However, in actual design, the absorption outside the cutoff wavelength
cannot be exactly zero, so the selection of the absorber's cut-off wavelength must give consideration to both the absorption and energy loss.
The device exhibited a peak response at a wavelength of 340 nm, which is in the UV-A region, with a 3dB bandwidth of 26 nm and a cutoff wavelength
of 353 nm.
Because the corresponding cutoff wavelength
[[lambda].sub.c] (nm) = 1240/[E.sub.g] = 1240/2.0 [approximately equal to] 620 nm, the enhanced short-wavelength responses within 400~700 nm were thought to be resulting from the light-absorption of NPS layers.
When [[lambda].sub.c] refers to the cutoff wavelength
of the dominant mode ([TE.sub.10]) in rectangular waveguides, i.e., [[lambda].sub.c] = 2[a.sub.1], the cutoff wavelength
ratio in waveguides with and without ridges is:
where [k.sub.c] = [omega] [square root of ([mu][epsilon])] = 2[pi]/[[lambda].sub.c] is the cutoff wavenumber with [OMEGA] denoting the angular frequency and [[lambda].sub.c] being the cutoff wavelength
. [OMEGA] is a simply or multiply connected domain with boundary [partial derivative][OMEGA].
The types of measurements discussed included attenuation/ loss, chromatic dispersion, cross talk, cutoff wavelength
, effective area, effective index, four-wave mixing efficiency, index of refraction profile, mode-field diameter, non-linear coefficients, polarization dependent loss and polarization-mode dispersion.
The cutoff wavelength
effect caused by the fictitiously created waveguide can be observed.
We also plotted the cutoff wavelength
at different widths in Figure 2(i).
It can easily be seen that under the same conditions, relative to without Ti[Cl.sub.4] pretreatment, the absorbance of ZnO films increased after Ti[Cl.sub.4] pretreatment and light absorption cutoff wavelength
presented a remarkable red shift, effectively broadening the range of ZnO on the absorption of sunlight.
In general, m and p have the same value; however, when the guided modes are near to the cutoff wavelength
, m and p can be different.