Vertical-Cavity Surface-Emitting Research Articles

Thermal characteristics of high-power vertical cavity surface emitting laser array

Due to the excellent characteristics such as good beam quality, dynamic single-longitudinal mode, low power consumption, and good wavelength stability, especially easy-to-integrate high-density 2D area arrays, vertical-cavity surface-emitting laser (VCSEL) is widely used in optical identification, optical interconnection systems, optical data storage and other fields. In recent years, with the improvement of materials and process technology, VCSEL has played an increasingly important role in the fields of smartphone face recognition, drone obstacle avoidance, virtual reality/augmented reality (VR/AR), sweeping robots, home cameras, etc., and with the rapid development and application of 5G communication, VCSEL will become an indispensable main component. However, due to the introduction of distributed Bragg mirrors, the thermal effect of VCSEL is very serious, especially when VCSEL is integrated into an array device, current-induced self-heating of each individual array cell and the thermal coupling among array cells have become the major factors contributing to thermal rollover and hence restraining the optical output performance of the VCSEL arrays. Therefor it is of great significance to study the thermal characteristics of VCSELs, in order to solve the problem of thermal crosstalk between single-tube devices, and increase the life of the device. This paper analyzes the influence of cell spacing and arrangement on the thermal crosstalk phenomenon and thermal diffusion performance of VCSEL array device based on the finite element model. The simulation results show that the maximum temperature of the device decays exponentially with the increase of cell spacing, the thermal crosstalk phenomenon and thermal diffusion performance of VCSEL array devices are significantly improved. When the cell spacing is 120 μm, the influence between the cells is small, the thermal crosstalk phenomenon is significantly improved, and the heat dissipation effect is better. On this basis, four non-square VCSEL arrays with 16 cells are designed, and it can be seen that compared with the square arrangement, the isosceles triangle, pentagonal and hexagonal configurations have improved the thermal crosstalk phenomenon and thermal diffusion performance, and the overall temperature rise of the VCSEL array is significantly reduced. The thermal crosstalk phenomenon of the pentagonal arrangement is significantly improved, and the device temperature is 37.32 ℃, which is the best effect among several arrangement methods. According to the results of theoretical simulation, the VCSEL array devices with different arrangements are prepared and characterized on the same epitaxial wafer by the same process. From the <i>P</i>-<i>I</i>-<i>V</i> characteristic curves, it can be seen that the threshold currents of isosceles triangles, pentagons and hexagons are lower than those of the square arrangement, and the maximum output power is higher than that of the square arrangement, especially the maximum output power value of the pentagonal is 150 mW. The results show that the new arrangement can effectively improve the thermal crosstalk phenomenon between the cells, increase the output power of the device, and make the VCSEL array device have good optoelectronic and thermal characteristics.

GeSn/Ge Multiquantum-Well Vertical-Cavity Surface-Emitting p-i-n Structures and Diode Emitters on a 200 mm Ge-on-Insulator Platform

An efficient monolithically integrated light source with complementary metal-oxide-semiconductor (CMOS) compatibility remains the missing component to enable Si photonics for various applications. In particular, vertical-cavity-surface-emitting (VCSE) light sources, such as resonant cavity light-emitting diodes (RCLEDs) and vertical-cavity surface-emitting lasers (VCSELs), are strong contenders due to their compact size, circular emission profile with low beam divergence, wafer-scale fabrication compatibility, high bandwidth, and high coupling efficiency to fiber optic cables. We report the first demonstration of 8-in. wafer-scale GeSn/Ge multiple-quantum-well VCSE p-i-n structures and diodes for laser or light-emitting diode (LED) applications in Si photonics by wafer bonding and layer transfer techniques, which are challenging for all-epitaxy routes. The wafer could be 12 in. (300 mm) since the MQW gain medium is grown on a 300 mm Si wafer, and the bonding is wafer-scale. Alternative dielectric layers (SiO2/SiN/SiO2), introduced by wafer bonding, under the emitting structure, serve as the bottom mirror for the vertical cavity. The Ge0.92Sn0.08/Ge MQW layer is utilized to improve the material quality and to confine injected carriers. As a result, more than 8× enhancement of light emission due to the vertical cavity resonance was demonstrated by photoluminescence spectroscopy. Besides, the spectral purity is enhanced by the single-longitudinal-mode cavity. The intensity of light emission is insensitive to the temperature range from 4 to 300 K and even becomes stronger at higher temperatures since the stronger resonant cavity effect at higher temperatures compensates for the drop in light emission efficiency caused by nonradiative centers. The vertical cavity effect on the light emission is further verified by reflectivity spectroscopy and optical simulations. A positive gain can be achieved as indicated by optical gain calculations. Room-temperature electroluminescence and an excellent carrier injection efficiency of the MQW VCSE diode are observed, showing its potential for electrically injected RCLEDs and VCSELs.

