Types Of Vertical-cavity Surface-emitting Lasers Research Articles

Low Noise VCSEL Driver for SERF Atomic Magnetometer

A new type of VCSEL (Vertical-Cavity Surface-Emitting Laser) which uses Pt1000 as a temperature sensitive component and non-magnetic heating membrane as a temperature actuator is designed for SERF (Spin-Exchange Relation-Free) atomic magnetometer, which can decrease the magnetic interference produced while heating or cooling VCSEL. Therefore a low noise driver for this kind of VCSEL is necessary. A driver for the novel VCSEL is designed in this paper. The output current is adjustable from 0 to 4.5 mA, and RMS (Root Mean Square) noise of current is less than 80 nA. The operating temperature of the VCSEL is adjustable between 30-110 °C and RMS noise of temperature is less than 0.6 mK. So that it can be ensured that the VCSEL outputs a laser with stable optical power and wavelength.

Advanced VCSEL Technology: Self-Heating and Intrinsic Modulation Response

Experimental data and modeling results are presented for a new type of vertical-cavity surface-emitting laser (VCSEL) that solves numerous problems with oxide VCSELs. In addition, the new oxide-free VCSEL can be scaled to small size. Modeling shows that this small size can dramatically increase the speed of the laser through control of self-heating. Modeling compared with both the oxide and the new oxide-free VCSEL predict intrinsic modulation speed for room temperature approaching 80 GHz, indicating the potential for > 100-Gb/s data speed from directly modulated VCSELs. The modeling is one of if not the first to include self-heating and spectral detuning between the gain and the cavity resonance that results from self-heating. The modeling results accurately accounts for the saturation in modulation speed in very high-speed oxide VCSELs operating at high temperature and accounts for the temperature of differential gain and photon density in limiting speed. Saturation of the photon density is found to limit the ultimate intrinsic speed. Differential gain decreases with increasing temperature but with sufficiently weak temperature dependence that it is not found to limit the VCSEL speed.

Transverse mode confinement in lithographic VCSELs

Index confinement is studied experimentally and through modelling for lithographic vertical-cavity surface-emitting lasers (VCSELs) and contrasted with other types of VCSELs. Modelling shows that the index confinement is set by the height of a shallow internal mesa that produces the optical mode confinement. Overgrowth with a semiconductor mirror enables a range of index confinement from zero (no index guiding) similar to proton-implanted VCSELs to much higher confinement than viable for oxide VCSELs. Lasing spectra are studied for side-mode-suppression ratio and beam patterns are compared for high and low indexes confined VCSELs of different sizes.

Design and analysis of a GaAs-based 850-nm vertical-cavity surface-emitting laser with different doping in the reflection regions

The present paper deals with the analysis of a non-oxide type of vertical-cavity surface-emitting laser (VCSEL) for operation at 850 nm. The modeling and characterization of the VCSEL is presented in the context of design considerations. Efforts are made to emphasize the behavioral features of the proposed VCSEL, in view of the analytical investigation, which has been performed through a series of simulations for various relevant parameters that are vital for the determination of the VCSEL characteristics. Some of these parameters are the intensity and refractive-index distributions, gain response, spontaneous emission, material gain variations, etc. The results obtained are compared with the oxide-confined VCSEL. It is observed that the proposed model of the VCSEL is suitable at the operating wavelength of 850 nm.

Temperature Profiling of VCSELs by Thermoreflectance Microscopy

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Surface temperature measurements with submicron spatial resolution are reported for operating vertical-cavity surface-emitting lasers (VCSELs) by means of thermoreflectance microscopy. We measure increasingly convex radial temperature distributions with increasing bias power for three types of VCSELs. The corresponding convex refractive index profiles are consistent with previously observed thermal lensing; this effect is far more prominent for the oxide confined single-mode (SM) VCSEL than for the broader aperture devices. For all samples, the change in the average surface temperature varies linearly with the change in dissipated power. A comparison with the temperature of the top distributed Bragg reflector mirror of an oxide confined SM VCSEL, obtained from the wavelength shift of the spontaneous emission, shows that both methods yield comparable results. </para>

High Q (33 000) all-epitaxial microcavity for quantum dot vertical-cavity surface-emitting lasers and quantum light sources

Data are presented on the modal and lasing characteristics of a new type of vertical-cavity surface-emitting laser that uses an intracavity mesa to confine the optical mode, with the mesa also confining the quantum dot active region. The quantum dot active region is lithographically isolated within the intracavity mesa using etching and epitaxial regrowth to form an all-epitaxial microcavity light source. Cavity quality factors as high as 33 000 are measured, and ground state lasing is demonstrated with a single quantum dot active layer for temperatures up to ∼110K.

