What are key technical terms used to describe bandpass filters, such as center wavelength, FWHM, and blocking?

Center wavelength (CWL) is the midpoint of the filter’s transmission band, usually defined at 50% of peak transmission. Full width at half maximum (FWHM) is the spectral width between the two wavelengths at which transmission falls to 50% of the peak value and indicates how narrow or broad the passband is. Blocking is specified as an optical density (OD), e.g., OD4 or OD6, and quantifies how strongly the filter attenuates light outside the passband (higher OD means stronger attenuation).

What are the main types of bandpass filters (e.g., thin-film interference, colored glass, and hybrid) and how do they differ?

Thin-film interference bandpass filters use multilayer dielectric stacks on glass substrates to achieve high peak transmission, steep edges, and high out-of-band blocking, suitable for laser and fluorescence applications. Colored glass bandpass filters rely on bulk absorption of doped glass, generally offering broader passbands, lower blocking, and lower sensitivity to angle of incidence but with less precise spectral control. Hybrid filters combine colored glass and thin-film coatings to improve blocking or edge steepness while keeping cost and angular sensitivity balanced for imaging and illumination systems.

Which specifications are most critical when selecting a bandpass filter for a laser or fluorescence application?

For laser and fluorescence use, critical parameters include center wavelength alignment with the source or emission peak, FWHM relative to the spectral line width, and peak transmission at the operating wavelength. You should also consider blocking level (OD) across the excitation band, transition slope (edge steepness), and the angle of incidence if the filter is used in converging beams or at a tilt. Substrate material, surface quality, and damage threshold become important when working with high-power or pulsed lasers.

How do angle of incidence, environmental conditions, and mechanical format affect bandpass filter performance and selection?

Angle of incidence causes a blue-shift of the passband in interference filters, so off-axis use requires specifying the intended angle and may require filters designed for non-normal incidence. Environmental factors such as operating temperature, humidity, and exposure to UV can shift the spectral response or degrade coatings, so you may need hard-coated, hermetically sealed, or space-qualified versions. Mechanical format—diameter or rectangular size, thickness, and mounting options (e.g., threaded cells, holders, or bare substrates)—must match the optomechanical design and available space in the instrument.

What typical lead times, customization options, and pricing drivers apply to bandpass filters?

Standard catalog bandpass filters in common sizes and wavelengths typically ship from stock or within a few weeks, while fully custom designs with nonstandard CWL, FWHM, or size can require lead times of 4–12 weeks depending on coating complexity and volume. Customization options include tailored center wavelength and bandwidth, specified blocking ranges and OD, custom substrate shapes or materials, AR coatings on one or both sides, and environmental or laser-damage qualifications. Pricing is primarily driven by coating complexity (narrower FWHM and higher OD increase cost), substrate size and tolerance, coating technology (hard vs soft coatings), and order quantity.

How can I find, compare, and request quotes for bandpass filters on FindLight without creating an account?

On FindLight, you can navigate to Optics > Filters > Bandpass Filters and then use filters such as center wavelength, bandwidth, substrate size, and manufacturer to narrow the catalog. Product listings expose key specs in a tabular view, allowing side-by-side comparison of parameters like CWL, FWHM, peak transmission, and blocking range. To request a quote without registration, you can use the contact or RFQ form on each product page, specifying required quantity and any custom requirements; the inquiry is then sent directly to the supplier for pricing and lead-time information.

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Bandpass Filters for Precise Optical Selection

Q: What is a bandpass filter and how does it work in an optical system?

A bandpass filter is an optical element that transmits light within a specified wavelength range (the passband) while attenuating wavelengths outside that range. It typically consists of multiple thin-film dielectric layers engineered to create constructive interference within the passband and destructive interference in the stopbands. In an optical system, bandpass filters are used to isolate emission lines, select laser lines, or define detection windows for sensors and cameras.