High minority carrier mobility and electronic diffusion length in annealed GaInAsSb/GaSb active layer in Vertical Cavity Surface Emitting Laser (VCSEL)

Owing to its important role as an active layer for Vertical Cavity Surface Emitting laser (VCSEL). We studied the transport properties in annealed GaInAsSb /GaSb by means of PTD technique. We remark that annealing time improve significantly the diffusion length and minority carrier mobility. For an annealed time duration of 60 min the diffusion length reach 25 µm (3.9%) and the minority carrier mobility reach 3673 cm2/V. (3.4%).We have observed that surface recombination velocity (SRV) decreased in respect of annealing time and was found to be 1450 m / s (± 3.6). Unfortunately, interface recombination velocity (IRV) is highly increased from 1196 m / s (± 5) to 6000 m/s (5%) for GaInAsSb as grown to that annealed during 60 min.

Folded resonators of vertical cavity surface-emitting stripe array of diode lasers

A folded resonator of vertical cavity surface-emitting (VCSE) stripe array of diode lasers is presented. The upper surfaces of VCSELs (vertical cavity surface emitting lasers) are anti-reflected, and the lower surfaces are Bragg mirrors. A strip plane-convex mirror and the Bragg mirrors are applied to form the folded resonator. This strip plane have some transparent partitions. Every VCSEL is connected by the axis of the resonator, and this axis is formed by linking the correspondent reflective points on the inner spherical surface of the mirror and the reflective points on the Bragg mirrors. One approach could be to fabricate the array directly on a plane of a GaAs (or Si) plano-convex mirror. The resonator is also a spatial filter, and can contain many VCSELs, and therefore can afford a high quality laser beam and high-power output.

A Vertical-Cavity Surface-Emitting Laser for the 1.55-μm Spectral Range with Tunnel Junction Based on n++-InGaAs/p++-InGaAs/p++-InAlGaAs Layers

A design of a tunnel junction (TJ) based on n++-InGaAs/p++-InGaAs/p++-InAlGaAs layers for vertical-cavity surface-emission lasers (VCSELs) for the 1.55-μm spectral range fabricated by wafer fusion of an InAlGaAsP/InP optical cavity and wafers with AlGaAs/GaAs distributed Bragg reflectors has been suggested and tested. The presence of the oxidation-resistant InGaAs layers makes it possible to employ the molecular-beam epitaxy in all stages of the fabrication technology of VCSELs, including the overgrowth of the surface profile in the TJ layer. Owing to the Burstein–Moss effect and to the thickness minimization of the p++-InGaAs layer, it was possible to avoid a buildup of the internal optical loss. As a result, the characteristics of the thus fabricated devices are comparable with those of VCSELs having an n++-/p++-InAlGaAs TJ and a similar level of the mirror losses.

Highly efficient heat extraction by double diamond heat-spreaders applied to a vertical external cavity surface-emitting laser

We compare the heat extraction efficiency for a standard Vertical External Cavity Surface-Emitting Laser and the distributed Bragg reflector (DBR)-free structure employing a single and double diamond heat-spreaders, respectively. Both heterostructures grown by Molecular Beam Epitaxy employ two identical active regions designed for emission at 980 nm. We show that the thermal resistance has been decreased 15 times when there is no DBR and heat is extracted from both side of active region. For DBR-free laser no thermal rollover of power conversion characteristic was observed in the range of considered input powers.

