大范围可调谐液晶/聚合物光栅有机半导体激光器

基于液晶/聚合物光栅,以MDMO-PPV为增益介质,在抽运增益介质层不同位置处对出射激光波长进行粗略调谐,通过施加外部电压对出射激光波长进行精密调谐,最终得到调谐范围为18 nm、可连续精密调谐的液晶/聚合物光栅有机半导体激光器。该研究可为改进可调谐分布反馈有机半导体激光器提供一些新思路。     

基于液晶/聚合物光栅的可调谐双波长有机激光器

本文报道了基于液晶/聚合物光栅的可调谐双波长有机激光器的制备,并研究了激光器出射激光的电调谐以及周期调谐性能。利用激光染料4-二氰亚甲基-2-甲基-6-对-二甲基氨基苯乙烯-4H-吡喃(DCM)和有机半导体材料聚[2-甲氧基-5-(2-乙基己氧基)-1,4-苯乙炔](MEH-PPV)同时作为增益介质,液晶/聚合物光栅作为谐振腔得到可调谐双波长有机激光器,对激光器施加电压或者改变液晶/聚合物光栅的周期可调谐激光器的出射波长。双波长有机激光器从DCM和MEH-PPV中出射的激光波长分别为608.3nm和632.1nm,在外加电场的作用下,出射激光波长分别蓝移了9.6nm和1.7nm。随着光栅周期从394nm增加到406nm,出射激光波长分别红移了18.4nm和19.2nm。本工作为可调谐有机双波长激光器的研究提供了有益的指导和借鉴意义。     

液晶分子取向对液晶/聚合物光栅电光特性以及激光出射特性的影响

报道了液晶分子不同取向对液晶/聚合物光栅电光特性以及激光出射的影响。通过扫描电子显微镜观察液晶/聚合物光栅的截面,成功观察到了光栅的体光栅结构。液晶分子垂直光栅矢量排列时,由于光栅形貌变差,衍射效率由液晶分子沿光栅矢量排列时的83.2%降低至72%,同时散射损耗由11.8%增加至19.1%。液晶分子垂直光栅矢量时,液晶/聚合物光栅的调谐电场由液晶分子沿光栅矢量时的13.6V/μm下降至3.1V/μm。液晶沿光栅矢量排列时,激光出射阈值更低,为利于激光出射的方向。本文工作为进一步加深对液晶/聚合物光栅以及染料掺杂分布式反馈选频的理解和认识,提供了指导和借鉴。     

纳米颗粒掺杂的聚合物稳定液晶微管随机激光器性能研究

为了优化液晶类微管激光器的性能,拓展其应用领域,本文研究了银纳米颗粒和氧化锌纳米颗粒对染料掺杂聚合物稳定液晶微管激光器出射激光的影响。通过掺杂不同浓度的银纳米颗粒和氧化锌纳米颗粒在聚合物稳定液晶的微管随机激光器中,探究其对微管激光器出射激光特征的影响,并对比两种纳米颗粒的影响效果。实验结果表明:当在聚合物稳定液晶微管激光器中掺入0.1%的银纳米颗粒后,随机激光出射强度增强,其激光阈值从23.2μJ/pulse减小至10.9μJ/pulse。当氧化锌纳米颗粒的掺杂浓度达到1.0%时,在随机激光出射强度增加的同时,激光出射阈值会减小至21.2μJ/pulse。然而,过量纳米颗粒的掺杂均会造成随机激光出射光强的降低和激光阈值的增加,其原因在于纳米颗粒团簇的产生,降低了纳米颗粒的散射作用。实验结果还表明,银纳米颗粒掺杂对微管激光器性能的提升明显优于氧化锌,这归因于银纳米颗粒所引发的局域表面等离共振效应会增强其散射作用。通过掺杂纳米颗粒,微管随机激光器的性能得到了提升,为其在通讯、加密以及液晶显示等领域奠定了基础。     

