F. Bugge

Fundamental-Lateral Mode Stabilized High-Power Ridge-Waveguide Lasers With a Low Beam Divergence

We compare ridge-waveguide lasers with trench widths of 5 and 20 mum. The emission wavelength is around 1064 nm and the ridge width is 5 m. The maximum output power exceeds 2 W. The 5-mum trench-width device exhibits a much more stable lateral far-field. The full-width at half-maximum of the vertical far-field profile is only 15deg due to a super-large optical cavity.

5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality

Distributed Bragg reflector tapered lasers emitting at a wavelength of about 1060 nm were realized. The expitaxial layer structure leads to a vertical far-field angle of 15deg (full-width at half-maximum). The devices with a total length of 4 mm consist of 2-mm-long ridge waveguide and tapered sections. The input currents to both sections can be independently controlled. The laser reached 5-W output power with a narrow spectral linewidth below 40 pm (95% power) and a nearly diffraction-limited beam quality.

High-Power 980-nm Broad-Area Lasers Spectrally Stabilized by Surface Bragg Gratings

We report on broad-area distributed Bragg reflector (DBR) lasers with a stripe width of 90 ¿m providing up to 14-W optical power and 50% maximum conversion efficiency. Ninety-five percent of the power is included within a wavelength range of less than 1 nm. The wavelength shift between threshold and the maximum output power is less than 3.5 nm. The wavelength stabilization is achieved with a 500-¿m -long DBR containing a sixth-order Bragg grating defined by i-line wafer stepper lithography and fabricated by reactive ion etching.

High-power highly strained InGaAs quantum-well lasers operating at 1.2 μm

High-power highly strained In/sub x/Ga/sub 1-x/As quantum-well lasers operating at 1.2 /spl mu/m are demonstrated. The edge emitting broad area (BA) laser diode structures are grown by metal organic vapor phase epitaxy at low growth temperatures using trimethylgallium, trimethylindium, and arsine sources. In the laser structure, an InGaAs QW is sandwiched between the GaAs waveguide and AlGaAs cladding layers. The operating wavelength for the laser diode at room temperature (20/spl deg/C) is about 1206 nm, which redshifts to 1219 nm at 46/spl deg/C. The transparency current density for the BA laser diodes is as low as 52 A/cm/sup 2/ and the characteristic temperature value is 76 K. High-power laser operation in the pulse mode (about 1.6 W) at room temperature was achieved.

Tilted Wave Lasers: A Way to High Brightness Sources of Light

Semiconductor laser diodes are conventionally based on a relatively thin waveguide structure grown epitaxially on a thick single crystalline substrate, wherein the latter serves as a medium for carrier flow and as mechanical support and plays no role in optics. Although earlier attempts to provide the outcoupling of light through a transparent substrate in leaky lasers realized a narrow leaky emission beam, either significant leakage losses led to the deterioration of the laser performance or/and a large fraction of the output optical power was concentrated in a co-existing angularly broad emission peak originating from the narrow active waveguide. Our solution, a tilted wave laser (TWL), includes polishing the back side of the substrate under the stripe providing mirror-like reflection for the leaky mode which can thus exhibit multiple reflection and amplification cycles before exiting the device from the substrate facet. Fulfillment of phase matching conditions allows wavelength-stabilized operation. At a wavelength of 1060 nm TWLs are shown to exhibit a very small thermal shift of the emission wavelength of 0.03 nm/K. A cw output power of 3.3 W for 2 mm long cavities with uncoated facets is obtained, wherein the entire power is concentrated in a single vertical lobe having a full width at half maximum of 0.8°. The scattering of the tilted optical wave by the back substrate surface roughness is modeled and found to be the main mechanism limiting the differential efficiency, wherein the scattering contributes up to 10 cm-1 to the losses for a present roughness of ~30 nm. The free carrier absorption in the n-doped substrate ( ~3 cm-1 for n ~1018 cm-3) dominates for a roughness <; 10 nm.

High-Power Distributed Feedback Lasers With Surface Gratings

We present the results for high-power broad-area distributed feedback lasers with surface gratings of 80th, 135th, and 270th Bragg orders. A maximum output power of 11 W for a laser with 80th order grating, emitting around 976 nm with a spectral width <; 1 nm has been achieved. Similar narrow linewidth operation occurs for devices with 135th Bragg order from 7- to 11-W output power. The technological approach to fabricating these devices based on stepper lithography and reactive ion etching is described.

Passively Cooled TM Polarized 808-nm Laser Bars With 70% Power Conversion at 80-W and 55-W Peak Power per 100-

Many solid state laser systems rely on transverse- magnetic polarized 808-nm diode lasers, whose efficiency is limited by the transparency current of the quantum well and whose peak power is limited by facet failure. Using optimized epitaxial growth, low voltage designs, and optimized facet reflectivity, we demonstrate 70% power conversion efficiency at 80 W in 1-cm laser bars under continuous-wave (CW) test conditions. We assess peak power limits in single emitters and find that 100-mum stripe lasers roll thermally under the CW condition at 13 W without failure, then reach >50 W under 300-ns pulse condition, where they fail at internal defects.

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In this letter, we report on monolithic distributed Bragg reflector ridge waveguide diode lasers. The lasers feature highly strained InGaAs quantum wells and fifth order surface gratings for a stabilized emission wavelength ~1120 nm. Output powers up to 1 W and a maximum conversion efficiency of ~34% were achieved in a spatial and spectral single-mode. In a preliminary reliability test, at 0.4 W a lifetime of could be demonstrated. Therefore, the laser sources should allow for an efficient non-linear frequency doubling to 560 nm.

m Stripe Width

The effect of variations in the vertical structure on the performance of AlGaAs-GaAs laser diodes with an InGaAs quantum well (QW) emitting around 1120 nm was investigated. With very thick waveguide layers, more than 95% of the output power is enclosed in an angle smaller than 35/spl deg/. This allows the use of fast axis collimators with a small numerical aperture. Broad area laser diodes with 100-/spl mu/m stripe width, an optimized doping profile, and a double QW emit more than 12 W and show reliable operation at 5 W.

High Brightness, Narrow Bandwidth DBR Diode Lasers at 1120 nm

This paper investigates the impact of lateral radiation losses in ridge waveguide (RW) lasers emitting around 1064 nm is investigated. The RWs are fabricated by dry etching of pairs of trenches with widths between 2.5 and 20 μm into the epitaxial layer structure in order to define the RWs.