W. Hudson Welch

Injection molding for diffractive optics

Diffractive optics is becoming a standard part of the optical designers toolkit. The transition from design to manufacturing, especially for elements larger than a few millimeters in diameter, has been impeded by the relatively high cost of producing diffractive elements by standard photolithographic means. Replications techniques, such as injection molding, have the potential to significantly lower the cost for such elements. We report on results of the application of injection molding techniques to the replication of diffractive elements. Several examples of diffractives fabricated by these techniques, as well as present process capability, are discussed.

Achromatic diffractive optics for laser diodes and fiber optic coupling

The design and fabrication of a low cost laser diode to fiber optic coupler is discussed. A single diffractive optical element was used to provide uniform coupling efficiency over a 40 nm bandwidth. The element was optimized to maintain constant coupling efficiency with small tilts and decenters. An iterative method referred to as radially symmetric iterative discrete on-axis (RSIDO) encoding was used to determine optimum fringe placement and profile.

Diffractive optics for head-mounted displays

Diffractive optics have the potential to play a key role in several areas of head mounted displays. They can reduce size and weight while providing some unique optical functions that would be difficult to implement with conventional refractives. There are four areas in which diffractive optics may contribute: Magnifier optics, combiner optics, head and hand tracking, and optical data interface. This paper is primarily concerned with the introduction of a new image combiner element based on Babinets principle.

Diffractive optics for photonic packaging of laser diodes and fiber optics

Diffractive optical elements (DOEs) have many advantages over refractive optical elements including the ability to implement exotic function (such as flat-tops, line generators and splitting and combining functions), the ability to easily incorporate a variety of functions in to one element, lower volume and less weight. In addition to these advantages, diffractives offer 3 potential positive characteristics which are sometimes cited as drawbacks. These are: diffraction efficiency, dispersion and cost. In some applications, such as wavelength division multiplexing (WDM) or other applications in which it is desirable for different wavelengths of light to be affected in different manners, the highly dispersive nature of diffractives is an advantage. In other applications when the spectral width of the illumination is large (e.g. laser diodes when the case temperature varies over a wide range), the dispersion of DOEs can be a disadvantage. Diffraction efficiency, defined as the power diffracted into the desired diffraction order divided by the power incident on the DOE, can be very high or low depending on the application and design procedure. This paper focuses on these 3 potential advantages of diffractives. In the remainder of this paper each characteristic is discussed individually in order to show how the negative effects of each can be minimized and the positive effects enhanced.

Injection molding of binary optical elements

Binary optical elements are finding increased use in a wide range of applications. Fabrication of binary optical elements generally remains a time consuming and expensive process. Even in high volume, costs can be prohibitive, especially for elements larger than a few millimeters in diameter. Replications techniques, such as injection molding, have recently begun to show promise as a means of manufacturing binary optical elements, and doing so at a significant cost reduction over conventional photolithographic means. We report on recent improvements in the application of injection molding techniques to the replication of binary optical elements. Several examples of binary elements fabricated by these techniques, as well as present process capability, will be discussed.