全息法制备二维电调谐聚合物/液晶光栅

介绍了利用激光干涉形成的亮条纹引发预聚物/液晶的混合物相分离,制备了二维电调谐光栅。在对样品进行一次曝光之后,将样品绕着基板中心的法线方向转动一定的角度(如90°),再进行一次曝光,获得格子结构的聚合物/液晶二维光栅。实验结果表明,光栅中的聚合物和液晶在二维空间上呈周期性分布,其衍射图样为空间点阵且衍射效率可以利用电场进行调节。     

光调控的偶氮染料掺杂聚合物分散液晶微管随机激光器（英文）

为了优化液晶类微管激光器的性能,本文研究了偶氮染料掺杂聚合物分散液晶微管激光器出射激光的性能及光控性。通过在不同纤芯直径的玻璃毛细管中制备掺杂偶氮染料的PDLC,并分别测量这些样品的随机激光阈值。增加紫外线照射强度,测量随机激光的光谱。实验结果表明,不同芯径毛细管样品(100μm,300μm,500μm)的随机激光阈值测量为11.8μJ/脉冲,8.6μJ/脉冲和13.2μJ/脉冲。实验结果还表明,随着紫外线照射强度的增加(从0mW/cm2增加到150mW/cm~2),随机激光强度逐渐减小,光谱的半高宽变宽。随机激光在光学调谐过程中在不同偏振方向的紫外光束下显示出相似的特性。该工作验证了在圆柱形约束结构中制造微型激光器件的可能性,并扩展了PDLC的应用范围。     

基于飞秒激光直写的液晶面外区域定向技术及其应用

随着激光加工技术和液晶取向工艺的发展,一种新型的基于飞秒激光直写的液晶面外区域定向技术问世。基于飞秒多光子光聚合激光直写技术制备出由聚合物条带构成的微结构,将其制成液晶盒,并充入不同种类的液晶,即可实现电光开关、磁光开关、光场调控等功能。每条聚合物条带的侧壁上都分布有表面浮雕光栅结构,使得液晶在聚合物条带通道内的定向成为可能。该技术不仅使不同区域内的液晶实现了物理隔离,还可以使液晶和聚合物实现完全的相分离。该技术快捷简单,在可调谐衍射光栅的实现、特殊光场的产生、光子晶体中的光场调控等方面具有重要的应用价值。     

含氟单体材料对全息聚合物分散液晶Bragg光栅电光特性的影响

在全息聚合物分散液晶的预聚物体系中添加含氟的单丙烯酸酯单体,制备全息聚合物分散液晶Bragg光栅,通过AFM、He-Ne激光器观察分析,发现甲基丙烯酸十二氟庚酯(Actyflon-G04)的添加不仅改善聚合物基质的形貌,同时也影响光栅的电光特性。实验结果表明,光栅的衍射效率从78%上升到90%,驱动电压V90大幅降低。分析认为,Actyflon-G04的添加降低了聚合物界面的表面张力,影响液晶微滴的分子取向,从而实现了光栅电光特性的改善。     

一次曝光法制备二维可调谐液晶光栅

设计了全息光路,采用一次曝光方法制备了基于聚合物分散液晶材料体系的二维可调谐液晶光栅.采用偏光显微镜和原子力显微镜对光栅的形貌进行检测,并利用He-Ne激光器对光栅的电光特性进行测定.结果表明,该光栅具有清晰的二维结构,衍射图样为空间点阵,衍射效率具有电场可调谐性.实验表明,改进的光路设计可制备多种形式的可调谐液晶器件.     

增塑剂对全息聚合物分散液晶光栅衍射性能的影响

在全息聚合物分散液晶的预聚物体系中添加增塑剂DOP,制备全息聚合物分散液晶光栅.通过红外光谱仪、AFM、He-Ne激光器观察分析发现,邻苯二甲酸二辛酯的添加不仅提高体系双键的转化率,改善聚合物基质的形貌,同时也提高光栅的衍射效率,降低驱动电压.针对实验结果进行分析,DOP的添加降低体系黏度、延长相分离的时间、提高单体的双键转化率,从而改善光栅电光特性.     

