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Dispersing prisms are optical workhorses that separate white light (or polychromatic laser light) into its constituent wavelengths through controlled refraction—a process enabled by the wavelength-dependent refractive index of optical materials (dispersion). Unlike diffraction gratings, which produce multiple overlapping spectral orders (leading to stray light and signal interference), these prisms generate a single, clean spectral output, making them ideal for applications requiring high spectral purity. Our Dispersing Prisms are engineered using high-dispersion materials (e.g., flint glasses) to maximize angular dispersion—the angle between two wavelengths (e.g., 400nm violet and 700nm red)—with configurations optimized for the minimum angle of deviation. At this angle, light travels parallel to the prism base, minimizing light loss (reducing transmission losses to <2%) and ensuring consistent spectral separation across the prism’s clear aperture .
• Material Diversity: Available in Schott SF11 (a flint glass with exceptional dispersion, Abbe number ~36—far lower than crown glasses like BK7, which have Abbe numbers ~65—making it ideal for visible spectroscopy), F2 (another flint glass with slightly lower dispersion than SF11, suitable for cost-sensitive applications), fused silica (high UV transmission, ideal for UV spectroscopy down to 185nm), and CaF₂ (calcium fluoride, a crystalline material with superior IR transmission). Each material targets specific spectral ranges: SF11 and F2 for 400-700nm, fused silica for 185-2100nm, and CaF₂ for 200nm-8000nm .
• Dimensional Range: Sizes from 10mm to 50mm (standard models, perfect for portable spectrometers and lab-scale instruments) with custom options up to 300mm (for large-format systems like astronomical spectrometers used in observatories). All models maintain ±0.25mm tolerance in length, width, and height, ensuring compatibility with standard optical mounts .
• Optical Quality: Boasts surface quality 20-10 (standard grade, suitable for most spectroscopy applications) and wavefront distortion <λ/4 (fused silica, critical for UV applications where wavefront errors degrade spectral resolution) or <λ/10 (CaF₂, ideal for high-precision IR spectroscopy). These specifications minimize light scatter (stray light <0.1% of incident intensity) and ensure sharp, well-defined spectral lines .
• Wavelength Coverage: Fused silica models operate from 185nm to 2100nm (covering UV, visible, and NIR ranges, making them versatile for environmental monitoring and material analysis), while CaF₂ extends into the mid-infrared up to 8000nm (used in molecular spectroscopy, where mid-IR wavelengths correspond to molecular vibration modes)
• Coating Options: Anti-reflective (AR) coatings tailored for specific spectral ranges reduce surface reflections to <0.5% per surface. For example, UV-enhanced AR coatings on fused silica prisms minimize losses in the 185-400nm range, while IR-optimized coatings on CaF₂ prisms improve transmission in the 2000-8000nm range. These coatings are also scratch-resistant (meeting MIL-C-675C standards), ensuring durability in frequent-use lab environments .
These prisms are foundational in:
• Spectroscopy: Enabling chemical analysis in combustion research (measuring pollutant emissions from industrial burners) and environmental monitoring (Continuous Emission Monitoring Systems, CEMS, which track SO₂, NOx, and CO₂ levels in power plant exhaust). In CEMS, dispersing prisms separate the absorption lines of target gases, allowing precise concentration measurements with detection limits as low as 1ppm .
• Laser Systems: Separating harmonics in ultrafast lasers (e.g., Ti:sapphire lasers that produce 800nm fundamental light and 400nm second harmonic) and compensating for group velocity dispersion (GVD)—a phenomenon where different wavelengths travel at different speeds in optical materials. By dispersing and re-combining wavelengths, prisms ensure ultrafast pulses (femtosecond-scale) maintain their shape, critical for applications like laser micromachining .
• Instrumentation: Powering wavelength calibration in Automatic Number Plate Recognition (ANPR) cameras (ensuring consistent color detection for license plate reading) and UV radiation detectors (used in sunscreen testing to measure UVB and UVA intensity). In UV detectors, prisms separate UV wavelengths, allowing accurate measurement of each range’s intensity .
• Education & Research: Demonstrating light dispersion in physics laboratories (e.g., Newton’s classic prism experiment, where white light splits into a rainbow spectrum) and advancing quantum optics studies (e.g., manipulating single photons of specific wavelengths for quantum computing). In quantum research, high-dispersion prisms enable precise wavelength filtering, a key step in generating entangled photon pairs .
Q: How does material choice affect dispersion?
A: Material choice directly determines dispersion, quantified by the Abbe number (lower Abbe numbers = higher dispersion). Flint glasses like SF11 (Abbe number ~36) provide significantly higher dispersion than crown glasses like BK7 (Abbe number ~65). This makes flint glasses preferred for visible-range spectroscopy, where sharp spectral separation is needed to distinguish closely spaced wavelengths (e.g., 589.0nm and 589.6nm, the two sodium D-lines). Crown glasses, by contrast, are better for applications where low dispersion is desired (e.g., imaging systems) .
Q: Can dispersing prisms replace diffraction gratings?
A: Yes, in applications where stray light and spectral purity are critical. Diffraction gratings produce multiple spectral orders (e.g., the first, second, and third order), which can overlap and cause signal interference—for example, in Raman spectroscopy, where weak Raman signals can be masked by higher-order grating reflections. Prisms, however, generate a single spectral order, eliminating this issue. Prisms also have higher damage thresholds than gratings (which have delicate etched surfaces), making them suitable for high-power lasers (e.g., 100W+ industrial lasers) where gratings might degrade .
Q: What's the advantage of CaF₂ prisms?
A: Calcium fluoride (CaF₂) offers two key advantages: superior transmission in UV and IR ranges, and low birefringence (minimal polarization effects). In the UV range (200-400nm), CaF₂ transmits >90% of light, whereas fused silica transmits ~80% at 200nm. In the IR range (2000-8000nm), CaF₂ avoids the absorption bands that limit other materials (e.g., fused silica absorbs strongly above 2100nm). These properties make CaF₂ ideal for semiconductor inspection (UV-based defect detection on silicon wafers) and thermal imaging (IR-based temperature measurement in industrial processes) .
