Reaching Atomic-level Precision: on G&H’s Custom Superpolished Optics

What is Superpolishing?

Superpolishing is a highly specialized optical finishing process that achieves an exceptional level of surface smoothness, with roughness lower than 1 Å (angstrom). This eliminates imperfections that cause scatter, minimizes optical losses, and ensures the highest possible performance in demanding applications. Unlike traditional polishing techniques, superpolishing refines the surface at the nanometer level, producing optically flawless components suited for extreme precision requirements.

At G&H (LON:GHH), we have developed manufacturing processes that cater to the most stringent performance specifications, based on our optics-focused legacy. Our superpolished elements adhere to quality parameters such as:

• Surface roughness below 1Å RMS for ultra-low scatter;
• Scratch/dig quality with zero defect in clear aperture;
• Surface accuracy of 1/20th wave Peak-to-Valley (PV);
• Optical contacting of superpolished surfaces - High surface quality and accuracy create opportunities for optically contacting high bond strength of pristine surfaces;
• 160x magnification inspection to ensure defect-free optics, which can go up to 300x magnification inspection on request;
• High laser damage threshold (LIDT) performance for demanding applications.

A key performance indicator for our products represents their reduced scattering loss. G&H’s proprietary superpolishing process eliminates localized scattering that could degrade optical performance. This ensures maximum clarity, precision, and reliability in applications where even the slightest imperfections can lead to inefficiencies or failures. For example, in high-energy laser systems, surface defects can absorb energy, leading to thermal damage that can be literally explosive. With G&H superpolished optical components in place, not only is the system performing to its maximum capacity, but it is first and foremost safe to use.

Ring Laser Gyroscopes (RLGs)

One of the most prominent applications of superpolished optics is in ring laser gyroscopes (RLGs), which are essential for inertial navigation systems in aircraft, spacecraft, and military applications. G&H has been a premier supplier of RLG optics for decades, providing flat and curved mirror substrates with surface roughness better than 1Å RMS. The high reflectivity of these mirrors, enhanced by ion beam sputtered coatings with reflectivity exceeding 99.998%, ensures optimal system accuracy and stability.

Additionally, G&H manufactures precision-machined RLG frames and mirror mounts, beam combiners, and prisms, all optimized for low scatter and high-performance navigation. G&H’s ability to provide turnkey RLG optical solutions, including polishing, coating, and optical contacting, makes us the preferred partner for major aerospace and defense contractors.

Synchrotron and X-ray Mirrors

In the field of synchrotron and X-ray optics, superpolished mirrors are indispensable for research facilities requiring extreme precision and ultra-low roughness surfaces. These optics are critical in beamline applications, where any surface imperfections can distort measurements and reduce the efficiency of experiments.

G&H produces high-performance silicon and fused silica mirrors, polished to sub-angstrom roughness, ensuring the lowest possible scatter. We also excel in fabricating precision-tapered mirrors, shaped to accommodate complex beamline geometries. G&H rigorously tests its optics to ensure they maintain stability and durability even in extreme conditions.

Our custom optics have enabled scientists to achieve prize-winning results in LIGO, NASA's Mars Curiosity Sky Crane, and in synchrotron facilities around the world.

Telecom Optics: Ultra-Thin Wafer Manufacturing

G&H also plays a crucial role in the telecommunications industry, where low loss optics are vital for efficient fiber-optic communication systems. Superpolished wafers, featuring total thickness variation (TTV) of less than 12nm, are used in tunable lasers and high-precision beam splitters. Depending on the application, it is best for the wafer polishing process to hit an absolute thickness target with a roughly +/- 75 nm tolerance for yield and reliability purposes.

In wavelength-division multiplexing (WDM) systems, where minimizing signal loss is essential, G&H’s polished etalons, beam combiners, and mirrors ensure high channel integrity and minimal interference. The ability to manufacture custom free spectral range (FSR) values up to 400GHz makes G&H a trusted partner for cutting-edge photonic technology development.

