Laser Rapid Prototyping In Nonlinear Medium

We have measured the second harmonic generation (SHG) using a 1.06 mu m Q-switched pump beam in powdered nonlinear crystals suspended in a photopolymeric solution. The powdered crystals used include lithium niobate, LiNbO3, and potassium titanyl phosphate. Measurements were made as a function of the grain size and the number of grains per unit volume. The photopolymeric solution is transparent at the pump beam frequency while it is highly absorbing at the SH and it is the SH which transforms the photopolymer from liquid to solid. The results show that relatively intense SH incoherent light is produced in powder after the pump intensity exceeds a certain threshold. SHG does not depend on the grain size up to a critical grain size beyond which SHG falls off rapidly. Furthermore, the emission increases linearly as a function of the number of grains per unit volume and eventually levels off and stays constant. A practical focus of these studies has been in the areas of laser induced rapid prototyping and three dimensional real time image formation. This study clearly demonstrates the application of a nonlinear optical medium in high resolution rapid prototyping. Furthermore, because efficient SHG occurs for very small powder grain size this technique may provide a way of realizing high resolution three dimensional imaging in which the feature size is only a few microns. (C) 2000 American Institute of Physics. [S0021-8979(00)05218-X].