RFQ Best Practices: Technical Information to Provide for Accurate Custom Optics Quotes

A well-prepared Request for Quotation (RFQ) is the single most important factor in getting accurate, competitive pricing for custom optical components. When you send incomplete specifications, suppliers must make assumptions—and those assumptions often translate into longer lead times, higher costs, or components that miss your performance targets. This guide walks through the exact technical details you need to compile before contacting an optical manufacturer, helping you streamline the quoting process and avoid costly revisions.

Key Takeaways

Provide complete optical specifications including wavelength range, focal length, and clear aperture to eliminate guesswork
Specify substrate material with refractive index requirements—this directly impacts cost and delivery time
Define surface quality using standard scales like scratch-dig and surface accuracy in waves or fringes
Include coating requirements with environmental durability tests to prevent performance failures
Share application context and operating conditions—suppliers can recommend better solutions when they understand your system
Attach mechanical drawings with tolerances to avoid miscommunication between optical and mechanical teams

What You Need Before Starting

Before you draft your RFQ document, gather the following foundational information. Missing any of these items will likely trigger clarifying questions from the supplier, adding days to your procurement cycle.

Wavelength range: Specify the design wavelength or bandwidth your system operates at, from UV (193 nm) through visible (400–700 nm) to IR (up to several microns)
Optical configuration: Determine whether you need a lens, window, prism, filter, or mirror—each category has different specification requirements
Mechanical envelope: Know the maximum dimensions your system can accommodate, including thickness constraints
Environmental conditions: Note operating temperature range, humidity exposure, and whether the component faces harsh conditions like salt spray or abrasion
Quantity and timeline: Estimate annual volume and target delivery date—these factors heavily influence manufacturing methods and pricing

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Step 1 — Define Your Optical Performance Requirements

What to Do

Start by documenting the optical parameters that determine how light interacts with your component. These specifications form the core of any RFQ and directly influence manufacturing complexity.

Specify the design wavelength or wavelength band. For laser applications, state the exact wavelength (for example, 1064 nm or 532 nm). For broadband systems, provide the full range such as 400–700 nm.
Define focal length for lenses, with tolerance. A typical tolerance might be ±1% for standard applications or ±0.5% for precision systems.
State the clear aperture—the usable diameter or area where optical performance must meet specifications. This is often 80–90% of the physical diameter.
Specify the back focal length or effective focal length depending on your mounting configuration.
Include any wavefront distortion requirements, expressed in waves at a reference wavelength, such as λ/4 or λ/10 at 632.8 nm.

Why This Matters

Optical performance specifications directly determine which manufacturing processes are viable. A lens requiring λ/10 wavefront accuracy demands different polishing techniques and metrology than one specified at λ/2. According to industry standards from ISO 10110, optical elements are classified by their surface form tolerances, and these classifications significantly affect production costs. When you provide complete optical parameters, suppliers can immediately assess feasibility and quote realistic pricing without building in contingency margins.

Common Mistakes to Avoid

Omitting wavelength context: A coating specified for "visible" without a precise range may not perform at your actual operating wavelength. Always state the specific wavelength or band.
Confusing clear aperture with physical diameter: These are different values. The clear aperture is where performance is guaranteed; the physical diameter includes edge margins for mounting.
Ignoring chromatic requirements: For systems operating over broad wavelength ranges, specify whether chromatic aberration correction is needed—this determines whether you need a singlet, doublet, or aspheric element.

Step 2 — Specify Substrate Material and Quality

What to Do

Material selection affects transmission, thermal stability, and cost. Provide the supplier with clear material preferences or performance requirements that guide their recommendation.

Choose a substrate material based on your wavelength range. Fused silica works well from 185 nm to 2.5 μm. BK7 is suitable for 350 nm to 2 μm. For infrared applications beyond 2 μm, consider materials like CaF₂, ZnSe, or germanium.
Specify the refractive index homogeneity grade if your application demands high wavefront quality. Grades range from standard (H2) to precision (H4) per ISO 10110.
State any environmental durability requirements. For aerospace or defense applications, materials must withstand thermal cycling and vibration per MIL-STD-810.
Indicate whether bubbles, inclusions, or striae are acceptable. These internal defects are graded per ISO 10110 and can be critical for laser applications.

Why This Matters

Material choice drives both optical performance and cost. Fused silica costs more than BK7 but offers superior thermal stability and broader transmission. For high-power laser systems, material purity becomes critical—inclusions can absorb energy and cause thermal damage. Industry data suggests that material costs typically represent 20–40% of the total component price for precision optics. By specifying material grade accurately, you avoid paying for premium material when standard grade suffices, or conversely, prevent failures from using inadequate material.

