Optical filter wavefront distortion: out-of-band to in-band predictions and the effect of the illumination source bandwidth. Read or download the full article in PDF format.

Band Pass Filters (BPFs) are used to pass (transmit) a range of wavelengths and to block (reflect) other wavelength on either side of the bandpass. The region of high transmittance is known…

A Solid Etalon Filter (SEF) is used to select a periodically spaced frequency grid from a broad spectral range. The key specifications

The Single Cavity Filter (SCF) is used to select a single frequency from a broad spectral range. SCFs are typically used for…

Linear Transmittance Filter (LTF) has a transmittance that is changing linearly over a specified wavelength range. LTFs are typically used for…

Coarse Wavelength Division Multiplexing (CWDM) filters are designed to multiplex and de-multiplex wavelength signals in metropolitan, access and enterprise networks and for Cable TV applications. In addition…

Gain Flattening Filter (GFFs), also known as gain equalizing filters, are used to flatten or smooth out unequal signal intensities over…

1       Introduction Large format (>100 mm diameter), narrow bandpass filters (NBPF) are required in many fields. Applications requiring a large...

The wavefront error (WE) of a surface with an optical coating (“filter”) is ideally measured at the in-band wavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-of-band wavelength (typically 633 nm), assuming that the filter transmits (for transmitted WE, or TWE) or reflects (for reflected WE, or RWE) at this wavelength. This out-of-band TWE/RWE is generally assumed to provide a good estimation of the desired in-band TWE/RWE. It will be shown in this paper that this is not the case for a large class of filters (i.e., bandpass) where the group delay is significantly different at the in-band and out-of-band wavelengths and where the optical filter exhibits a thickness non-uniformity across the surface.