Catastrophic Optical Damage Level Research Articles

Design and fabrication of high power InGaN blue laser diode over 8 W

The impact of multi quantum wells (MQWs) structure on the homogeneity of spontaneous luminescence and quantum efficiency of the high power InGaN blue laser diode (LD) is numerically investigated. The structure with 2QWs in the active region is found to be the optimal choice for the high power InGaN LD. Accordingly, the edge emitting LD structure is grown and fabricated. To study the facet coating effect on the catastrophic optical damage (COD) level, three types of LDs are coated with different materials by different techniques, respectively. The characterization results confirm that the single blue LD coated with the Al2O3 and Al2O3/Ta2O5 films by electron cyclotron resonance deposition exhibits the highest COD level, due to the better crystal quality and interfacial quality of the coated films. The LD starts to operate at 1.04 kA/cm2 with slope efficiency of 1.8 W/A and the wavelength of 444.9 nm. As a result, the output power as high as 8.04 W is achieved at 5.5 A.

Thermoreflectance Measurements of the Temperature Distributions in Laser Diodes with Non Injected Facet

AbstractNon Injected Facet (NIF) lasers were developed to increase catastrophic optical damage level of the devices. In this work we present the analysis of the laser diodes (LD) front facet temperature distribution. Micro-thermoreflectance technique is used to perform a detailed temperature maps of the operating LDs. Such a technique gives us temperature maps with a spatial resolution better than 1mm and area of the maps covers active region and substrate crystal. We demonstrate micro thermoreflectance as a perfect tool to determine real temperature distribution of the operating laser diode front facet. Examined series of LDs under investigation have been made in two different ways. Major point of this work is comparison of the front facet temperature distribution of devices with and without injected facets. We compare temperature value and temperature distribution in the waveguide region in both types of the LDs. In our experiment NIF laser diodes exhibit facet temperatures increased by a factor of 1.4.

Analysis of the Front Facet Temperature in Laser Diode With Non Absorbing Mirror

ABSTRACTNon-absorbing mirror (NAM) lasers, also known as window lasers, were developed to increase catastrophic optical damage level of the devices. In this work we present the analysis of the laser diodes (LD) front facet temperature distribution. Micro-thermoreflectance technique is used to perform a detailed temperature maps of the operating LDs. Such a technique gives us temperature maps with a high spatial resolution equal 0.6μm. We demonstrate micro thermoreflectance as a perfect tool to determine real temperature distribution of the operating laser diode front facet.

Improved catastrophic optical damage level from laser with nonabsorbing mirrors

The authors demonstrate an improved catastrophic optical damage (COD) level from a ridge laser with nonabsorbing mirrors (NAMs) fabricated by quantum well intermixing. Under destructive testing conditions, the COD level of the NAM laser was improved by a factor of 2.6 compared to the standard laser, attributed to reduced absorption induced facet degradation. Verification of the degradation mechanism was confirmed by inspection and removal of damaged facets.

High power operation of real refractive index guidedself-alignedAlGaInP laser diodes with window structure

A window-mirror structure has been applied by Zn diffusion to real refractive index guided self-aligned AlGaInP laser diodes for the first time. Both a high catastrophic optical damage level of 152 mW and a high slope efficiency of 0.83 W/A have been obtained, resulting in an extremely low operating current of 225 mA, for a pulse output power of 150 mW at room temperature.

High Power Operations of 980 nm Ga0.8In0.2As/GaxIn1-xAsyP1-y/Ga0.51In0.49P/GaAs Pump Lasers Prepared by Multi-step Metalorganic Vapor Phase Epitaxial Growth with Ion Implanted Channels

The silicon (Si) or boron (B) implantation process in Ga0.8In0.2As/GaxIn1-xAsyP1-y/Ga0.51In0.49P/GaAs quantum well structures can be used not only for maintaining single lateral mode during high power operation but also for increasing the catastrophic optical damage (COD) level of 980 nm pump lasers. The fabricated 980 nm pump lasers with partially ion implanted channels after ridge waveguide structure formation exhibited high power operation up to 250 mW without any kink and beam steering. A photoluminescence peak shift of 70 meV was obtained by 120 keV Si-implantation and annealing at 900°C. Improvement of the COD level by a minimum of 1.65 times is obtained by forming transparent windows near facets by Si implantation and annealing. A highly nonradiative polycrystalline phase of the active area may be the major cause of COD failure in the Al-free 980 nm lasers.

