Ultrafast laser and nonlinear crystals for intense terahertz irradiation and vibrational spectroscopy of energetic materials
Abstract
Abstract We are requesting new instrumentation that will enable dramatic enhancement of our unique capabilities for intense THz-driven energetic material decomposition and for observation of the products. The equipment will allow us to reach roughly 10x stronger THz fields than those we can generate currently, spanning a widely expanded THz frequency range. The stronger fields will drastically accelerate the energetic material decomposition that we are studying, very likely yielding significant decomposition in a single laser shot. The instrumentation will also allow greatly improved characterization of the decomposition dynamics and products. The present steady-state and post-mortem measurements will be supplemented with femtosecond stimulated Raman and infrared spectroscopy for direct measurement of the disappearance of initially present molecular vibrational features and the appearance of new features that reveal energy flow and decomposition dynamics and permit identification of intermediate species and long-lived products. The new instrumentation is based on an upgrade to our amplified femtosecond laser system that will almost double its output 800-nm pulse energy, from 7.5 mJ to 12 mJ. Most of the pulse energy will be used to pump a high-power optical parametric amplifier (OPA) for generating near-IR femtosecond pulses with several mJ pulse energies. The near-IR pulses will be used for generation of intense THz pulses in newly available organic nonlinear optical crystals OH1 and DSTMS. These will produce THz pulses with peak fields of up to 5 MV/cm Ñ a nearly tenfold improvement on our current field strengths Ñ in the 0.2-7 THz frequency range, which substantially exceeds our current 0.2-2 THz range. With far greater induced decomposition, we will be able to monitor the products through femtosecond IR (generated using a differencefrequency mixing module) and stimulated Raman spectroscopy on a shot-by-shot basis, unlike our current conditions in which a great many laser shots are needed to produce measurable effects.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 22, 2016
- Source ID
- N000141512879
Entities
People
- Keith A. Nelson
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy