Large Optical Cavity Structure Research Articles

Monolithic Integrated Semiconductor Optical Amplifier With Broad Spectrum, High Power, and Small Linewidth Expansion

Semiconductor optical amplifiers (SOAs) offer direct electrical injection, power consumption, integration, and anti-radiation advantages over optical fiber amplifiers. However, saturation output power and gain bandwidth have been limited in traditional structure SOAs. We demonstrate a monolithic integrated SOA with broad spectrum, high power, high gain, and small spectral linewidth expansion. The device adopts a two-stage amplified large optical cavity structure, and a lower optical field confinement factor is obtained by adjusting the thickness of the waveguide layer. The lower optical field confinement factor is conducive to improving the coupling efficiency and the maximum output power. Our device, fabricated only by standard i-line lithography with micron-scale precision, obtains excellent and stable performance. When the input power is set to 1 mW, the output power is 419 mW with a gain of 26.23 dB. When the input power is set to 25 mW at 25 °C, the output power increases to 600 mW with a gain of 13.8 dB. The corresponding gain bandwidth of 3 dB measures at least 70 nm. The spectral linewidth after the SOA is 1.15 times wider than that of the seed laser.

Investigation of lasers based on coupled waveguides by near-field scanning optical microscopy

We have investigated near field intensity distributions of InGaAs/GaAs/AlGaAs lasers possessing broadened waveguides based on coupled large optical cavity structures (CLOC) by scanning near-field optical microscopy (SNOM). The concept allows effective suppressing of the transverse high-order mode lasing. The obtained results can be considered to be the direct proof of pure transverse single-mode emission of the CLOC lasers.

Impurity-free quantum well intermixing for large optical cavity high-power laser diode structures

We report on the correlation of atomic concentration profiles of diffusing species with the blueshift of the quantum well luminescence from both as-grown and impurity free quantum wells intermixed on actual large optical cavity high power laser diode structures. Because it is critical to suppress catastrophic optical mirror damage, sputtered SiO2 and thermally evaporated SrF2 were used both to enhance and suppress quantum well intermixing, respectively, in these (Al)GaAs large optical cavity structures. A luminescence blueshift of 55 nm (130 meV) was obtained for samples with 400 nm thick sputtered SiO2. These layers were used to generate point defects by annealing the samples at 950 °C for 3 min. The ensuing Ga diffusion observed as a shifting front towards the surface at the interface of the GaAs cap and AlGaAs cladding, as well as Al diffusion into the GaAs cap layer, correlates well with the observed luminescence blue shift, as determined by x-ray photoelectron spectroscopy. Although this technique is well-known, the correlation between the photoluminescence peak blue shift and diffusion of Ga and Al during impurity free quantum well intermixing on actual large optical cavity laser diode structures was demonstrated with both x ray photoelectron and photoluminescence spectroscopy, for the first time.

A tunnel regenerated coupled multi-active-region large optical cavity laser with a high quality beam

A novel coupled multi-active-region large optical cavity structure cascaded by a tunnel junction is proposed to solve the problems of facet catastrophic optical damage (COD) and the large vertical divergence caused by the thin emitting area in conventional laser diodes. For a laser with three active regions, a slope efficiency as high as 1.49 W/A, a vertical divergence angle of 17.4°, and a threshold current density of 271 A/cm2 are achieved. By optimizing the structural parameters, the beam quality is greatly improved, and the level of the COD power increases by more than two times compared with that of the conventional laser.

InGaAsP/InP Electroabsorption Modulator with Single-Sided Large Optical Cavity by Low-Pressure MOCVD

An InGaAsP/InP Electroabsorption Modulator (EAM) with single-sided large optical cavity (LOC) was studied and fabricated by low-pressure Metal Organic Chemical Vapor Deposition (MOCVD). Results show that the optical profile of EAM is greatly improved by the LOC structure, which is expected to increase the coupling efficiency and the optical saturation power.

835-nm GaAs/AlGaAs High-Power Laser Diode for Up-Conversion Fiber Lasers

High-power and high-efficiency 835-nm GaAs/AlGaAs single-quantum-well pumping laser diodes (LDs) for visible up-conversion fiber laser applications were fabricated. To achieve the highly efficient pump laser diode, a 1.0-μm-thick separate confinement heterostructure layer was inserted; namely, a large optical cavity (LOC) structure was adopted. This LOC structure minimizes the overlap between the optical modal fields and the highly doped cladding layers, which reduces the optical internal loss and increases the slope efficiency of the pumping LDs. LD arrays of 10 emitters with a 1,000-μm total emitter width were fabricated to evaluate the high-power LD characteristics and to check the feasibility of the up-conversion fiber lasers. A LD array with a small total emitter size of 1,000 μm operated at over 20 W with a very high 20-mW/μm optical power density. The threshold current and the slope efficiency of the LD array were about 4.1 A and 1.17 W/A, respectively. We present a visible up-conversion fiber laser pumped by using our developed high-power, high-efficiency 835-nm LD array.

