Invention:
This technology is a novel technique for monitoring the diffraction efficiency of Volume Holographic Elements (VHOEs) in real time. The technique works by using a shutter or chopper to periodically block one of the exposing beams during the fabrication and measuring the power of the diffracted beam using a power meter. This technique has the potential for a higher accuracy calculation of the diffraction efficiency of VHOEs at a greater simplicity.
Background:
Volume Holographic Elements (VHOEs) have many applications ranging from display systems, medical devices, and solar energy systems. An important characteristic of VHOEs is diffraction efficiency, which measures how much power is diffracted into a designated direction compared to the power incident onto the diffractive element. Most VHOEs much attain a certain diffraction efficiency; in many designs, the diffraction efficiency should be maximized while in others, the diffraction efficiency is intentionally a lower value. The most common method of controlling the diffraction efficiency is to characterize the holographic material’s diffraction efficiency as a function of exposure energy by fabricating a set of holograms with different exposure energies and measuring the diffraction efficiency of each, with the hologram most closely matching the design constraint used to fabricate the desired VHOE. Another method uses additional equipment and complicated experimental setups to measure the diffraction efficiency by shining light from a separate laser at the construction wavelength from the VHOE. This technique, which works by using a shutter or chopper to periodically block one of the exposing beams during the fabrication and measuring the power of the diffracted beam using a power meter, can calculate the diffraction efficiency at a higher accuracy at a greater simplicity. The calculations are performed in real time, meaning the technique has the potential to account for local variations in the material or laser power that causes the necessary exposure time to fluctuate between samples, which allows for a more precise reading of the diffraction efficiency. This technique is particularly useful for VHOEs used in display systems where precise diffusion efficiency needs to be attained.
Applications:
- Precisely calculates the diffusion efficiency of VHOEs
Advantages:
- More precise that current methods
- Less additional equipment is needed
