To grow YCl3, anhydrous, high-purity powdered YCl3 and TmCl3 were mixed. In all cases, the powdered mixtures were melted and allowed to sit molten under approximately 100 Torr of Cl2 for several hours to reduce oxide impurities. The melt, contained in a 10-mm inner diameter fused silica ampoule with a tapered tip, was cooled over a period of 5 days while remaining under the Cl2 atmosphere. The finished samples buy IWR-1 were polycrystalline with large grains and were un-oriented. Spectroscopy Unpolarized fluorescence spectra between 1,600 and 5,500 nm were collected with a 0.20-m monochrometer. Fluorescence was induced with laser diodes gated to see more produce 50-ms pulses. The diode
pump powers were between 0.25 and 2.0 W. A pulse repetition rate of 10 Hz was used to synchronize a lock-in amplifier
that received its input from a photo-detector mounted at the exit slits of the monochrometer. Spectra were collected using three passes – one for the 1,100- to 1,700-nm range, one for the 1,550- to 3,000-nm range, and one for the 3,000- to 5,500-nm range. An InGaAs photo-detector was used for the 1,100- to 1,700-nm range. For the other two spectral ranges that covered 1,550 to 5,500 nm, a liquid nitrogen-cooled InSb was used for photo-detection. For the 3,000- to 5,500-nm range, a long pass filter that blocked TPCA-1 mw wavelengths less than 2,500 nm was in place to eliminate the short wavelength features from appearing in higher order. Also, for spectral acquisition at wavelengths greater than 2,500 nm, the monochrometer PRKACG was purged with dry nitrogen gas in order to reduce a strong absorption feature at 4,300 nm resulting from atmospheric CO2. Emission was measured with the Tm3+:YCl3 remaining sealed in the fused silica ampoules to prevent degradation from exposure to atmospheric moisture. Fused silica is transparent for the range of emission wavelengths studied. For Tm3+:KPb2Cl5, no environmental precautions were used. In each case, the wavelength dependence of the complete light collection and detection
system was calibrated using a blackbody source. Spectra were corrected using the system response function obtained from the blackbody calibration. To observe fluorescent decays, the laser diodes were operated in pulsed mode to pump the 3H4 level of Tm3+, and a digitizing oscilloscope recorded the transient response from the photo-detectors. During fluorescent decay measurements, the monochrometer acted as a filter to isolate emission at wavelengths associated with specific energy levels. Results and discussion Spectroscopy of singly doped Tm3+ crystals Figure 2 shows a fluorescence spectrum at 300 K between 1,100 and 2,000 nm of Tm3+:KPb2Cl5 that results from pumping with a 1.5-W, 805-nm laser diode [32]. The spectrum has three features that are typical of Tm3+ spectra in low phonon energy hosts.