Round-Trip Operator Technique Applied for Optical Resonators with Dispersion Elements

ABSTRACTAn electrically pumped 1.24um GaxIn1-xAsyP1-y Vertical Cavity Surface Emitting Laser (VCSEL) has been designed and simulated. Threshold gain of 153cm-1 and threshold current of 1.00mA was obtained. The external efficiency predicted is 0.31. Also the optimized design of VCSEL structure is presented in this article. GaInAsP and AlInAs constitute the Distributed Bragg Reflectors (DBRs) multilayer stack. Reflectivity of the top DBRs is 0.97 and reflectivity of the bottom DBRs is 0.9978 and is shown to provide a good resonant cavity and sufficient lasing intensity. Compared with other reported structures, the present VCSEL has a lower threshold current and higher threshold gain.

The threshold gain and the cavity loss are important parameters for the optimum design of vertical-cavity surface-emitting lasers (VCSEL). Here we try to determine the cavity loss by varying the amount of light fed back to the VCSEL using an external mirror. The tested VCSEL consists of a superlattice active region surrounded by AlAs/Al/sub 0.3/Ga/sub 0.7/As distributed Bragg reflectors. The nonlinear gain effect is introduced in estimating the internal parameters of VCSELs. Since most VCSELs operate at a carrier density much higher than the transparency level, the nonlinear gain effect should be nonnegligible and be considered. Therefore, this method is appropriate even for a large threshold-gain (like the VCSEL) and/or a large amount of the feedback light (more than a few percents).

Scalabilities of light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs) with tunnel-regenerated multi-active-region (TRMAR) structure were investigated. It was found that the output optical power and quantum efficiency of these new LEDs with TRMAR increased with the number of its active regions, but the threshold gain and threshold current density decreased. However, for VCSELs with TRMAR, the differential quantum efficiency and optical power increased with the number of the active region. The results suggest that LEDs and VCSELs with the TRMAR structure have some potential advantages over the conventional LEDs or VCSELs in high internal quantum efficiency, low heat generation, high round-trip gain, and so on. These advantages will make TRMAR LEDs or VCSELs more attractive for the industrial application.

Colloidal quantum‐dot (CQD) vertical‐cavity surface‐emitting lasers (VCSELs) enable a solution‐processable directional‐emitting coherent light source, which is desirable for various applications, including near‐eye display, sensing, and communication. However, it remains challenging to construct a controllable, high‐quality VCSEL cavity without damaging the photoluminescence of CQDs to achieve the desired lasing characteristics. Here, high‐quality CQDs with an engineered CdZnSe/ZnSe/ZnxCd1‐xS core/interlayer/graded shell structure are developed to ensure excellent stability and sub‐single‐exciton gain threshold, facilitating the achievement of high‐performance VCSEL. Subsequently, CQD VCSELs with distributed Bragg reflectors deposited on CQDs in situ by thermal evaporation are demonstrated. The proposed fabrication process not only enables precise control over the cavity structure but also a high cavity quality without compromising the optical properties of CQDs. Consequently, the developed CQD VCSEL exhibits a low lasing threshold of 58 µJ cm−2 and a high lasing quality factor up to 2395, setting a record for VCSELs based on CQDs or colloidal quantum‐wells. It also demonstrates stable operation for 300 h at room temperature, corresponding to 1.08 × 108 stable lasing pulses, placing it among the most stable nanocrystal lasers reported. This work presents an effective strategy for achieving high‐performance CQD‐based VCSEL, which is significant for the future development towards non‐epitaxial laser diodes.

This work focuses on the effects of external feedback on the transient response of antiresonant reflecting optical waveguide (ARROW) vertical cavity surface emitting lasers (VCSELs). The study uses a self-consistent system, which is incorporated by the field transfer matrix method, laser rate equations and the reflective index change model, to simulate the dynamics of the VCSELs under optical feedback.

The design of an electrically pumped InGaAs quantum well based vertical cavity surface emitting laser (VCSEL) on InP substrate is presented. Such optically pumped VCSELs have already been demonstrated. To design electrically pumped VCSEL, three simulations steps are needed: optical simulation gives access to the standing-wave electric field distribution, to design the active region and the Bragg mirrors. Thermal simulation is helpful to design metallic contacts while the energy band diagram is obtained by electrical simulation to design the buried tunnel junction useful for carrier injection. All these simulations are compared to experiment.

We report on the theoretical analysis and fabrication of a novel type of vertical-cavity surface-emitting laser (VCSEL) that provides selection of a certain higher-order transverse mode. This selection is based on a spatial variation of the threshold gain by adding an antiphase layer with an etched relief structure. The field intensity profile emitted from this laser is calculated numerically as well as with an analytical approach. The main factors that control the selected mode such as the threshold gain, the confinement factor, and the phase parameter are calculated as a function of the active aperture, aiming to achieve single higher-order transverse mode emission. For a given aspect ratio of a rectangular oxide aperture, the threshold gain difference between the selected and neighboring modes is maximized via the relief diameter and the size of the aperture. The fabrication process involves selective etching of the antiphase layer, passivation of the relief, oxidation of an AlAs layer to the desired aperture after reaching this layer using wet-chemical etching. N- and p-metalization processes are applied, followed by polyimide passivation. Finally, bondpad metalization is carried out for electrical contacting. Mode selection is successfully achieved. Attractive applications for such devices are found in optical manipulation of micro-particles such as sorting and separation.

