Output spectrum

The frill width at half maximum of the autocorrelation signal, 21 fs, corresponds to a pulse width of 13.5 fs if a sech shape for the l(t) fiinction is assumed. The corresponding output spectrum shown in fignre B2.1.3(T)) exhibits a width at half maximum of approximately 700 cm The time-bandwidth product A i A v is close to 0.3. This result implies that the pulse was compressed nearly to the Heisenberg indetenninacy (or Fourier transfonn) limit [53] by the double-passed prism pair placed in the beam path prior to the autocorrelator. 

The corrosion process is observed as a series of events which all contribute to the overall corrosion rate. Measurement of rest potential fluctuations between two identical electrodes of potential fluctuations with respect to a fixed reference can be carried out. The electrochemical noise output spectrum is analysed using digitised data. The interpretation requires electrochemical expertise, and the method is therefore usually provided as a specialised service. 

Fig. 9.16 The calculated output spectrum of a silicon waveguide ring resonator sensor at critical coupling (t a) and for t 0.8a. The assumed ring radius is R 150 pm...

The calculated ring resonator output spectrum in Fig. 9.16 is based on (9.9) and shows a series of resonance minima spaced at intervals known as the free spectral range A/.,.SR ... 

Fig. 16.3 Simulation of transmission spectrum for a four resonator array. FDTD simulation showing the steady state electric field distributions when the device is excited at the (a) resonant wavelength and (b) nonresonant wavelength. Note that the color levels in this image are scaled to the maximum field intensity in each image not to each other. The field levels in (b) are roughly of 20 times greater magnitude than those shown in (a), (c) Output spectrum for a device consisting of a waveguide with four evanescently coupled side cavities adjacent to it. Here each resonator consists of a cavity with four holes on either side. Reprinted from Ref. 37 with permission. 2008 Optical Society of America...

A typical, experimentally obtained, output spectrum of a waveguide with five resonators of differing sizes is shown in Fig. 16.5a. In this first case, all the five resonators had water as the surrounding medium. As can be seen, each resonator contributes a sharp dip to the output spectrum of the device. We observe that each ID resonator possesses a large -factor varying from 1,500 to 3,000 and a full... 

Fig. 16.5 Response to refractive index interrogation of a single NOSA waveguide, (a) Output spectrum for a NOSA where one of the five resonators is fluidically targeted, first with water and then with a CaCl2 solution. The resonance of the targeted resonator shifts toward the red end of the spectrum due to the higher refractive index of the CaCl2 solution, (b) Experimental data (with error bars indicating inter device variability) showing the redshifts for various refractive index solutions. The solid line is the theoretically predicted redshift from FDTD simulations. The experimental data is in excellent agreement with the theory. Reprinted from Ref. 37 with permission. 2008 Optical Society of America...

IR spectrometers have the same components as UY/visible, except the materials need to be specially selected for their transmission properties in the IR (e.g., NaCl prisms for the monochromators). The radiation source is simply an inert substance heated to about 1500 °C (e.g., the Nernst glower, which uses a cylinder composed of rare earth oxides). Detection is usually by a thermal detector, such as a simple thermocouple, or some similar device. Two-beam system instruments often work on the null principle, in which the power of the reference beam is mechanically attenuated by the gradual insertion of a wedge-shaped absorber inserted into the beam, until it matches the power in the sample beam. In a simple ( flatbed ) system with a chart recorder, the movement of the mechanical attenuator is directly linked to the chart recorder. The output spectrum is essentially a record of the degree of... 

Figure 5.4 X-ray tube output spectrum, showing continuous emission and line spectra of the target material (in this case gold). The K absorption edges for major elements in silicate glasses are shown below the diagram, indicating that the gold M lines are particularly effective for the analysis of the light elements Na to P.

The data im are the measured output spectrum at the exit slit. This is simply the convolution of the number-count object at the entrance slit with the point spread function s(x) of the intervening optics and following electronics,... 

Figure 144 (a) An edge emitting microcavity structure with two metal electrode/100% mirrors, based on the Alq3 emitter and PDA as HTL and (b) the EL spectra of two such different thickness structures (1) D = 350 nm and (2) D = 160 nm, detected at 0 = 0 the surface light output spectrum is shown for comparison (broken line). After Ref. 553. Copyright 1993 SPIE, with permission. 

Figure 6 Overlap region of the absorption spectrum of sulfamethoxazole and the output spectrum of sunlight.

The modelled output signal is then calculated by performing the inverse FFT on the modelled output spectrum. The model parameters of the model of the combustion camber arc found by fitting the modelled output signal with the output signal measured. The fitting is effected by minimising the least square error. 

The arc lamp with the best resemblance to sunlight is the xenon arc lamp, although the development of new metal-halide lamps has led to competition for that claim. The spectral outputs of these two types are shown in Figure 3.2 and Figure 3.3. The xenon arc has a relatively smooth continuous output spectrum with some line emissions superimposed in the region of 450 to 500 nm, whereas the metal-halide lamp is more uniform across the 350 to 550 nm region. 

Recent photolysis studies considered the effect of the wavelength on the rate curve [207,212,213]. Specifically, photolysis of alkali and alkaline-earth azides using a low-pressure mercury lamp gave curves (Figure 26) whose characteristic shape was sensitive to the spectral content of the photolyzing light [198,207]. If the 180-nm line was filtered from the output spectrum of a low-pressure... 

Figure 3.13. White noise input spectrum (top) versus BiQuad filtered output spectrum (bottom). The BiQuad has a resonator pole pair at 3000 Hz with r = 0.99, and a zero pair at 5000 Hz with r = 1.0 (same filter as shown in the z-plane view of Figure 3.12).

As will be discussed in Chapter 6, one of the main uses of the Fomier transform is for analyzing sounds. We can pick peaks in the frequency domain and determine whether they behave like sinusoids. Those peaks can be used to calibrate an additive or modal synthesizer model like we did with the coffee mug in Chapter 4. We can look at gross spectral envelope features, and use those to control a filter-based model. We can also use frequency domain convolution to implement filters, multiplying the spectnun of an input signal by a shaping function spectrum to yield the final filtered output spectrum. 

In order to detect the intensity change of one mode in the presence of many others, the laser output has to be dispersed by a monochromator or an interferometer. The absorbing molecules may have many absorption lines within the broadband gain profile of a multimode dye laser. Those laser modes that overlap with absorption lines are attenuated or are even completely quenched. This results in spectral holes in the output spectrum of the laser and allows the sensitive simultaneous recording of the whoie absorption spectrum within the laser bandwidth, if the laser output is photographically recorded behind a spectrograph or if an optical multichannel analyzer (Vol. 1, Sect. 4.5) is used. 

Figure 4 Effect of the X-ray tube current / (mA), potential V (kV), and target atomic number Z on the output spectrum of an X-ray tube. The dotted line indicates the maximum of the distribution.

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