BK7 Plano-Convex Lenses

Name: BK7 Plano-Convex Lenses
Brand: PhotonEdge
SKU: PE-LENS-PCX-001
Availability: LimitedAvailability

Key Specifications

Material	N-BK7 (K9)
Diameter Range	2.5 mm - 75 mm
Focal Length Range	3.9 mm - 1000 mm
Wavelength Range	350 - 2000 nm (VIS/NIR)
Surface Quality	40-20 (standard) / 20-10 (precision)
Surface Flatness	λ/4 @ 632.8 nm
Clear Aperture	> 90%
Coating Options	AR 350-650nm / AR 650-950nm / AR 950-1250nm / Custom

What Is a Plano-Convex Lenses?

A plano-convex lens has one flat (plano) surface and one convex (curved outward) surface. It is a positive focal length lens that converges incoming light to a focal point. BK7 (N-BK7) is the most widely used optical glass for visible and near-infrared applications, offering excellent homogeneity and low cost.

When the curved surface faces the longest conjugate distance, plano-convex lenses minimize spherical aberration, making them ideal for focusing collimated beams or collimating divergent sources.

When Should You Use This Product?

✔ Good Choice When

✓ Focusing or collimating laser beams in the visible/NIR range
✓ General-purpose imaging where chromatic correction is not critical
✓ Beam conditioning in optical setups
✓ Cost-sensitive applications requiring reliable optical performance

⚠ Consider an Alternative When

✗ Broadband chromatic correction is critical → Achromatic Doublet

✗ Very high NA or minimal spherical aberration needed → Aspheric Lens

✗ Deep UV transmission (< 350nm) required → UV Fused Silica Plano-Convex Lens

✗ Extreme imaging resolution required → Custom Optical Design

Available Optical Materials

Select the optimal substrate material based on your wavelength, environment, and budget requirements.

Material	Transmission	Key Advantage	Considerations
N-BK7	VIS / NIR (350-2000nm)	General-purpose, low cost, good homogeneity	Not suitable for UV < 350nm
UV Fused Silica	UV / VIS / NIR (185-2100nm)	Excellent UV transmission, low absorption, high laser damage threshold	Higher cost than BK7
CaF₂	Deep UV / VIS / IR (130-7800nm)	Broadest transmission range, low refractive index	Fragile, higher cost
Sapphire	UV / VIS / NIR (150-5500nm)	Extremely hard (9H), scratch resistant	Higher refractive index, birefringent

Not sure which material to choose?

Ask AI Optical Engineer

Optical Coating Options

AR Coating (350-650nm)

Broadband anti-reflection for visible range. Reduces surface reflection to R < 0.5% per surface.

Typical use: General visible laser and imaging systems

AR Coating (650-950nm)

Anti-reflection for NIR range (e.g., 780nm, 808nm, 850nm diode lasers).

Typical use: NIR laser diode collimation and fiber coupling

AR Coating (950-1250nm)

Anti-reflection for 1064nm and nearby wavelengths.

Typical use: Nd:YAG and fiber laser systems

BBAR (Broadband)

Low reflection across a wide band (e.g., 400-1000nm).

Typical use: Multispectral or broadband applications

Uncoated

No coating. Raw BK7 surface reflection ~4% per surface.

Typical use: Non-critical applications or where reflection is acceptable

How to Specify Your Coating

To select the right coating, please provide: (1) Operating wavelength, (2) Angle of incidence, (3) Required transmission or reflectivity, (4) Laser power density (if applicable), (5) Operating environment.

Engineering Considerations

Key factors to evaluate when specifying this optical component for your system.

Wavelength

BK7 transmits well from 350nm to 2000nm. For wavelengths below 350nm, use UV Fused Silica to avoid absorption and solarization.

Laser Power

For high-power CW or pulsed lasers, verify that the coating laser damage threshold (LIDT) exceeds your operating fluence. Uncoated BK7 surfaces may suffer thermal lensing at high average powers.

Surface Quality

40-20 is suitable for most laser and imaging applications. For precision imaging or scattering-sensitive systems, specify 20-10 or better.

Flatness

λ/4 is standard for focusing applications. If the lens is used as a reference or in interferometric setups, request λ/10 or λ/20.

Centration

< 3 arc min is standard. For systems sensitive to beam deviation (e.g., multi-element assemblies), specify < 1 arc min.

Orientation

For minimum spherical aberration, orient the convex surface toward the collimated (longest conjugate) side.

Applications

Laser Systems

Focusing laser beams onto targets, detectors, or fibers. Collimating output from laser diodes and fiber sources.

Machine Vision

Image formation in inspection systems, barcode readers, and quality control cameras.

Spectroscopy

Beam conditioning in spectrometers, monochromators, and optical measurement setups.

Research & Education

Laboratory optics, teaching setups, and experimental beam paths.

Manufacturing & Customization

PhotonEdge supports optical component sourcing, engineering review, and qualified manufacturing through our optical manufacturing network. We coordinate production, coating, and inspection to deliver components that meet your specifications.

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Prototype

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Low Volume

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Volume Production

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Custom Specification

Quality Assurance

Dimensional Inspection

Diameter, thickness, focal length verified per specification

Surface Quality

Scratch-dig inspection under calibrated illumination

Coating Verification

Spectrophotometric measurement of transmission/reflectance

Inspection documentation available according to project requirements. Certificates of Conformance, material test reports, and coating curves can be provided.

You May Also Need

Related Knowledge

Engineering Documentation

The following documentation is available upon request for qualified engineering projects:

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Dimensional Drawing

CAD & dimensional specs per your requirements

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Material Data Sheet

Material properties, transmission curves & certificates

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Coating Performance Curve

Spectrophotometric measurement data

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Inspection Report

Surface quality, flatness, centration & dimensional data

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Certificate of Conformance

CoC with full traceability per project requirements

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Custom Specification Sheet

Application-specific specification documentation

Documentation availability depends on project scope and order quantity. Request details during RFQ.

Frequently Asked Questions

What is a plano-convex lens used for?

A plano-convex lens is used to focus collimated light to a point or to collimate light from a point source. Common applications include laser beam focusing, fiber coupling, and imaging systems.

What is the transmission range of BK7?

N-BK7 transmits well from approximately 350nm to 2000nm. For wavelengths below 350nm, UV Fused Silica is recommended due to BK7's increasing absorption in the deep UV.

Can I order custom focal lengths?

Yes. PhotonEdge offers custom focal lengths and diameters outside the standard catalog range. Custom specifications typically require 4-6 weeks lead time.

What coating should I choose for a 1064nm laser?

For 1064nm Nd:YAG or fiber laser systems, we recommend our AR coating optimized for 950-1250nm. This reduces surface reflection to below 0.5% per surface at your operating wavelength.

What is the difference between 40-20 and 20-10 surface quality?

Surface quality is specified as scratch-dig width in hundredths of mm. 40-20 (40 scratch, 20 dig) is suitable for most laser and imaging applications. 20-10 is for precision systems where scattering must be minimized.

Do you provide inspection reports?

Yes. Inspection documentation including dimensional reports, surface quality verification, and coating performance data can be provided according to project requirements.

What is the maximum diameter available?

Standard catalog goes up to 75mm diameter. Larger diameters can be manufactured upon request with extended lead time.

How do I request a quote?

Click the 'Request Engineering Quote' button on this page. Please provide your required diameter, focal length, wavelength, coating, surface quality, and quantity for an accurate quotation.

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MaterialDiameter RangeFocal Length RangeWavelength RangeSurface QualitySurface FlatnessClear ApertureCoating Options

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