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We have fabricated phototubes with photocathodes consisting of the Mg-doped GaN films. The spectral shapes of the response and the quantum efficiency (QE) strongly depend on the Mg-doping concentration. The calibrated QE of the photocathode is maximized to be 71.9% at a photon energy of 5.4 eV by a Mg-doping concentration of 3.0×1019cm−3. Consequently, a phototube with the GaN-based photocathode is realized to demonstrate a very high QE, more than 50% and sharp cutoff characteristic over three orders of magnitude.

The experimental demonstration of a broad-area Quasi-continuous-wave (QCW) laser-diode array pumped cesium vapor laser is reported in this letter according to our experimental results. We used a volume-Bragg grating to narrow the spectral linewidth for acquirement of enough resonance transitions. A glass cylindrical cell filled with cesium/buffer gas was set in an end-pumped flat-concave cavity and the gas pressure was set lower than 1atm. Using the QCW drive mode with the repetitive rate and pulse width of 1kHz and 50μs, respectively, 13.45μJ pulse energy has been achieved with the slope efficiency of about ∼1.8%.

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A high quantum efficiency of photoemission to a 1.35 μm threshold has been achieved from an externally biased InP/InGaAsP photocathode which has a p/n junction instead of a Schottky contact. The quantum efficiency at 1.3 μm is 5% (electron per incident photon) with the photocathode cooled to −80 °C. The photocathode consists of a n+InP contact layer, a p−InP photoelectron-emitting layer and a p−InGaAsP photon-absorbing layer on a p+InP substrate.