Bandpass Filters

Precision wavelength selection from 193nm to 15μm

Bandpass Filters Andover Corporation

Andover Bandpass Filters

Precision light control, from UV to IR, in one elegant solution

Bandpass filters are one of the most effective and economical solutions for isolating specific wavelengths of light while blocking all others. Like their name suggests, they act as selective gates - allowing a precise "band" of wavelengths to pass through while rejecting everything else. Each filter is defined by three key characteristics:

  • Center Wavelength (CWL): The central wavelength the filter is designed to transmit
  • Bandwidth (FWHM): The width of the transmitted band, measured at 50% of peak transmission
  • Peak Transmission (T): The maximum transmission level achieved

Andover Corporation offers multiple construction variations of these filters, each optimized for different applications. Using advanced thin-film technology and precision materials, we can produce bandwidths ranging from less than an Ångström to several hundred nanometers, allowing you to select the exact specifications needed for your application.

Bandpass Filter Selection Guide

Find the right optical filter for your application!


Beneficial for new users and industry veterans alike, this go-to resource includes:

  • Descriptions of standard filter types
  • Information on how to select a semi-custom filter
  • Technical specifications
  • Spectral profiles
  • Typical applications

Filter Construction Technologies

Bandpass filters are built using two distinct construction methods, each offering unique performance advantages. Understanding these differences is key to selecting the optimal filter for your application:

All-Dielectric Type

Dielectric, or bandpass filters, are a type of optical interference filter, designed to selectively transmit specific wavelength ranges while rejecting or blocking other wavelengths. They are constructed from multiple thin layers of non-conductive materials, known as dielectrics, with varying refractive indices.

Metal-Dielectric Type

Similar to all-dielectric but utilizes a metal spacer layer. Offers excellent out-of-band blocking and high passband transmission, mainly used for bandpass filters in the ultraviolet.
By partnering with Andover Corporation, you gain access to over 45 years of expertise in designing and manufacturing environmentally stable optical filters.
 

Emission Line Filters

Precision isolation of common spectral lines

Emission Line Filters are precision-engineered narrowband filters designed to isolate specific spectral lines emitted by gases, elements, and laser sources. These filters deliver ultra-narrow bandwidths with steep edges and high transmission, optimized for applications where selectivity and signal-to-noise ratio are critical.

Andover Corporation offers a wide range of emission line filters targeting common lines including:

  • H-Alpha
  • H-Beta
  • HeNe
  • Kr
  • Ar
  • Na
  • Rb
  • Hg
  • Nd:YAG
  • Ruby
  • GaAs
  • HeCd
  • N2

Additional filters are available for specialized sources like methane, biomedical fluorescence, LED, Sapphire, and NaYAG. Each filter is manufactured in-house for precision center wavelength control, blocking, and consistent spectral performance.

Bandpass Filter Solutions

From standard to specialized designs

Every application has unique spectral requirements. Our comprehensive range of bandpass filters spans from proven industry standards to specialized designs for demanding environments and custom specifications. Select from six distinct filter types, each optimized for specific performance characteristics.

Frequently Asked Questions

What are bandpass filters?

Bandpass filters are optical filters that allow a specific range of wavelengths to pass through while blocking light outside that range. These wavelength-selective filters are essential for isolating desired signals in applications like laser systems, fluorescence imaging, and environmental monitoring.

What’s the difference between a narrowband filter and a standard bandpass filter?

A narrowband filter is a type of bandpass filter with a very small full width at half maximum (FWHM), typically used when you need to isolate a very precise wavelength. Both fall under the category of optical bandpass filters, but narrowband filters offer tighter spectral control.

What is an emission line filter?

Emission Line Filters are a specialized type of bandpass filter designed to isolate extremely narrow spectral lines emitted by gases, elements, or laser sources. They're commonly used in laser-based systems, spectroscopy, fluorescence imaging, and astronomy. At Andover Corporation, we offer these filters as a dedicated subcategory of our Bandpass Filters — engineered for precision and available for many standard emission lines, including H-alpha, HeNe, Nd:YAG, and more.

What specifications define a bandpass filter?

Key specifications include:

  • Center Wavelength (CWL): The central point of the passband
  • FWHM (Bandwidth): The width of the transmission window, expressed as "full width at half-maximum"
  • Peak Transmission: Maximum efficiency within the passband
  • Blocking Range: How well the filter rejects out-of-band light

These precision optical filters are engineered for high transmission in the passband and strong attenuation elsewhere.

In what industries or systems are bandpass filters used?

Bandpass filters are widely used in biomedical instruments, laser systems, spectroscopy, machine vision, and astronomy. Whether you need UV-VIS bandpass filters for fluorescence microscopy or IR bandpass filters for remote sensing, these filters play a critical role in optimizing performance.

Can Andover Corporation design custom bandpass filters?

Yes — we specialize in custom bandpass filters tailored to specific wavelengths, bandwidths, and environmental conditions. Our in-house coating and fabrication capabilities allow us to deliver optimized solutions for even the most specialized optical systems.

What is the lead time for custom filters?

Typical lead times range from 4 to 6 weeks, depending on complexity and order size. Contact us to discuss your project timeline and technical requirements.

From Prototype to Production

Custom Fabrication and High-Volume Manufacturing

Collaborate with Andover Corporation on custom optical products, prototype development, and specialized optical solutions supported by vertically integrated manufacturing.

With in-house fabrication, coating, assembly, and metrology capabilities, Andover can support everything from rapid prototypes to high-volume production programs with responsive lead times and consistent quality.

Quality isn't just a metric

- it's our foundation.

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