Influence of mirror reflectivity on laser performance ofvery-low-threshold vertical-cavity surface-emitting lasers

The influeuce of mirror reflectivity on laser performance of InGaAs-GaAs vertical-cavity surface-emitting lasers fabricated by selective oxidation is investigated by the stepwise change of the number of pairs in top mirror stack after device fabrication. Devices with 18-pair stacks in the top mirror, which is the optimized number of pairs in this structure, show an output power over 1.9 mW and a slope efficiency of 55% while maintaining a low threshold current of 212 μA. The analysis of the threshold current and differential efficiency related to mirror reflectivity shows an internal quantum efficiency of 95%, an internal round-trip loss of 0.072, and a transparency current density of 71 A/cm²     

可调谐激光器的宽带高反射镜

选择了适当的制备工艺,并改善膜系以减弱膜内的电场强度,获得低损耗可见光区的宽带高反射镜。     

Vertical-cavity surface-emitting lasers with spatially adjustableDBR reflectivity to enable free-space photonic repeaters

We have created bidirectional high-performance top- and bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) from a single epitaxial wafer. Using a spatially selective oxidation of AlAs layers in hybrid distributed Bragg reflectors (DBRs) of a VCSEL structure, devices processed for top emission had threshold currents of 100-110 μA with slope efficiencies of 18%-20%. Devices from the same wafer processed for bottom substrate emission had thresholds of 110-120 μA and slope efficiencies of 17% and 18%. This technology will greatly simplify the use of VCSEL's in large three-dimensional (3-D) parallel interconnects, photonic repeaters, and smart pixels     

Analysis of reflectivity for a beveled corner mirror insemiconductor ring lasers

A semiconductor ring laser is expected to be used as a tiny ring laser gyro with low power consumption, which is suitable for mobile systems. However, its corner mirrors may be beveled due to its fabrication processes. Therefore, in this paper, reflectivities of beveled corner mirrors in the semiconductor ring laser are examined. In the analysis here, a guided fundamental mode is expanded into plane waves, and thus vertical confinement of the guided mode is completely incorporated. It is revealed that there is an optimum guiding layer thickness of approximately 0.3 μm to minimize mirror losses in the beveled mirrors. Also, facet reflectivities of equilateral n-polygon shaped ring lasers with beveled mirrors are studied, and it is found that a large n leads to a low threshold current     

Nonlinear analysis of surface-emitting distributed feedback lasers

An analysis of surface-emitting distributed feedback lasers under conditions above threshold is presented. The coupled-wave equations are integrated numerically using a self-consistent technique that includes the effects of gain saturation, carrier diffusion, antiguiding, and free carrier loss. The laser threshold current and slope efficiency are determined as a function of the strip length and p-layer thickness where it is found that the device efficiency can be very high. Antiguiding, which varies when the grating is mistuned with respect to the gain peak, influences the slope, threshold, and shape of the emission far field. Small variations in the longitudinal index of refraction are shown to affect the far-field intensity profile significantly     

Bow-tie surface-emitting lasers

We report a new design for surface emitting semiconductor lasers operating at 940 nm, incorporating a double-flare cavity, and distributed Bragg reflector (DBR) mirrors also providing surface emission. This design can take advantage of the modal behavior of the unstable resonator, and has shown very good mode control, with coherent emission from two facets in the same direction. We report preliminary performance results showing very promising characteristics including single-mode diffraction limited operation, and spectral behavior with 42 dB side-mode suppression. This design has exhibited promising results for increasing the current range between the lasing threshold and the filament threshold     

InGaAs vertical-cavity surface-emitting lasers

The authors give theoretical and experimental results for vertical-cavity surface-emitting lasers (VCSELs). The modeling is applied to the design of InGaAs VCSELs. A simple method to calculate the reflectivity of semiconductor stack mirrors with graded interfaces and compound metal/semiconductor stack mirrors is introduced. The theoretical predictions are compared to results from actual device measurements. A novel technique is introduced to determine material parameters: fabrication of in-plane lasers from VCSEL material. The procedure used to determine the optical mode in such an in-plane laser is described. Using the insight gained from modeling, the external efficiency was increased to >30% with a threshold current density of 1 kA/cm²     

Threshold analysis of vertical-cavity surface-emitting lasers with intracavity contacts

A numerical analysis of vertical-cavity surface-emitting lasers (VCSELs) incorporating intracavity contacts and distributed Bragg reflectors (DBRs) is presented. The model considers polarization dependent reflection at the DBRs, current spreading, and nonuniform carrier density distribution self consistently. Analytic expressions for the current spreading and the corresponding series resistance for VCSELs incorporating intracavity contacts are derived. It is shown that current spreading strongly affects the lateral gain profile, the threshold current density, the transverse mode shape and the transverse mode discrimination through the creation of intracavity optical phase and gain apertures. The series resistance and the depth of the dip in the current density distribution are used as figures-of-merit to provide guidelines for device optimization, as illustrated by means of two examples of long wavelength VCSEL designs.     

Wide temperature range of stable single-mode operation in weakly coupled asymmetric mirror reflectivity DFB lasers

A maximum difference between the peak gain wavelength and the lasing wavelength where stable DFB mode operation is achieved has been obtained for weakly coupled (KL?; 0?7), asymmetric mirror structure (Rf = 5%, Rr = 31%) DFB lasers. DFB lasers optimally fabricated exhibit single-longitudinal-mode operation over a wide temperature range of 5?100°C.     

