We experimentally demonstrate an autonomous, fully tunable and scalable optical neural network of 400+ parallel nodes based on a large area, multimode semiconductor laser. We implement hardware compatible, online learning strategies based on reinforcement learning and evolutionary strategies and evaluate them in terms of performance and energy cost. Our system achieves high performance and a high classification bandwidth of 15KHz for the MNIST dataset. Our approach is highly scalable both in terms of classification bandwidth and neural network size due to our device's short response time (nanosecond).
We design, fabricate, characterize, and compare 980 nm vertical cavity surface emitting lasers (VCSELs) with monolithic high contrast gratings (MHCGs) as top coupling mirrors. The MHCG is a series of parallel, rectangular stripes etched into a uniform GaAs epitaxial surface layer via electron-beam lithography and inductively coupled reactive ion etching, with specific grating period, height, and fill factor (defined as the grating bar width divided by the grating period). To boost the MHCG’s optical power reflectance at 980 nm and the width of the optical stopband we add a 5.5-period p-doped distributed Bragg reflector (DBR) beneath the MHCG grating, thus forming a composite DBR plus MHCG top coupling mirror. The bottom n-doped DBR is a conventional all-semiconductor AlGaAs/GaAs DBR with 37-periods on a GaAs substrate. We fabricate single 980 nm DBR MHCG VCSELs with two oxide aperture diameters on quarter wafer pieces from starting 3- inch diameter VCSEL epitaxial wafers. Each quarter wafer contains six complete unit cells, and each unit cell is a twodimensional array of single VCSELs in 16 rows and 15 columns. We for example set a constant but different grating period in five of the unit cells and vary the grating fill factors from column to column and we vary the oxide aperture diameters from 1 to 9 Pm in the rows, thus yielding a large variety of VCSEL diodes with differing MHCG parameters for us to compare. We perform room temperature on-wafer probe testing of the static optical output power-current-voltage (LIV) characteristics and emission spectra and compare the impact of the grating designs on these test results. We report record static LIV performance for our DBR MHCG VCSELs with threshold current below 1 mA and optical output power exceeding 1.3 mW. We observe room temperature bias current dependent mode emission for example single mode wavelength tuning ranges up to 12 nm.
The common understanding of laser operation is based on the non-equilibrium balance between the optical gain and the losses of the device, resulting in the stimulated emission of light above critical pumping threshold. In this contribution, we demonstrate that a broad-area VCSEL can operate in a state close to thermal equilibrium, enabling the Bose-Einstein condensation of photons. We observe condensation to the fundamental optical mode of the 23 µm-diameter device, followed by a thermalised distribution of photons in higher-order modes. Moreover, we extracted experimentally the thermodynamic properties of the photon gas and found that it closely follows the equation of state of a 2D boson gas in thermal equilibrium. This work offers a novel avenue for collective quantum phenomena in a well-established VCSEL platform.
The design of transparent conductive electrodes (TCEs) for optoelectronic devices requires a trade-off between high conductivity or transmittivity, limiting their efficiency. This paper demonstrates a novel approach to fabricating TCEs: a monolithic GaAs high contrast grating integrated with metal (metalMHCG). The technology and influence of fabricated different configurations of metalMHCG on the optical parameters will be shown. We will demonstrate above 90% absolute transmittiance of unpolarized light, resulting in 130% transmittance relative to plain GaAs substrate. Despite record high transmittance, the sheet resistance of the metalMHCG is several times lower than any other TCE, ranging from 0.5 to 1 OhmSq−1.
We present an extensive experimental analysis of two-dimensional gallium-arsenide-based VCSEL arrays considering the impact on performance of the VCSEL density (inter-VCSEL spacing and mesa diameters), the number and arrangement of VCSEL elements, and the VCSEL vertical epitaxial design. We include computer simulations that explain well the behavior and trends we observe in our experiments. We present the most efficient modifications of the lateral and vertical VCSEL arrays designs to optimize heat dissipation, optical output power scaling, and wall plug efficiency.
We experimentally demonstrate that circular oxide apertures with small side deformations of large-area 980 nm VCSELs contribute to an increase in the optical output power by more than 60% and in the quantum efficiency by more than 10%. We elaborate on the physical background of this behavior and its applicability to small aperture VCSELs. We show that the efficiency of stimulated emission can be enhanced by engineering the spectral structure of the resonator. Such an approach is used already to enhance spontaneous emission,but has been left unexplored in the context of the stimulated emission of VCSELs.