Improving the optical profile of electroabsorption modulator using single-sided large optical cavity structure

An electroabsorption modulator with large optical cavity was designed and fabricated successfully. Both the simulated and experimental results show that, the larger optical cavity structure introduced could obviously improve the optical profile of EA modulator, the traditional elliptical near-field spot becomes more rounded, so it will match better with the optical fiber and is beneficial for raising the coupling efficiency.

Beam quality of high power 800 nm broad-area laser diodes with 1 and 2 μm large optical cavity structures

The beam quality of 800 nm AlGaAs/GaAsP broad-area (BA) laser diodes with large optical cavity (LOC) waveguide structures was studied under high power conditions. The LOC structures consist of a tensile-strained GaAsP single quantum well embedded in AlGaAs layers forming 1 and 2 μm thick waveguide cores. A low beam divergence of 51° respectively 46° (full width at 1/ e 2 maximum) is obtained in fast axis direction. BA diode lasers with 2 mm cavity length and stripe widths of 60, 100 and 200 μm show beam quality factors M 2 along the slow axis of about 12, 16 and 35 at 2 W output power, respectively. M 2 also weakly depends upon the waveguide width and is slightly smaller for the 2 μm waveguide core if the stripe width is less than 100 μm .

2 W reliable operation of λ = 735 nm GaAsP/AlGaAslaser diodes

Reliable operation of 735 nm laser diodes based on a tensile-strained GaAsP quantum well embedded in an AlGaAs large optical cavity structure is reported. The 100 /spl mu/m stripe width laser diodes were aged at a record high output power of 2W for 2000 hours. The degradation rates were 3.6/spl times/10/sup -5/ h/sup -1/.

Tensile-strained GaAsP-AlGaAs laser diodes for reliable 1.2-W continuous-wave operation at 735 nm

Tensile-strained GaAsP quantum wells embedded in AlGaAs large optical cavity structure were investigated at an emission wavelength of 735 nm. 1.2-W continuous-wave operation for 100-μm stripe width diode lasers over 1000 h is reported. Experiments with different stripe widths showed a high stability at an output power of 12-mW/μm stripe widths with degradation rates below 5/spl middot/10/sup -5/ h/sup -1/, i.e., lifetimes larger than 5000 h could be expected.

The impact of LOC structures on 670-nm (Al)GaInP high-power lasers

We investigate the potential of large optical cavity (LOC)-laser structures for AlGaInP high-power lasers. For that we study large series of broad area lasers with varying waveguide widths to obtain statistically relevant data. We study in detail I/sub th/, /spl alpha//sub i/, /spl eta//sub i/, and P/sub max/, and analyze above-threshold behavior including temperature stability and leakage current. We got as expected for LOC structures minimal /spl alpha//sub i//spl les/1 cm/sup -1/ resulting in /spl eta//sup d/=1.1 W/A for 64/spl times/2000 /spl mu/m/sup 2/ uncoated devices. We obtain total output powers /spl ges/3.2 W (qCW) and /spl ges/1.5 W (CW) at 20/spl deg/C.

High-power tensile-strained GaAsP-AlGaAs quantum-well lasers emitting between 715 and 790 nm

Tensile-strained GaAsP quantum wells embedded in AlGaAs large optical cavity structures were studied. In the wavelength range between 715 and 790 nm, very high output power and excellent conversion efficiencies of broad-area lasers have been obtained.

Far-field pattern of transverse modes in LOC structures

An investigation was made of the emission from GaAlAs large-optical-cavity (LOC) laser heterostructures with an active layer more than 2 μm thick. The far-field radiation pattern, representing a superposition of the fundamental and several higher-order transverse modes, had a central maximum. The gain, mirror losses, near- and far-field patterns of each propagation mode, as well as mode competition were analyzed on the basis of a simple model. The far-field pattern of single modes was determined by selecting separate spectral intervals from the total emission spectrum of the laser.

Room-temperature operation of GaAs/AlGaAs diode lasers fabricated on a monolithic GaAs/Si substrate

Room-temperature operation has been achieved for GaAs/AlGaAs heterostructure diode lasers fabricated on a monolithic GaAs/Si substrate. These devices, which incorporate a large optical cavity structure grown by molecular beam epitaxy directly on a Si wafer, have exhibited threshold currents as low as 775 mA and power outputs as high as 27 mW/facet in pulsed operation.

Lead salt quantum well diode lasers

Lead-salt diode lasers are useful for spectroscopic applications in the 2.5–30 μm wavelength range. These devices have previously required cryogenic cooling <100 K) for CW operation. The use of quantum well, large optical cavity structures has improved the operating temperatures to 174 K CW (at 4.39 μm) and to 270 K pulsed (at 3.88 μm). These diodes have a single PbTe quantum well with lattice-matched Pb 1−xEu xSe yTe 1−y confinement layers grown by molecular beam epitaxy. The emission energy shifts have been calculated using a finite square well with nonparabolicity effects included. Initial work has also been done on multiple quantum well lasers. The maximum operating temperatures were comparable to those of single quantum well lasers, with leakage current and possibly Auger recombination limiting device performance.