Spatio-temporal modeling of the optical properties of VCSELs in the presence of polarization effects

We develop an optical dynamical model for vertical-cavity surface-emitting lasers (VCSELs) which describes, in an unified way, polarization and spatial effects. The model is based on equations for the lateral dependence of the slowly-varying amplitudes of the optical field in both circular polarizations, and equations for the carrier density in both spin orientations. This provides a natural generalization of the spin flip model for the description of polarization properties of VCSELs extensively used in the literature. In its present form, the model assumes given functional dependence of the guiding mechanisms (built-in refractive index and thermal lensing) as well as the spatial dependence of the current density. We investigate the transverse mode behavior of gain-guided, bottom and top-emitter VCSELs by implementing the model with an analytical approximation to the susceptibility of quantum-well semiconductors. We demonstrate that the stronger the thermal lens, the stronger the tendency toward multimode operation, which indicates that high lateral uniformity of the temperature is required in order to maintain single mode operation in gain-guided VCSELs. We perform analytical calculations of the threshold curves in both types of VCSELs. Also, close-to-threshold numerical simulations show that, depending on the current shape, thermal lensing strength and relative detuning, different transverse modes can be selected.

Influence of varying N-environments on the properties of (GaIn)(NAs) vertical-cavity surface-emitting lasers

We report electromodulated reflectance studies on the band structure of a dilute-N (∼1%) (GaIn)(NAs)/GaAs/AlAs vertical-cavity surface-emitting laser (VCSEL), as a function of temperature and incidence angle. The wide range of operating temperatures observed for this type of VCSEL (∼360 K here) is due to the reduced temperature variation of the effective band gap of the active (GaIn)(NAs) quantum wells, and broad gain. By comparing lasing properties and band structure we argue that the gain broadening is not simply due to alloy disorder but arises from a recently-proposed intrinsic property of (GaIn)(NAs): the existence of different band gaps for the five possible nearest-neighbor configurations of the N substitutional impurity.

All MOCVD grown 850-nm-wavelength refractive-index-guided semiconductor-buried vertical-cavity surface-emitting lasers with p/n-InGaP current blocking layers

All metal-organic chemical vapor deposition (MOCVD) grown 850-nm-wavelength refractive-index-guided semiconductor-buried vertical-cavity surface-emitting laser is proposed and their performance is investigated. P/n-InGaP current-blocking region enables both selective regrowth and the formation of refractive-index-guided region which surrounds multiquantum-well active/core regions. We have achieved room temperature CW operation of the new types of vertical-cavity surface-emitting lasers. The minimum threshold current was 9.5 mA with 18 /spl mu/m square mesa size at 30/spl deg/C. The device lased at up to 70/spl deg/C, and the maximum output power exceeds 1 mW at above 30/spl deg/C. The near field pattern indicates the single-lobed output beam at low bias current.

Mode-coupling effects on the small-signal modulation of multitransverse-mode vertical-cavity semiconductor lasers

We explored in detail the dynamics of multitransverse-mode vertical-cavity surface-emitting lasers (VCSELs), which are important for optical interconnection applications. We found that the small-signal modulation response exhibits a rich structure including multiresonance peaks as well as response notches. The detailed theoretical and experimental study enabled us to attribute the various features to the coupling level between the participating modes. The generality of the predictions was tested and approved for several types of multitransverse-mode VCSELs and even for a coherent VCSEL array.

Novel design of a hybrid-cavity surface-emitting laser

A new type of vertical-cavity surface-emitting laser (VCSEL) is proposed and analyzed to show the possibility of optical pumping from an integrated edge-emitting laser. With this scheme, it may be possible to make VCSEL's of very small dimensions and VCSEL arrays. The laser design utilizes dopant induced intermixing of quantum wells (QW's) to provide different gain regions for the surface and edge-emitting sections. The multimode rate equations are used to evaluate the possibility of such a laser and the roles of the various design parameters are discussed. It is seen that efficient surface photon emission is possible for high vertical-cavity mirror reflectivities and sufficient separation of bandgap energies for the two QW gain regions.

A comparative study on the thermal characteristics of vertical-cavity surface-emitting lasers

This paper presents a comparative study of the thermal characteristics of four types of vertical-cavity surface-emitting lasers (VCSELs). They include the dielectric-isolated top-emitting p-type substrate VCSEL, the ion-implantation isolated top-emitting n-type substrate VCSEL, the dielectric-isolated bottom-emitting n-type substrate VCSEL, and the junction-isolated etched-well n-type substrate VCSEL. Microscale electrical and heat conduction effects are taken into account by employing reduced and anisotropic electrical and thermal conductivities for the Bragg reflectors. Solutions for both the electrical potential and temperature fields are obtained numerically. The calculated device temperature rise compares well with available experimental data. The simulation results show that among the studied lasers the p-type substrate laser has the best intrinsic thermal performance. Local temperature distributions in these lasers reveal that a large temperature drop occurs across the Bragg reflectors. This study demonstrates that the AlAs concentration and the structure of the Bragg reflectors strongly affect the device temperature rise due to the difference in thermal conductivity. The study also suggests that a thicker top contact should be used to reduce the thermal resistance of these devices.