In this paper, we designed a novel tunable VCSEL structure with a top wave-like mirror for polarization control. Based on rigorous coupled-wave theory, the reflection characteristics of the top wave-like mirror structure for different polarization modes was analyzed. The wave-like structure was designed and optimized to control the output polarization mode of tunable VCSEL. The results show the threshold gain of TM mode is always greater than the TE mode during 84.5nm wavelength tuning range, the maximum increase is more than 10 times. It is indicated that the designed structure of tunable VCSEL can effectively realize stable polarization mode.
A large size vertical-cavity surface-emitting laser (VCSEL) with multiple concentric ring apertures (MCRA) is investigated. Compared with a typical VCSEL with the same outer dimension, the 804nm VCSEL with MCRA has maximal continuous wave(CW) light output power 0.23 W which is about 3 times that of a typical device. The novel laser also exhibits a stable single-lobed far field pattern with low beam divergence angle, which is suitable for free-space optical communication and optical interconnection applications.
In this paper, the new structure of 980nm VCSEL was designed and fabricated in order to
improve thermal problem and photo-electricity characteristic. From the point of view reduced
equivalent resistance, P-side electrode was designed as intra-cavity contact structure. The VCSEL with
conventional flip bottom emission structure and intra-cavity contact structure have been fabricated
with the same aperture and tested comparatively. the new structure has a differential resistance of 21Ω,
but the conventional structure has a differential resistance of 25.5Ω. The tested results showed that this
new-type structure VCSEL is expected to improve the thermal characteristics of the device and the
Wet etching process is a key technology in fabrication of VCSEL and their array in order to
improve opto-electric characteristics of high-power VCSEL, devices with multi-ring distribution hole
VCSEL is fabricated. The H3PO4 etching solution was used in the wet etching progress and etching
rate is studied by changing etching solution concentration and etching time. The optimum
technological conditions were determined by studying the etching morphology and etching depth of
the GaAs-VCSEL. The tested results show that the complete morphology and the appropriate depth
can be obtained by using the concentration ratio of 1:1:10, which can meet the requirements of
GaAs-based VCSEL micro- structure etching process.
Wet-oxidation experiments in a nitrogen environment at high temperatures are conducted to improve the photoelectricity performance of the 850nm VCSELs. It is very important to accurately control the oxidation aperture.We have carried out upon the wafer of VCSELs with the same structure by changing the furnace temperature and oxidation time, then micro-probe analyses have been examined at different oxidation depth by scanning electron microscope (SEM) and by X-ray. Oxidation products are examined at different oxidation depths of oxidation layer and each component content is analyzed, we get the law of the wet-oxidation. The oxidation process thermal stability and precision can be improved by lowering the oxidation temperature and prolonging the oxidation time.
The high-performance InGaAsSb/GaAsSb/GaAs lasers emitting 1300 nm is simulated. Compared to the type-II quantum well GaAsSb/GaAs, In0.48Ga0.52As0.98Sb0.02/GaAs0.98Sb0.22 has large bandoffset which will offer a better electron confinement. And GaAs0.98Sb0.22 can reduce the effective strain of the highly lattice mismatched InGaAsSb quantum well. The transparent carrier densities of active unit is as low as 0.72×1018 cm-3. The threshold current and slope efficiency of the InGaAsSb/GaAsSb/GaAs three quantum wells laser is equal to 83 mA and 0.62W/A. When the current is over 93 mA, external efficiency will reach 0.72. In order to further enhance the performance of InGaAsSb/GaAsSb quantum well (QW) laser, the asymmetric (0.5 μm/1.5 μm) waveguide structure is also studied.
In this study, uniform InAs QDs were grown on the GaAs (001) substrate by MBE by the S-K mode. The effects of strain reducing layer and rapid thermal anneling on the optical properties of InAs/(In)GaAs QDs were investigated by PL measurements. The annealing results in PL peak energy red-shift which strongly depends on In composition of InxGaAs strained reducing layer , QDs with lower density and/or capped by an InGaAs layer are very sensitive to the annealing. At given annealing conditions, PL peak energy blue-shift of low-density QDs is much larger than that of high density QDs.
Semiconductor Lasers (also known as Laser Diodes, LDs), have many
unique properties and advantages and found wide applications in variouse fields. The
super high conversion efficiency of high power single emitter semiconductor lasers
and their arrays, commonly achievable values of them being in the range of 50%-80%,
makes them particularly suitable for applications as the ideal pumping source for solid
state lasers and also as widely used in material processing and medicine. Yet
semiconductor lasers also have shortcomings, the poor beam quality of multi-mode
semiconductor lasers and laser arrays usually severely restricted their applications.