Peculiarities of catastrophic optical damage in single quantum well InGaAsP/InGaP buried-heterostructure lasers

For investigation of the catastrophic optical damage (COD) of InGaAsP material systems emitting at 0.8 μm, separate-confinement-heterostructure single-quantum-well structures grown on (100) GaAs substrate by liquid-phase epitaxy were mesa-etched for buried heterostructure (BH) laser diodes. The single mode InGaAsP/InGaP diodes were cw operated at room temperature. The measured COD level of a BH InGaAsP/InGaP laser with a cavity length of 470 μm was 8.6±0.7 (MW/cm2). Particularly, we could not observe COD in the long cavity InGaAsP/InGaP lasers, but they showed thermal saturation which is reversible. Also, InGaAsP lasers were found to sustain high current injection three times more strongly than AlGaAs counterparts.

Improvement of catastrophic optical damage level of AlGaInP visible laser diodes by sulfur treatment

An increase of 70% in the catastrophic optical damage (COD) level of AlGaInP visible laser diodes is achieved by sulfur treatment. From transmission electron microscope and energy dispersive microanalysis, we have confirmed that most of the oxide at the mirror facets is replaced by sulfur after this treatment. It is thought that oxide at the facets introduces surface states which cause the COD, and removal of the oxide by sulfur treatment results in the higher COD level.

Long-term 60 mW operation of 780 nm AlGaAa lasers with extended beam by additional low-Al-content layer in p -type cladding layer

The catastrophic optical damage level of a 780 nm AlGaAs laser diode is increased by extending the optical beam profile by using a low-Al-content layer in the cladding layer. A higher light output power can be obtained without increasing threshold current, and reliable operation for more than 1000 h at 60 mW output and 50 degrees C ambient is obtained. >

Reliability of 780-nm High-Power Laser Diodes with Thin Quantum Well Active Layer

The reliability of 780-nm-(AlGa)As high-power laser diodes with a thin triple-quantum-well or a single-quantum-well active layer is investigated. The thin active layers achieve high catastrophic optical damage levels above 170 mW. In these laser diodes, a gradual increase of the operation current limits the lifetime of the laser diode. The gradual degradation rate is higher in the single-quantum-well laser diodes than to the triple-quantum-well laser diodes, and is also higher in shorter-cavity-length laser diodes. The power dependence of the gradual degradation rate is very small compared with the dependence on cavity length or active layer structure. The gradual degradation mainly depends on the threshold current density per active layer thickness. As a result, 60-mW reliable operation for more than 1000 hours was achieved at 50°C in 600-µm-length triple-quantum-well lasers.

Integrated quantum-well manifold laser

An integrated manifold of quantum-well lasers with up to three quantum wells has been fabricated by metalorganic chemical vapor deposition. cw threshold current densities per well and differential quantum efficiencies are comparable to those for individual devices, and transverse far-field patterns are single lobed. Catastrophic optical damage levels increase with increasing quantum-well count and are substantially higher than those achieved with a single quantum-well laser. Thermal effects in cw operation have been mitigated by using an efficient design with a high characteristic temperature in a low thermal resistance configuration.

An AlGaAs laser with high-quality dry etched mirrors fabricated using an ultrahigh vacuum in situ dry etching and deposition processing system

Highly reliable AlGaAs lasers with dry etched mirrors have been successfully fabricated with an ultrahigh-vacuum in situ processing system, equipped with reactive ion-beam etching (RIBE) and dielectric film deposition chambers. Etched mirror surfaces are protected against air-exposure contamination and nonvolatile-reaction-products adsorption with in situ Al/sub 2/O/sub 3/ passivation subsequent to the CI/sub 2/ RIBE mirror formation. Ion-bombardment-induced damage is repaired by thermal annealing. The annealing effect is enhanced by a contamination-free interface between the etched mirror surface and Al/sub 2/O/sub 3/ passivation film. The lasers exhibit an increase in catastrophic optical damage (COD) level and long-life operation. Their COD levels are twice as high as that for as-etched lasers and are almost the same as those for conventional cleaved lasers. >