1.3 /spl mu/m vertical-cavity surface-emitting lasers (VCSELs) will have important applications in local access optical networks and high-speed data links. In our earlier paper, we reported low CW threshold current 1.3 /spl mu/m VCSELs which contain InGaAlAs strain-compensated quantum wells, bonded GaAs/AlGaAs Bragg mirrors, and oxygen implanted current confinement regions. It is believed that oxygen implantation is the key for low threshold current because oxygen atoms have less lateral and vertical straggling than hydrogen atoms and the implanted region can preserve its high resistivity after high temperature wafer-bonding. In this paper we report our studies of the oxygen dosage effects on 1.3 /spl mu/m VCSELs. We have measured the threshold current, slope efficiency, and series resistance for VCSELs with two different oxygen doses but otherwise the same structure.

We investigated the lasing spectra, threshold gain values, and modal fields of two-dimensional elliptical microcavity lasers with centrally located circular active regions. Our numerical experiments were based on the Muller boundary equations solved by the Nystrom method. They showed that the whispering gallery modes (WGM) and the bow-tie modes (BTM) exist in such resonators. We studied the field patterns and the lasing characteristics as a function of the radius of the active region. The calculations demonstrated that the radius of the active region can be used as a tool for manipulating the threshold gains of both BTM and WGM.

Tunable vertical cavity devices including an air-gap integrated in the cavity have been designed, fabricated, and investigated. The ultrawide wavelength tuning is realized by micromechanical actuation of Bragg mirror membranes. Based on optical and mechanical model calculations, the air-gap filters and vertical cavity surface emitting lasers (VCSELs) are designed for investigating mainly the optical tuning efficiency. In our research, we focus on two different mirror material systems, dielectric Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and InP/air-gap Bragg mirrors and on two tuning concepts, respectively. For the dielectric mirrors, continuous tuning is achieved by thermal actuation of the Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mirror membranes, and for InP/air-gap mirrors, electrostatic actuation of the InP membranes is used. To verify the optical and mechanical simulations, InP/air-gap filters are characterized by measuring reflectance spectra and the tuning behavior. The measured results agree with the simulations used to optimize the micromechanical and optical characteristics of air-gap filters and VCSELs for optical communication applications.

A fluidic cavity vertical-cavity surface-emitting laser (VCSEL) is presented for the detection of biological agents via introducing the analytic biofluid into the high finesse laser cavity. The optical properties of the fluid as modified by the biological cells they contain are sensed by monitoring the output optical intensity and wavelength of the laser. As a preliminary study, our first generation electrically pumped GaAs/AlGaAs based fluidic cavity VCSEL is described, with emphasis on the system design and techniques for the system construction. The device shows a strong spontaneous emission and a considerable wavelength shift when DI water is capillarily fed into the fluidic cavity.

In this article, a record-high single-mode output power from a multi-junction vertical-cavity surface emitting laser (VCSEL) emitting at 905 nm is achieved. Single spectral mode emission of the VCSEL is realized by using an anti-phase mode filter, placed at the top surface of the device, that acts as a relief layer to suppress the higher order transverse modes. Placement of such anti-phase layer at the surface areas in which the higher order modes are expected to emit, leads to reduction in the effective mirror reflectivity at those areas, increased optical losses, and consequently, increased threshold gain for the higher order modes compared to the fundamental mode. The room-temperature light-current-voltage characteristics of a 6-junction 905 nm VCSEL with an oxide aperture size of ∼8 μm and mode filter size of 5 μm shows a single-mode optical power of 12.55 mW and maximum power conversion efficiency of 56.48%. Moreover, the emission spectrum of this device shows a stable side-mode suppression ration of >30 dB in the single-mode operation regime. The VCSEL remains reliably single-mode at higher temperatures, generating a maximum optical output power of 9.48 mW at 60 °C. Such remarkable single-mode performance can be mainly attributed to the multi-junction epitaxial structure of the device, in which the output optical power is expected to proportionally increase according to the number of bipolar cascade active regions.

A simple transfer matrix method is proposed to calculate the radiation losses of a cylindrical antiresonant-reflecting optical waveguide (ARROW). It is found that the planar approximation underestimates the radiation losses but overestimates the design tolerance of the ARROW-type vertical-cavity surface-emitting lasers (VCSELs). An iteration technique, which is incorporated with the transfer matrix method, is also developed to design ARROW-type VCSELs for minimum radiation losses in a more effective manner.

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 &lt;i&gt;P&lt;/i&gt;-&lt;i&gt;I&lt;/i&gt;-&lt;i&gt;V&lt;/i&gt; 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.

We present a numerical optical model for calculating threshold material gain in vertical-cavity surface-emitting lasers. It is based on a vectorial solution of Maxwell's equations and therefore gives exact results where other approaches fail, e.g., in the case of oxide-confined devices, which have high lateral index contrasts. Results are given concerning the influence of oxide window thickness and position on threshold gain and modal stability. We also propose an intuitive plane-wave model to enhance the physical understanding of these effects.