MiXran Meg1116 Absorptive Neutral Density (ND) Filter

Overview

The MiXran Meg1116 is a precision-engineered absorptive neutral density (ND) filter series designed for stable, wavelength-independent attenuation of light intensity in demanding optical laboratory and industrial metrology applications. Unlike reflective ND filters—whose performance varies with angle of incidence and polarization—the Meg1116 employs homogeneously doped optical glass substrates to achieve consistent, spectrally flat attenuation across the visible to near-infrared spectrum (350–1100 nm). Its absorption-based design eliminates ghost reflections, beam displacement, and polarization-dependent loss—critical requirements in interferometry, laser power stabilization, photodetector calibration, and quantitative imaging systems.

Key Features

• True absorptive architecture: No metallic coatings; minimal back-reflection (<0.2% per surface) and zero spectral shift with incident angle variation.
• High OD accuracy and repeatability: Each filter is individually calibrated using NIST-traceable spectrophotometry; OD tolerance ±0.05 over specified spectral band.
• Thermal and environmental stability: Low coefficient of thermal expansion (CTE ≈ 7.1 × 10⁻⁶ /°C) ensures OD drift <0.01 OD/°C across –20°C to +60°C operating range.
• Mechanically robust substrate: Precision-polished optical crown glass (BK7-equivalent) with 60-40 scratch-dig surface quality and λ/4 wavefront distortion.
• Standardized mounting compatibility: Round variants (Φ12.5 mm, Φ25 mm, Φ50 mm) feature industry-standard outer diameters for integration into SM1, SM25, and C-mount optical housings; square 50 × 50 mm filters include alignment fiducials and optional kinematic mounting notches.

Sample Compatibility & Compliance

The Meg1116 series is compatible with continuous-wave (CW) and pulsed laser sources up to 500 mW/cm² average power density (for OD ≤ 2.0) and peak fluences below 0.1 J/cm² at 10 ns pulse width (1064 nm). All filters comply with ISO 10110-7:2017 for optical element surface imperfections and ISO 9001:2015 manufacturing quality control protocols. While not certified to MIL-PRF-13830B, they meet its visual inspection criteria for cosmetic defects. For regulated environments—including ISO/IEC 17025-accredited calibration labs—the filters support documented traceability via supplied calibration certificates (optional add-on), listing measurement uncertainty (k = 2) for each OD value at 532 nm, 633 nm, and 780 nm.

Software & Data Management

Each Meg1116 filter is assigned a unique product ID (e.g., GANF-D25-007) linked to a digital certificate accessible via MiXran’s secure portal. This certificate includes spectral transmittance data (350–1100 nm, 1 nm resolution), OD verification report, and batch-level metrological history. The portal supports CSV export for integration into LIMS or instrument control software (e.g., LabVIEW, Python-based PyVISA workflows). No proprietary drivers or firmware are required—filters operate passively and require no electrical interface or configuration.

Applications

• Laser power management: Attenuating high-intensity beams prior to photodiode or thermal sensor input without introducing nonlinearity or saturation.
• Quantitative microscopy: Enabling precise exposure control in fluorescence lifetime imaging (FLIM) and confocal reflectance measurements.
• Spectrometer calibration: Serving as reference attenuators in radiometric validation of CCD/CMOS array detectors.
• Optical system alignment: Providing controlled intensity reduction during beam profiling and M² factor measurement without perturbing spatial mode structure.
• Education and training: Supporting undergraduate optics laboratories in teaching Beer–Lambert law fundamentals, dynamic range extension, and detector linearity assessment.

FAQ

What is the damage threshold for Meg1116 filters under CW laser illumination?
For OD ≤ 2.0 filters, the maximum permissible average power density is 500 mW/cm² at 532 nm and 633 nm; for OD > 2.0, reduce to 200 mW/cm² to avoid localized heating-induced transmission drift.
Can Meg1116 filters be used with ultraviolet (UV) light below 350 nm?
No—substrate absorption increases significantly below 350 nm, causing nonlinear OD behavior and potential solarization; UV-grade fused silica ND filters are recommended for wavelengths <350 nm.
Is there polarization-dependent loss (PDL) in these absorptive ND filters?
PDL is <0.02 OD across all standard OD values when measured at 0° AOI; remains <0.05 OD even at 15° incidence—well within typical alignment tolerances of free-space optical benches.
Do you provide custom OD values or non-standard dimensions?
Yes—custom OD values (±0.01 OD resolution) and dimensions (e.g., Φ10 mm, 25.4 × 36 mm rectangular) are available under OEM agreement with minimum order quantities and extended lead times.
How should Meg1116 filters be cleaned and handled?
Use only spectroscopic-grade acetone or isopropanol on lint-free optical wipes; avoid ultrasonic cleaning or abrasive solvents. Always handle by edges with powder-free nitrile gloves to prevent skin-oil contamination of polished surfaces.