应用微波技术实现纳米精度微光学对准和实时粘合

本文讨论纳米精确度光学对准技术，以用于采用热固化树脂的微光学包装。为了达到一个快速固化过程，直接将微波能量作用于需要进行光学粘合的地方。然而常规微波加热技术，依赖于树脂和元件之间的高质量比。为了改进微光学包装中微量粘合剂的热吸收率，我们先将接合面抛光，再镀上金属薄层。这样一来，微波能量将被镀层快速吸收。为防止接合面过热，采用一个红外（IR）温度传感器，以监测粘合剂的温度。根据温度的高低，一个自动化的系统则可以调整微波的功率输出，以便达到相对恒定的固化温度。在快速固化过程中，预先调准好的微光系统，如光纤耦合器，将由于加热的不均匀性而不可避免地遭受干扰。为补偿这个副效应，开发了一个实时光学对准监控和反馈系统。以包装光纤耦合器为例，该系统可实时监测当粘舍剂由微波固化时器件的插入损失（IL）。我们采用的一种三维压电变换装置（PZT）可达到x-、y-和z-方向的的对准。该PZT的10nm调节精度可监测出0．004dB的IL敏感性。与常规的固化烤箱比较，该系统的微光学包装效率可提高150倍。由于采用实时监控和反馈系统，批量生产中产品的合格率也将大大改善。

Micro Optics Alignment with Nanometer Precision and Real-Time Bonding Using Microwave Technology

This paper discusses a nanometer level precision alignment technique as applied to highly efficient micro optics packaging using heat curable adhesives. To achieve a fast curing process, we deposit microwave energy to the spot where optical bonding is desired. Conventional microwave heating technique, however, as we know it, relies on large mass ratio between the epoxy and the components to be bonded. In order to improve the efficiency of heat absorption by the tiny amount of adhesive used for micro optics packaging, we pre-process the components to be bonded, by first polishing the bonding surfaces and then depositing a very thin layer of metalized film on them. An infrared (IR) remote temperature sensor is utilized to monitor the temperature of the adhesive (to prevent over heating). An automated system can then adjust the power output of the microwave so that a fairly constant curing temperature can be maintained. During the fast curing process, pre-alignment of micro optics, such as fiber optic coupler, will inevitably suffer minor misalignment due to non-uniform heating of the components. To compensate for this side-effect, we have developed a real time alignment monitoring and feedback controlled system. As an example to packaging fiber couplers, such a system can monitor the insertion loss (IL) of a component in real time while the adhesive is being cured by the microwave energy. A 3-dimensional piezo-electric transducer (PZT) is employed to achieve the x-, y-, and z-axis alignment. A level of 10 nanometer alignment can be readily achieved which in turn leads to an IL sensitivity of as small as 0.004dB. An improvement of a packaging efficiency as high as 150 times has been demonstrated, compared to conventional blind oven curing process. Yield of micro optics packaging is also expected to increase due to the use of real time alignment process.