Experimental Set Up
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Note: High Performance Black Masking Tape was used to cover metal which might reflect laser light. A MFF101 Motorized Flipper with an empty LMR05 is not being used.
Engineered Diffusers are designed to create non-Gaussian intensity distributions in cicular or square beam profiles that diverge from the plane of incidence. The Graphs tab on this page has both theoretical approximations of the intensity through the center of the diverging beam profile when illuminating the engineered diffusers with a 633 nm collimated beam and data compiled from independent tests with laser wavelengths of 488 nm, 637 nm, 785 nm, and 1064 nm. These tests demonstrate the change in output profile with wavelength between diffusers across wavelengths.
Four wavelenghts of light were chosen for study: 488 nm, 637 nm, 785 nm, and 1064 nm. These were prepared using the equipment to the right (a full list of all parts used can be found under the photo of the Experimental Set Up). The optical path was approximately 35 cm above the surface of the breadboard; it began when fiber-coupled light sources were collimated with triplet collimators, using a design wavelength as close to the source wavelength as possible. In free space, the beams were incident upon one of the Engineered Diffusers. The exiting divergent profile was isolated and focused by an with an LA1304 plano-convex lens attached to an SM05L20 lens tube. The signal was sampled every 0.5° by a SM05PD1A photodiode. This assembly was mounted on the end of an XT34-500 rail. The opposite end of the rail was mounted to a NR360S rotation stage centered with the engineered diffuser under test in order to sweep the detector and lens assembly through the center of the profile, as illustrated in the diagram to the upper right, and plot normalized intensity versus output angle. The distance between the diffuser and the detector was approximately 43 cm. The output angle was defined with respect to the original optical axis when the diffuser was not within the path. In order to control for ambient light, a 1 kHz sine wave was used to modulate the drive current applied to the laser diode and the signal was acquired with a lock-in amplifier. A LabVIEW program was written to control the setup and acquire the data.
Only one of each Item # was testeda. Stability may have been compromised by the experiment being performed on a PBG11113b breadboard without any isolation. Only the middle of each diffuse shape was measured, so variances in other areas of the shape are possible, including the corners of the square profiles.
It was found that there was little variance in diffuse beam profile with respect to wavelength across the middle of each beam profile. In the Graphs tab, there are data compiled from independent tests with various laser wavelengths to verify the theoretical models. The same graphs can be found in the table below.
Circular Pattern Diffusers Transmitted Intensity Plots
Square Pattern Diffusers Transmitted Intensity Plots
Line Pattern Diffuser Transmitted Intensity Plot
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Theoretical Data for ED1-L4100