Widely tunable S-band ring-cavity Tm3+-doped fluorotellurite fiber laser.

Tm3+-doped fluorotellurite fibers (TDFTFs) are fabricated by using a rod-in-tube method. A 2.1 m long TDFTF is used as the gain medium, in which both ends of the TDFTF are connected to a short piece of a silica fiber by direct fusion splicing. By inserting the above TDFTF and a tunable optical bandpass filter into a ring cavity and employing a 1400/1570 nm dual-wavelength pumping technique, tunable lasing from 1460 to 1526 nm is obtained, which almost covers the whole S-band. To the best of our knowledge, this is the first report of tunable Tm3+-doped fiber laser with a tunable range almost covering the whole S-band. Furthermore, by removing the tunable optical bandpass filter from the ring cavity, free-running multi-wavelength lasers at 1500 and 1901 nm are achieved. Our results show that TDFTFs are promising gain media for constructing S-band fiber lasers.

Intense emission at 605†nm from Pr3+-doped fluorotellurite glass fibers.

Pr3+-doped fluorotellurite glass fibers (PDFTFs) were fabricated by using a rod-in-tube method. By using a 976/1400 nm dual-wavelength upconversion pump technique, an intense emission at 605 nm was obtained from a 6 cm long PDFTF, which was attributed to the transition 1D2 → 3H4 of Pr3+ ions. With an increase in power of the 1400 nm laser from ∼34 to ∼136 mW, the spectral bandwidth of the 605 nm emission decreased and the intensity of the 605 nm emission increased monotonically, indicating the generation of 605 nm amplified spontaneous emission (ASE). To the best of our knowledge, this is the first report of 605 nm ASE in PDFTFs. Our results showed that PDFTFs had the potential for constructing red fiber lasers and amplifiers.

Watt-level 815†nm lasing from Tm3+-doped fluorotellurite glass fibers.

Tm3+-doped fluorotellurite fibers based on TeO2-BaF2-Y2O3(TBY) glasses were fabricated by using a rod-in-tube method. By using an 81 cm-long Tm3+-doped fluorotellurite fiber as the gain medium and a 1400 / 1570 nm dual-wavelength pump technique, lasing at 815 nm was obtained for a threshold pump power of 629 mW at 1400 nm and a fixed pump power of 960 mW at 1570 nm. As the 1400 nm pump power is increased to 1803 mW, the obtained maximum output power was about 1616 mW. The corresponding optical-to-optical conversion efficiency was about 58.5%. Our results show that Tm3+-doped fluorotellurite fibers are promising gain media for constructing 815 nm fiber lasers.

Thulium-doped fluorotellurite glass fibers for broadband S-band amplifiers.

We demonstrated broadband S-band (1460-1530 nm) amplification in Tm3+-doped fluorotellurite glass fibers (TDFTFs) by using a 1400/1570 nm dual-wavelength pump technique. TDFTFs based on TeO2-BaF2-Y2O3 (TBY) glass were fabricated by using a rod-in-tube method. For an input signal power of 0 dBm (or 1 mW), a broadband positive net gain ranging from <1440 nm to 1546 nm was achieved in a 1.55-m-long TDFTF with a Tm3+ doping concentration of ∼4000 ppm, as the pump powers of the 1400 nm and 1570 nm lasers were 1.7 W and 0.14 W, respectively. The corresponding bandwidth for a net gain of >20 dB was ∼66 nm (1458-1524 nm), and the measured saturated output power was ∼24.84 dBm at 1490 nm. In addition, numerical simulation was performed by using the parameters of the TDFTFs and the pump lasers, and the noise figure was calculated to be <5.6 dB in the S band. Our results showed that the TDFTFs were promising gain media for constructing efficient broadband S-band fiber amplifiers.

Directly Linking Low-Angle Grain Boundary Misorientation to Device Functionality for GaAs Grown on Flexible Metal Substrates.

A new growth method to make highly oriented GaAs thin films on flexible metal substrates has been developed, enabling roll-to-roll manufacturing of flexible semiconductor devices. The grains are oriented in the <001> direction with <1° misorientations between them, and they have a comparable mobility to single-crystalline GaAs at high doping concentrations. At the moment, the role of low-angle grain boundaries (LAGBs) on device performance is unknown. A series of electron backscatter diffraction (EBSD) and cathodoluminesence (CL) studies reveal that increased doping concentrations decrease the grain size and increase the LAGB misorientation. Cross-sectional scanning transmission electron microscopy (STEM) reveals the complex dislocation structures within LAGBs. Most importantly, a correlative EBSD/electron beam-induced current (EBIC) experiment reveals that LAGBs are carrier recombination centers and that the magnitude of recombination is dependent on the degree of misorientation. The presented results directly link increased LAGB misorientation to degraded device performance, and therefore, strategies to reduce LAGB misorientations and densities would improve highly oriented semiconductor devices.

[Genetic alteration of p16 gene in oral and maxillofacial squamous cell carcinomas].

OBJECTIVE: To detect p16 gene alteration in oral and maxillofacial squamous cell carcinomas (OMSCC) and its relation with this tumor type. METHODS: To examine 33 paraffin-embedded cases of primary oral and maxillofacial squamous cell carcinoma by PCR-SSCP method and analyze relationship of p16 gene alteration with clinical stages, histological grades, lymphatic metastasis in OMSCC. RESULTS: It revealed 9 of 33(27%) with p16 gene change including 7 (21%) homozygous deletions and 2 (6%) point mutations. There were no significant differences among clinical stage I-IV each other (P>0.05),but there were significant differences between clinical stage I+II and clinical stage III+IV (P<0.05); P16 gene alteration did not significantly differ among histological grading, lymphatic metastasis positive group and negative group in OMSCC. CONCLUSION: Genetic deletion and mutation of p16 gene are frequent molecular events in this kind of tumor, its inactivation has played a important role in the developmental course of OMSCC. p16 gene alteration closely correlates with clinical stages, and the frequency of its alteration may increase following the development of tumor clinical course. The results can be used to evaluate the prognosis and assist in diagnosis of the patients. But no relation with histological grades and lymphatic metastasis which still remains to further study.