Short Radius of Curvature (SROC) Optics

Short radius of curvature optics present unique manufacturing challenges due to their steep curvature and stringent precision requirements. G&H has mastered the fabrication of SROC optics with extreme accuracy, ensuring surface roughness below 1Å RMS. These optics are critical in ultrafast laser research, high-energy laser cavities, and advanced precision metrology instruments.

The steep curvature of these optics places unique demands on polishing techniques and metrology verification, but G&H’s expertise ensures they meet the highest performance standards. With polished or acid-etched bevels, these components maintain enhanced durability and cleanliness, making them ideal for high-power laser applications.

Research-Grade Mirror Substrates

For research-grade mirror substrates, G&H delivers optics that set the industry standard for precision. Flat and concave superpolished mirrors, designed for high-precision interferometry and quantum optics experiments, undergo rigorous surface verification using advanced metrology tools such as Zygo NexView NX2 and cavity ring-down spectroscopy (CRDS).

These mirrors, produced in fused silica, silicon, and Zerodur®, provide unmatched reflectivity, minimal scatter, and exceptional durability, making them the preferred choice for scientific applications where optical performance cannot be compromised.

Innovation in Metrology and Coatings

To maintain the highest levels of quality and consistency, G&H invests heavily in state-of-the-art metrology and coating technologies, such as:

• Zygo NexView NX2 with objectives of 2.75x, 10x, 100x (0.5x, 1x, 2x zooms), with a non-contact surface profiler, provides surface roughness measurements at the sub-angstrom scale;
• Zygo Verifier Laser Interferometers (18 inch and 4-inch systems with option to be converted to a 6-inch) facilitate fast and precise surface form and flatness measurements;
• Cavity Ring Down Spectroscopy (CRDS) ensures ultra-low loss coatings with reflectivity exceeding 99.999%;
• Ion Beam Sputtering (IBS) coatings provide high-reflectivity, low-loss optical coatings that maintain superior abrasion and climate resistance;
• Advanced environmental testing simulates real-world conditions, ensuring that G&H optics retain their performance under extreme humidity, temperature fluctuations, and mechanical stress.

All final measurements, optical contacting, and packaging are done in a Class 100 Cleanroom environment, providing the highest safeguarding standard for end products.

Excellence in High-Volume Production and Industry Leadership

G&H’s superpolishing processes are designed to accommodate both high-volume production and low-volume specialized research and development requirements. Our AS9100-certified facilities uphold strict quality control measures, ensuring repeatability and precision across large production runs. At G&H Moorpark, we have the capacity to produce thousands of superpolished optics per week, with diameters ranging from 5 to 200 mm. While we excel in superpolishing, our capabilities extend beyond this, allowing us to address other precision optical requirements tailored to our customers' needs.

G&H Moorpark, formerly known as General Optics, has a long-standing heritage in manufacturing ultra-precision optical components. Founded in 1974 in Southern California, the site has developed proprietary manufacturing processes that enable the achievement of surface roughness below 1 Angstrom. In addition to superpolishing, G&H Moorpark has pioneered the development of unique ion beam sputtered (IBS) coating designs, delivering high-reflection and low-loss coatings optimized for demanding optical applications.

With decades of experience, G&H has successfully manufactured millions of superpolished components for aerospace, defense, semiconductor, and scientific applications. Custom optical solutions, including complex geometries such as plano/plano mirrors, concave mirrors, and windows with wedges, further reinforce G&H’s ability to meet the diverse needs of the optics industry.

This commitment to excellence has positioned G&H as a trusted provider of superpolished optics for some of the most demanding applications in the world. From NASA’s Mars Curiosity mission to cutting-edge synchrotron experiments, G&H optics have enabled groundbreaking discoveries and technological advancements. With a combination of precision engineering, advanced metrology, and innovative coating technologies, G&H continues to push the boundaries of what is possible in optical manufacturing.

Whether for advanced research and development or high-volume OEM production, G&H’s superpolished optics offer the highest levels of precision, durability, and performance. Contact us today to discover how our expertise in superpolishing can enhance your optical systems and drive innovation in your industry.