Common Mistakes to Avoid

Specifying material without grade: "BK7" alone is insufficient. Specify grade A or B per ISO 12123, or state your homogeneity requirement.
Overlooking thermal properties: For systems experiencing temperature changes, coefficient of thermal expansion (CTE) matters. BK7 has a CTE of approximately 7.1 × 10⁻⁶/K, while fused silica is about 0.55 × 10⁻⁶/K.
Ignoring laser damage threshold: For laser applications, specify the required laser-induced damage threshold (LIDT) in J/cm² at your pulse duration and wavelength.

Step 3 — Document Surface Quality and Figure Requirements

What to Do

Surface specifications determine how precisely the optical surface matches its ideal shape and how free it is from defects. These parameters are measured on different scales and must be stated separately.

Specify surface figure (irregularity) in waves or fringes. A common specification is λ/4 at 632.8 nm for general applications, λ/10 for precision systems.
Define surface quality using the scratch-dig scale per MIL-PRF-13830B. Typical specifications range from 80-50 for commercial optics to 20-10 for precision applications and 10-5 for laser optics.
State surface roughness (Ra) if your application involves scattering-sensitive measurements. Typical values range from 1 nm to 10 nm Ra depending on wavelength and application.
Specify whether both surfaces have the same requirements. Often the second surface can have relaxed tolerances, reducing cost.

Why This Matters

Surface quality directly affects scattered light, which degrades contrast in imaging systems and can cause damage in laser systems. The scratch-dig specification of 20-10 means no scratch wider than 20 microns and no dig larger than 10 microns—these numbers are not arbitrary. According to ISO 10110, surface imperfections are classified by their size and number per unit area. Tighter specifications require more inspection time and higher rejection rates, which increases cost. A realistic assessment of your actual requirements prevents over-specification.

Common Mistakes to Avoid

Over-specifying surface quality: A 10-5 scratch-dig specification can double the cost compared to 40-20. Use precision grades only where system performance demands them.
Confusing surface figure with surface roughness: These measure different characteristics. Figure describes the overall shape error; roughness describes fine-scale texture.
Forgetting edge chips: Specify acceptable edge chip size per ISO 10110 or your internal standards. Edge chips are common and can be controlled with proper beveling.

Step 4 — Define Coating Requirements

What to Do

Coatings determine how much light transmits, reflects, or is filtered at specific wavelengths. They are often the most misunderstood part of an RFQ.

Specify the coating type: anti-reflective (AR), high-reflective (HR), partial-reflective, bandpass filter, or polarizing coating.
State the wavelength range and angle of incidence. A typical AR coating might be specified for 400–700 nm at 0° incidence, while a laser line AR coating targets a specific wavelength like 1064 nm.
Define performance thresholds: transmission percentage (for example, >99.5% for V-coatings at a single wavelength) or reflection percentage for mirrors.
Specify environmental durability tests per MIL-C-48497 or ISO 9211, including adhesion, abrasion, humidity, and salt spray tests.
Indicate the laser damage threshold if applicable. For pulsed lasers, specify the fluence in J/cm² and pulse duration.

Why This Matters

Coating performance is wavelength-specific and angle-sensitive. A coating designed for 45° incidence will not perform optimally at 0°. Environmental durability requirements determine which coating materials and deposition processes are used—harder coatings like Ta₂O₅/SiO₂ offer better durability than softer MgF₂ coatings but cost more to deposit. Industry standard MIL-C-48497 specifies tests including 24-hour humidity exposure and cheesecloth abrasion testing. When you specify coatings precisely, suppliers can select the appropriate deposition method (IAD, IBS, or e-beam) and provide accurate pricing.

Common Mistakes to Avoid

Specifying "AR coating" without wavelength: This is the most common RFQ error. Always state the design wavelength and acceptable reflection percentage.
Ignoring angle of incidence: Coatings are designed for specific angles. A coating optimized for normal incidence will show spectral shift at oblique angles.
Overlooking environmental requirements: If your component operates in high humidity or temperature extremes, specify this. Standard coatings may fail without proper sealing or hard coating materials.

Step 5 — Provide Mechanical Drawings and Mounting Details

What to Do

The interface between your optical component and its mechanical mount is where many design issues surface. Provide complete mechanical context to avoid integration problems.

Attach a mechanical drawing with dimensions, tolerances, and edge treatment specifications. Include diameter tolerance (for example, +0.0/−0.1 mm) and thickness tolerance (±0.1 mm typical).
Specify edge bevel or chamfer dimensions. A typical specification is 0.2–0.5 mm at 45° to prevent edge chipping.
State mounting method: threaded ring, adhesive bond, spring clip, or optical cement. Each method imposes different constraints on edge thickness and surface access.
Indicate whether the component needs centering marks or fiducials for alignment during assembly.
Note any space constraints that limit the outer diameter or center thickness.

