Laser emerald

A particularly efficient cw vibronic laser is the emerald laser (BeaAliSiaOigtCr " ). When pumped by a 3.6-W krypton laser at Xp = 641 nm, it reaches an output power of up to 1.6 W and can be tuned between 720 and 842nm [5.131]. The slope efficiency dPout/dPin reaches 64% The erbium YAG laser, tunable around X = 2.8 p.m, has found a wide application range in medical physics. 

Table 5.3 compiles the operational modes and tuning ranges of different tunable vibronic lasers. A particularly efficient cw vibronic laser is the emerald laser... 

Synthetic gemstone materials often have multiple uses. Synthetic mby and colodess sapphire are used for watch bearings, unscratchable watch crystals, and bar-code reader windows. Synthetic quartz oscillators are used for precision time-keeping, citizen s band radio (CB) crystals, and filters. Synthetic mby, emerald, and garnets are used for masers and lasers (qv). 

The natural beryl and emerald in our study consisted of seven samples. The laser-induced time-resolved technique enables us to detect Cr, Fe " and possibly Mn emission centers (Figs. 4.52-4.53). 

Fig. 4.53. a-d Laser-induced time-resolved luminescence spectra of emerald demonstrating Cr " center... 

Laser-induced time-resolved luminescence spectra of natural emeralds also demonstrate l -lines of Cr at 680 and 684 nm accompanied by a narrow band peaking at 715 nm, which have similar decay times of approximately 55ps(Fig. 4.53). 

The radio-luminescence of transition metal doped natural beryl has been studied (Chithambo et al. 1995). It was found that Mn containing samples gave intense red radio-luminescence with sharp emission lines, while the Mn activated beryl (morganite) emission is more than twice as bright as that from emerald. Such luminescence has been ascribed to Mn ", but it may be supposed that such emission is connected with Mn luminescence. The laser-induced time-resolved luminescence spectra of natural morganite revealed a band peaking at 730 nm, which may be preliminary ascribed to the Mn center (Fig. 4.52). 

The broad band peaking at 730 nm accompanied by a narrow doublet at 692 and 694 nm (Fig. 4.52) with a mutual decay time of 100 ps in the laser-induced time-resolved luminescence spectrum of beryl is not similar to the Cr emission in emerald. Thus we suppose that such typical emission may be connected with the center. 

Because chemical and structural properties of natural and artificial gems are very similar in this case, the possibilities of Raman and LIBS methods are rather limited. It was found that another laser-based techniques could be very effective for rapid spectroscopic discrimination between natural and synthetic emeralds, rubies, and alexandrite (Armstrong et al. 2000a,b). The first one is DRIFTS (Diffuse Reflectance Fourier Transformed Infra-Red Spectroscopy)... 

Emerald (Cr3+ Be3Al2(Si03)6, chromium-doped beryllium aluminium silicate or beryl) is a well known gem, and its beautiful green color has been attracted people for a long time. Nowadays, emerald crystal is also known as a tunable solid-state laser material, and its optical properties have been smdied (1-10). 

In solid-state laser materials, such as ruby (chromium doped alumina, AljOjiCr " ) (1) and emerald (chromium doped beryl, Be,Al,(Si03)5 Cr ) (2), transitions between multiplets of impurity states are utilized. These states mainly consist of 3d orbitals of the impurity chromium ions. For the analysis of these multiplet structures, the semi-empirical ligand-field theory (LFT) has been frequently used (3). However, this theory can be applied only to the high symmetry systems such as O, (or T ). Therefore, the effect of low symmetry is always ignored in the analysis based on the LFT, although most of the practical solid-state laser materials actually possess more or less distorted local structures. For example, in ruby and emerald, the impurity chromium ions are substituted for the aluminum ions in the host crystals and the site symmetry of the aluminum ions are C, in alumina and D, in beryl. Therefore, it is important to clarify the effect of low symmetry on the multiplet structure, in order to understand the electronic structure of ruby and emerald. 

---