We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.

We have successfully realized practical self‐pulsating laser diodes (SP‐LDs) based on AlGaInN systems that exhibit low noise characteristics even with an optical feedback of 1% at a high temperature of 75 °C. Our fabricated SP‐LD employs a saturable absorber layer (SAL). We adopt new approaches to realize practical SP operation; specifically, (i) we inserted an AlGaN layer between the active layer and the SAL in order to reduce the threshold current, and (ii) we intentionally introduced reactive ion etching (RIE) damage to the SAL in order to reduce the carrier lifetime in the SAL by controlling the distance between the SAL and the dry‐etched surface. The threshold currents for the fabricated SP‐LD at 25 °C and 75 °C were 38.8 mA and 54.4 mA, respectively. We also demonstrated that it is possible to suppress the relative intensity noise (RIN < –125 dB/Hz) even under the conditions of high temperature (75 °C) and an optical feedback of 1%. These results indicate that practical SP‐LDs for use in optical storage devices can be realized by inducing dry etching damage in the SAL. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)