Kejian Luo

High-power highly reliable single emitter laser diodes at 808 nm

High power laser diodes and diode arrays emitting at the wavelength of 808nm are widely used for pumping neodymium (Nd+) doped solid state lasers and fiber lasers, medical surgery, dental treatment and material processing. In general, the power is limited by catastrophic optical mirror damage (COMD) and heat dissipation. In this paper we demonstrate 29W CW output power at 808 nm from a 400 &mgr;m single emitter with 2mm cavity length. The device thermally rolls over due to the excess heat. The L-I curve rolls over at 29.5W, the laser is still alive, and we can repeat the test again and again without catastrophic optical mirror-damage (COMD). The device consists of an InAlGaAs/AlGaAs/GaAs, optimized special graded-index separated-confinement heterostructure (GRINSCH) broad waveguide (BW), single quantum well (SQW) and barriers between waveguide and cladding layers. A weak temperature dependence characteristic, which is desirable for high power and reliable operation, is obtained from these devices.

Highly reliable, high-brightness 915nm laser diodes for fiber laser applications

High brightness, high power, and highly reliable 915nm InAlGaAs laser diodes with optimized design are reported in this paper. The laser diodes exhibit excellent performance, such as, high slope efficiency, low threshold current, low voltage, etc., which make them suitable for high brightness operation. The aging test data shows no failures during aging test and more than 220,000 hours estimated lifetime for 90um emitter laser diodes at 8W CW operation. The aging test with the same emitter size at higher stress conditions showed sudden failure that corresponds to catastrophic optical damage (COD) on the facet. A novel large optical cavity (LOC) epi-structure with flat-top near field intensity distribution was developed. The maximum output power is up to 23W under CW testing condition at 25 °C, which is highest level achieved so far. The output power is limited by thermal roll over and there is no COD occurring. This data shows Axcels technologies can further increase the brightness to over 110mW per micron for 915nm laser diodes. This type of laser diodes is essential for pumping fiber lasers to replace CO2 lasers for industry applications.

High-power single-mode 915-nm, InAlGaAs quantum-well lasers grown by MOCVD

We report results on single-mode, InAlGaAs/AlGaAs/GaAs, 915 nm, lser-diodes operating reliably at 300 mW. The graded-index, separate-confinement, strained, single quantum-well structure was grown by metal-organic chemical-vapor deposition. Carbon, rather than zinc, was used as the p-doping srouce to reduce internal loss and potential reliability issues due to the thermal diffusion of zinc. A threshold current density of 133 A/cm2, internal loss of 2.0 cm-1 and internal quatnum efficiency of 93% were achieved. FOr 1500 μm long ridge waveguide lasers, a record single-mode output-power of 500mW was obtained for devices mounted epitaxial-side up onto AlN submounts using eutectic Au80Sn20 solder. Ten burned-in devices have now been aged at a constant current of 450 mA at 85°C for more than 1500 hours wihtout measurable degradation.

Long-term reliability of high-power single-mode 980-nm pump laser diodes

The long-term reliability of high-power, single-mode, 980 nm, InGaAs/GaAlAs/GaAs, laser diodes is reported. We have performed constant-current aging at at 85°C for three operating currents, 450 mA (~300 mW), 550 mA (~350 mW) and 700 mA (~420 mW). The data for 450 mA aging indicate a total failure rate of less than 250 FITs at a confidence level of 60%. For 550 mA and 700 mA operating currents, no degradation in laser performance within the 5% measurement accuracy of our test equipment have been observed during the first thousand hours of testing.

Low-divergence high-power 980-nm single-mode diode lasers with asymmetric epitaxial structure

A ridge-waveguide, InGaAs/GaAlAs/GaAs, 980 nm, pump laser-diode emitting more than 600 mW of kink-free power and a FWHM divergence angle less than 22 degrees using an asymmetric-waveguide structure is presented. No catastrophic optical-damage was observed on p-up mounted devices up to a quasi-CW output power of 2 Watts where the power was limited by thermal effects.

High-power 1060-nm InGaAs/GaAs single-mode laser diodes

High power, 1060 nm, InGaAs/GaAs/AlGaAs graded-index, separate-confinement (GRINSCH), strained single quantum-well (SQW), single mode (SM) laser diodes grown by Metal-Organic Chemical-Vapor Deposition (MOCVD) are reported. The high quality quantum well with high strain, which is the key issue to make high performance 1060 nm laser diode, was obtained by optimizing growth conditions. For realizing SM lasers and modules, the ridge-waveguide lasers with 5 um width and 1500 μm cavity length are successfully fabricated and mounted epitaxial-side up onto AlN submounts using eutectic Au80Sn20 solder to allow easy access to the emission region for fiber coupling and to minimize the effects of die bonding stress on the ridge. These devices exhibit threshold current of less than 30 mA, slope efficiency of up to 1.0 W/A and high kink-free power of 500 mW at 25°C. The devices that were subjected to long-term aging test at 85°C, operating at 300 mW, first show very good reliability. The coupled module with more than 70% fiber coupling efficiency and more than 200 mW output power from a single mode fiber or polarization maintained (PM) fiber in 14-pin butterfly case is demonstrated.

Reliable high-power single-mode GaAlAs/GaAs laser diodes mounted epi-side up

Reliable, high-power, single-mode, GaAlAs/GaAs, laser-diodes in the spectral region of 780 - 900 nm have been designed with procedures developed for telecom-grade, 980 nm, InGaAs/GaAlAs/GaAs pump diodes. Fifteen 808 nm, single-mode laser-diodes, mounted epitaxial-side up onto AlN submounts with eutectic Au80Sn20 solder, have been operated reliably for 3500 hours at 150 mW.

High power high brightness single emitter laser diodes at Axcel Photonics

High power, high brightness, single emitter laser diodes with different apertures from 5 μm to 1000 μm are reported on, in the wavelength range from 780 nm to 1060 nm. On going progress at Axcel Photonics for both single-mode and multi-mode laser diodes will be presented. These diode lasers show high slope efficiency, low threshold current and low voltage, etc. Laser diodes with different emitting apertures at 5μm, 50 μm, 90 μm, 200 μm, 400 μm, 1000 μm, are reported on and discussed in detail. The reliability data for different sized emitters is presented. These results demonstrated that Axcels technologies enable laser diodes made from Al based material grown on GaAs substrates, which can reliably operate at high brightness and high power in the near infrared-wavelength range under wide range of emitting apertures. These laser diodes are suitable for a wide variety of applications including medical, material processing, graphics, pumping solid-state lasers and fiber lasers.

30W CW operation of single-chip laser diodes

We report CW operation of 30 W from single chip laser diodes at 808 nm, with an estimated lifetime of over 40,000 hours. They are designed with broad waveguides using InAlGaAs/AlGaAs/GaAs material system grown by MOCVD.

Low-divergence-angle 808-nm GaAlAs/GaAs laser diode using an asymmetric-cladding structure

We present a single-mode, 808 nm, AlInGaAs/AlGaAs/GaAs, strained, quantum-well laser with a record low, vertical divergence-angle of 12 degrees and high slope-efficiency of 1.0 W/A. Epitaxial-up mounted devices have operated with no measurable degradation at 150 mW, 50°C for 3500 hours.