Features
- High Transmission Efficiency: Delivers >90% transmission above the cutoff wavelength, ensuring maximum light throughput and excellent optical efficiency.
- High Damage Threshold: Designed for high-energy and laser-based applications, capable of withstanding intense optical power.
- Excellent Thermal Stability: Maintains stable spectral performance under temperature variations, suitable for demanding environments.
- Low Wavefront Distortion: High surface quality minimizes optical distortion, supporting high-resolution imaging and precision measurements.
- Flexible Customization: Available with custom cutoff wavelengths, substrates, coatings, angles of incidence, and sizes.
General Description
Shape Optics supplies high-performance Long Pass Filters, also known as long-wave pass filters, designed to transmit wavelengths longer than a specified cutoff wavelength while blocking shorter wavelengths.
These filters are essential in applications requiring selective spectral transmission, such as fluorescence instrumentation, heat rejection, color separation, and multi-band optical systems. SOT long pass filters feature high transmission, deep blocking (OD > 4), excellent laser damage resistance, and superior thermal stability, ensuring reliable performance in scientific, medical, and industrial environments.
Manufactured using advanced multi-layer dielectric coating technology on substrates such as BK7, fused silica, and ZnSe, SOT long pass filters deliver sharp spectral edges, minimal wavelength shift, and long-term durability. Custom designs are available to meet specific system requirements.
Spectrum Transmission Curves
Standard cutoff wavelengths are available across UV, VIS, and IR ranges.
If standard components do not meet your needs, custom long pass filters can be engineered to your exact cutoff wavelength, blocking level, angle of incidence, and substrate material.
Contact us to discuss your application or request a custom quotation.
Coating Quality & Environmental Reliability
All SOT long pass filters are qualified to MIL-C-675C and CCC-C-440 standards:
- Adhesion Test: LT-90 tape test (3 removals), no blistering or peeling
- Temperature Cycling: −62 °C to 71 °C, no coating detachment
- Abrasion Resistance: 1.0 lb gauze test, 25 cycles, no surface damage
- Humidity Resistance: 49 ±2 °C, 95–100% RH for 24 h, film intact
- Solvent & Cleaning: Acetone and alcohol exposure, no defects
- Salt Spray: 100 h at 35 °C, 5% NaCl, no corrosion or degradation
Standard Specifications
| Parameter | Specification |
|---|---|
| Substrate | BK7, ZnSe, Fused Silica (others on request) |
| Transmission | > 90% |
| Blocking | OD > 4 |
| Angle of Incidence | 0° or 45° |
| Surface Quality | 40/20 |
| Clear Aperture | > 90% |
| Wavelength Shift | < 0.25 nm / °C |
| Damage Threshold | 300 MW/cm² (CW), 1 J/cm² (pulsed) |
| Design Wavelength | 380–2000 nm (BK7), 250–2500 nm (Fused Silica) |
| Calibration Wavelength | 550 nm |
Standard Products
| Description | Cut-on (nm) | Thickness (mm) | Item # (Ø25 mm) | Item # (50 × 50 mm) |
|---|---|---|---|---|
| UV Long Pass | 250 | 1.0 | XUL0250 | ZUL0250 |
| UV Long Pass | 275 | 1.0 | XUL0275 | ZUL0275 |
| UV Long Pass | 300 | 1.0 | XUL0300 | ZUL0300 |
| UV Long Pass | 325 | 1.0 | XUL0325 | ZUL0325 |
| UV Long Pass | 350 | 1.0 | XUL0350 | ZUL0350 |
| UV Long Pass | 385 | 1.0 | XUL0385 | ZUL0385 |
| UV Long Pass | 400 | 1.0 | XUL0400 | ZUL0400 |
| VIS Long Pass | 430 | 1.0 | XVL0430 | ZVL0430 |
| VIS Long Pass | 450 | 1.0 | XVL0450 | ZVL0450 |
| VIS Long Pass | 510 | 1.0 | XVL0510 | ZVL0510 |
| VIS Long Pass | 550 | 1.5 | XVL0550 | ZVL0550 |
| VIS Long Pass | 630 | 1.5 | XVL0630 | ZVL0630 |
| IR Long Pass | 750 | 2.0 | XIL0750 | ZIL0750 |
| IR Long Pass | 900 | 2.0 | XIL0900 | ZIL0900 |
| IR Long Pass | 960 | 2.0 | XIL0960 | ZIL0960 |
| IR Long Pass | 990 | 2.0 | XIL0990 | ZIL0990 |
Applications
Long pass optical filters are widely used in:
- Fluorescence Instrumentation – Isolation of emission wavelengths with high contrast
- Heat Rejection Systems – Blocking unwanted short-wavelength or thermal radiation
- Color Filtering & Imaging – Enhanced color fidelity and image clarity
- Optical Instruments – Precise wavelength selection in microscopes and analyzers
- Multi-Band Detection Systems – Controlled spectral separation for advanced sensing
SOT Strengths & Capabilities
SOT combines advanced thin-film coating design, precision substrate processing, and strict quality control to deliver long pass filters with high reliability and optical accuracy. We provide standard catalog products and fully customized solutions for scientific research, medical devices, industrial optics, and environmental monitoring.