Spectrogon Bandpass, Narrowband, Shortwave/Longwave, and Neutral Density Optical Filters
| Brand | Spectrogon |
|---|---|
| Origin | Sweden |
| Model Series | BP, NB, LP, SP, ND |
| Substrate Materials | N-BK7, Fused Silica (Quartz), Sapphire, Silicon, Germanium, Cemented Glass |
| Diameter Tolerance | ±0.2 mm (Std. Ø25.4 mm) |
| Thickness Tolerance | ±0.2 mm |
| Out-of-Band Blocking | Avg. < 0.1% (OD > 3) |
| CWL Accuracy | ±3–10 nm (varies by model & wavelength region) |
| HW (FWHM) Tolerance | ±3–50 nm (model-dependent) |
| Peak Transmission | 40–90% (material- and design-dependent) |
Overview
Spectrogon optical filters are precision thin-film interference components engineered for spectral selectivity across ultraviolet (UV), visible (VIS), near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) spectral regions (193 nm to 14,200 nm). These filters operate on the principle of constructive and destructive interference within multi-layer dielectric coatings deposited via physical vapor deposition (PVD) under ultra-high vacuum conditions. Each filter type serves a distinct spectral function: bandpass (BP) filters transmit a defined spectral window centered at a specified central wavelength (CWL); narrowband (NB) variants offer sub-1% relative bandwidth (HW/CWL < 0.01 in many cases), enabling high-resolution laser line isolation and fluorescence excitation; longpass (LP) and shortpass (SP) filters implement edge-based spectral separation based on 5% transmission cutoff (λc); neutral density (ND) filters provide calibrated, spectrally flat attenuation via controlled absorption or reflection—critical for photodetector protection and intensity balancing in interferometric or imaging systems. All filters are optimized for normal incidence (0° AOI) and ambient temperature operation unless otherwise specified.
Key Features
- High optical density blocking: Average out-of-band transmission < 0.1% (OD ≥ 3) across UV-VIS-NIR and IR ranges—validated per ISO 9050 and ASTM E430 spectral measurement standards.
- Multiple substrate options: N-BK7 (350–2,000 nm), fused silica (193–2,500 nm), sapphire (250–5,500 nm), silicon (1,200–7,000 nm), germanium (2,000–14,200 nm), and cemented glass assemblies for enhanced thermal stability and broadband rejection.
- Tight dimensional tolerances: Standard diameter Ø25.4 mm ±0.2 mm; thickness tolerance ±0.2 mm; custom diameters (e.g., Ø12.7 mm, Ø50.8 mm) and thicknesses available upon request.
- Robust coating architecture: Hard-coated dielectric stacks with high laser-induced damage threshold (LIDT), compliant with ISO 21254 for pulsed lasers up to 10 ns duration in NIR/SWIR bands.
- Traceable metrology: Every batch undergoes spectral characterization using calibrated double-monochromator spectrophotometers traceable to NIST SRM standards; spectral curves provided with each shipment.
Sample Compatibility & Compliance
Spectrogon filters are compatible with standard optomechanical mounts (e.g., SM1-threaded lens tubes, kinematic mirror mounts) and integrate seamlessly into spectroscopic instrumentation (FTIR, Raman, LIBS), laser safety systems, hyperspectral imaging platforms, environmental monitoring sensors, and space-qualified optical payloads. All filters meet RoHS Directive 2011/65/EU and REACH Annex XVII compliance. IR-grade substrates (Si, Ge, Sapphire) conform to MIL-O-13830A surface quality specifications (scratch-dig 60-40). For regulated applications—including FDA-compliant medical diagnostics, aerospace telemetry, and defense electro-optical systems—filters support full documentation packages (CoC, CoA, spectral test reports) required for ISO 13485 and AS9100 audits. No proprietary adhesives or organic binders are used in cemented designs—ensuring long-term vacuum compatibility and thermal cycling stability from –40°C to +85°C.
Software & Data Management
Spectrogon provides comprehensive spectral data in machine-readable formats (CSV, SDF, and plain-text ASCII) aligned with the CIE 15:2018 and ISO 11664-3 spectral data exchange conventions. Customers may access the Spectrogon Filter Selector Tool—a web-based parametric search engine supporting filtering by CWL, HW, OD, substrate, and application domain (e.g., “1550 nm telecom”, “CO2 laser line @ 10.6 µm”). All spectral curves include uncertainty annotations per GUM (JCGM 100:2018) guidelines. For integration into automated optical alignment or calibration workflows, Spectrogon supports SCPI command sets over USB/Virtual COM for spectral verification systems and offers API-accessible metadata via secure customer portal (TLS 1.3 encrypted).
Applications
- Laser Systems: Isolation of fundamental and harmonic lines (e.g., 532 nm, 1064 nm, 1550 nm, 10.6 µm) in DPSS, fiber, and quantum cascade lasers—enabling pump-probe experiments and cavity dumping.
- Remote Sensing & Environmental Monitoring: SWIR/MWIR bandpass filters for gas detection (CH4, CO, NOx, H2O) in open-path FTIR and tunable diode laser absorption spectroscopy (TDLAS).
- Biomedical Imaging: High-contrast fluorescence excitation/emission filtering in confocal microscopy and flow cytometry—particularly NB filters for Alexa Fluor® and Cy™ dye pairs.
- Astronomy & Space Optics: Low-outgassing, radiation-hardened sapphire and silicon filters for satellite-borne spectrometers (e.g., ESA Sentinel missions, NASA JPL instruments).
- Industrial Process Control: Robust LP/SP combinations for thermal imaging pyrometry and combustion analysis in harsh industrial environments.
FAQ
What is the difference between BP and NB filters?
Bandpass (BP) filters typically feature full-width-at-half-maximum (FWHM) values ranging from ~1% to >10% of CWL, while narrowband (NB) filters maintain FWHM ≤ 1% of CWL—optimized for laser line selection and high signal-to-noise ratio in monochromatic applications.
Can these filters be used at non-normal angles of incidence?
All standard Spectrogon filters are characterized and optimized for 0° AOI. Off-axis use induces blue-shift of CWL and reduced peak transmission; angular tuning curves are available upon request for specific models.
Do you provide custom coating designs?
Yes—Spectrogon offers bespoke interference filter design services including multi-cavity structures, steep-edge roll-offs (< 1% per nm), and multi-band configurations (e.g., dual-band BP), supported by rigorous thin-film modeling (TFCalc, Essential Macleod) and prototype validation.
Are these filters suitable for high-power laser applications?
Many BP/NB filters on sapphire, silicon, and germanium substrates meet ISO 21254 LIDT requirements for nanosecond-pulsed lasers; continuous-wave power handling depends on substrate thermal conductivity and coating absorption—consult Spectrogon’s LIDT datasheets for model-specific ratings.
How is spectral performance verified and documented?
Each filter lot undergoes full-spectrum scanning (193–14,200 nm) on double-beam spectrophotometers calibrated against NIST-traceable standards; certified spectral curves, OD maps, and uncertainty budgets accompany every delivery.