Measurements of gas temperatures at 100 kHz within the annulus of a rotating detonation engine

Cycle-resolved measurements of H2O temperatures and number densities taken within the detonation channel of a hydrogen—air rotating detonation engine (RDE) at a 100 kHz repetition rate using laser absorption spectroscopy are presented. The laser source used is an MEMS-tunable Vertical-Cavity Surface Emitting laser which scans from 1330 to 1360 nm. Optical access into and out of the RDE is achieved using a dual-core fiber optic. Light is pitched into the RDE through a sapphire window via a single-mode core, retroreflected off the mirror-polished inner radius of the RDE annulus, and collected with the multi-mode fiber core. The resulting absorption spectra are used to determine gas temperatures as a function of time. These measurements allow characterization of the transient-temperature response of the RDE.

亚波长光栅对微机电系统波长可调谐垂直腔面发射激光器的影响

亚波长光栅对微机电系统波长可调谐垂直腔面发射激光器的影响

Low–Frequency Noise Measurements Used For Quality Assessment Of GaSb Based Laser Diodes Prepared By Molecular Beam Epitaxy

Abstract The paper reports on a non-destructive method of reliability prediction for semiconductor lasers diodes GaSb based VCSE (vertical cavity surface emitting). Transport and noise characteristic of forward biased were measured in order to evaluate the new MBE (molecular beam epitaxy) technology. The results demonstrate that the lasers prepared by new MBE technology have higher quality than the samples prepared by using the classic MBE technology.

Lasing on surface states in vertical-cavity surface-emission lasers.

We report experimental observation of lasing on surface states, in the form of standing waves at the termination of a defect-free photonic crystal on top of vertical-cavity surface-emission lasers. Direct images of lasing modes at the truncated periodic potential, along one side of a square lattice, are demonstrated by collecting near-field radiation patterns, as well as in numerical simulations. Our results provide a step toward realizing surface and edge states in optical cavities.

Multicore Fiber Optimization for Application to Chip-to-Chip Optical Interconnects

We present the design of a holey microstructured multicore optical fiber optimized to meet the stringent requirements of chip-to-chip optical interconnects, namely, be compatible with high-speed vertical-cavity surface-emission lasers, feature ultrahigh channel density, low crosstalk, and millimeter-bend resistance to sustain the tight bends required on an electronic circuit board. We show that the shortcomings of the standard hexagonal microstructure can be overcome by the use of seven-rod cores. We present the detailed simulation results of the crosstalk and bend loss as a function of all the important microstructure parameters that led to the optimized solution. We discuss the crosstalk dependence on the bending radius. To our knowledge, the multicore fiber presented here achieves the highest normalized core density proposed to date, low enough crosstalk for meter-long transmission at 10 Gb/s and bend loss <; 0.02 dB/loop at a 1-mm bend radius. Maximizing space-division multiplexing, it has the potential to allow Tb/s·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> optical interconnects without the need for wavelength-division multiplexing.

The Generation of a Compact Azimuthally Polarized Vertical-Cavity Surface Emitting Laser Beam with Radial Slits

We propose the simple and efficient generation of a compact azimuthally polarized laser beam. Radial slits with annular distribution are patterned onto the output facet of a standard vertical-cavity surface emitting laser. Due to the polarization modulation of the surface plasmon polariton mode excited by the radial slits, a compact azimuthally polarized laser beam at 850 nm is experimentally demonstrated. The finite-difference time-domain method is introduced to analyze the polarization characteristics of the transmitted light through the radial slit, which agrees well with our experimental results.

Various Elements of Heat Sources within an Optimized Photonic Crystal Vertical Cavity Surface Emitting Laser: Influence of Hole Etching Depth

Various Elements of Heat Sources within an Optimized Photonic Crystal Vertical Cavity Surface Emitting Laser: Influence of Hole Etching Depth

Giant Wavelength–Temperature Dependence of a Micro Machined Vertical Cavity Surface Emitting Laser with a Thermally Actuated Cantilever Structure

Giant Wavelength–Temperature Dependence of a Micro Machined Vertical Cavity Surface Emitting Laser with a Thermally Actuated Cantilever Structure

Giant Wavelength–Temperature Dependence of a Micro Machined Vertical Cavity Surface Emitting Laser with a Thermally Actuated Cantilever Structure

We present the modeling and the experimental result of a micro machined vertical cavity surface emitting laser with a thermally actuated semiconductor/SiO2 cantilever structure. The modeling result shows a giant wavelength–temperature dependence of over 3.5 nm/K. The fabricated device exhibits a temperature dependence of 0.79 nm/K, which is 10 times larger than that of conventional vertical cavity surface emitting lasers (VCSELs).

