Absorption of 1535-nm Laser Pulses in Insulating Oils

The Applied Pulsed Energy, Ionization, and Discharge Center (APERIODIC) research group at The University of New Mexico, Albuquerque, NM, USA, has been investigating the use of low-energy diode-pumped solid-state (DPSS) passively q-switched lasers operating at a wavelength of 1535 nm to trigger gas switches. This wavelength was chosen due to the improved eye safety and ready supply of commercial microlasers at this wavelength. Laser triggering of switches in a pulsed power system often presents challenges in beam transport from the laser to the switch optics. In many cases, it is most convenient if the beam transport can be accomplished directly through the insulating medium of the device. It is also possible that this laser wavelength could be used to trigger an oil-insulated spark gap switch. Thus, the absorption of the laser wavelength in insulating oils is of interest. In this work, the absorption coefficient of the 1535-nm laser pulses has been measured for various common insulating oils. The results indicate that beam transport through oil at this wavelength will likely be impractical due to relatively high absorption. However, the absorption is low enough that the use of this wavelength to trigger an oil-insulated gap could be possible.