NIR Telecom mode field analysis

NIR Laser beam analysis

Software included

Low Cost NIR Camera Technology

ASP 503U-1550 series, phosphor coated CCD cameras, provide a new low cost alternative for measuring and viewing the output of NIR telecom devices and NIR lasers. The thin phosphor film coating is an anti-Stokes material that up-converts NIR radiation in the 1440nm to 1605nm range to visible light measurable by the CCD.

Phosphor Coating Technology

The up-conversion from NIR to visible light in the 1550 series cameras is nonlinear. The anti-Stokes phosphor coating produces visible photons at a rate roughly the square of the input signal. This is shown dramatically in Figure 1, where the camera total output increases dramatically faster than a linear output shown in the bottom line.

Wavelength Response

The anti-Stokes up-conversion efficiency is very wavelength dependent. Figure 3 shows the typical spectral response curve of a new, high response coating. As seen, we have calibrated the response from 1527nm to 1605nm. We have extrapolated the shorter wavelength region by comparing our measured response to data published over the entire range. The significance of this non-linearity is that from the CCD camera saturation in the center of a beam, the up-converted visible signal drops as the square of the input signal. Thus the lower signal wings of a beam are suppressed, resulting in the appearance and measurement of a beam width much smaller than actual.