Electrical control of the distributed feedback organic semiconductor laser based on holographic polymer dispersed liquid crystal grating

In this paper, we demonstrate the electrical control of the distributed feedback (DFB) organic semiconductor laser based on a holographic polymer dispersed liquid crystal (HPDLC) grating for the first time. The grating is fabricated on the top of the organic semiconductor film to act as an external feedback structure. Experimental results show that the lasing intensity can be decreased by increasing the external electric field, and the lasing wavelength exhibits a slight blue-shift of 1.4 nm during the modulation process, indicating a good stability. The modulated performances are attributed to the decreases in the refractive index modulation and average refractive index of the HPDLC grating respectively as a result of the field-induced liquid crystal reorientation. This study provides some new ideas for the improvement of DFB organic semiconductor laser to enable envisioned applications in laser displays and integrated photonic circuits.     

Thermal annealing effect on organic semiconducting polymer laser with an external holographic grating feedback layer

Thermal annealing effect on an organic distributed feedback (DFB) laser excited from a semiconducting polymer gain layer, poly(2-methoxy-5-(2’-ethyl-hexyloxy)-p-phenyl-envinylene) (MEH-PPV), is reported. The morphology, absorption and photoluminescence (PL) spectral characteristics of the MEH-PPV film annealed at different temperatures were analyzed. The amplified spontaneous emission (ASE), the optical gain and loss coefficients were also investigated. The organic lasing behaviors including threshold, energy conversion efficiency and polarization state in a DFB laser device were studied. The results show that the optical properties of the organic semiconducting laser can be enhanced by thermal annealing effect. The single mode laser emission at 622.4 nm with lower lasing threshold 0.2 μJ/pulse and higher energy conversion efficiency 6.71% was achieved with thermal annealing at 120 °C. The thermal annealing treatment decreases laser threshold and increases laser energy conversion efficiency dramatically, which shows the potential in ultra-low cost organic semiconducting polymer DFB lasers.     

Distributed feedback polymer laser with an external feedback structure fabricated by holographic polymerization technique

Distributed feedback polymer laser with a grating in the waveguide cladding layer was prepared by holographic polymer dispersed liquid crystals (HPDLCs). The holographic polymerization technique enables one-step formation of an organic grating on top of a homogenous semiconducting polymer poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV) layer. Under optical pumping, a lasing threshold of 21 μJ/cm² and a bandwidth of 0.7 nm were obtained in a single longitudinal mode operation. Further studies on the effect of the semiconducting polymer thickness show the amount of evanescent wave spread into the grating layer determines the laser performance of the proposed device.     

聚合物分散液晶薄膜中随机激光辐射的实现

设计制作染料掺杂聚合物分散液晶薄膜激光器件,研究随机激光辐射行为。利用微胶囊法将激光染料、向列相液晶、手性剂、聚乙烯醇混合,制备掺杂两种激光染料的聚合物分散液晶薄膜。利用输出激光532 nm的Nd:YAG倍频脉冲激光器进行泵浦,在582～607 nm波段获得尖锐、离散的随机激光输出,阈值能量约为9 mJ,线宽约为0.3～0.4 nm。对于器件产生激光辐射的机制,利用环形腔理论进行了分析。对比掺杂单种激光染料的聚合物分散液晶薄膜激光器件,实验结果显示,同时混合不同类型的激光染料制备的聚合物分散液晶薄膜,能够实现较宽波段的随机激光输出。     

