Pioneering 100-kHz Laser Diagnostics for Hypersonic Velocity and Non-Equilibrium Temperature

Hypersonic systems offer transformative capabilities for defense and aerospace, but extreme flight conditions—dominated by strong shocks, turbulence, and high-temperature chemistry—pose significant challenges. A key obstacle in hypersonic research is the lack of high-speed, non-intrusive diagnostics capable of capturing velocity and non-equilibrium temperature fluctuations at 100 kHz rates. Existing techniques lack the resolution and repetition rate necessary for turbulence and chemical kinetics characterization, hindering accurate computational modeling and material performance predictions.To address this, Spectral Energies, LLC (SE), in collaboration with Dr. Terry Meyer and Dr. Joseph Jewell at Purdue University (PU), proposes a 100 kHz all-in-one laser diagnostic system for simultaneous velocity and non-equilibrium temperature measurements in hypersonic flows. This system integrates femtosecond laser electronic excitation tagging (FLEET) for high-resolution velocity measurements and hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (CARS) for rotational and vibrational temperature diagnostics. Phase I wind tunnel demonstrations at PU will validate the feasibility of the system under representative hypersonic conditions.Key innovations include a fully integrated 100 kHz laser architecture, optimized probe pulse generation for enhanced signal sensitivity, and time-resolved temperature fitting for accurate diagnostics. Phase I will demonstrate non-simultaneous FLEET and CARS at 100 kHz using a rented femtosecond amplifier to establish system feasibility. In Phase II, SE will augment a commercial 80 W femtosecond system with high-energy SE-built amplifiers, ensuring sufficient pulse energy for simultaneous velocity and temperature diagnostics. This system will provide the DoD with the first continuous 100 kHz diagnostic tool for turbulence and chemical kinetics in hypersonic ground-test facilities, advancing computational model validation, vehicle design optimization, and next-generation hypersonic technology development.