Surface-Emitting Active Photonic Lattices for Watt-Range Coherent Power

提出的是研究和使用具有调制光学增益的周期性介电结构，即有源光子晶格（apl），以实现具有新颖设计的二阶光栅的二维（2-D）水平腔器件的瓦特范围相干表面发射功率。与传统api形成鲜明对比的是，所提出的器件在低折射率点阵中具有增益。反过来，通过低折射率点阵位之间的共振漏波耦合，行波的长距离（相干）耦合将成为可能。所提出的二维api结合了反制导锁相阵列和二阶DFB/DBR光栅结构的表面发射。与所有先前报道的二阶光栅DFB表面发射器不同，所提出的结构采用了大约pi的中心光栅相移，这确保了在不影响器件效率的情况下在正交的单瓣光束中发射。此外，光栅结构，除了确保单纵向模式的操作，将作为一个非常有效的选择单一横向模式：相控阵模式。因此，大孔径（200mm x 1200mm）几乎均匀的二维引导场轮廓的相干光源将能够在稳定的单衍射限制光束中工作，输出功率为瓦特范围的连续波输出功率。首先，将建立bloch函数模型来分析所提出的二维apl型器件。然后，将该模型应用于器件设计优化，通过金属有机化学气相沉积制备器件结构，然后通过全息干涉测量和湿化学蚀刻制备光栅。为了产生必要的光栅p相移，将使用双色光刻胶。为了创建锁相阵列（横向），将在顶部表面蚀刻狭窄的周期性沟槽，然后重新生长高折射率材料（GaAs）以提供反制导阵列。在器件p侧沉积必要的金属化后，将在器件n侧金属化中创建条纹窗口，以允许一阶衍射光在与激光芯片表面垂直的方向上发射。最初的工作将在20元阵列上进行，以证明通过二阶衍射光栅进行横向阵列模式选择的概念，并确认由于光栅仅存在于反导阵列核心中而对光束亮度的增强。然后将开发40个元素的阵列。为了有效地选择横向模式，将使用纵向锥形DBR反射器。对于这种多模态识别的分析，将采用波束传播法。器件将被制造（通过在dbr光栅（反射器）区域使用标准光刻和湿化学蚀刻）。

What is proposed is the study and use of periodic dielectric structures with modulated optical gain, so called active photonic lattices (APLs), for the realization of watt-range coherent, surface-emitted powers from two-dimensional (2-D) horizontal-cavity devices with 2nd-order gratings of novel design. In sharp contrast to conventional APLs, the proposed devices have gain in the low-index lattice sites. In turn, long range (coherent) coupling via traveling waves will become possible via resonant leaky-wave coupling between the low-index lattice sites.The proposed 2-D APLs combine antiguided phase-locked arrays with surface emission from 2nd-order DFB/DBR grating structures. Unlike all previously reported 2nd-order grating DFB surface emitters, the proposed structures employ central grating phase shifts of around pi, which insure emission in an orthonormal, single-lobe beam at no penalty in device efficiency. In addition, the grating structure, besides insuring single-longitudinal-mode operation, will act as a highly effective selector of a single lateral mode: the in-phase array mode. As a consequence large-aperture (200mm x 1200mm) coherent sources of nearly uniform 2-D guided-field profiles will be capable to operate in a stable, single diffraction-limited beam to watt-range CW output powers.First, a Bloch-function model will be developed for analyzing the proposed 2-D APL-type device. Then, upon applying the model for device-design optimization, the device structure will be fabricated by metal-organic chemical vapor deposition, followed by grating fabrication via holographic interferometry and wet chemical etching. To create the necessary grating p phase shift, a dual-tone photoresist will be used. To create the phase-locked array (in the lateral direction), narrow periodic trenches will be etched into the top surface, and then high-index material (GaAs) will be regrown as to provide an antiguided array. After depositing the necessary metallization on the device p-side, a stripe window will be created in the device n-side metallization, to allow 1st-order diffracted light to be emitted in a direction normal to the laser-chip surface.Initial work will be done on 20-element arrays to prove the concept of lateral-array-mode selection via the 2nd-order diffraction grating as well as to confirm enhancement in beam brightness due to the grating existence only in the antiguided-array cores. 40-element arrays will then be developed. For effective lateral-mode selection, longitudinally tapered DBR reflectors will be used. For analysis of such intermodal discrimination the beam-propagation method will be employed. Devices will be fabricated (by using standard photolithrography and wet chemical etching in the DBR-grating (reflector) regions).