染料掺杂手性向列相液晶激光器的制备和研究

设计制作了PM597染料掺杂手性向列相液晶器件,研究了其激光辐射行为。混合激光染料PM597、手性剂S-811、向列相液晶TEB30A,制成平面态织构的手性向列相液晶激光器件。采用固体Nd∶YAG倍频532nm波长激光作为抽运光,在光子禁带短波和长波边沿同时获得波长分别为571.1、615.5nm的激光输出。对于器件产生激光辐射的机理,采用光子态密度理论进行了分析,根据实际样品各成分的配比,模拟出态密度随波长的变化曲线。在器件中,光子禁带边沿处光子态密度最大,此处器件阈值较低,容易产生激光辐射。     

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。     

染料掺杂手性向列相液晶器件中实现随机激光辐射

设计制作了染料掺杂手性向列相液晶器件,研究了其随机激光辐射行为。均匀混合激光染料DCM和PM597、手性剂S-811、向列相液晶TEB30A,注入无摩擦取向的40μm液晶盒,制成焦锥织构态的手性向列相液晶激光器件。采用固体Nd:YAG倍频532nm波长的脉冲激光作为抽运光泵浦样品。掺杂激光染料PM597和DCM的液晶器件分别在575～588nm和600～620nm范围显示了尖锐、分立的随机激光辐射峰,线宽约为0.3nm。探测了器件在不同方向上的激光辐射谱,在与样品表面夹角约为45°～150°的范围内均能探测到随机激光。在器件中,手性向列相液晶焦锥织构态对光的强散射作用是随机激光产生的主要原因。     

胆甾相液晶多重乳液微结构激光特性的研究进展

染料掺杂的带边胆甾相液晶微激光器因阈值低、无需反射镜的特点,自提出以来便一直是研究热点。具有复杂微结构的胆甾相液晶液滴是一种新颖的三维全向微激光器,兼具有小型化、集成化与波长可调谐的特性,更是引起了液晶非显示领域研究者们的广泛兴趣。其复杂的球形核壳微结构,促使诸如分布反馈、回音壁和法布-珀罗等多种激光模式的产生。而玻璃毛细管微流控技术的出现,使大规模制备单分散、尺寸可控的胆甾相液晶液滴成为可能,同时为制备结构复杂的多重乳液提供了必要条件。本文简要介绍了制备液晶乳液所使用的玻璃毛细管微流控技术,并综述了近年来与单重乳液胆甾相液晶液滴及多重乳液胆甾相液晶核壳微结构中的激光行为相关的研究工作。     

向列相液晶激光器件侧面辐射谱研究

研究了向列相液晶激光器件侧面激光辐射谱,并深入分析了激光辐射机制。分别制备了传统液晶盒和引入SU-8光栅结构的两种器件,并注入向列相液晶TEB30A和激光染料PM597的混合物。利用Nd:YAG固体脉冲激光器倍频出的532 nm激光作为泵浦源正面入射器件,侧面探测激光辐射谱。在传统液晶盒器件侧面,测得575～600 nm范围的随机激光辐射谱。而具有周期100μm和8μm的SU-8光栅结构器件侧面,获得了多波长激光辐射谱。随着泵浦能量增大,最高强度激光辐射峰波长位置出现在583～585 nm和588～592 nm附近,FWHM约0.3 nm。基于光波导理论结合器件结构分析得出,在传统液晶盒中引入SU-8光栅结构增强了液晶器件的光波导效应,是获得多波长激光辐射谱的主要原因。     

光调谐的胆甾相液晶应用的发展

胆甾相液晶具有自发的螺旋排列,是一个有趣又引人入胜的手性超分子各向异性体系。近几年胆甾相液晶体系,特别是光调谐的胆甾相液晶在新领域的应用出现令人欣喜的研究结果。本文综述了近几年光调谐的胆甾相液晶在滤波、液晶光栅以及液晶激光中的研究成果。具有光调谐特性胆甾相液晶在特殊需求的光学器件中的应用将是胆甾相液晶研究的一个很有潜力的研究方向。     

聚合物稳定胆甾相滤色液晶光阀的显示研究

本文研究了在平面态和场致向列相之间快速切换的聚合物稳定胆甾相(PSCT)液晶光阀的彩色显示。采用紫外光诱导相分离法(PIPS)制备具有染料掺杂的聚合物稳定胆甾相液晶光阀,通过3种染料在可见光区的吸收作用,对入射白光进行选择性吸收过滤,得到不同颜色的出射光。结果表明:当PSCT处在平面态下,分子螺旋排列,染料对入射光波的吸收不受光波偏振方向的影响,器件具有很强的吸收作用,呈现有色态;当处于场致向列相,染料的吸收作用微小,器件呈透明态,因此器件具有一定的对比度,且不需要偏振片;器件在平面态和场致向列相之间快速切换的响应时间短于7ms。PSCT光阀可以用作滤色器,在多种染料的共同作用下,快速选择滤色得到多种彩色可见光,组成彩色显示平面。     

