A. Linz

High‐Efficiency Room‐Temperature 2.06‐μm Laser Using Sensitized Ho3+:YLF

Pulsed room‐temperature laser action at 2.06 μm has been achieved using Ho3+:YLF (LiF4) sensitized with Er3+ and Tm3+. An unoptimized cavity gave a threshold of 35 J and a slope efficiency of 1.3% in normal mode with an output mirror of 62% T. A slope efficiency of 2% and a 65‐J threshold were observed in Q‐switched operation along with Q‐switched energy of >500 mJ from a 0.9×⅛‐in. rod. The sensitizer ions have broad absorption bands and transfer times (to the active ion) of 150–200 μsec.

Blue light emission by a Pr : LiYF4 − laser operated at room temperature

Room‐temperature operation of a solid‐state laser has been achieved for the first time in the blue region using Pr : YLF. The 0.2% Pr : YLF crystal was longitudinally pumped at 444 nm using a pulsed dye laser. Laser emission was observed at 479 nm and required a pump‐energy density of 8 J/cm2 at threshold.

Optical spectra and laser action in Nd3+‐doped CaY2Mg2Ge3O12

Crystals of the garnet‐structured germanate CaY2Mg2Ge3O12 have been grown from a melt containing 6 mole% Nd3+. The fluorescence, absorption, excitation spectra, lifetime, and linewidths have been measured and were compared with the results for Nd3+:YAG. The important spectroscopic features of Nd3+:CaY2Mg2Ge3O12 are a lifetime of 305 μsec, a strong absorption in the near infrared, a very intense fluorescence line at 941 nm, and a linewidth at this wavelength of approximately 37 cm−1. Laser action has been achieved at 1058.96 nm at room temperature. An estimate of the laser transition cross section gives a value of σ=6×10−20 cm2.

Magneto‐optical properties of KTb3F10 and LiTbF4 crystals

Single crystals of KTb3F10, LiTbF4, LiTb0.5Y0.5F4 and LiTb0.25Gd0.75F4 were prepared and the wavelength, temperature, and magnetic field dependence of the Faraday rotation measured. Optical‐absorption spectra and refractive indices are also reported. The Faraday effect in these materials is described by a paramagnetic rotation with the primary oscillator strength arising from 4f8→4f75d electronic transitions of the Tb3+ ions. Whereas LiTbF4 orders ferromagnetically at low temperatures, the mixed crystals exhibited no ordering at T?1.25 K. Low‐temperature Faraday rotation measurements of KTb3F10 do not indicate ferromagnetic order above 1.66 K. KTb3F10 and LiTbF4 crystals have large Verdet constants, are transparent in the visible and near infrared and have small nonlinear refractive‐index coefficients. These materials are therefore useful for optical rotators and in high‐power laser applications.

Magneto-optical properties of KTb/sub 3/F/sub 1/0 and LiTbF/sub 4/ crystals

Single crystals of KTb3F10, LiTbF4, LiTb0.5Y0.5F4 and LiTb0.25Gd0.75F4 were prepared and the wavelength, temperature, and magnetic field dependence of the Faraday rotation measured. Optical‐absorption spectra and refractive indices are also reported. The Faraday effect in these materials is described by a paramagnetic rotation with the primary oscillator strength arising from 4f8→4f75d electronic transitions of the Tb3+ ions. Whereas LiTbF4 orders ferromagnetically at low temperatures, the mixed crystals exhibited no ordering at T?1.25 K. Low‐temperature Faraday rotation measurements of KTb3F10 do not indicate ferromagnetic order above 1.66 K. KTb3F10 and LiTbF4 crystals have large Verdet constants, are transparent in the visible and near infrared and have small nonlinear refractive‐index coefficients. These materials are therefore useful for optical rotators and in high‐power laser applications.

Defect property correlations in garnet crystals. II. Electrical conductivity and optical absorption in Ca3Al2Ge3O12

Electrical conductivity and ionic transference measurements performed at varying temperatures and partial pressures of oxygen show that CALGAR (Ca3Al2Ge3O12), a luminescent garnet, is a mixed ionic‐electronic conductor. An activation energy of 1 eV for ionic diffusion is measured. An absorption band at 400 nm, whose magnitude can be controlled by varying the annealing atmosphere, is attributed to an O− center.

Halogen vapor deposition of chalcogenide crystals: Lead sulfide

n‐type single crystals of lead sulfide, PbS, have been grown by a novel chemical vapor deposition method of potential importance for growing a variety of chalcogenide crystals. A reduced‐pressure flowing system was developed based on the following chemical reactions: Pb+Cl2→PbCl2 and PbCl2+H2S→PbS+2HCl. Additional Cl2 is used for fine control of the growth rate. The optimal growth conditions are a temperature of 650 to 750°C and a pressure of 8 Torr. Important to the furnace design is a quartz concentric gas injection arrangement which prevents premature mixing and reacting of the gases. n‐type single crystals of PbS having carrier concentrations of the order of 1019 cm−3 and Hall mobilities of 600 cm2/V sec at 300°K and as high as 14 000 cm2/V sec at 77°K have been grown. An isothermal anneal at 850°C for 15 days will convert the crystals to p type. Possible extensions of the technique to mixed lead‐tin salts, including tellurides and selenides, and to other chalcogenides are discussed.

Inelastic Neutron Scattering Studies of Critical Fluctuations in MnF2 Above and Below TN

Detailed inelastic neutron scattering measurements have yielded the behavior of the scattering function S(q, ω) for both the transverse and the longitudinal fluctuations throughout the critical region of the uniaxial antiferromagnet MnF2. The results are discussed in the light of the theory of dynamic scaling. The results below TN are discussed with reference to quasihydrodynamic theories of the spin fluctuations in the ordered state.