Tuning range

A further advantage, compared with the alexandrite laser, apart from a wider tuning range, is that it can operate in the CW as well as in the pulsed mode. In the CW mode the Ti -sapphire laser may be pumped by a CW argon ion laser (see Section 9.2.6) and is capable of producing an output power of 5 W. In the pulsed mode pumping is usually achieved by a pulsed Nd YAG laser (see Section 9.2.3) and a pulse energy of 100 mJ may be achieved. 

In the near-infrared, Al Ga As and In Ga As P lasers, and in the far-infrared lead compound semiconductor lasers are tunable by varying temperature and operating current. Many exceUent spectroscopic studies have been performed using them. However, they do have relatively limited tuning ranges for any one device. 

The free-electron laser (EEL) offers the ultimate in tunabiHty, in principle being unlimited in its tuning range. A EEL represents a very large investment, however. 

Tuni 7g The interferometer is tuned by electrode voltage control. The band-pass center wavelength is displaced accordingly. The FWHM of the transmission pass band is approximately 70 nm at the 4.2 pm wavelength. The stable tuning range of L is... 

However, the applications of the phenomenon of the modal transition are not limited to the chemical sensing field. Indeed, cladding etching and an HRI layer of sputtered indium tin oxide were exploited to achieve an LPG-based tunable filter with a large tuning range and with limited reduction in the loss peak65. 

Fig. 5.4 From top down the measured absorption profiles of methane, methyl chloride, and ethylene obtained using a WGM locked to the laser. In each case, the top trace shows the amplified variation in dip depth and the bottom trace is the transmission profile of the gas in a 16 cm absorption cell. The frequency axis shows the tuning range. Reprinted from Ref. 4 with permission. 2008 Optical Society of America...

Figure 2.12 Tuning ranges for different dye lasers, illustrating the spectral regions covered by these lasers (pulsed condition) (courtesy of Spectra Physics).

Therefore, it is clear that different frequency conversion processes, together with the variety of lasers, have led to a great variety of coherent sources with large and differing tuning ranges. The whole spectral range of 185-3400 nm can be covered by different methods. 

Tunability of the blue light from 418 mn to 429 mn was also possible, via simple tuning of the CnLiSAF pump laser. This 11 nm tuning range eoineides with the fundamental aeeeptanee bandwidth of 11 nm for whieh the appKTP waveguide was designed. 

Instead of tuning the laser line, one can also shift the absorption lines across the laser line by Zeeman or Stark effects. This is especially advantageous in the far-infrared region where the tuning range of laser lines is restricted. 

Emerald, Cr " doped beryl, has a beryl structure with the Cr " impurity ions in highly distorted octahedron sites. The discovery of lasing action in emerald stimulated investigation of its luminescence properties. It was established that its tuning range is approximately 730-810 nm, while luminescence consists of a narrow line at 684 nm and a band peaking at 715 nm with similar decay times of 62 ps. The relative intensities of those line and band are different in a- and 7T-polarized spectra (Fabeni et al. 1991). 

Puthoff et al. 77) found two polaritons associated with TO phonons of species Aj with tuning ranges from 630 to 500 cm 1 and 250 to nearly 0 cm-1. The Raman scattering at these extraordinary polaritons was used to study 36) the directional dispersion of the phonons in LiNb03. Recently Winter and Claus 78> also investigated the polaritons associated with the E phonons at 582 and 154 cm-1 by both photographic and photoelectric methods. These branches were important for the assignment of the phonon spectrum 39>. 

The large scattering cross section of the extraordinary polaritons and their wide tuning range made tunable stimulated polariton scattering possible. 

In Table I we summarize the tuning ranges of stimulated emission obtained so far by stimulated polariton and spin-flip Raman scattering. 

Table I. Tuning ranges of stimulated infrared emission...

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