Fiber lasers are normally considered to be low-power devices and not competitive with diode-pumped Nd:YAG lasers. However, by employing special glass fiber technology and a novel inner-cladding geometry we demonstrate here a Nd3+-doped single-mode fiber laser emitting an output power of 1.07 W at a wavelength of 1.057 μm.
Three thulium doped tellurite glass compositions have been investigated. The 1470 nm transition is radiative in these tellurite glasses and the radiative lifetimes are in the range of 350 to 470 μs. The 1470 nm fluorescence is broad with a full width at half maximum of 105 nm. Fibers have been drawn from these glasses with a loss of 0.7 dB/m at 1300 nm. A fiber with an OH fundamental absorption of 200 dB/m at 2.99 μm has an OH first overtone absorption of 0.3 dB/m at 1480 nm. The overlap between the thulium ion 1470 nm emission and the hydroxyl absorption depends on glass composition. Tellurite glasses can accept large concentrations of Tm3+ ions and, as long as the hydroxyl level can be kept low, the effect of concentration quenching can be minimized. Tm3+-doped tellurite glasses represent a viable alternative for the next generation of active components for S-band optical amplifiers. It can be pumped at 795 nm with an absorption of ∼38 dB/km/ppm and codoped with Ho3+ to avoid self-termination of the 1470 nm transition. It can also be pumped at 1212 nm as efficiently as at 795 nm, but diodes are not yet available at this wavelength. Using available pump wavelengths of 1064 nm and 1047 nm will require fiber lengths 15 times longer than pumping at 1212 nm.
Solution-focused therapists do not believe in resistance but rather that when the client does not want to attend therapy, the onus remains on the therapist to find unique ways to cooperate with the client. Motivating the client often depends on whether the client considers himself part of the problem or its solution. Clients come to therapy because they feel they have a problem and want to do something about it, because others have a problem and the client wants others to change, or because they are mandated to attend therapy. Regardless of why the client attends therapy, the therapist accepts the client's perspective and assists the client in finding ways to do what is needed so they do not need to come anymore. When working with children and adolescents, the therapist must also consider external hindrances that may interfere with therapy and enlist the cooperation of significant others in the client's life.
The author provides a brief overview of some of the landmark studies on resilience conducted by Werner and Smith and Garmezy and Masten. A discussion follows of positive psychology and the movement from the exclusive diagnosis and treatment of psychopathology to the inclusion of strengths and virtues and that which helps an individual survive and thrive. The chapter continues by discussing the constructivist postmodern approaches of solution-focused and narrative therapies emphasizing client strengths and resiliencies. With a focus on psychological, philosophical, and artistic areas of understanding, postmodern therapists seek new ways to create new preferred futures. The postmodern shift entails a cooperative and interactive negotiation of reality between therapist and client that opens new possibilities for the client to consider. The author provides a brief overview of the similarities and differences between narrative and solution-focused therapy and their approaches in assisting clients to find solutions.
High-brightness, low-coherence sources are required in a number of optical sensor applications, particularly the fiber-optic gyro. An efficient superfluorescent, neodymium-doped phosphate glass fiber source has been developed which fulfils this requirement. The fiber shows a high-gain efficiency at 1.053 mu m of 1 dB/mW pump power and this permits pumping with an 810 nm single-stripe AlGaAs laser diode to obtain >5 mW CW output power at a wavelength of 1.053 mu m for only 45 mW of pump power.< >
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