H. P. Jenssen

Tunable alexandrite lasers

Wavelength tunable laser operation has been obtained from the solid-state crystal alexandrite (BeAl 2 O 4 :Cr3+) over the continuous range from 701 to 818 nm. The tunable emission was observed at room temperature and above in a homogeneously broadened, vibronic, four-level mode of laser action. In this mode the laser gain cross section increases from 7 \times 10^{-21} cm2at 300K to 2 \times 10^{-20} cm2at 475K, which results in improved laser performance at elevated temperatures. Efficient 2.5 percent, low-threshold (10 J) operation has been obtained with xenon-flashlamp excitation of the 6 mm diameter × 76 mm length laser rods. Output pulses of greater than 5 J and average power outputs of 35 W have been demonstrated, limited by the available power supply. The emission is strongly polarized E\parallelb , with a gain that is 10 times that in the alternate polarization. The 262 μs, room-temperature fluorescence lifetime permits effective energy storage and Q -switched operation. Tunable Q -switched pulses as large as 500 mJ have been obtained with pulsewidths ranging between 33 and 200 ns depending on the laser gain. Laser action has also been demonstrated on the high-gain ( 3 \times 10^{-19} cm2emission cross section) R line at 680.4 nm and is also polarized E\parallelb . This three-level mode is analogous to the lasing in ruby except that the stimulated emission cross section in alexandrite is ten times larger than for ruby.

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.

Tunable-laser performance in BeAl 2 O 4 :Cr 3+

Broadly tunable laser operation has been obtained at room temperature from the vibronic bands of single-crystal BeAl(2)O(4):Cr(3+) under Xe-flashlamp excitation. Continuous tuning is obtained from 701 to 794 nm, with maximum power at 750 nm. Long-pulse operation employing 6.3-mm x 76-mm rods easily provides 500 mJ in 200-microsec bursts, whereas 70-mJ, 120-nsec pulses are obtained under Q-switch operation.

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.

High beam-coupling gain and deep- and shallow-trap effects in cobalt-doped barium titanate, BaTiO 3 :Co

A series of cobalt-doped barium titanate (BaTiO3) crystals were grown; these crystals have the highest beam-coupling gain reported to date, 7.9 cm−1, measured by using the smallest electro-optic coefficient of BaTiO3. The intensity dependence of the absorption and the gain indicate that there are at least two active photorefractive species. These samples show light-induced absorption and negative absorptive coupling, which is indicative of crystals with deep and shallow traps. However, doping with cobalt diminishes the intensity dependence of the electro-optic gain and increases the electro-optic and absorptive coupling, which indicates that cobalt is a deep-level photorefractive dopant. The higher gain is attributed to an increase of the total effective trap density and to an increase in the deep- and shallow-trap intensity-dependent factor η(I), with higher cobalt doping.

Performance of a diode-pumped high PRF Tm, Ho:YLF laser

The authors report a diode-pumped Q-switched Tm, Ho:YLF TEM/sub 00/ oscillator emitting 1.75 W average (1.75 mJ) and 175 kW of peak power at 2 mu m Q-switched at 1 KHz, operating at 77 K. Stable Q-switched performance from 1 to 90 KHz is also reported. >

Spectroscopic properties and laser performance of Nd3+ in lanthanum beryllate

The neodymium‐doped lanthanum beryllate (La2Be2O5 : Nd3+ or BEL : Nd) laser crystal is monoclinic, space group C2h6‐C2/c. The fundamental vibration directions of light and the corresponding refractive indices have been determined as a function of wavelength. At 1 μm the indices are nX=1.9641, nY=1.9974, and nZ=2.0348. The energy levels of Nd3+ for the five lowest manifolds are presented. The low concentration limit for the Nd3+ 4F3/2 fluorescent lifetime in this crystal is 150 μsec and the two observed laser transitions have stimulated emission cross sections of 2.1×10−19 cm2 for E∥X and 1.5×10−19 cm2 for E∥Y. The laser wavelengths are 1.070 and 1.079 μm, respectively. In laser testing a higher slope efficiency was obtained in La2Be2O5 : Nd than in Y3Al5O12 : Nd (YAG : Nd). A Q‐switched output of 450 mJ from a 6.4‐mm‐diam by 76‐mm‐long X‐axis rod of BEL : Nd has been achieved for the 1.079‐μm transition, while a YAG : Nd rod of the same size in the same system yielded 160 mJ. The higher Q‐switched output ...

Phase diagram and single crystal growth of pure and Sr doped La2CuO4

Abstract Single crystals of pure and Sr doped La 2 CuO 4 have been grown from excess CuO with a top seeded solution growth technique. Crystals have been grown both in air and in oxygen. Growth in air leads to an oxygen deficiency as evidenced by a reduction in the lattice parameters. Differential Thermal Analysis measurements in oxygen on this system reveal a eutectic temperature of 1075°C for the composition 87.5 mol% CuO. Measurements in air show a reduction in the eutectic temperature to 1040°C and the formation of a 3 component system with the partial reduction of CuO to Cu 2 O.

Top seeded solution growth of La4CuO4

Abstract Single crystals of La 2 CuO 4 have been grown from a flux with a top seeded solution growth technique. X-ray and chemical analyses indicate the presence of some flux impurities that are detrimental to superconductive properties. Strontium addition was also attempted to produce superconductive crystals.

High photorefractive sensitivity in an n-type 45°-cut BaTiO 3 crystal

We report the beam-coupling properties of a cobalt-doped oxygen-reduced n-type barium titanate crystal in the 0° and 45° crystallographic orientations. Oxygen reduction improved the response time of the 0°-cut crystal by a factor of ~4.5 without diminishing the beam-coupling gain. The 45°-cut crystal has a peak gain of ~38.7 cm−1, a response time of ~21 ms, and a photorefractive sensitivity of 3.44 cm3/kJ. We infer from response time measurements an equivalent percentage change in the dc dielectric constant and the mobility with respect to crystallographic orientation.