Optically‐Pumped Lasing in Hybrid Organic–Inorganic Light‐Emitting Diodes

Here, the use of metal oxide layers both for charge transport and injection into an emissive semiconducting polymer and also for the control of the in‐plane waveguided optical modes in light‐emitting diodes (LEDs) is reported. The high refractive index of zinc oxide is used to confine these modes away from the absorbing electrodes, and include a nano‐imprinted grating in the polymer layer to introduce distributed feedback and enhance optical out‐coupling. These structures show a large increase in the luminescence efficiency over conventional devices, with photoluminescence efficiency increased by up to 45%. Furthermore, optically‐pumped lasing in hybrid oxide polymer LEDs is demonstrated. A tuneable lasing emission is also obtained in a single device structure by employing a graduated thickness of a zinc oxide inter‐layer. This demonstrates the scope for using such architectures to improve the external efficiency of organic semiconductor LEDs, and opens new possibilities for the realization of polymer injection lasers.     

全息聚合物分散液晶膜的干涉图像存储及衍射特性

用激光干涉形成的亮条纹引发预聚物／液晶混合物相分离,在相分离稳定后,干涉图样被存储在聚合物／液晶复合膜中,被称之为全息聚合物分散液晶（HPDLC）。研究了相关因素对HPDLC膜信息存储的影响,并且光学显微镜观察了膜结构。给出了具有栅式结构膜的衍射特性。实验结果表明,形成的HPDLC膜其存储的栅结构稳定持久,而且其衍射效率可用电或热来调节。     

Ag纳米颗粒有机薄膜受激辐射增强研究

为进一步降低有机半导体材料的激射阈值,文章研究利用银纳米颗粒的表面等离子体共振效应来实现对有机半导体薄膜受激辐射的增强.将制备好的Ag纳米溶液旋涂于玻璃基底上,然后在其上再旋涂PS:Alq3:DCJTB有机薄膜发光层,构成平面波导结构.用355nm波长的YAG激光泵浦样品.实验发现:相比于无Ag纳米颗粒情况,有Ag纳米...     

非线性光栅自调制光限幅器件研究

研制出一种三角槽型透明高分子聚合物光栅与该聚合物平板间填充有机非线性光学液体的夹层结构器件，具有非线性自调制光限幅功能。实验测得该器件对较弱的532nm波长的YAG倍频激光透过率大于60％。对较强激光透过率小于2％～3％。理论预期在激光波长400-700nm都有光限幅特性。且愈靠近532nm波长。激光限幅功能愈强。首次从实验上验证了该非线性光栅具有自适应宽带光限幅的功能。它不仅可以实现可调谐光限幅。且对所设计的激光波长，达到能量低于人眼安全阈值的高效激光防护成为可能。     

Distributed Feedback Lasers Based on Thiophene/Phenylene Co‐Oligomer Single Crystals

Organic crystals have great potential for the applications in laser devices. This article presents an effective approach for fabrication of distributed feedback single crystal lasers. With the laser interference ablation method, high quality grating structures have been fabricated on the organic single‐crystalline thin film materials. The relationship between the depth, periodicity, and laser fluence is discussed. The optical properties, such as photoluminescence, and diffractive properties are studied in detail. With the appropriate period, strong laser emission has been observed from these devices. Distributed feedback lasing is demonstrated from the laser interference ablated organic single crystals for the first time.     

Second-order distributed feedback polymer laser based on holographic polymer dispersed liquid crystal grating

We report on the fabrication and characterization of a second-order distributed feedback (DFB) polymer laser based on a holographic polymer dispersed liquid crystal (HPDLC) transmission grating. The fine organic grating is fabricated on top of the homogeneous conjugated polymer layer in a one-step process. The device shows surface-emitting, single mode laser emission with a threshold of 13.3 μJ/cm², and the working characteristics merely degrade after 10 months of storage in ambient atmosphere. We further explain the dependence of threshold on pumping length, and demonstrate the small refractive index modulation of this all-organic grating is sufficient to maintain efficient DFB laser action. This simple working structure, combined with large processing area provided by the holographic polymerization technique, is extremely promising in realizing ultra-low cost plastic lasers.