Baoxue Bo

High-power InAlGaAs/GaAs and AlGaAs/GaAs semiconductor laser arrays emitting at 808 nm

Molecular beam epitaxy (MBE) growth, device fabrication, and reliable operation of high-power InAlGaAs/GaAs and GaAlAs/GaAs laser arrays are described. Both InAlGaAs/GaAs and AlGaAs/GaAs laser arrays reached maximum continuous wave output powers of 40 W at room temperature. The external quantum efficiency was 50% and 45% for the InAlGaAs/GaAs and AlGaAs/GaAs laser arrays, respectively. Threshold current density for InAlGaAs/GaAs and AlGaAs/GaAs lasers was 303 A/cm/sup 2/ and 379 A/cm/sup 2/, respectively. While the current of AlGaAs laser arrays went up significantly after 1000 h of operation at a constant power of 40 W, InAlGaAs laser arrays had an increase in the injection current of less than 4% after 3000 h at 40 W.

High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.

Facet Passivation of GaAs Based LDs by N2 Plasma Pretreatment and RF Sputtered AlxNy Film Coating

RF sputtered Al_xN_y thin film is deposited on the cavity surface of LD (laser diode) by N₂ plasma pretreatment. Firstly optimize the preparation process of Al_xN_y film, and test the chemical ratio, reflectivity and optical absorption of the optimized Al_xN_y film by EDX, spectrophotometer and surface thermal lens technology respectively, which verify the feasibility of Al_xN_y used for facet coating film in LD process; then optimize the N₂ plasma cleaning process, and use PL to find out that sputtered Al_xN_y passivation film by N₂ plasma pretreatment can increase the GaAs surface photoluminescence efficiency by 119%. Finally, a 10 nm thick Al_xN_y passivation film is coated on cavity surface of LD with optimized N₂ plasma pretreatment, which leads to a higher reliability than the traditional LD.

A novel structure for high peak power semiconductor lasers

A novel structure for high peak power output of semiconductor lasers has been designed with a weak optical absorption region near cavity facet and a low optical energy density distribution on both front and back cavity facets has been realized simultaneously. The device has been fabricated with a standard MBE grown AlGaAs/GaAs material wafer, and a stack assembly of five laser chips has been finally obtained. The measured stack has a maximum peak power output of 300W with a whole emitting aperture of 2×0.5mm2 and a satisfactory farfield (θ⊥) output property is also achieved with θ⊥ of 31o.

Optical properties of 1.3-\mum InAs/GaAs quantum dots grown by metal organic chemical vapor deposition

The optical properties of self-assembled InAs quantum dots (QDs) on GaAs substrate grown by metal-organic chemical vapor deposition (MOCVD) are reported. Photoluminescence (PL) measurements prove the good optical quality of InAs QDs, which are achieved using lower growth temperature and higher InAs coverage. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1305 nm and 30 meV, respectively, which are obtained as the QDs are finally capped with 5-nm In0.06Ga0.94As strain-reducing layer (SRL). The PL spectra exhibit two emission peaks at 1305 and 1198 nm, which correspond to the ground state (GS) and the excited state (ES) of the QDs, respectively.

Process investigation of a-Si:H thin films prepared by DC magnetron sputtering

Hydrogenated amorphous silicon (a-Si:H) thin films have been prepared by DC magnetron sputtering, and the effect of sputtering power, the hydrogen flow rate on deposition rate and the optical properties of a-Si:H thin films have been investigated. The hydrogen content (CH) of the films was calculated by Fourier transform infrared (FTIR) spectroscopy method, the maximum CH was obtained at 11at. %,and a bandgap of a-Si:H thin films was changed from 1.43 to 2.25 eV with different CH. It was found that the refractive index (n) and extinction coefficient (k) of the prepared films decreased with the increase of CH. The results provided experimental basis for preparing a-Si:H thin films with special performance and structure .

Analysis of thermal characteristics based on a new type diode laser packaging structure

In order to improve the thermal characteristics of single-chip semiconductor lasers and increase the output power of the device, a new type of vertical packaging structure of heat sink is proposed and analyzed. The heat sink retains the advantages of simplicity and being easy to apply, and the performance of heat dissipation has been improved obviously. The new heat sink structure is believed to be more suitable for packaging of the high-power semiconductor laser chips by heat conduction. Finite-element thermal analysis was used to simulate the thermal field distribution and thermal vector distribution in the conventional structure and the new structure. The simulation results show that the thermal resistance of the conventional structure is 2.0  K/W and the thermal resistance of the new heat sink is less than 1.6  K/W. The theoretical calculation results show that the output power of the packaged laser by new heat sinks can be significantly improved.

