Transmission maxima

Luminosity curves for PETN of loading d 1.60 detonated in vacuum are represented nere. The left curve was photographed, using optical filters, with transmission maxima at A=6870, while for the right one A was 4510. In this type of curve, the intensities of the peaks with maximum deflection during the deton interval were used for the evaluation of temperature of detonation... 

Similar tests were conducted for Tetryl of loading d 1.60 and for TNT of d 1.55. Their luminosity curves for deton in air at atm pressure are given below. The left curves were taken using optical filters with transmission maxima at A=6870A, while the right ones used A= 4510 (Ref 5, Progr-Rept, Apr-June 1949)... 

Interference bands in slab transmission may be observed because of the oscillatory term cos in (2.75). Transmission maxima occur when f = 2irp( pX = 2nxh), where p = 1,2,3,. ... If a maximum occurs at a wavelength X, neighboring maxima occur at X + AX, where... 

The classical response of such a Fabry-Perot interferometer is shown in Fig. 11. Transmission maxima correspond to reflection minima and vice versa. If the reflectivities of the two mirrors are unequal, then the reflected power has a minimum that is different from zero. This case is illustrated by Fig. 12a, where one mirror has a variable reflectivity 0.7 < < 0.9 and... 

For an isolated or Beutler-Fano resonance, q = 0 implies a symmetric window. In the present situation, the presence of other resonances arranged as a Rydberg series, with energy intervals which are not the same on both sides of any given resonance means that the lineshapes are not symmetrical even for q = 0. However, when q = 0 and B = tan7r/x, from the first equation (8.44), the transmission maxima coincide with the resonance energies as they do for isolated resonances. 

The comb of equally spaced (in cm-1) transmission maxima from an etalon is useful as relative frequency markers to linearize the scan of a tunable laser. This makes it possible to interpolate between irregularly distributed absolute frequency standard lines (e.g., atomic lines, Fourier Transform Spectrometric Atlases of Molecular I2, Br2, Te2, and small polyatomic molecules) and to measure frequency separations between features in the spectrum being recorded. Pattern recognition methods, such as Loomis-Wood (see Section 1.1.4) and searches for repeated combination differences, work best when applied to spectra in which the frequency separations between lines are determined at the highest possible precision (better than 1/10 the average line spacing). 

Figure 2. Current-voltage characteristic (solid curve) and transmission maxima energies vs. voltage (dashed curves) for the disordered structure with well width fluctuations, <7= 33%.

Figure 13.3 FP interferometer configuration (a) scanning confocalFP interferometer with collimated input beam and single-element detector (b) fixed-spacing FP etalon with divergent input beam and ID array detector. A typical fringe pattern and recorded transmission maxima are shown in the bottom part (note the change in fringe spacing)...

The ratio 8v/Av of free spectral range 8v to the halfwidth Av of the transmission maxima is called ht finesse F of the interferometer. From (4.51b) and (4.52c) we obtain for the finesse... 

Since we have assumed an ideal plane-parallel plate with a perfect surface quality, the finesse (4.53a) is determined only by the reflectivity R of the surfaces. In practice, however, deviations of the surfaces from an ideal plane and slight inclinations of the two surfaces cause imperfect superposition of the interfering waves. This results in a decrease and a broadening of the transmission maxima, which decreases the total finesse. If, for instance, a reflecting surface deviates by the amount X/q from an ideal plane, the finesse cannot be larger than q. One can define the total finesse F of an interferometer by... 

Tunable coherent light sources can be realized in different ways. One possibility, which has already been discussed in Sect. 5.5, relies on lasers with a broad gain profile. Wavelength-selecting elements inside the laser resonator restrict laser oscillation to a narrow spectral interval, and the laser wavelength may be continuously tuned across the gain profile by varying the transmission maxima of these elements. Dye lasers, color-center lasers, and excimer lasers are examples of this type of tunable device. 

Fig. 5.66. (a) Axial resonator modes within the spectral gain profile (b) temperature tuning of the gain maximum and (c) mode hops of a quasi-continuously tunable cw PbS Te diode laser in a helium cryostat. The points correspond to the transmission maxima of an external Ge etalon with a free spectral range of 1.955 GHz [5.112]... 

This results in a decrease and a broadening of the transmission maxima, which decreases the total finesse. If, for instance, a reflecting surface deviates by the amount Xjq from an ideal plane, the finesse cannot be larger than q. One can define the total finesse F of an interferometer by... 

A line filter is essentially a Fabry-Perot etalon with a very small optical path nd between the two reflecting surfaces. The technical realization uses two highly reflecting coatings (either silver coatings or dielectric multilayer coatings) that are separated by a nonabsorbing layer with a low refractive index (Fig. 4.60). For instance, for nd = 0.5 p,m the transmission maxima for vertical incidence are obtained from (4.62a) at Ai = 1 xm, A2 = 0.5 p,m, A3 = 0.33 p,m, etc. In the... 

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