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Often referred to as long wave pass (LWP) and short wave pass (SWP) filters, edge filters provide a well-defined transition between reflecting and transmitting regions. Essentially a modified quarter-wave stack, the filters use interference effects rather than absorption to isolate their spectral bands. Because edge filters will shift shorter with an increase in the angle of incidence, they are a good choice for fine-tuning the cut-on/cut-off wavelength. With their durable, first-surface dielectric coatings, Andover’s edge filters are built to withstand the normal cleaning and handling required by any high-quality optical component.
Our steep-edge long pass filters employ magnetron sputtered hard oxide coatings to yield deep rejection and a sharp transition to very high transmission. The coatings are deposited on precision polished Fused Silica substrates, and do not employ any absorbing filter glasses, making them suitable for high-temperature applications. They are offered in three standard sizes, with custom sizes available on request.