This paper presents the design and experimental study of a coupled-cavity laser based on the micromachining technology for wide tuning range and improved spectral purity. The core part of this design utilizes a deep-etched movable parabolic mirror to couple two identical Fabry-Pérot chips and thus allows the active adjustment of the cavity gap so as to optimize the mode selection and to increase the tuning range as well. In experiment, the laser achieves the single longitudinal mode output over 51.3 nm and an average side-mode-suppression ratio of 22 dB when the tuning current varies from 5.7-10.8 mA. The measured wavelength tuning speed is 1.2 micros and the single mode output is stable at any wavelength when the tuning current is varied within +/- 0.06 mA. Compared with the conventional fixed cavity gap coupled-cavity lasers, such design overcomes the phase mismatching and mode instability problems while maintaining the merit of high-speed wavelength tuning using electrical current.

This letter presents a miniature tunable coupled-cavity laser by integrating a Fabry-Pérot chip, a gain chip and a deep-etched parabolic mirror using micromachining technology. The mirror is to actively adjust the gap between chips, enabling the optimal mode selection. Single-mode operation with a tuning range of 16.55 nm and a side-mode-suppression ratio of Ͼ25.1 dB is demonstrated. The device overcomes phase mismatching and instability problems encountered in conventional fixed-gap coupled-cavity lasers.

This paper presents a tunable dual-wavelength laser by integration of a semiconductor gain chip with silicon-micromachined grating and mirrors onto a silicon substrate. The wavelength tuning is demonstrated by rotating the micromirror. With one wavelength being tuned and the other fixed, the laser output presents a tunable spectral separation from −28.38 to + 24.18 nm. The laser output reaches 2.9 mW with far-field divergences of 37°and 30°in the vertical and horizontal directions, respectively. Besides, line broadening is observed with the reduction of the spectral separation.

Moldability is a crucial aspect of flip chip technology. It is an increasing challenge to ensure moldability with rapid advances in flip chip technology such as decreasing bump pitch and stand-off height, especially when commercial molded underfill (MUF) is used and, in particular, during panel level molding. One key challenge faced is severe void entrapment beneath the die. Typically, large DOE matrix experiments are used to address this issue, which require significant time and process resources. 3D flow simulation can be used to optimize the process to reduce defects with a smaller number of actual runs. By correlating theoretical and experimental phenomena, flow simulation enhances the understanding of the complex fluid dynamics during the molding process. 3D flow simulation can assist in widening the process window, which is limited by the inherent machine and material challenges. This can be achieved by prediction of the effect of varying design, material, and process parameters on melt front behavior and void locations. 3D mold flow simulation using Moldex3D V10 is used to optimize the MUF transfer molding on selected flip chip devices. This paper proposes and verifies a systematic flow simulation methodology designed to save computational resources by using a three step analysis. The initial step, simplified panel level simulation, is to optimize the process parameters to obtain a balanced melt front. Next, on the package level, we studied the effect of various parameters. This analysis provides a prediction of the void location and an insight into the appropriate parameters to minimize the void problem. The optimized parameters from the preliminary simulation were used as guidelines. For the second step, a full validation was conducted. A complete full panel-level flow model was built, where the process and design parameters adopted in the actual molding were implemented. The actual void location and size from the experiment were captured by scanning acoustic microscope (SAM) machine and parallel lapping (p-lapping). Short shots were also obtained to study the melt front behavior. The panel mold filling simulations showed good correlation with the experimental short shots and actual void locations. The prediction capability is further enhanced by zooming in to the column level, and this enhanced model was able to predict the other lower risk voids away from the main problem areas. This was correlated with actual CSAM data and p-lapping. The 3D flow simulation enhances the understanding of causes of flow imbalance, void signature, void formation, and the effect of varying bump height, die thickness, mold cap thickness, gate height, die orientation, transfer profile, and mold temperature as potential enhancement measures. With a successful correlation between simulation and process data as shown in this paper, we have demonstrated that mold flow simulation is a reliable tool to effectively reduce the design-to-implementation cycle time, identifying potential key problems during actual fabrication and potential solutions to reduce defects.

This paper presents a digital mirror for tunable laser wavelength selection using microelectromechanical systems (MEMS) technology. The digital mirror which has discrete reflection spectrum is totally different compared to the current broadband mirrors MEMS tunable lasers [1][2][3]. The reflection of the digital mirror can be tuned by digital pumping signals which promise fast output wavelength switching. The experimental results show that the output wavelength of the MEMS tunable laser using the digital mirror has high tuning resolution without increasing the physical length of the internal cavity of the tunable laser. The output wavelength of tuning resolution can reach 0.2 nm and the bandwidth is around 0.04 nm.