A new type of laser beam homogenizer has been developed which “field-maps” an illumination by using spherical, cylindrical, axicon or prism optical segments, or in some applications combination of these various elements, and placing the optical segments in a configuration whereby light passing through each optical segment directs the light to overlap at a homogenized plane with the desired shape (rectangle, square, rectangular or circular ring illumination). The geometry of the homogenized field is limited only by the fabrication techniques used in segmenting and how the segments are physically arranged. This optical concept could be called a Fresnel Homogenizer as it functions like a Fresnel lens. Fabricated in its basic form from spherical or cylindrical lenses, the lenses can be either negative or positive, depending upon the type of illumination, size and numerical aperture required. Typical fly’s eye homogenizers require 5 optical elements this new homogenizer is comprised of a single element; thereby significantly reducing the losses in the system due to diffraction and reflectance.

A new laser beam homogenizer has been developed which converts a highly spatial coherent, Gaussian laser beam into a collimated, square homogenized field. The optical device converts a laser’s Gaussian input beam through multiplexing and recombination without optical interference and yet is collimated over > 5 meters. Laser beam property variations do not adversely affect the performance of the homogenizer in contrast to phase shifting homogenizers and can be utilized from the laser’s objective lens’ entrance pupil to its focus while maintaining the relative degree of homogenization. The degree of homogenization is limited only by diffraction effects and the input diameter of the laser beam.

Athermalization of focusing objectives is a common technique for optimizing imaging systems in infrared where thermal effects are a major concern. The athermalization is generally done within the spectrum of interest and not generally applied to a single wavelength. By applying athermalization techniques to a laser system, a significant reduction in thermal lensing of the laser system can be realized. We describe a passive method minimizing thermal lensing of high power lasers.

An effort was under taken to mitigate thermal lensing and have an easy and compact means of monitoring thermal lensing in a high power laser system. Utilizing the negative temperature coefficient of refractive index in CaF2 with the nearly opposing positive temperature coefficient of refractive index in SiO2, a multi-element focusing objective was fabricated to reduce the amount of thermal lensing experienced with a multi-kilowatt, cw fiber laser. In addition, an all-passive optical design beam analyzer was developed to accurately measure the focus shift of an all SiO2 lens objective in contrast to the CaF2/SiO2 multi-element lens to compare their perspective thermal lensing values.