Hot Sales Infrared Silicon Narrow Bandpass Filter for Laser Wavelength Separation and Sensing Systems

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Sold by: Henan UM Optics Ltd Ships from: China

Specifications
Central Wavelength:	4260 nm
Bandwidth (FWHM):	90 nm
Peak Transmittance:	80 %
Material:	Silicon
Diameter:	101.6 mm

Optical Band-Pass Filter

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Sold by: Albrighter Technology Co.,Ltd. Ships from: China

Specifications
Central Wavelength:	550 nm
Bandwidth (FWHM):	10 nm
Peak Transmittance:	95 %
CWL(nm):	550±2
FWHM(nm):	10±2

High-Precision Bandpass Filters

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Sold by: CRYSTECH Inc. Ships from: China

Specifications
Central Wavelength:	1064 nm
Bandwidth (FWHM):	5 nm
Peak Transmittance:	95 %
Surface Quality:	10/5
Flatness:	<10″

Dual Wavelength 3nm Filter

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Sold by: Lasertec Inc Ships from: China

Specifications
Central Wavelength:	500.7 nm
Bandwidth (FWHM):	3 nm
Peak Transmittance:	90 %
Contract No:	PO No.
Coating:	BP500nm-3nm

1535nm filters

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Sold by: Lasertec Inc Ships from: China

Specifications
Central Wavelength:	1535 nm
Bandwidth (FWHM):	60 nm
Peak Transmittance:	90 %

Bandpass Filter

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Sold by: Lasertec Inc Ships from: China

Specifications
Central Wavelength:	300 nm
Bandwidth (FWHM):	2 nm
Peak Transmittance:	95 %
Blocking:	200-1200 nm

Bandpass Filter 532nm

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Sold by: Sherlan Optics Ships from: China

Specifications
Central Wavelength:	532 nm
Bandwidth (FWHM):	30 nm
Peak Transmittance:	90 %
Material:	BK7
Wavelength Range:	300-1100 nm

Did You Know?

Optical Bandpass filters (BP Filters) are used in spectral photometry, clinical diagnostics, chemical analysis, colourimetry, astronomy, and numerous applications where spectral isolation is required. A Band-pass Filter transmits light only within a defined spectral band ranging from less than one to many nanometers wide and can be made by combining a Long pass and a Short Pass filter. Examples of bandpass filters are the Lyot filter and the Fabry-Pérot interferometer. The Dutch Open Telescope and Swedish Solar Telescope are examples where Lyot and Fabry-Pérot filters are being used.

Related Resources

Frequently Asked Questions

A bandpass filter is an optical element that transmits light within a specified wavelength range (the passband) while attenuating wavelengths outside that range. It typically consists of multiple thin-film dielectric layers engineered to create constructive interference within the passband and destructive interference in the stopbands. In an optical system, bandpass filters are used to isolate emission lines, select laser lines, or define detection windows for sensors and cameras.

What Are Bandpass Filters?

Bandpass Filters are optical elements that transmit a specified wavelength band while attenuating light outside that range. In photonics and light transport systems, they are used to isolate spectral features, separate channels, and improve signal-to-noise ratio in detection paths. On FindLight you can source Bandpass Filters suitable for broadband sources, lasers, LEDs, and fluorescence systems.

Typical Specifications for Bandpass Filters

When comparing Bandpass Filters, engineers typically evaluate:

Center wavelength (CWL): Nominal passband center, often from UV (200–400 nm) through VIS (400–700 nm) to NIR/MIR.
Bandwidth / FWHM: Full width at half maximum, ranging from a few nanometers for narrowband laser work to tens of nanometers for imaging or illumination.
Peak transmission: Maximum in-band transmission, typically expressed as a percentage at the CWL.
Optical density (OD) blocking: Out-of-band attenuation, e.g., OD3–OD6 over specified wavelength ranges.
Substrate and size: Common substrates include fused silica, BK7, and other optical glasses, with circular or rectangular formats and standard diameters or custom cuts.
Coatings: Hard-coated or soft-coated interference designs with optional AR coatings to minimize surface reflections.
Environmental and power handling: Laser damage threshold, temperature range, and humidity stability for long-term deployment.

Use Cases for Bandpass Filters

Bandpass Filters are used in fluorescence microscopy, Raman and absorption spectroscopy, laser line selection, multispectral imaging, machine vision, flow cytometry, LIDAR receiver chains, and general scientific instrumentation. They enable precise channel selection in complex light transport assemblies and optical detection modules.

Buyer Guidance on FindLight

When sourcing Bandpass Filters on FindLight, begin by matching CWL and bandwidth to your source and detector requirements, then verify OD blocking across unwanted spectral regions. Check substrate compatibility, physical dimensions, and mounting constraints in your optical path. For laser applications, confirm the laser damage threshold and angle-of-incidence performance. You can compare detailed specifications across multiple Bandpass Filters and request quotes directly from suppliers without registration. Use the platform filters to narrow by wavelength range, FWHM, size, and coating type, then contact vendors with your drawings or system parameters to confirm integration details.