Design of athermalized proximity coupled (APC) synthetic green laser opto-electronic package for microprojector displays: Numerical modeling and experiments

Micro-projector based displays are proposed for information display for a number of consumer devices. These displays would provide larger images than existing fixed Liquid crystal displays. The two major components of micro-projector technology are the Light source and the Imaging technology. Three primary colors, red, blue and green are required to create full color images. The light sources in the projection technology would be semiconductor devices that emit these colors. These devices could be either light emitting diodes (LEDs) or lasers. To enable the laser based projection technology, red and blue lasers are commerically available. Native semiconductor green lasers are still in development. As an alternative, synthetic green light can be produced by passing 1060nm infra-red light emitted from a GaAs based semiconductor laser diode (LD) through second harmonic generation (SHG) crystal, thereby emitting the green light at 530 nm. The current research work proposes bringing the SHG structure in close proximity to the LD, thereby eliminating the use of any optics in between. The proximity coupling approach promises to reduce the number of package components and process cost significantly. This paper presents the mechanical package design, coefficient of thermal expansion based displacement estimates, thermal analysis wherein the thermal impedance is predicted and measured, thermo-mechanical analysis wherein the thermo-mechanical stresses and strains are predicted. Shock modeling has been done to understand the displacements of the waveguides during the shock event. Optical modeling is performed to estimate the coupling efficiency change as a function of lateral and longitudinal offset between the LD and SHG waveguides. Finally, an assembled package that generated green light using this design is presented.