講演情報
[15p-P04-4]Sub-Cycle MIR Pulse Stabilization by Application of Electric Field on the Laser Filament
〇(PC)Neil Irvin Cabello1, Shuto Nakamura1, Takao Fuji1 (1.Toyota Tech. Inst.)
キーワード：
ultrafast phenomenon、nonlinear optical processes、mid-infrared
In imaging systems, the stability of the light source is a critical parameter for obtaining high-quality images. In our previous work, we utilized mid-infrared (MIR) sub-cycle pulses generated by filamentation as the light source for MIR hyperspectral imaging. While the MIR radiation generated by filamentation is broadband and intense, jitters can occur in the millisecond range due to the plasma recombination inherent in filamentation at kHz repetition rates. These jitters can manifest in the acquired hyperspectral images, necessitating multiple data acquisitions to minimize their effects. In a recent study done by Liu et al., the application of a strong electric field suppresses these plasma recombinations, and consequently helps stabilize the laser filament based on direct measurements on the filament itself. In this work, we similarly utilize the application of a strong electric field onto the laser filament to stabilize the generated MIR sub-cycle pulses. The MIR generation scheme is identical to our previous work, with the addition of an electrode situated 5 mm above the laser filament. High voltage is applied onto the electrode, which consequently applies an electric field onto the filament. Direct MIR intensity measurements by MCT detector showed an improvement of the stability from ~7% at no voltage to ~2% with applied voltage. Chirped-pulse upconversion by four-wave difference frequency generation (FWDFG) in CaF2 was performed to characterize the MIR pulses (1/λMIR = 2/λref - 1/λFWDFG). The upconverted spectrum was observed to have a slightly increased intensity when 2.5 kV of voltage was applied on the electrode. More importantly, the intensity stability throughout the whole spectral range was observed to improve with the application of the voltage.