Tunable Vertical-Cavity Surface-Emitting Lasers Integrated with Two Wafers

A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs) is presented. The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a “half-VCSEL" wafer consisting of a fixed bottom mirror and an amplifying active region. The measurement results of the electricity pumped tunable VCSEL with more than 9 mW output power at room temperature over the tuning range prove the feasibility of the proposition.

Wavelength Extension Effect on Lasing Characteristics of Highly-Strained GaInAs/GaAs Vertical-Cavity Surface-Emitting Lasers with Cavity Detuning

Cavity detuned highly-strained GaInAs/GaAs vertical cavity surface emitting lasers (VCSELs) were investigated. Devices emitting beyond 1.2 µm of the wavelength were realized by combining conventional quantum wells emitting at 1.18 µm and large wavelength detuned cavities. Various detuning conditions from -35 to 80 nm were compared for clarifying the detuning effect. The longest wavelength was 1.27 µm for an 80 nm detuned device. The highest operating temperature of a 55 nm detuned device was 140 °C under cw operation. It was found that approximately 50 nm detuning was necessary to reach the threshold gain level for a large detuned device and the condition was produced by self-heating. Relaxation resonance frequencies were characterized and over 2 GHz was observed even for a 1.27 µm VCSEL.

Photoacoustic detection of oxygen using cantilever enhanced technique

A tunable diode laser photoacoustic setup based on a recently demonstrated cantilever technique was used for sensitive detection of oxygen. As light sources, we used a distributed feedback (DFB) diode laser and a vertical-cavity surface-emitting (VCSEL) laser, both operating near 760 nm. With the 30 mW DFB laser a noise-equivalent detection limit of 20 ppm for oxygen was obtained, while a detection limit of 5 ‰ was achieved with the VCSEL having an output power of 0.5 mW. Our results yield a noise-equivalent sensitivity of 4.8×10-9 cm-1W Hz-1/2 and demonstrate the potential of this technique for compact and sensitive measurement of oxygen.

Validity of Scalar Approaches to Radiation Modes of the GaAs-Based 1.3-μm Diode Lasers Designed for the Optical–Fibre Communication

The work presents a comparison between results of optical simulations based on the scalar and vectorial models applied to both stripe – geometry Fabry-Perot (FPL) as well as vertical-cavity surface-emitting (VCSEL) diode lasers designed for the 1.3-μm optical–fibre communication. As compared to vectorial optical approaches, scalar ones are known to be less exact but simultaneously they need as many as approximately 100 times shorter computation time, which favours those models in many applications. Therefore, vectorial models should be applied only in cases of confirmed faulty performance of scalar ones. While the Effective Index Method and the Effective Frequency Method have been chosen as scalar approaches to FPLs and VCSELs, respectively, simulations, the Method of Lines has been used in both cases as a vectorial one. Scalar models have been found to be quite exact in the case of a determination of the effective refractive index and wavelength of emitted radiation, whereas their exactness in the lasing threshold analysis is much worse, especially in the case of higher-order modes. Our analysis is concluded with the determination of the regions where both models give satisfactorily close results.

Misalignment tolerance analysis of combined thick convex lens and lensed fiber scheme between vertical-cavity surface-emission lasers and single-model fibers

High coupling efficiency and large misalignment tolerance are two important optical requirements of packaging a laser diode [or vertical-cavity surface-emission laser (VCSEL)] for various applications in optical fiber communication. An integrated lens at the end of a single-mode fiber can increase the coupling efficiency between fibers and VCSELs. We present a theoretical analysis of a coupling scheme, which involves a combination of both a convex lens and a hemispherical lensed fiber configuration. The theoretical analysis is conducted to include the influence of lens aberration. The results show that lens aberration reduce coupling efficiency from 40 to 34% for a VCSEL operating at a 850-nm wavelength under the TO52H package. On the other hand, the lateral tolerance of the two lens coupling scheme improved compared to the TO can-butt coupling fiber scheme.