Tsuyoshi Ohgoh

Diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with 40-GHz repetition rate

We present two different diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with a repetition rate of 40 GHz. This is the highest repetition rate demonstrated so far with diode-pumped 1-/spl mu/m solid-state lasers. The first laser design allows short pulses of 2.7-ps duration whereas the second laser design is optimized for high average output power of up to 288 mW. We compare both design approaches and show that there is a tradeoff between output power and pulse duration.

Effects of broad-waveguide structure in 0.8 μm high-power InGaAsP/InGaP/AlGaAs lasers

Systematic study on the effects of the waveguide thickness Wg has been carried out for 200-μm-wide stripe separate-confinement-heterostructure lasers in the range of Wg=0.22–1.2 μm while the width of single quantum well is kept constant at 10 nm. The internal loss αi is reduced from 1.7 to 1 cm−1 when Wg is increased from 0.22 to 1.2 μm. It is shown that αi is not determined by the free-carrier absorption of clad layers, but primarily by Γ, the optical confinement factor, most probably due to scattering at the quantum well/waveguide interfaces. The external differential quantum efficiency ηd monotonically increases with Wg for pulsed operation. By contrast, ηd is maximum at Wg=0.8 μm for continuous-wave (cw) operation. Both the threshold carrier density and the threshold temperature sensitivity increases with Wg for Wg⩾0.8 μm, which decreases ηd in cw operation. When 200-μm-wide devices (20%/97% coated) were life tested at 2 W and 30 °C, the median degradation rate shows a minimal value of 3×10−6 h−1 at W...

Demonstration of 1.0 µm InGaAs High-Power and Broad Spectral Bandwidth Superluminescent Diodes by Using Dual Quantum Well Structure

We demonstrate 1.0 µm InGaAs high-power and broad spectral bandwidth superluminescent diodes (SLDs). Based on the experimental analysis, it is clarified that the important design parameters are the emission wavelength difference between the dual quantum wells, and the optical confinement factor in the dual quantum well structure to achieve high power and broad spectral bandwidth simultaneously. As a result, we obtained SLDs with 33.4 mW CW power and 77.5 nm full width at half maximum (FWHM) spectral bandwidth. These results correspond to a 1.4-fold increase in spectral bandwidth and a 1.65-fold increase in output power, compared with the single quantum well SLD.

Improved characteristics of 660nm AlGaInP red laser diodes by precise control of the V/III ratio in metal-organic vapor phase epitaxy

The effects of the group V/III ratio during low-pressure metal-organic vapor phase epitaxy on laser performance have been investigated for GaInP∕AlGaInP laser diodes. The quality of GaInP is found to be better at a V/III ratio much lower than an optimal V/III ratio for AlGaInP. GaInP∕AlGaInP laser diodes with the emission wavelength of 660nm were grown at a low V/III ratio for GaInP quantum wells and at a high V/III ratio for AlGaInP waveguide and clad layers. As a result, device characteristics, particularly operating lifetime, are much improved as compared with those of devices grown with a constant high V/III ratio.