Robert S. F. Chang

Upconversion-pumped blue laser in Tm:YAG

We have demonstrated an upconversion-pumped blue laser on the (1)G(4)-(3)H(6) band of Tm:YAG at cryogenic temperatures. Measurements were also made to assess the possibility of room-temperature upconversion-pumped lasers in Tm:YAG on both the (1)G(4) -(3)H(6) and the (1)D(2)-(3)F(4) bands.

Efficient 1.94-μm Tm 3+ laser in YVO 4 host

A room-temperature Tm:YVO4 laser at 1.94 μm has been demonstrated for the first time to our knowledge. This laser is characterized by a broad bandwidth and a large absorption cross section for the 800-nm pump band. A slope efficiency of 25% was obtained under nonoptimal conditions.

Efficient blue emission from an intracavity-doubled 946-nm Nd:YAG laser

We report the first observation to our knowledge of coherent emission at 473 nm from an intracavity-doubled Nd:YAG microlaser. The d32 coefficient of potassium niobate was used in a 90-deg, temperature-tuned, Type I phase-matching configuration to generate the second harmonic of the 946-nm intracavity field. Output powers in excess of 5 mW at optical conversion efficiencies of approximately 2% have been observed with dye-laser pumping at 588 nm.

Cladding of a crystal fiber by high-energy ion implantation

The feasibility of using a multi-MeV He(+)-ion beam to convert the outer portion of a crystal fiber into cladding is demonstrated. When applied to a-axis LiNbO(3) fiber, the resulting structure has been found to show good waveguiding characteristics.

Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers

A new version of laser heated pedestal growth system is described which is amenable for the rapid growth of single crystal fibers. The system incorporates a Gaussian reflector to reshape the radial intensity profile of the CO2 laser beam. When He is used as the growth atmosphere, high optical quality sapphire fibers can be produced at rates as high as 2 cm/min with this apparatus.

Recent advances in sapphire fibers

Sapphire fibers grown at 20 mm/min in helium, using an improved laser-heated pedestal growth apparatus, have been shown to exhibit very low losses. The laser damage threshold and bending loss of these fibers have been evaluated. The best fiber forms for energy delivery may be a 100-micron diameter fiber with flared ends to increase the power handling capability while retaining the flexibility. Such a fiber has been successfully grown in our laboratory.

Rare earth doped YLF grown by laser-heated pedestal growth technique

Abstract The laser-heated pedestal growth technique has been used in conjunction with a unique feedstock preparation method to grow small single crystal rods of Nd-doped and Tm-doped YLF. Starting powder materials were purified by hydrofluorination and melted to form a solidified mass from which feed rods were fabricated. Oriented crystal rods of 1–3 mm diameter were grown with good optical quality. Due to the large difference in their segregation coefficient, Tm-doped samples showed uniform dopant distribution along the growth axis while Nd-doped YLF showed increasing Nd concentration with grown length.

Growth Of Small Laser Crystals For Study Of Energy Kinetics And Spectroscopy

The laser heated pedestal growth technique is presented as a fast and cost effective means of supplying small crystals for laser material evaluation. A simple method of preparing source rods to feed this crystal growth is described. High quality crystals of rare earth doped garnets are grown for laser induced fluorescence study. This results in a comprehensive study of energy kinetics in Tm:YAG and the determination of the microparameter CDA for cross relaxation of Tm3+.(3H4).

Lasing performance of Tm:YAG minirod grown by laser-heated pedestal growth technique

A 2- mu m Tm:YAG laser using a 1-mm diameter laser rod fabricated from material grown by the laser-heated pedestal growth technique has been characterized. Laser performance was found to be essentially identical to that obtained with bulk grown crystals. This demonstrates the usefulness of this technique for solid-state laser material evaluation and for the growth of laser-quality crystals in sizes suitable for laser diode pumping.<<ETX>>

Fabrication of laser materials by laser-heated pedestal growth

Recent progress in rapid growth of high optical quality laser crystals is reported. Small rods of 1 to 3 mm diameter of singly or multiply doped garnets and fluorides can be grown at low cost for material evaluation and for use in diode pumping.