Vertical-external-cavity surface-emitting lasers and quantum dot lasers

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and quantum information devices....     

Mode-partition noise in vertical-cavity surface-emitting lasers

We present a numerical study of the effects of carrier diffusion and spatial hole-burning on the noise characteristics of vertical-cavity surface-emitting lasers (VCSEL's) under both single-mode and multimode operations. In the case of single-mode operation, VCSEL noise characteristics are similar to those of edge-emitting lasers except for a diffusion-induced damping of relaxation oscillations. Under multimode operation, VCSEL's exhibit low-frequency noise enhancement due to mode partition. However, depending on the spatial distributions of the transverse modes excited, the mode-partition noise characteristics can be quite different.     

Optical feedback in vertical-cavity surface-emitting lasers

Optical feedback in a vertical-cavity surface-emitting laser due to a fiber facet of varying position is studied in experiment and theory. Measured spectra and light-current curves show periodic variations in resonant wavelength, threshold current, differential quantum efficiency, and output power as a function of fiber position. Theoretical results were obtained using a 2 × 2 vector propagation matrix method which models the laser and fiber in a single structure and shows good agreement with experimental results. A novel method for determining the linewidth enhancement factor α by analyzing the wavelength variation as a function of fiber position is presented and a value of α = 2.8 was obtained     

长波长GaInNAs垂直腔面发射激光器

新出现的直接跃迁GaInNAs与具有高反射率的AlAs／GaAs分布布拉格反射镜相结合构成了GaAs基长波长(1．3—1．6μm)垂直腔面发射激光器(VCSEL)，将成为光纤通信、光互联和光信息处理等的关键元件。本文从材料的选取、外延技术和GaInNAs VCSEL国外和国内的发展状况等方面对长波长GaInNAs VCSEL进行了综合阐述。     

Longitudinal analysis of semiconductor lasers with low reflectivity facets

An analysis is made of longitudinal effects in semiconductor lasers with low facet reflectivities. For this purpose, a self-consistent model is used based on the beam propagation method, which takes into account both the lateral and longitudinal dimension. The calculations show that longitudinal effects have a significant influence on the output fields in the laser.     

Electrically gain-switched vertical-cavity surface-emitting lasers

The authors report electrical gain-switching of a packaged vertical-cavity surface-emitting laser (VCSEL). Pulse durations as short as 24 ps at repetition rates up to 2 GHz were obtained from a four-quantum-well GaAs/AlGaAs VCSEL, which emits 0.8 mW continuous wave power in a single mode at room temperature and has a current threshold of 5 mA. Simultaneous measurement of the optical spectrum showed an almost transform limited linewidth indicating ultralow chirp. Optical pumping with subpicosecond pulses of the same packaged devices, held at a constant electrical bias, yielded 22 ps pulses, in good agreement with the electrical pumping. Simple calculations show that the pulse duration obtained by gain-switching is limited by the design constraints necessary to operate the VCSEL continuous wave at room temperature with low-threshold current, high-quantum efficiency, and reasonable output power     

High-speed modulation of vertical-cavity surface-emitting lasers

The IM (intensity modulation) and FM (frequency modulation) characteristics of vertical-cavity surface-emitting lasers are studied. The laser has high FM efficiency and broad IM bandwidth (near 8 GHz) at a very low bias (4.5 mA). Five Gb/s pseudorandom direct intensity modulation of this laser with open eyes is demonstrated.<>     

High reflectivity Te-doped GaAsSb/AlAsSb Bragg mirror for 1.5 μmsurface emitting lasers

A high reflectivity GaAsSb/AlAsSb Bragg mirror lattice matched to InP is reported. Operation at 1.5 μm is obtained owing to a large Burstein-Moss shift of GaAsSb absorption caused by a strong N-doping up to 10¹⁹ cm^-2. Peak reflectivity up to 94% has been measured with only 11.5 periods     

Theoretical analysis of modulation response and second-orderharmonic distortion in vertical-cavity surface-emitting lasers

A rate-equation model is developed, with the consideration of size effects, to analyze the steady state and dynamic behavior of index-guided vertical-cavity surface-emitting lasers. The size dependence of spatial hole burning, cavity loss, as well as thermal resistance of device cavity are taken into account. Using this model, the influence of size effects on the amplitude modulation response and second-order harmonic distortion are studied. It is found that a laser with a small core radius exhibits better modulation response and less harmonic distortion than that of a large waveguide device, however, there is a tradeoff between the output power and modulation efficiency of the lasers     

The effect of facet mirror reflectivity on the spectrum of single-mode CW constricted double-heterojunction diode lasers

In this paper we show that the spectral mode content of mode-stabilized constricted douhle-heterojunction lasers can be altered by changes in facet reflectivity. If the facet reflectivity is substantially reduced below the nominal value of 30 percent, then the lasers will exhibit multilongitudinal mode operation. Nearly planar-geometry lasers that show instabilities can be made to operate in a stable single mode by increasing the facet reflectivity to values above 50 percent.     

Analysis of below-threshold spectrum and linewidth of surface-emitting lambda /4-shifted DFB lasers with DBR mirror

The frequency distribution of spontaneous emission noise below lasing threshold and the spectral linewidth in lasing operation are analysed for surface-emitting lambda /4-shifted distributed feedback (DFB) lasers consisting of alternating active and passive layers with a distributed Bragg reflector (DBR) mirror.<>