Organic waveguide laser by a surface-relief holographic grating formed by photoisomerization

衍射光栅是集成光学中的重要元件，在光谱滤波、光反馈、光与光波导之间的耦合等方面有着广泛的应用。最近，一些研究人员报道了在室温下通过反式顺式光异构化一步在含偶氮苯的聚合物上形成光诱导表面浮雕全息图。这种方法将聚合物暴露在简单的双光束干涉图案下，可以快速制作具有小周期的大面积光栅，并且可以很好地控制光栅参数。在这项研究中，我们提出了一种基于光诱导表面浮雕全息的分布反馈的聚合物光波导的激光振荡。它的厚度约为1μm。基于表面遗迹…的分布反馈光栅干涉照射系统可形成更多的全息图，作为记录光源的二极管泵浦的连续激光，被准直，并通过薄膜。记录光强为100 mW/cm2。记录激光的偏振方向垂直于浮雕全息图的光栅矢量。胶片和调谐镜固定在旋转支架上。并且通过改变底座的旋转角度来控制在薄膜上形成的光栅周期。全息记录通常在任何光栅期进行2000年。在2000年后，衍射效率几乎达到最大值。浮雕光栅的高度约为25 nm，周期为370 nm。利用旋涂技术在偶氮苯聚合物薄膜上涂覆了掺杂激光染料(DCM)的PVK薄膜，得到了高达60 nm、周期550 nm的浮雕光栅。该器件采用锁模开关二极管泵浦的脉冲宽度为20ps、重复频率为10 Hz的λ绿光激光器作为泵浦光源。该器件的周期为370 nm，激光波长为630 nm，激光阈值为20mJ/cm~2。

Diffraction gratings have been important elements in integrated optics for many applications such as spectral filtering, optical feedback, and coupling light into and out of optical waveguides. Recently, several re-searchers have reported that a light-induced surface relief hologram can be formed on azo-benzene containing polymers by trans-cis photoisomerization in a one step process at room temperature. This method involves exposing the polymer to a simple two- beam interference pattern, and can allow quick fabrication of large area gratings having small periods, with good control over the grating parameters.In this research, we present a laser oscillation of a poly-mer waveguide with distributed feedback based on a light-induced surface relief hologram.The polymer thin-film fabricated by spin-coating technique was composed of azo-benzene containing polymer Poly-Orange-Tom-1 film. Its thickness was approximately 1 μm. Distributed-feedback gratings (DFB gratings) based on surface relie … More f hologram were formed by the interferential irradiation system.A diode-pumped, continuous-wave Nd:YAG green laser used for a recording light source was collimated, and passed through the film. Its intensity on the film was 100mW/cm^2. The polarization of the recording laser was perpendicular to the grating vector of the relief hologram. The film and the tuning mirror were fixed on the rotational mount. And the grating period formed on the film was controlled by varying a rotational angle of the mount. The holographic recording was typically conducted for 2000s at any grating periods. After 2000s, the diffraction efficiency almost reached up to the maximum level. And then, a height of the relief gratings was 〜25 nm with a period of 370 nm. A height of the relief gratings was 〜60 nm with a period of 550 nm.In order to fabricate the waveguide laser, a laser dye (DCM) doped PVK film was over-coated onto the azo-benzene polymer film with DFB gratings by the spin-coating technique. This device was pumped by a mode-locked Q-switched di-ode-pumped Nd:YAG green laser (λ=532 nm) with a pulse duration of 20ps at a repetition rate of 10 Hz. The device with the grating period of 370nm lased at 630nm, and then, the lasing threshold was 20mJ/cm^2. Less