Barium borate

Figure B2.1.1 Femtosecond light source based on an amplified titanium-sapphire laser and an optical parametric amplifier. Symbols used P, Brewster dispersing prism X, titanium-sapphire crystal OC, output coupler B, acousto-optic pulse selector (Bragg cell) FR, Faraday rotator and polarizer assembly DG, diffraction grating BBO, p-barium borate nonlinear crystal.

Figure B2.1.3 Output of a self-mode-locked titanium-sapphire oscillator (a) non-collinear intensity autocorrelation signal, obtained with a 100 pm p-barium borate nonlinear crystal (b) intensity spectrum.

Greenfield S R and Wasielewski M R 1995 Near-transform-limited visible and near-IR femtosecond pulses from optical parametric amplification using Type II p-barium borate Opt. Lett. 20 1394-6... 

Hache F, Zeboulon A, Gallot G and Gale G M 1995 Cascaded second-order effects in the femtosecond regime in p-barium borate self-compression in a visible femtosecond optical parametric oscillator Opt. Lett. 20 1556-8... 

CERAMCS - NONLINEAROPTICAL AND ELECTROOPTIC CERAMICS] (Vol 5) b-Barium borate [13701-59-2]... 

Only certain types of crystalline materials can exhibit second harmonic generation (61). Because of symmetry considerations, the coefficient must be identically equal to zero in any material having a center of symmetry. Thus the only candidates for second harmonic generation are materials that lack a center of symmetry. Some common materials which are used in nonlinear optics include barium sodium niobate [12323-03-4] Ba2NaNb O lithium niobate [12031 -63-9] LiNbO potassium titanyl phosphate [12690-20-9], KTiOPO beta-barium borate [13701 -59-2], p-BaB204 and lithium triborate... 

Currently used nonlinear optical crystals are potassium dihydrogen phosphate (KDP) and barium borate (BBO). Compared to KDP, the advantages of BBO are its transparency in the UV and its larger quantum efficiency of up-conversion by a factor of 4—6. For a given position of the crystal, only a narrow band of the fluorescence spectrum is up-converted. Therefore, if the full fluorescence spectrum is of interest, the crystal must be rotated at a series of angles. An example of experimental set-up is presented in Figure 11.2. The fwhm of the response is 210 fs. 

In 1969, Hubner[35] reported that the space group of the low-temperature form of barium borate is C2/C, a centrosymmetric structure. However, in 1979, by using a powder second-harmonic generation (SHG) test, my group found that the low-temperature form of barium borate possesses a large NLO coefficient, about six times... 

Very few studies of hydrated barium borates have been published. 

Fig. 12. Experimental setup for the frequency comparison between the IS — 3S and 2S — 6S/D transitions (TiSa titanium sapphire laser, LBO lithium tri-borate crystal, BBO /3-barium borate crystal)...

These features are exploited in an experiment which is taking place in our laboratory. A schematic diagram of this experiment is shown in figure 4. The system consists of an all-lines violet mode-locked Kr+ ion laser operating at a repetition rate of about 250 MHz Which synchronously pumps a C102 dye laser. The dye laser typically produces about 300 mW of average power and pulse durations of about 3 psec. This is frequency doubled to 243 nm in a crystal of p-barium borate to produce in excess of 2 mW average power. The output from the second harmonic crystal is then mode-matched into an ultra-violet enhancement cavity. The free... 

Figure 5 Schematic diagram of an experimental set-up for the state-selective study of laser-induced desorption. KDP potassium dideuterium phosphate crystal, BBO p-barium borate crystal, MCP microchannel plate [11].

Experiments were performed using a visible optical parametric amplifier based on noncollinear phase-matching in /3-barium borate, followed by a pulse compressor using chirped dielectric mirrors. This optical source provides ultrabroadband pulses, with bandwidth extending from 500 to 720 nm, compressed to an almost transform-limited duration of 5-6 fs. The pump-... 

Figure 6 Block diagram of the two-color optical parametric amplifier (OPA) and IR-Raman apparatus. CPA = Chirped pulse amplification system Fs OSC = femtosecond Ti sapphire oscillator Stretch = pulse stretcher Regen = regenerative pulse amplifier SHGYAG = intracavity frequency-doubled Q-switched Nd YAG laser YAG = diode-pumped, single longitudinal mode, Q-switched Nd YAG laser KTA = potassium titanyl arsenate crystals BBO = /J-barium borate crystal PMT = photomultiplier tube HNF = holographic notch filter IF = narrow-band interference filter CCD = charge-coupled device optical array detector. (From Ref. 96.)...

In general, alkaline earth metal borates exhibit framework structures made up of BO4 tetrahedra and BO3 triangles. Only a few compounds show isolated islands, and layered structural feature and chain arrangement are absent. Moreover, most of these compounds contain both BO4 and BO3. No chain structure of barium borate has been discovered yet prior to our work [22]. 

Both hydrated and anhydrous metal borates have numerous industrial uses. Some of the major uses of hydrated metal borates are the manufacture of glasses, ceramics, and industrial fluids, and as micronutrient fertilizers, fire retardants, and biostats. Anhydrous borates find use as heterogeneous catalysts, scintillation hosts, and in the fabrication of optoelectronic devices. Anhydrous aluminum borates are used as additives in oxide ceramics to promote the formation of desirable phases. Also, aluminum borate whiskers are used as reinforcing additives in composite materials. Specific nses of sodium, calcium, zinc, and barium borates are discussed in sections below. 

Both hydrated and anhydrous barium borates find significant commercial use. Barium metaborate monohydrate,... 

Ba0-B203-H20, is used as a corrosion inhibitor in industrial paints and primers, a biocide in paints and plastics, and to a lesser extent as a fire retardant additive. It is generally manufactmed by reacting barium sulfate with a sodium tetraborate hydrate in water. Several other crystalhne hydrated barium borates are also known but have less industrial importance. 

---