Merging compound semiconductor technology
with precision optics
High-reflectivity optical coatings are key components in a wide variety of laser-based applications. With continued advancement in laser performance, state-of-the-art optical coatings have now become a major limitation, particularly in the areas of laser-based manufacturing and precision optical metrology and instrumentation.
Substrate-transferred crystalline coatings represent a game-changing technology that enables the integration of single-crystal films onto arbitrary, including curved, optical substrates. For the first time, the unique properties of monocrystalline semiconductor materials can be exploited for the construction of high-performance laser optics. This technological breakthrough enables new performance metrics for existing optical systems, as well as enabling the development of radically new application areas in communications, sensing, and manufacturing.
The merger of advanced microfabrication techniques with bulk optical technology has culminated in the development of “Semiconductor Supermirrors” with 3 key performance advantages:
measurements of space and time
Ultra-precise measurements of space and time
With our proprietary crystalline coating technology, we can construct optical cavities capable of significantly improved thermal noise performance. Mirror assemblies produced with our Semiconductor Supermirrors offer up to a 10x reduction in thermo-mechanical (i.e., Brownian) noise compared to current state-of-the-art technology. We have demonstrated this unique thermal noise performance in collaboration with the Ye group at NIST/JILA (1). This substantial reduction in thermal fluctuations enables a significant improvement in the overall frequency stability of optical reference cavities, pushing the ultimate limits of linewidth and noise performance that can be achieved in stabilized laser systems. These results represent a long-awaited breakthrough for the precision measurement community. There are presently no viable alternatives that can achieve such low levels of thermal noise, while maintaining sufficient optical performance.
in trace gas sensing
High resolution in trace gas sensing
IBS-deposited dielectric multilayers have been the most commonly used materials systems for low-loss mirrors in the NIR. One major limitation for these materials is significant levels of optical absorption for wavelengths beyond ~2 μm, which excludes operation of such low-loss reflectors in the mid-infrared (MIR). Compared to typical dielectric materials, GaAs/AlGaAs-based DBRs can achieve much lower optical losses in the important spectral mid-IR region between 2 and 5 μm, with absorption losses below 10 ppm. In first tests using substrate-transferred semiconductor materials, performed in the Ye group at JILA/NIST, a cavity with a finesse exceeding 10,000 was demonstrated, while simultaneously exhibiting a cavity reflection contrast of 71%.
for high-power lasers
High thermal conductivity for high-power lasers
High-power lasers, employed in a large number of industrial applications, are limited by the unavoidable residual absorption of the reflective optics. The low thermal conductivity of IBS coatings (on the order of 1 W/(m*K)) limits the effectiveness of any heat sink solution and attempts to avoid heat-induced structural damage in both the coating and laser system. GaAs/AlGaAs DBRs exhibit a thermal conductivity at least 30x greater than traditional sputtered coatings. This significant performance improvement makes substrate-transferred crystalline coatings an ideal choice for optical systems requiring superior thermal management for operation in harsh environments. Additionally, our direct bonding process allows for the integration of the DBR onto arbitrary substrates, including high-performance SiC or diamond materials.
Coating and Production Technology
Using Molecular Beam Epitaxy (MBE), we deposit high purity and low defect density single-crystal GaAs/AlGaAs multilayers, generating an optical interference coating with an engineered reflectivity that is typically greater than 99.99%. In the near-IR, scattering + absorption losses can be <5 ppm. The coating can be precisely defined in any arbitrary shape using semiconductor process technology and then removed from the GaAs growth wafer as a precursor to direct bonding.
Our experience and proprietary direct bonding process enables dissimilar materials to be permanently bonded with no interlayers or solders. The result: The best mirror possible on the ideal substrate.