Monolithic Fabrication of InGaAs/GaAs/AlGaAs Multiple Wavelength Quantum Well Laser Diodes via Impurity-Free Vacancy Disordering Quantum Well Intermixing

InGaAs/GaAs/AlGaAs multiple wavelength quantum well (QW) semiconductor laser diodes (LDs) have been fabricated by impurity-free vacancy disordering (IFVD) QW intermixing (QWI) method. The IFVD-QWI process was carried out by sputtering-depositing SiO2 mask layers on top of the complete InGaAs/GaAs/AlGaAs QW laser structure, emitting at 980 nm wavelength, and followed by a rapid thermal annealing at 880 °C for 60 s. The lasing wavelength of the devices fabricated from the intermixed wafer was blue-shifted with the increase of the mask layer thickness. The maximum emission wavelength blue shift of a processed as-cleaved laser reached 112 nm with the output-power more than 1000 mW. By using such an IFVD-QWI technique, multi-wavelength integrated LDs have also been successfully fabricated from a single chip.

The High Vacuum Cleaving Passivation Characteristic on 980nm Diode Laser

The high vacuum cleaving passivation characteristic on 980nm diode laser is presented. In this research, diode lasers are cleaved in high vacuum cleaving system, and then coated with thin ZnSe passivation layer in the front and the back facet. The function of the passivation layer is to protect diode lasers facet, and prevent impurity particles diffusing into the facet. Finally optical coatings are applied to the AR and HR facets of 5% and 98% respectively in the front and the back facets. The test results of diode lasers output power show that the output power with ZnSe passivation layer method is 9% higher than Si passivation layer, and 21% higher than that uncoated with passivation layer. The diode of uncoated passivation layer is failed when input current is 3.9A, and the diode coated with Si passivation layer is failed when input current is 4.6A, the final failed of the diode is coated ZnSe passivation layer. In conclusion, the method of coated ZnSe passivation layer in high vacuum cleaving system on the diode lasers facet can effectively prevent the catastrophic optical mirror damage, and increase the output power of diode lasers. Introduction Nowadays, Diode lasers are widely used in many fields, pumping fibre lasers, medical treatments, processing materials and so on[1]. Diode Lasers as the pumping sources of fibre lasers are affected by output light power, input current and thermal effect during their operation [2-3]. diode lasers facets is easy to generate light absorption, and the light absorption results to generate heat, the heat will increase laser diodes degradation, and even lead to catastrophic optical mirror damage [4], which makes the diode lasers failed. In order to improve the output power of diode lasers, many facets coating technology are developed. One is facet sulfur disposing technology. The diode lasers facets react with sulfur compounds, remove the natural facets oxide layer and generate a stable sulfide layer to protect facets. Additionally, the current non injection zone at front facet is introduced to limit the current flow into facets, and reduce facets carriers’ concentration [5]. Furthermore, the non absorption window technology is introduced to improve diode lasers characteristics[6]. In these facets technologies, facet sulfur passivation technology is not stable enough[7]. Non absorption window technology involves the second epitaxial growth technology, which is difficult in technology and has a low reproducibility[8]. The high vacuum facet passivation technology is simple and has a good consistency. The output power of a single emitter of 980nm diode laser is up to 4.3W by using the high vacuum cleaving facet passviation technology. High vacuum cleaving system The high vacuum cleaving system contain four Chambers: Loadlock Chamber, Buffer Chamber, Cleaving Chamber and Deposition Chamber. The vacuum level of Loadlock Chamber is 2×10 torr, the vacuum level of Buffer Chamber is 5×10 torr, the vacuum level of Cleaving Chamber is 5×10 torr, and the vacuum level of Deposition Chamber is 2×10 torr. A mechanical fixture was developed that is capable of cleaving diode laser bars in Cleaving Chamber. The bars can have widths ranging from 1000μm to 4000 μm and thicknesses ranging from 100 to 400μm. The diode International Conference on Materials, Environmental and Biological Engineering (MEBE 2015)

2.2 μm InGaAsSb/AlGaAsSb laser diode under continuous wave operating at room temperature

Abstract2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity lengths of 1000 μm and stripe width of 150 μm. The high output performance was achieved with the threshold current density of the device is as low as 187 A/cm2, slope efficiency of 0.2 W/A, and vertical and parallel divergent angles ϑ⊥ = 42° and ϑ| = 10°, respectively. The continuous wave operating up to 320 mW at room temperature (RT) were achieved.