Damage Measurements on Optical Materials for Use in High-Peak-Power Lasers

Defense application for a chemical oxygen laser (COL) is explained. Although a COL has not yet been successful in lasing, the oscillator was estimated to produce a giant pulse with the full width at half maximum (FWHM) of ~0.05ms which makes the damage threshold for the mirrors several-order higher than that for a typical solid-state laser with a ~10ns pulse width. Therefore it has a potential to produce MJ class output considering the simple scalability of being a chemical laser. Since within 0.05ms a supersonic aircraft can move only a few centimeters which is roughly equal to the spot size of the focused beam at ~10km away using a large-diameter focusing mirror, a COL has a potential to make a damage to an enemy aircraft by a single shot without beam tracking. But since the extracted beam can propagate up to a few kilometers due to the absorption in the air, it may be suitable to use in space. While a chemical oxygen-iodine laser (COIL) can give a pulsed output with a width of ~2 ms using a high-pressure singlet oxygen generator (SOG). Therefore a pulsed COIL may also not require beam tracking if a target aircraft is approaching. Another advantage for these pulsed high-energy lasers (HELs) is that, in case of propagating in cloud or fog, much less energy is required for a laser for aerosol vaporization (LAV) than that of a LAV for a CW HEL. Considerations to use a COL as a directed energy weapon (DEW) in a point defense system are shown.

“…14) Since excellent high-reflectivity mirrors have a LIDT of ~190J/cm 2 at 1064nm with 10ns, 15) the LIDT at 1.27μm with the pulse width of 0.05ms is estimated to be 4-15kJ/cm 2 .…”

Section: Introductionmentioning

confidence: 99%

Proposal of a defense application for a chemical oxygen laser

Takehisa¹

2015

“…While the relationship between structural defects and laser induced damage in optical coatings has been generally established [1][2][3], the exact nature of the interaction between laser light and defects is still not resolved. It has been commonly accepted that laser damage can occur at peaks in the standing wave of the electric field [4], which results in initiation events such as ionization, particle emission, or bond breakage.…”

Section: Introductionmentioning

confidence: 99%

<title>Enhancement factors for local electric fields in inhomogeneous media</title>

Ferris

Risser

1995

The microstructure of dielectric films provides a significant influence on the electric field distribution in these materials. In this paper, we focus on the relationship between the electric field distribution and organization of film constituents. Using our self-consistent determination of the local electric field in inhomogeneous media, we have shown that enhanced fields can result from columnar microstructures such as typically generated by CVD-type fabrication processes, and low dielectric components in optical coatings. In addition to the microstructural enhancement, a surface specific enhancement due to presence of low dielectric components is observed.

“…Even in ideal situations, both voided volumes and structural defects are introduced in the fabrication process, and have been suggested to play important roles in film damage mechanisms [3]. These structural details also affect the determination of optical properties.…”

Section: Introductionmentioning

confidence: 99%

Defect-induced variations in the local electric fields in inhomogeneous media

Ferris

Risser

1993

Using a finite element representation of a dielectric film, we have examined the effects of surface defects on the local electric field and its intensity. Surface defects possess the potential to affect the local electric fields in a dielectric film in a manner similar to those introduced in the bulk solid. Both raised and removed regions tend to focus the electric field vector about the defect, and the interaction of two defects can lead to an enhanced local electric field intensity. In these cases, effective medium methods would approximate the film by an idealized defect-free structure, and thus would not note the sensitivity of the electric field to surface structure.