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A new class of laser materials based on tetrahedrally coordinated Cr2+ ions as dopants in II-VI crystals are analyzed. Spectroscopic data relevant to the understanding, design and engineering of lasers based on the materials are examined. The materials represent the first widely tunable diode-pumpable mid-infrared lasers functioning at room temperature. The materials are major components for the expected realization of compact, diode-pumped Cr2+ lasers.

The absorption and emission spectroscopic properties of divalent zinc chalcogenides doped with Cr, Co, Fe and Ni reveal that Cr2+ ion is a suitable laser ion for mid-IR. Destructive effects of nonradiative decay are absent in the Cr2+ ion which has an emission lifetime of around 8 micro sec. Cr has strong luminescence at room temperature. Laser demonstrations of Cr:ZnS and Cr:ZnSe in a laser-pumped cavity with a CO:MgFe pump laser indicate that the output of both lasers have a peak at 2.35 micrometer and have a maximum slope efficiency of about 20%.

We have performed several physical and optical measurements on the Cr:LiSAF (LiSrAl[F.sub.6]) laser material that are relevant to its laser performance, including thermal and mechanical properties, water durabilities, and Auger upconversion constants. The expansion coefficient, Young's modulus, fracture toughness, thermal conductivity, and heat capacity are all used to determine an overall thermomechanical figure of merit for the crystal. An investigation of the water durability suggests that the cooling solution should be maintained at pH = 7 to ameliorate problems associated with water dissolution. The Auger constant was found to become much more significant at higher Cr doping, in whic excited-state migration leads to a substantial increase in the upconversion rate. We propose a design for a 50-W Cr:LiSAF laser system that is based on a detailed knowledge of all the relevant material parameters.

Substantial range of laser parameters are derived from a Yb3+ ion-based laser media. Low and high emission cross-sections are observed in two complexes. Changes in emission life-time is related to the alteration in the emission-cross-section. Increased pump bandwidths of the order of 10-12 nanometers are observed with mixed crystals of Yb. Czochralski method is employed for the growth of high quality optical laser materials.

The use of Ti:sapphire laser as pump source enables the study of Yb-doped fluorapatite to reveal slope efficiencies of up to 79%. The passive loss of the 1043-nanometer laser wavelength causes the residual decrement of quantum defect limited efficiency. The emission and absorption cross sections of Yb3+ are high in the study material in comparison with those of other Yb-doped media.

The absorption and emission characteristics of Yb3+-doped crystals are studied. Experiments are performed wherein the emission spectra of several Yb3+-doped oxide and fluoride crystals is measured and analyze by emission spectroscopy. The emission cross section are determined using the method of reciprocity and the Fuchtbauer-Ladenburg formula. Results show that only the Y3Al5O12 and Ca5(PO4)3F specimens are capable of generating adequate emission cross sections.

The infrared cross-sections of lasers doped with Er3+, Tm3+ and Ho3+ ions are measured during the transition period between ground-state and least excited state. LiYF4, BaY2F8, Y3Al5O12, LaF3, KCaF3, YAlO3 and La2Be2O5 crystal materials are examined. A good fit is shown between actual and computed radiative emission lifetimes. The Ho-doped LiYF4, BaY2F8 and Y3AlO12 laser crystals are observed to be the most suitable for pulsed laser applications.

The spectroscopic analysis of heavily doped chromium lithium strontium aluminum flouride (Cr:LiSAF) lasers is presented. Experiments were conducted with the laser under wing pumping at 752 nm and 780 nm and showed efficient laser pumping for the spectral region bounded by the two values. Meanwhile, the derived optical and thermal characteristics suggest that AlGaAs laser diode arrays are suitable for diode pumped tunable solid state lasers.

The excited state absorption spectrum of Sm2+ diluted as an impurity in the single crystal hosts SrF2 and SrCl2 has been observed. The absorption peaks associated with the 5D0(4f6) excited state were found to be displaced by approximately 3000 cm-1 from the absorption bands arising from the 7F0(4f6) ground state when the 5D0–7F0 energy was taken into account. The observed peak separation is ascribed to the 4f–5d exchange interaction. From the measured peak positions and band intensities, the exchange energy for the Sm2+ impurity in the two host crystals was determined to be about the same order of magnitude as that expected for the free ion. The implications of the properties of the excited state absorption bands for the performance of CaF2:Sm2+ and SrF2:Sm2+ lasers are considered. [ABSTRACT FROM AUTHOR]

We have examined the optical properties of Cr3+ in MgF2 and in the fluorite-structure hosts: CdF2, CaF2, SrF2, and BaF2. The properties of Cr3+ in MgF2 are similar to those observed for other fluoride crystals that have octahedral substitutional metal sites. Interestingly, Cr3+ is also found to be sixfold coordinated in the fluorite hosts, despite the fact that the metal sites of these crystal lattices are eightfold coordinated. The smaller ionic radius of Cr3+ compared to, say, Ca2+, undoubtedly results in considerable relaxation at the metal site. However, the crystal field stabilization energy present in the 4A2(d3) ground state also provides for the energetic preference of sixfold vs eightfold coordination. The similarity of the observed absorption spectra of Cr3+ in MgF2 and in fluorite give evidence that the ground state is octahedrally coordinated in all of these hosts. The reduction of this electronic stabilization energy in the 4T2(d3) excited state is considered to produce a configurational shift relative to the ground state. This shift may be the reason why Cr3+ luminesces effectively in MgF2 whereas it is largely quenched in the fluorite-structure materials. [ABSTRACT FROM AUTHOR]

Discusses a study which measured the lifetimes of μm emission band for erbium and holmium cations-doped fluorides. Emission lifetimes obtained; Information on emission quantum yields and radiative lifetimes; Analysis of emission cross section.

The February 4, 1968, UFO sighting at Redlands, California, was accompanied by an intense, distinctive sound that was recorded as a background sound on a magnetic tape recording being made by Reverend Julian Vigh at the Bethel Christian Church. A rescue Emergency Vehicle (EV), with its siren operating, happened to be deployed in Redlands at the time of the UFO sightings. An inquiry by several Redlands University professors attributed the background sound on the Vigh recording to the EV siren. Reported here for the first time is an independent, comprehensive, detailed sonic analysis of the tape background sound and the EV siren, originally prepared in 1969, and intended for inclusion as an independent technical appendix in a book on the Redlands UFO sightings then in preparation. That book was never completed and published. The result of detailed tape analysis concurred with Professor Seff 's conclusion that the EV siren was the source of background sound on the Vigh tape; however, a number of sonic anomalies in the time dependence of sound intensity and Doppler shift were identified and quantified. [ABSTRACT FROM AUTHOR]