Preparation of thermoluminscence (TL) dosimetric grade A12O3 powder and pellets five times more sensitive than TLD-100 is described. Glow peaks at 50, 125, 250, 325, 475 and 625 degrees C with emission in the blue region have been observed; Si and Ti have been identified as the impurities responsible for TL in this phosphor. Studies of the TL growth rate with exposure showed that the 250 degrees c peak grew linearly up to 400 R and then at a supralinear rate of (exposure). The growth of the 475 degrees c peak was almost linear at a rate of (exposure) 1-05, while that for the 625 degrees C peak was sublinear at (exposure) 0-85. The 250 and 475 degrees peaks together show a linear response up to 40 000 R. The phosphor had no light sensitivity and is very well suited for gamma dosimetry as pellets or powder. Studies of sensitization and supralinearity, with sensitizing exposure, sensitizing anneal temperature and test gamma and alpha exposures are reported. Initially filled 625 degrees C TL related traps were found to be essential for sensitizaiton. Supralinearity and sensitization in Al2O3 phosphor could be consistently explained by the deep trap model.

A system of radiative transfer equations is used to calculate the loss coefficient for amplified luminescence fluxes propagating along and transverse to the cavity axis in the active layer of high-power laser diode arrays taking the spreading of charge carriers in the cladding and contact layers of InGaAs/GaAs/AlGaAs heterostructures into account. It is shown that the spreading of charge carriers leads to a significant change in the amplified luminescence flux which can contribute up to 18% to the lasing threshold of these laser diode arrays. The calculated loss coefficients can greatly simplify the determination of the amplified luminescence fluxes in laser diode arrays with an error of less that 16% and can be used to determine how much the amplified luminescence affects the power and dynamic characteristics of diode arrays.Introduction. High-power laser diode arrays (LDAs) are coming into ever wide use as compact, highly efficient sources of optical excitation for solid state lasers [1][2][3]. Reducing the energy demand by these emitters requires optimization of the parameters of the LDAs, as well as of the solid state lasers. The power of modern LDAs used as pumps is approaching 80-150 W [1, 4]. These relatively high LDA powers have been achieved by substantial increase in the length of the cavities and the total widths of the heterostructure lasing elements. In most cases of practical interest, the LDA is characterized by a relatively high area of the active layer of the laser heterostucture. Thus, it is to be expected that, in accordance with [5-10], intense fluxes of amplified luminescence should develop in the active layers of LDAs; these result in an increase in the threshold and a reduction in the laser output power. It has been shown [5, 6, 8-10] that the AL fluxes for single laser diodes (with a single emitting region, or strip contact) can be analyzed by introducing an AL loss coefficient α lum determined from the balance between emission, amplification, and absorption of spontaneous emission ]11]. The value of α lum depends on many factors, in particular, on the composition of the active layer, the geometry of the laser structure, the excitation conditions, etc. Thus, as opposed to the loss coefficient for the laser emission, finding α lum is a rather complicated task in most cases of practical importance. This paper deals with the determination of the loss coefficient for AL produced in the active layer of highpower LDAs with as many as a few hundred regions. The resulting values of α lum can be used to estimate how much AL affects the threshold, dynamic, and power properties of LDAs and to determine methods for further improvement in the characteristics of LDAs and of diode pumped solid state lasers.Propagation of Fluxes of Amplified Luminescence in LDAs. The AL characteristics of concern for the parameters of LDAs (output wavelengths 940-980 nm) used to pump solid state erbium lasers are studied here. These LDAs are generally based on InGaAs/GaAs/AlGaAs heterostructures with two quantum-dimension...

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It has been theoretically ascertained that for defect-free InGaAs and InGaN compounds the uniform distribution of indium atoms is more energetically preferable than the clustering distribution. The presence of gallium and arsenic vacancy in InGaAs and nitrogen vacancy in InGaN facilitates indium atom clustering distribution. It has been shown that the increase in the indium content in InGaAs and InGaN compounds leads to the decrease of the formation energy of gallium, arsenic and nitrogen vacancies.

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