuning range of such a discrete wavelength tunable laser with respect to the external cavity and laser parameters.     

Enhancing Coherent Combining Efficiency via Choosing Appropriate Lasing Wavelength in a Michelson Compound Cavity Based on Two 3 dB Fibre Loop Mirrors and One Fibre Bragg Grating

Enhancing coherent combining efficiency via choosing appropriate lasing wavelength in a Michelson compound cavity based on two 3 dB fibre loop mirrors and one fibre Bragg grating （FBG） has been experimentally demonstrated. The FBG with 4.5% reflectivity is replaced at the cleaved facet with 4% Fresnel reflection. A high coherent combining efficiency of 93.5% is obtained when the FBG with central wavelength at 1559.845nm is introduced into the cavity, while it is only 90.1% combining efficiency with the FBG at central wavelength 1557.830 nm. In comparison with other reports, the proposed compound-cavity laser has the advantage of needless tuning FBG to obtain the coherent condition, and it is facile to ascertain the seemly wavelength lasing for a Michelson compound cavity.     

基于等离子体增强化学气相沉积技术的光电子器件多层抗反膜的设计和制作

针对光电子器件端面抗反镀膜的要求,研究了基于等离子体增强化学气相沉积(PECVD)技术的多层抗反膜的设计和制作.首先,对影响SiN_x折射率的因素进行了实验研究,确定了具有大折射率差的SiO₂/SiN_x材料的PECVD沉积条件.根据理论计算分析,设计了四层SiO₂/SiN_x抗反膜结构,能够在70 nm的波长范围内实现低于10^-4的反射率