改变直流电场方向调控聚合物稳定胆甾相液晶的反射带隙

具有宽带反射特性的胆甾相液晶在众多领域有广泛的应用前景。为了拓展调控反射带隙的方法,实现在所需波谱范围内的带隙调控,本文通过添加紫外吸收染料,制备了一种聚合物网络梯度分布的新型聚合物稳定胆甾相液晶器件。实验结果表明,聚合物网络的梯度分布使液晶盒上下表面附近的聚合物网络弹性产生了显著的差异,因此,其电诱导的反射带隙拓宽可以改变直流电场的方向进行调谐。当液晶盒厚度为40μm,染料浓度为1.2%的PSCLC,在施加12V的直流电场时,面向光源为正极时的反射带隙位于570～778nm,改变电场方向后,反射带隙红移至598～816nm。这项研究为宽带反射胆甾相液晶材料提供了一种新的策略,在智能窗户、激光防护、数据存储等方面具有潜在的应用。     

温度对染料掺杂胆甾相液晶激光波长的影响及应用

研究了温度对激光染料掺杂胆甾相液晶的激光波长的影响,发现胆甾相液晶输出的激光波长总体上随温度的升高而红移,但是不同厚度的样品随温度变化的趋势略有不同。样品较薄时,激光波长随温度变化呈周期性的跳变式增长,而在相邻两个跳变温度之间的一小段温度范围内则随温度的升高而蓝移,且激光波长随温度变化产生突变的周期随样品厚度增加而减小。当样品厚度足够大时,激光波长随温度变化产生的突变消失,几乎随温度呈线性增长。分析了产生该现象的物理机制,并对其进行了理论模拟。模拟结果与实验结果一致。厚的染料掺杂胆甾相液晶样品产生的激光波长随温度线性变化的这一特性,可以用于温度传感。     

SiO2/TiO2多层膜结构一维光子晶体光子禁带研究

制作了SiO2/TiO2多层膜结构一维光子晶体,研究了其光子禁带特性.通过测量红外透射谱,分析了入射线偏振方向、入射角度以及引入缺陷层对光子禁带的影响.随着入射角度的增大,在TE模式和TM模式线偏振光下,光子禁带边沿产生蓝移现象.引入TEB30A型向列相液晶缺陷后,光子禁带中在波长约为l810nm(TE模式)和182l...     

Lasing band-edge identification for a surface-emitting photonic crystal laser

The possibility of single-mode oscillation over a large cavity area for photonic crystal lasers emitting at the photonic band edge has resulted in much interest in such materials for new forms of solid-state laser. In this paper, we measure the photonic bandstructure in our sample and identify the lasing band edge. By mapping out the bandstructure at the /spl Gamma/-point, we have observed fine structure at the band edge. The experimental results are in good agreement with the theoretically predicted bandstructure. Above threshold, we observe a lasing peak at 965 nm at one of the band edges. The far-field distribution of the laser is measured, showing an annular profile and azimuthal polarization. Calculations on the far-field distribution at the lasing band edge suggest the annular profile is due to an anti-symmetric resonant mode.     

Electrotunable Non‐reciprocal Laser Emission from a Liquid‐Crystal Photonic Device

A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage.     

基于液晶/聚合物光栅选频的高效率有机半导体激光器

报道了一种基于液晶/聚合物光栅选频的高效率有机半导体激光器的制备方法。首先在一片玻璃基板上旋涂有机半导体荧光薄膜MEH-PPV作为增益介质,然后在其上通过光场中的定域光聚合制备液晶/聚合物光栅,形成分布式反馈(DFB)有机半导体激光器。激光出射阈值0.32μJ/pulse,斜率转化效率高达7.8%,呈现良好的s偏振特性。采集了激光束的光斑,轮廓清晰,呈现扇形结构。通过改变光栅周期,实现了53.4nm激光出射范围。本工作为新型有机激光器的制备提供了有益的指导和借鉴意义。     

Electrically injected single-defect photonic bandgapsurface-emitting laser at room temperature

An electrically injected defect-mode photonic bandgap microcavity surface-emitting laser at room temperature is demonstrated for the first time. 931 nm lasing is observed under pulsed excitation conditions. With a threshold current of 300 μA. Near- and far-field modal characteristics of the emission confirm lasing from the defect-related microcavity in the photonic bandgap crystal     

Photonic crystal heterostructure cavity lasers using kagome lattices

The lasing characteristics of a photonic crystal membrane heterostructure cavity that utilises a kagome type lattice is demonstrated. A heterostucture cavity is formed by interfacing two photonic crystals such that the dispersion maximum of the inner lattice falls within the photonic bandgap of the surrounding lattice. Feedback to slow Bloch modes allows for localisation of band edge modes and a reduction of in-plane losses. Singlemode lasing is observed in relatively large area lasers at 1550 nm.     

胆甾型液晶溶液膜中的随机激光

研究了激光染料若丹明6G(R6G)在乙基氰乙基纤维素[(E-CE)C]/丙烯酸(AA)胆甾型液晶溶液中的随机激光行为.发现在没有添加任何固体散射粒子的情况下,在(E.CE)C/AA/R6G溶液中观察到多个分离激光峰,最小半峰全宽(FWHM)为0.3 nm,表现出相干反馈行为.这种相干反馈激光行为的形成可能与液晶溶液中胆甾型微区的选择性反射和其折光指数各向异性密切相关.     

塑料激光介质的激光特性研究

通过化学处理，将Ｒ－６４０、Ｒ－６Ｇ等激光染料掺入到聚甲基丙烯酸甲脂中制成塑料激光介质，研究了这种激光工作物质的有关激光特性。     

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.