Rejection Band & Baffle Notch Filters
These filters block a
narrow spectral band, such as the monochromatic light from a laser,
while transmitting other wavelengths.
Rejection Band (RB)
filters block more than 99.9% of light in a 15 to 40nm bandwidth. The
average transmission outside the stopband is 75% except in those
spectral regions where higher and lower harmonics cause relatively
high reflection. Specially designed rejection band filters reflect
more than one spectral band, or perform at off-normal angles of incidence.
is a 632.8RB
filter. Bandwidth of principle rejection is about 25nm at 10%
transmission (OD1). Rejection regions recur at harmonic wavelengths
both longer and shorter than the principle rejection band
Baffle Notch (BN) filters
consist of four laser-aligned interference filters in a Chevron
baffle configuration sealed in a rectangular housing. These filters
are designed to provide a band of deep attenuation (greater than OD
5) with high throughput on both sides of the rejection band. The
width of the rejection band, measured at 10% transmission, may be as
narrow as 6nm or as wide as 100nm.
Baffle notch filters are
useful in applications where highly efficient elimination of an
interfering optical line or band is necessary and there is sufficient
room in the optical system for the Chevron baffle configuration. Best
performance is achieved with a well-collimated incident light beam,
although these filters may be used with halfcone angles up to
approximately 20 degrees, depending on the width of the rejection band.
spectral traces of two 514.5BN baffle filters, having bandwidths of
10 and 50nm at 10% transmission (OD 1).