Crystal growth of optical materials for advanced lasers

During FY96, two specific projects were addressed, Yb-doped fluoroapatite and Cr:ZnSe crystals, which are being used as the gain media to develop diode-pumped solid-state lasers. Both materials have unique properties for near infrared to mid-infrared applications. However, defects in the crystals create optical losses and reduce the efficiency of the lasers. The source of the losses in the crystals were studied and techniques developed to reduce and/or eliminate defects to aid in the growth of high optical quality crystals to increase laser efficiency

Spectroscopy and decay kinetics of Pr{sup 3+}-doped chloride crystals for 1300-nm optical amplifiers

Several Pr{sup 3+}-doped chloride crystals have been tested spectroscopically for suitability as 1300-nm optical amplifiers operating on the {sup 1}G{sub 4} - {sup 3}H{sub 5} transition. {sup 1}G{sub 4} lifetimes are much longer than in fluoride hosts, ranging up to 1300 {mu}sec and suggesting a near-unity luminescence quantum yield. Emission spectra are typically broad (FWHM {approximately} 70 nm) and include the 1310-nm zero-dispersion wavelength of standard telecommunications fiber

Analysis of Sr{sub 5{minus}x}Ba{sub x}(PO{sub 4}){sub 3}F:Yb{sup 3+} crystals for improved laser performance with diode-pumping

Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increases the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping