Intrinsic scattering losses

The multiphonon edge, although somewhat difficult to measure accurately, is not always strictly exponential, probably due to intrinsic compositional characteristics. In addition, non-Rayleigh scattering has often been measured, e.g. exhibiting 1/A or 1/A° dependence, perhaps due to microcrystals, bubbles, etc., and residual transition metal ion, lanthanide ion and OH group absorptions will always be present. In conclusion, the estimates for intrinsic minimum loss in HMFG systems appear optimistic but, ultimately, the actual values at ultralow loss levels will be determined mostly by extrinsic factors. 

Figure Pl.l Conceptual laser resonator, including optional components for wavelength selection and temporal shaping of the laser output. Intrinsic photon loss processes, which reduce the useful laser radiation absorption, spontaneous emission and non-radiative losses in optical media scattering losses at resonator components imperfect reflection/ antireflection coatings...

By combining the above relationships, the isothermal compressibility of polymers at Til can be calculated from the intrinsic molecular volume Vj, . However, the value of P at is necessary to estimate the light scattering loss in the glassy state, p increases linearly with T from to Tjj. It is interesting that the values of (1/ at between and Tn for many amorphous polymers are... 

We developed a GI POF with an acrylic-polymer-based heterogeneous core, whose attenuation was 200 dB/km at 670 nm. The attenuation produces a radiation loss of around 50 dB/km because of the intrinsic scattering due to microscopic core heterogeneities. The core diameter and NA were 200 pm and 0.3, respectively. Figure 3.17 shows microscopic images of the input beams on the fiber near-end faces and the output beams on the PD for the GI POF under the center launching condition. As shown in Figure 3.17b, the output beam pattern of the GI POF... 

D substitution. This shows that with increasing substitution of hydrogen atoms by fluorine atoms, the intrinsic attenuation loss will approach that of a Rayleigh scattering contribution. 

Ultimate loss will be obtained by using a polymer with fluorine and deuterium in its structure, where the intrinsic loss of the polymer (i.e., molecular vibrational loss and Rayleigh scattering loss) will be reduced to an ideal level. Table 7.7 shows the loss factors and the loss limit estimate for deuterated and fluorinated alkyl methacrylate polymer, trideutero-hexafluorobutyl, pentadeutero-methacrylate polymer. This polymer will have a refractive index almost the same as the fluorinated methacrylate polymers. As shown in this table, the lowest loss around 6 dB/km will be attained if a POF using this polymer as a core is developed. As discussed, the value of 6 dB/km is the limit of the polymer transparency in the visible wavelengths that has been obtained to date. 

If x = 1, critical coupling is obtained and the dip depth attains its maximum value of 100% the microresonator is said to be undercoupled if x < 1 and overcoupled for x > 1. While the coupling loss remains constant, the effective intrinsic loss can be changed by interaction of the evanescent fraction (/) of the WGM with the surrounding medium. The effective loss coefficient can then be written as a = a +/aa f /as, where the three terms denote true intrinsic loss, absorption (and perhaps also scattering) by the analyte, and absorption in the solvent (or ambient). 

Let the effective loss coefficient now include, in addition to intrinsic loss, a contribution due to absorption (and scattering) by the analyte contained in the evanescent fraction/of the WGM y = yx +/xa. The effect of the analyte on the resonant (single-frequency) drop signal D0a, when analyte absorption is a small fraction of the total loss, can be written in terms of an approximate effective absorption path length Leff as defined below ... 

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