Holographic filters

Filters, acoustooptic Filters, holographic Filters, metallic Filter types Filtration... 

D.E. Battey, J.B. Slater, R. Wludyka, H. Owen, D.M. Pallister and M.D. Morris, Axial transmissive f/1.8 imaging Raman spectrograph with volume-phase holographic filter and grating, Appl. Spectrosc., 47, 1913-1919 (1993). 

Battey, D.E. Slater, J.B. Wludyka, R. Owen, H. Pallister, D.M. Morris, M.D. Axial Transmissive f/1.8 Imaging Raman Spectrograph with Volume-Phase Holographic Filter and Grating Appl. Spectrosc. 1993, 47, 1913-1919. 

Caltech Astronomy Holographic Filter Allows Astronomers to Read between the Lines. http //www.astro.caltech.edu/palomar/ohfilter.html (accessed on June 25, 2008). 

Figure 7-31 Diagram of instrumental setup for monitoring polymer curing (a) CCD detector (b) spectrograph (c) holographic filter (d) beam splitter (e) lens (f) ST-connector ( fiberoptic connector) (g) fiberoptic (h) Teflon tube filled with polymer (i) bulk polymer (j) laser with bandpass filter (k) mirror. (Reproduced with permission from Ref. 20.)...

An efficient mechanism for rejection of the scattered laser-line radiation has to be incorporated. The major new development in this area is the introduction of holographic filters. These devices have the sharp cut-off characteristics of the multilayer dielectrics, but do not exhibit a harmonic structure in the transmission curve. The transmission is high (80-90%) and featureless, as opposed to the dielectrics which have numerous features in the transmission curve because of interference among the multiple layers. Two filters are sufficient to give Rayleigh-line rejection, and spectral information down to 150 cm" can be obtained. Another filter type is the Chevron unit [41] which has been shown by Nicolet, and possibly Bruker, to give Raman data down to 60 cm. Additionally, data can be obtained on both the Stokes and anti-Stokes bands [42]. 

In order to design a tunable holographic filter with a -3dB passband width, BW, of 1 nm (125 GHz), for each wavelength channel tuned, we take d = 3.5 pm for the spatial period of the fixed grating. To use the same device for CWDM/DWDM, a SLM with a value of N = 720 and D = 7 pm for the spatial period, is chosen. The output singlemode fibers used in our device have a core diameter, cpme, of 9 pm. Then, from (7),/must be greater than 23.9 mra As a practical value we assume/= 25 mm. 

Fig. 7. Holographic filter shape. For wavelengths dose to the central value, X < Xo +/-1.5 nm, the shap>e is Gaussian and like a Bessel function for wavelengths X > Xo +/-1.5 nm...

In this section two complementary experiments have been made. The first one is related to diffraction patterns measurements for different bars holograms and the second one to a SLM characterization for holographic filters, demultiplexers and routers use with reference to the devices whose design and characteristics have been described in the ptrevious sections. Due to the unavailability of components in the laboratory with the characteristics previously described, the experimental optical bench is somewhat different from the aprpropaiate one, but, the measurements obtained are in agreement with the calculations. 

Horche P.R. Alarc6n A et al. (2004), "Spatii Light Modulator holographic filter for WDM systems". International Union of Radio Science URSr04... 

FIGURE 6 A simple, yet versatile, optical system for using holographic filters for image processing. 

Holographic optical devices and. in particular, holographic filters - arc among a growing repertoire of optical devices and materials that have resulted from the... 

The behavior of holographic filters and gratings is described by coupled wave theory. The Bragg wavelength A, for a holographic optical clement is given by... 

---