R. E. Fahey

Crystal growth, spectroscopy, and laser characteristics of Ti:Al/sub 2/O/sub 3/

The vertical-gradient-freeze technique has been used to grow laser-quality Ti:Al/sub 2/O/sub 3/ single crystals. Ti/sup 3+/-Ti/sup 4+/ pairs have been shown to be responsible for the residual infrared absorption. Room-temperature oscillator and amplifier experiments are reviewed. >

Residual infrared absorption in as-grown and annealed crystals of Ti:Al/sub 2/O/sub 3/

Data for as-grown and partially oxidized samples of Ti:Al/sub 2/O/sub 3/ grown by the vertical-gradient-freeze technique show that the residual infrared absorption in these samples is largely due to Ti/sup 3+/-Ti/sup 4+/ pairs. In agreement with this pair model, the residual absorption in as-grown samples has been substantially decreased by annealing in a reducing atmosphere. Data for an as-grown crystal grown by the heat exchanger method indicate the presence of a second mechanism for residual absorption that may set a lower limit on the ratio of this absorption to the Ti/sup +3/ absorption used to pump laser emission. >

Room-temperature continuous-wave operation of a Ti:Al2O3 laser.

Room-temperature cw operation of a Ti:Al(2)O(3) laser has been demonstrated for the first reported time. Laser emission at 770 nm was excited with an all-line Ar-ion laser pump. The maximum output power was 1.6 W. Values of (64 +/- 10)% for the internal quantum efficiency and (2.4 +/- 0.5)% for the round-trip cavity loss are obtained from the thresholds and slope efficiencies measured with 0.7 and 4.9% output couplers. The cavity-loss value places an upper bound of 0.007 cm(-1) on the absorption coefficient of the laser rod for the pi polarization (E ||ĉ) || at 770 nm, compared with 0.73 cm(-1) measured at 490 nm, the peak of the Ti(3+) pump band.

Optically induced nonresonant changes in the refractive index of Ti:Al(2)O(3).

Changes in the refractive index of Ti:Al(2)O(3) induced by 10-nsec, 532-nm pump pulses from a frequency-doubled Nd:YAG laser have been measured interferometrically at 632.8 nm for signal polarizations parallel (pi) and perpendicular (sigma) to the c axis. The nonthermal portion of these changes decays on a 3-microsec time scale characteristic of the fluorescence lifetime of Ti(3+). For the sigma polarization, the nonthermal index change is equal to the concentration of excited Ti(3) ions times (4 +/- 2) x 10(-24) cm(3). The change for the pi polarization is lower by a factor of 3.7 +/- 0.6. The average change is consistent with the value estimated from a harmonic oscillator model that considers virtual transitions to a charge-transfer band.

Magnetic and optical measurements on Ti:Al2O3 crystals for laser applications: Concentration and absorption cross section of Ti3+ ions

The optical absorption coefficient of Ti:Al2O3 samples at 490 nm for the π polarization (E∥c) is found to be proportional to the concentration of Ti3+ ions, as determined by measurement of the paramagnetic moment as a function of temperature and magnetic field. The experimental data yield the value σ=(9.3±1.0)×10−20 cm2 for the absorption cross section of Ti3+, the active ion in the tunable Ti:Al2O3 laser, at the peak of the laser pump band.

Small-signal gain measurement in a Ti:Al/sub 2/O/sub 3/ amplifier

A small-signal single-pass power gain of e/sup 5.2/=180 has been measured for a signal in the pi polarization at 790.7 nm in a longitudinally pumped Ti:Al/sub 2/O/sub 3/ amplifier. A double-pass power gain of e/sup 5.2/ approximately=10/sup 4/ has been attained for the same polarization at 799.8 nm. The ratio of the gain cross sections at 632.8 and 790.7 nm is 1/25. The gain anisotropy at 632.8 nm is g/sub pi //g/sub sigma /=2.3. The lifetime of the upper lasing level decreases with increased pumping, probably as the result of amplified spontaneous emission. >

Growth of single Ti2O3 crystals from the melt

Procedures are described for growth of large single crystals of TiOx, (1.501 ⩽ x ⩽ 1.512) that are reasonably free of cationic impurities and of C and N. Data concerning the stoichiometry and the segregation of impurities during crystal growth are presented. The electrical properties of doped and pure single crystal materials are briefly described.

Growth of Ni-doped MgF2 crystals in self-sealing graphite crucibles

Abstract Large Ni-doped MgF2 single crystals of excellent optical quality have been grown in self-sealing graphite crucibles by a vertical gradient freeze technique. This relatively simple technique always yields single crystals having excellent optical quality and should be applicable to the melt growth of other crystals that are too volatile to permit the use of open systems.

Room-Temperature cw Operation of the Ti:Al2O3 Laser

This paper reports on the room-temperature cw operation of several Ti:Al2O3 laser rods pumped by an Ar-ion laser. For one rod, a threshold of 2.3 W, maximum output of 1.6 W, and slope power efficiency of 19% were obtained at 770 nm, and continuous tuning was observed from 693 to 948 nm.

Growth of Laser-Quality Ti:Al2O3 Crystals by a Seeded Gradient-Freeze Technique

A seeded vertical gradient-freeze technique has been used to grow laser-quality Ti:Al2O3 single crystals with low residual infrared absorption from charges containing between 0.15 and 1.0 wt.% Ti2O3 in tungsten crucibles.