High-Temperature Vacuum Probing and Phase Noise Measurement for Advanced RF-GHz MEMS Resonators and Oscillators
Abstract
Directed energy (DE) systems may aim sources and perform imaging across multiple spectral bands, for example, 1.07 Ohm for the high energy laser (HEL), and longer wavelengths for the beacon illuminator (BIL) and tracking illuminator (TIL). Further, some of these bands may utilize long-pulse operation with high peak powers and a substantial spectral width to support imaging (e.g. TIL), which complicates the design of all of the optics and coatings involved in the DE system fabrication. The wavefronts in all bands must maintain high phase purity so that target images and laser spots have the highest resolution possible. However, DE adaptive optics (AO) typically sense wavefronts at a single wavelength and correct accordingly. If there are propagation differences between wavelengths through the optical system, the AO correction may be in error. There are multiple possible sources of this wavelength dependence including thermal expansion within the system, which will induce different phase shifts at different wavelengths, and atmospheric propagation, absorption, and turbulence differences. However, perhaps the most wavelength critical portion of the system involves the many multilayer optical coatings that sources must reflect off or pass through in order to exit the system and reach the target. A constant phase offset between widely separated wavelengths in an AO system will have no impact on the correction; however, differences in the phase variation across an optic at different wavelengths will have major impacts. Multilayer optical coatings inherently have phase variations across a coated optic that vary with wavelength, angle of incidence, thickness, and temperature. It is the goal of this program to investigate and quantify these dependences and to develop optical coating design techniques that minimize them.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 05, 2025
- Source ID
- FA95502410032
Entities
People
- Philip X-L Feng
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Florida