Which material should I choose for a subsea optical dome — sapphire, BK7 or fused silica?
4. Sapphire vs BK7 vs fused silica — how do I choose?
There is no single "best" material. Pick against your optical band, mechanical needs and environment:
| Material | Best optical range | Strengths | Typical use |
|---|---|---|---|
| Sapphire | Visible to near-IR | Extremely scratch-resistant, high hardness, strong in marine service | Demanding ROV/AUV ports, foul-prone or abrasion-exposed systems |
| BK7 optical glass | Visible | Good imaging, cost-efficient, easy to coat | Wide-angle / fisheye camera ports, visible-light underwater imaging |
| Fused silica | UV through visible / near-IR | High UV transmission, very low thermal expansion | UV fluorescence, scientific sensing, thermally sensitive systems |
Tell us your optical band and environment, and we'll confirm a grade. If you need sapphire, specify the crystal grade and any orientation requirement where relevant. Browse the full underwater optical dome product family.
5. Does the material alone set the depth rating?
No — and this is the line we won't blur.
A sapphire dome is not automatically a "deeper" dome than a BK7 one. Actual pressure performance depends on wall thickness, curvature, thickness uniformity, mounting support, surface defects, seal condition, and pressure-cycle history — not on the material name on the drawing.
That's why you won't see a fixed "3000 m" or "7000 m" tag on our domes. A depth rating is something you and we define and validate together for your specific dome + mount + seal arrangement.
6. How should I specify coatings (AR / BBAR / DLC) for quoting and acceptance?
Coatings are where quotes drift and acceptance disputes start, because "anti-reflection" by itself means nothing. In your inquiry, specify:
- Working wavelength band (e.g. 400–700 nm, or the IR band you image in).
- Angle of incidence the dome actually sees.
- Performance target — residual reflectance or transmission range you'll accept.
- Whether you need DLC — for IR transmission or extra abrasion resistance.
Not every imaging dome needs a coating. Specify the real requirement and we'll quote the right one — and we'll agree the inspection record up front, so there's no argument about whether the coating passed.
Related: browse the underwater optical dome product family, read the subsea optical dome engineering hub, or explore the subsea dome FAQ library.
- What is the minimum order quantity for custom precision optical glass components?
FELIX OPTICAL GLASS offers highly flexible MOQs to support customer projects, including prototype testing, small-batch trial orders, and high-volume production. All products can be fully customized to your drawings, tolerances, and application standards. Please send us your specifications, and we will reply within 1-5 hours and provide an accurate quotation after careful evaluation within 1-2 days.
- Can I get free glass samples for testing before bulk order?
Yes, our FELIX GLASS factory supports sample testing for a wide range of precision optical glass components and assemblies. The lead time for sample production is 3 to 7 working days. Please contact us today to arrange samples and obtain a customized solution that meets your needs.
- What is the production lead time for custom optical glass components?
A: The production cycle for standard samples is 3-10 working days, while mass production requires 15-35 working days, depending on the complexity of the product and the order quantity. We provide reliable precision optical glass components and fast delivery services for orders from industries such as defense, industrial equipment, medical devices, shipbuilding, robotics, automotive, and aerospace. Please submit your project details so we can provide you with an accurate delivery schedule.
- Are your optical glass products ISO, CE and RoHS certified?
All precision optical glass components from FELIX OPTICAL GLASS comply with ISO quality system standards as well as CE and RoHS requirements. We provide comprehensive test reports, spectral graphs, material certificates, and inspection documents for customer review. Please feel free to request complete certification details and a formal quotation at any time.
- Do you offer one-stop custom optical glass processing services?
Yes. We offer a full range of precision optical glass component processing services, including CNC machining, precision grinding, optical polishing, chemical/physical tempering, vacuum coating (AR anti-reflective coating, AF anti-fingerprint coating, AG anti-glare coating, IR infrared coating), and screen printing. From raw materials to finished products, every step is completed in our own factory. Please tell us your needs, and we will provide you with the most cost-effective solution.
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