The present paper mainly addresses the semiconductor laser arrays design and
fabrication technologies, with particular emphasis placed on the beam shaping
principles and methods. The high power semiconductor lasers in the wavelength range
between 800nm and 1100nm have been reviewed and analyzed. The topic of the
electrical-to-optical conversion efficiency enhancement has been addressed in some
detail. The high power single emitter lasers and LD bars have been fabricated and
their performance characterized. The beam divergences of LDs in the vertical and
parallel directions have been addressed and analyzed. The beam collimation has been
analyzed and experimentally performed for the single emitter and LD bars. Beam
combining methods and fiber coupling have been summarized and experimentally verified, with specific efficiency data for beam combining and fiber coupling being
presented and analyzed.
High quality crack-free GaN layers were successfully grown and the InGaN/GaN based blue LEDs
fabricated on patterned Si (111) substrates. In addition to using the patterned growth technique, thin AlN and SiNx
interlayers grown at high temperatures were also employed to partially release the residual stress and to further
improve the crystalline quality. 300 µm square blue LEDs fabricated on the islands, without thinning and package,
exhibited a high output power of around 0.68 mW at a drive current of 20 mA.
The AlGaAs/GaAs double quantum well semiconductor lasers grown by molecular beam epitaxy show high
external quantum efficiency and high power conversion efficiency at continuous-wave power output using an
asymmetric structure. The threshold current density and slope efficiency of the device are 200A/cm2 and 1.25W/A,
respectively. The high external quantum efficiency and maximum conversion efficiency are 81% and 66%, respectively.
Anti-laser films have been used for decreasing the intensity of laser to protect human's eyes. Nd:YAG is widely used in military and industry, and its working wavelengths are 532nm and 1064nm. In this paper, we attempted to design a dense film based on a new complex material to improve manufacture efficiency. The frequency-doubling film is G|(HxL)n|A according to the working characteristics of Nd:YAG laser. H4 and SiO2 were selected in consideration of absorption, dispersion, index of refraction, mechanical robustness. x is equal to 2 by optimized the frequency-doubling film (G|(HxL)n |A).
The film is fabricated by Leybold SUSPRO-1110 full automatic vacuum coating machine, which is completed with Plasma Ion Assisted Deposition system. UV3150PC spectrophotometer was used to test the spectrum characteristics in the range of 532nm and 1064nm. The testing results showed that the transmission at 532nm and 1064nm are 0.0064% and 0.0041%, respectively. The integral transmission of visibility region is higher than 73%. We can entirely eliminate damages to eyes from Nd:YAG laser by this way.
Space laser communications (SLC) possess a series of advantages, such as higher data rates, large capacity of information, very good secrecy, et al. So SLC has been attracting great attention the throughout western and developed countries. USA, EU and Japan are making great efforts in establishing space-air-ground integrated communications network, with satellites, planes or ground vehicles as platforms. China has also carried out laser communication research
activities in recent years. Changchun University of Science and technology (CUST) has been doing research studies on space laser communications with plane as the platform, and relatively thorough study on some of the key technologies such as airborne lasercom terminal design. The present paper will address some of these topics.
The characteristics of GaAs-based semiconductor Laser with antireflective and high reflective coatings are studied. The film designs are optimized with programmed software using the film design program for a double-layer scheme. According to the numerical simulations, the different double-layer with proper parameters is coated onto GaAs-based semiconductor Laser. The thickness of double layers is also calculated using the software taking account of antireflective and high reflective coating in the design of double layer film. With the optimized design of double-layer film, the power properties of GaAs-based semiconductor Laser are improved, and the experimental results satisfy the application requirements as semiconductor Laser.
The GaSb characteristics grown by molecular beam epitaxy (MBE) on GaAs substrates was reported. The abruptness of the interfaces, the degree of intermixing and the anion incorporation greatly affect the material quality. The RHEED patterns provide information on the surface structure and morphology of the sample and dictate surface reconstruction, accumulation and segregation. The structure parameters of samples are obtained from the rocking curve. The first and second satellite peaks appear around the main 0th-order peak. The experimental and simulated results of samples A and B with x-ray rocking curves show there is a GaAsSb layer because of As-for-Sb exchange at the GaSb/GaAs interface.
This paper presents the structure design and fabrication technology of 850nm wavelength high power wide spectrum Superluminescent Diodes (SLDs) as non-coherent light source, for the application of fiber gyroscope and other areas. Quantum Well epitaxial structure, unpumped absorbing region structure and facet coating methods have been adopted for enhancing the gain coefficient, output power and the reduction or elimination of lasing oscillation. As typical device performance results, SLDs have been demonstrated with central wavelength of 848-851nm, spectrum FWHM no less than 20nm, and no less than 7mW output under 120mA injection current. The devices operated up to 100°C.