Takenori Morita

High power density vertical-cavity surface-emitting lasers with ion implanted isolated current aperture

We report on GaAs-based high power density vertical-cavity surface-emitting laser diodes (VCSELs) with ion implanted isolated current apertures. A continuous-wave output power of over 380 mW and the power density of 4.9 kW/cm2 have been achieved at 15 °C from the 100-μm-diameter aperture, which is the highest output characteristic ever reported for an ion implanted VCSEL. A high background suppression ratio of over 40 dB has also been obtained at the emission wavelength of 970 nm. The ion implantation technique provides an excellent current isolation in the apertures and would be a key to realize high power output from a VCSEL array.

Efficient and Reliable High-Power Laser Diode Bars With Low-Smile Implementation

We report on our recent development of high power 940 nm laser diodes (LDs) bars. The optimization of the laser structure and thermal management allow over 200-W continuous wave (CW) operation with 58% conversion efficiency from the 1-cm LD bar. We have also developed an assembly technique, and have suppressed the smile of LD bars mounted even on Cu heatsinks with hard solder to less than 1 μm. Long term stability have also be confirmed under 200-W CW operation.

High-Efficient and Reliable Broad-Area Laser Diodes With a Window Structure

We report on high-power 915-nm broad-area laser diodes with a window structure formed by a impurity-free vacancy disordering method. A maximum conversion efficiency of 68% and high output power of 19.8 W have been achieved at 20°C. A stable operation over 2000 h has also been confirmed under the condition of an output power of 15 W at 25°C. Far-field patterns suggest that the laser diode is suitable for coupling into an optical fiber with 105-μm core diameter and 0.15 numerical aperture.

Short-Pulse Operation of a High-Power-Density Proton-Implanted Vertical-Cavity Surface-Emitting Laser Array

We report on a GaAs-based high-power-density vertical-cavity surface-emitting laser diode (VCSEL) array with ion-implanted isolated current apertures. A peak output power of 40.6 W has been achieved from the VCSEL array with seven emitters under 100-ns-pulse operation. This is the first demonstration of a ten-watt-class output power for a VCSEL array with ion-implanted isolated current aperture configuration. The corresponding power-density is estimated to be 73.8 kW/cm2, which is three times greater than the record power-density of the short-pulse-operated oxide-confined VCSEL.

High-power 2D laser diode arrays for pumping solid state lasers

Long life, high power and high repetition frequency 2D laser diode (LD) arrays are needed for pumping solid state lasers. The reliability of AlGaAs/GaAs high-power lasers has been studied. Over 1 X 109 operation shots in 4-stack 2D LD arrays with 350 W peak output power and over 1 X 1013 shots in single-stripe laser diodes with 2.3 W peak output power have been obtained. 2D LD arrays of 3.5 kW (emitting area 3.2 cm x 1.0 cm), 2.5 kW (emitting area 1.0 cm x 1.0 cm) and 2.2 kW (emitting area 6.5 cm x 0.12 cm) were demonstrated under quasi continuous wave operation.

200-W Operation of an Ion-Implanted Vertical-Cavity Surface-Emitting Laser Array

We have demonstrated a high-power 980-nm vertical-cavity surface-emitting laser diode (VCSEL) array with ion-implanted current apertures. The device was characterized on an exclusively developed water-cooled heat sink for the VCSEL array. A peak output power of over 200 W has been achieved under quasi-continuous-wave operation at a cooling water temperature of 10 °C. The VCSEL array consists of 635 emitters, which were defined by proton implantation and arranged in a closest packed arrangement with 175-μm-spacing in 5 mm × 5 mm square. The results provide a chance to the next step for a higher-power VCSEL array.

High-Brightness Narrow-Bandwidth Operation of a Broad-Area Laser Diode with a Rear External Cavity

We demonstrate a high-brightness, narrow-bandwidth, broad-area laser diode with a rear external cavity that consists of a micro-cylindrical lens and a volume Bragg grating in the rear facet of the diode. Using this external-cavity technique, a broad-area laser diode achieved a bandwidths full width at half-maximum (FWHM) of 0.22 nm and a divergence angle (FWHM) of 1.1° with an output power of 446 mW.

Long-Term Reliability of 915-nm Broad-Area Laser Diodes Under 20-W CW Operation

We report on the long-term reliable continuous wave (CW) operation of high-power and high-efficiency 915-nm broad-area laser diodes (BA-LDs). An output power of over 20 W and a maximum power-conversion efficiency of over 65% have been marked at a heat-sink temperature of 20 °C. Stable operations of over 5000 h have also been achieved for the 915-nm and 976-nm BA-LDs with CW output powers of 20 W, respectively. The window structure with a bandgap difference of 100 meV provides the reliable operation at the high-output power range.

Development of a high-power vertical-cavity surface-emitting laser array with ion-implanted current apertures

Vertical-Cavity Surface-Emitting Lasers (VCSELs) are very attractive to high power light sources owing to the advantageous configuration of two-dimensional arrays and being free from catastrophic optical damage. Although oxideconfined VCSELs have been employed in most of applications with VCSELs, ion-implanted VCSELs have a potential to be the better light sources for high power applications. In spite of the fact, the detailed characteristics of the ionimplanted VCSELs had been researched only in ten milliwatt-class output power. Here we report on a high power VCSEL-array with proton-implanted current apertures. A peak output power of over 40 W under short-pulse operation has been achieved. This is the first demonstration of ten watt-class output power for ion-implanted VCSELs.

Development of High-Power Quasi-CW Laser Bar Stacks With Enhanced Assembly Structure

We report on our recent development of quasi-continuous-wave 940-nm laser diode (LD) bars with passive cooled type. The 10 LD bar stacks with a narrow pitch of 1.54 mm have demonstrated a high output power of 10.1 kW, corresponding to 1 kW/bar, under 200-μs pulses at 50-Hz operating frequency. The maximum conversion efficiency of 58% has been achieved at an output power of 300 W. In condition of 1000 μs pulses at 10-Hz operating frequency, we have achieved an output power of 0.93 kW and a conversion efficiency of 59%, respectively. We consider that the LD bar stacks are suitable for diode pumped high-energy class solid-state lasers.