355nm Bandpass Filters

355nm bandpass filters are designed to transmit a selected ultraviolet band centered near 355nm while reducing unwanted out-of-band light.

Applications:
- 355nm third-harmonic Nd:YAG or Nd:YVO₄ laser line cleanup
- UV laser excitation for spectroscopy, fluorescence, and optical measurement
- Harmonic separation in systems involving 1064nm, 532nm, 355nm, or 266nm light
- Detector-side 355nm signal isolation before UV-sensitive photodiodes, PMTs, spectrometers, or UV-capable cameras
- Broadband UV source filtering for inspection, measurement, or excitation setups

Bandwidth options:
- 3nm and 10nm FWHM for 355nm laser-line isolation and UV detector-side signal filtering
- 30nm FWHM for UV excitation or broadband source filtering with more usable signal
- 60nm FWHM for broader UV illumination, inspection, or higher signal collection

Select the bandwidth based on the UV source, target signal, detector sensitivity, transmission requirement, blocking range, and optical power level.

Third-harmonic Nd:YAG / Nd:YVO₄ laser at 355nm

Use CWL 355nm with 3–10nm FWHM for 355nm third-harmonic laser line cleanup, source isolation, or detector-side laser signal selection.

355nm is commonly generated as the third harmonic of 1064nm Nd:YAG or Nd:YVO₄ lasers. For laser-line filtering, key specs include CWL match near 355nm, FWHM, transmission at 355nm, OD blocking over the unwanted wavelength range, and laser power handling for the beam size.

355nm UV laser spectroscopy or excitation

Use CWL 355nm with 3–10nm FWHM for UV laser spectroscopy, laser-induced fluorescence, or narrow excitation cleanup.

For UV laser excitation systems, the filter helps define the 355nm source band before the sample or optical path. The main selection points are CWL accuracy, FWHM, transmission at 355nm, blocking range, and coating suitability for the UV beam condition.

Broadband UV source filtering

se CWL 355nm with 30–60nm FWHM to select a useful UV band from xenon, deuterium, mercury-xenon, or other broadband UV sources.

For broadband UV illumination or measurement, the filter extracts a 355nm-centered band from a wider spectrum. Use 30nm FWHM for more defined UV-band selection, or 60nm FWHM when higher transmitted UV signal is more important for illumination, inspection, or detection.

Detector-side 355nm signal isolation

Use CWL 355nm with 3–30nm FWHM before a UV-sensitive photodiode, PMT, UV spectrometer, or UV-capable camera when the target signal is near 355nm.

For detector-side filtering, the filter improves signal-to-background ratio by passing the 355nm signal and reducing unwanted UV or visible background. Use 3–10nm FWHM for stronger 355nm isolation, or 30nm FWHM when more signal level is needed.

US5530565A - Holographic transmission bandpass filter

Context: This patent describes a system for purifying laser beams, specifically improving upon standard dielectric filters which often have lower transmission efficiency for UV wavelengths.

Usage of Filter: The bandpass filter is constructed as a holographic optical element (transmission grating) sandwiched between prisms. It is placed directly in the path of the incident laser beam.

Function: It diffracts the specific nominal wavelength (e.g., 355nm) through a specific angle to pass through an aperture, while undiffracted or differently diffracted wavelengths (noise/sidebands) are blocked by the mask.

Result: The system achieves an "ultra-pure" light beam with transmission efficiency approximately twice that of conventional dielectric filters available at the time, eliminating the need for complex realignment of folding mirrors.

US8175423B2 - Multi-spectroscopy fiber probe (Raman/Fluorescence)

Context: This patent details a fiber optic probe capable of performing both Fluorescence Lifetime Imaging (FLIm) and Raman spectroscopy simultaneously for medical diagnostics (e.g., identifying tissue types).

Usage of Filter: A small 355nm bandpass filter is positioned directly in front of the excitation fiber (the fiber delivering the laser light to the tissue).

Function: It acts as a "laser line clean-up" filter. It ensures that only the precise 355nm excitation light exits the probe tip, blocking any broadband fluorescence or Raman scattering that might have been generated inside the fiber optic cable itself as the light traveled to the tip.

Result: It prevents "fiber background" noise from overwhelming the extremely weak Raman signal returning from the tissue, significantly improving the signal-to-noise ratio for accurate disease detection.

US20220082488A1 - Methods of forming multi-color fluorescence-based flow cytometry panel

Context: This patent describes advanced flow cytometry systems (like the Cytek Aurora or similar spectral analyzers) that use multiple lasers to analyze biological cells.

Usage of Filter: The filter is used in the detection module associated with the UV laser (355nm) excitation line.

Function: It isolates the fluorescence emission of specific UV-excited fluorochromes (such as BUV395 or DAPI) while blocking the intense 355nm laser reflection (Rayleigh scatter) and emissions from other lasers.

Result: It enables the "unmixing" of highly complex cellular data, allowing researchers to track significantly more cell markers simultaneously (high-parameter analysis) without signal cross-talk.

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