Diamond-Based High-Power Optical Components
Abstract
Many high-energy and high-power laser applications (e.g. medical, industrial, military) depend crucially on the availability of reliable optical components, including optical windows, mirrors, filters, and polarizers. For example, high-transmittance optical windows are used in conjunction with high power lasers either as windows into vacuum systems or as a part of the laser output facets themselves. Similarly, high-reflectivity mirrors are used to steer high-power laser beams or to reliably and efficiently combine optical beams from multiple laser sources thus further increasing the available power. Both mirror and window functionalities are currently implemented as stacks of thin dielectric films deposited on high-quality substrates. Unfortunately, even the smallest imperfections in these films form sites where laser energy can be absorbed, thus generating a tremendous amount of heat. This causes local melting or extreme thermal stress in the stack, thus degrading the performance of the mirror. To address this, we will develop a line of high-power optical components made completely from diamond. Diamond is a natural choice for high-power optics applications due to its extremely broad transmission spectrum, low absorption, chemical inertness, mechanical strength, and the highest room temperature thermal conductivity of any material. By nano-structuring the diamond surface the optical properties can be engineered, while maintaining the advantages of high thermal conductivity bulk diamonds provide. These so called meta-surfaces are implemented as planar arrays of sub-wavelength diamond nano-structures (cones in the case of an optical window and hourglass shaped pillars in the case of a mirror) that feature optical resonances with engineered spectral and polarization response. Using this concept, we will develop three main high-power optical components: i) high transmission optical windows that take advantage of anti-reflective meta-surfaces (ARMS), ii) high reflectivity meta-surface (HiReMS) mirrors, and iii) optical filters. Owing to their monolithic nature, we expect our devices to be less susceptible to both stress-related problems (e.g. delamination) and thermally-induced failure mechanisms that are inherent to thin-film based optics. We have already demonstrated all-diamond mirrors that feature reflectivity of R = 99.3% (experiment), which is comparable to commercial dielectric thin-film based product (R > 99.9). Importantly, our diamond HiReMS mirrors already outperform conventional thin-film based mirrors when it comes to the amount of power that they can handle: laser-induced damage threshold (LIDT) of our mirrors is nearly two orders of magnitude better than the commercial (250 MW/cm for diamond mirror, versus 5 MW/cm2 for thin-film based mirror) Therefore, we believe that our monolithic all-diamond components will be very robust and never need to be replaced, which ensures consistent device productivity and uninterrupted function of the application. Maintenance and downtown are all but eliminated.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2017
- Source ID
- W911NF1710226
Entities
People
- Marko Loncar
Organizations
- Army Contracting Command
- Harvard University
- Office of the Secretary of Defense