Why This Matters

Mechanical specifications affect manufacturability and cost. Tight diameter tolerances require precision grinding rather than standard edging processes. Unusual shapes or thin edges increase the risk of breakage during fabrication. For demanding applications like defense and aerospace, components must survive vibration and thermal cycling—We supply glass lenses and mirrors to regular customers who need components that meet stringent military standards. When you provide complete mechanical drawings, suppliers can identify potential manufacturing issues before they become costly problems.

Common Mistakes to Avoid

Submitting optical-only specifications: Without mechanical context, suppliers cannot assess mounting compatibility or edge treatment needs.
Overspecifying tolerances: A diameter tolerance of ±0.01 mm may be unnecessary for a component mounted with a spring clip. Match tolerances to actual requirements.
Forgetting about the second surface: For windows and beamsplitters, both surfaces need specification. For lenses, the center thickness tolerance affects focal length.

Step 6 — Include Application Context and Operating Conditions

What to Do

Suppliers can provide better recommendations when they understand how your component fits into a complete system. Share relevant application details without revealing proprietary information.

Describe the application type: imaging, laser processing, illumination, sensing, or telecommunications.
State operating temperature range and whether the component experiences thermal shock.
Indicate power levels for laser applications—both average power in watts and peak power for pulsed systems.
Note any vibration, shock, or acceleration requirements per MIL-STD-810 or similar standards.
Specify lifetime expectations and whether the component will be exposed to cleaning cycles.

Why This Matters

Application context helps suppliers recommend appropriate materials, coatings, and manufacturing approaches. For a Laser Optical System , components need high LIDT and low absorption coatings. For imaging systems, surface quality and figure accuracy take priority. When suppliers understand your operating environment, they can flag potential issues—like coating failure under high humidity or thermal expansion mismatches—before you commit to a design. This collaborative approach reduces the risk of field failures and extends component lifetime.

Common Mistakes to Avoid

Withholding application details: Suppliers do not need your full system design, but basic context helps them make better recommendations.
Ignoring cleaning requirements: If your component needs regular cleaning, specify this. Some coatings cannot withstand repeated cleaning with solvents.
Failing to mention volume forecasts: Production volumes influence manufacturing methods. High volumes justify tooling investments that reduce unit costs.

Pro Tips for Success

Use standard formats: Reference ISO 10110 or MIL-PRF-13830B in your specifications. Suppliers worldwide understand these standards, reducing misinterpretation risk.
Request a tolerance analysis: Ask suppliers to identify which specifications drive cost. Often, relaxing one parameter—like surface quality from 20-10 to 40-20—significantly reduces price without affecting performance.
Provide a sample or reference part: If you have an existing component that performs well, send it for benchmarking. This gives suppliers a concrete reference point.
Ask about stock items first: Many manufacturers, including those offering optical glass filters , maintain inventory of standard components. Standard parts ship faster and cost less than custom fabrication.
Plan for prototyping: Budget for prototype iterations. First-article inspection reports help verify that specifications are achievable before committing to production volumes.

Frequently Asked Questions

What is the difference between surface figure and surface quality?

Surface figure describes the overall shape accuracy of the optical surface, measured in waves or fringes. Surface quality refers to localized defects like scratches and digs, measured on the scratch-dig scale. Figure errors affect wavefront performance, while surface defects scatter light and reduce contrast.

How much detail should I include in my RFQ?

Include every specification that affects performance, cost, or delivery. At minimum, provide wavelength, material, dimensions, surface quality, figure, and coating requirements. The more complete your RFQ, the fewer clarifying questions and the faster you receive accurate pricing.

Can I send a drawing instead of written specifications?

Yes, but include written specifications alongside the drawing. Drawings show dimensions and tolerances, while written specifications clarify optical performance requirements. Both formats together provide the complete picture suppliers need.

How do I know if my specifications are realistic?

Compare your requirements against industry-standard manufacturing capabilities. For example, surface quality of 20-10 is achievable in production, while 5-2 requires special handling and inspection. Consult with suppliers early to validate your specifications before finalizing the RFQ.

Conclusion

RFQ best practices for custom optics quotes come down to providing complete, precise technical information that eliminates ambiguity. By documenting optical performance requirements, substrate material, surface quality, coating specifications, mechanical details, and application context, you enable suppliers to quote accurately the first time. This approach reduces quoting cycles from weeks to days, minimizes costly revisions, and ensures the delivered components meet your system requirements. The effort you invest in preparing a thorough RFQ pays dividends in faster delivery, competitive pricing, and components that perform as specified. Start with the fundamentals—wavelength, material, and surface specifications—then layer in mechanical and environmental details. Your supplier can only meet your needs when you clearly communicate them.

For your next project, compile a specification sheet using the six steps outlined here before contacting suppliers. This disciplined approach transforms the RFQ process from a guessing game into a precise engineering exchange—one that delivers components that work correctly the first time, on schedule and within budget.