Monolithic High Contrast Gratings (MHCGs) are a special type of high-contrast grating (HCGs). In MHCGs, the stripes and the substrate on which they are implemented are made of the same material. MHCGs provide up to 100% power reflectance and thus are expected to find numerous applications in modern optoelectronics. We present thorough experimental analysis of spectral properties of GaAs MHCG mirrors designed at the wavelength of 1000 nm. Our results show that MHCG mirrors can be high-reflectivity mirrors as well as efficient polarizer and their properties can be modified by variation of lateral parameters of MHCG stripes.
Monolithic high contrast grating (MHCG) is a particular type of a grating where both substrate and grating bars are made of the same material, in our case this is GaAs.
Here we present the numerical simulations of GaAs-based planar focusing MHCG mirrors. In particular we compare the dependence of their reflectivity and the maximum intensity of the reflected light at the focal point with conventional parabolic reflectors of the same size and identical focal lengths. Our study is performed for both TE and TM polarizations. Moreover, we analyze the influence of geometrical imperfections (i.e. local disturbance of the height, period or fill factor of the grating) on the focusing properties of the grating mirrors.
The project (POIR.04.04.00-00-4358/17) is carried out within the HOMING programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund.
High contrast gratings (HCGs) are diffraction gratings whose period is less than the wavelength of light, made of a material with a high refractive index. Monolithic HCGs (MHCGs) are made of the same material as the cladding. They can be made of almost any material used in optoelectronics. We show experimentally and via simulations that shaping the cross-section of the MHCG stripes enables very broad high reflection spectrum.
We experimentally demonstrate and elucidate by numerical simulations that breaking circular symmetry of large apertures of vertical-cavity surface-emitting lasers (VCSELs) significantly enhances their emission properties by increasing the optical density of states. Specifically, deformed shapes of circular oxide apertures of VCSELs enhance stimulated emission and suppress undesired non-radiative recombination contributing to an increase in output optical output power of more than 60% and in quantum efficiency of more than 10%. Our example deformed VCSEL structures demonstrate that the optical density of states appears to be of high importance for conventional optoelectronic devices in accordance to the predictions of quantum electrodynamics theory.
Here we present how the monolithic high contrast grating (MHCG) mirror focuses light. The studied grating has a shape of a square with 300 micrometers side. The light focuses along one of the sides of the square. As a light source in our experiment we use a vertical-cavity surface-emitting laser that emits 980 nm. In our setup the light shines from above and the grating is on the bottom of the substrate. Based on numerous images taken by a camera attached to an optical microscope we generated a movie showing how the light intensity changes as a function of height above the grating. The FWHM at the focal point is around 5 micrometers and is observed around 200 micrometers above the top surface of the substrate. The measured focal length is in perfect agreement with the simulated data. Moreover, the light intensity at the focal point is more than 10 times larger as compared to the light intensity reflected by Au mirror reference.
The project (POIR.04.04.00-00-4358/17) is financed by FNP
We design and process more than 100 different 980 nm MHCG mirror designs, to determine optimal parameters for the use of the MHCGs as mirrors for VCSELs. We present measured power reflectance spectra and compare the results to our with numerical simulations. We discuss the impact of the actual processed geometric shape of the MHCG stripes on the measured power reflectance of the MHCGs..
We show our latest results on electrically-driven VCSELs incorporating a monolithic high contrast grating (MHCG) mirror. Via optimized processing techniques we achieve a 3-fold improvement in threshold current and optical output power and a 2-fold improvement in the small-signal modulation bandwidth frequency with respect to the first generation of our MHCG VCSELs.
980 nm VCSELs with different numbers of top dielectric DBR periods added to a 5.5-period top semiconductor DBR and with various oxide aperture diameters are investigated to determine the impact of the added dielectric DBR’s impact on the static and dynamic properties of the VCSELs. For VCSELs with the same oxide aperture diameter we observe smaller small-signal modulation bandwidth and lower D-factor for the VCSELs with more pairs of dielectric DBRs. For the VCSELs with 4 μm oxide aperture diameters with 8 and 12 periods of added top dielectric DBRs we measured bandwidths of 29 and 26 GHz, respectively.
High contrast gratings (HCGs) are nowadays very popular in research due to small dimensions and their highly reflective or transmissive properties. By proper alignment of HCG bars they may become focusing reflectors or lenses. Here we present simulations of GaAs-based planar focusing reflectors realized by monolithic HCGs. We present how to design focusing reflectors and discuss how to tune their reflectivity.
We design, produce, characterize, and compare 850 nm vertical cavity surface emitting lasers (VCSELs) with one and two oxide aperture layers, and with cavity optical thicknesses of 0.5λ and 1.5λ. We process five VCSEL wafers side by side with varying oxide aperture diameters from about 4 to 16 m and perform on-wafer static and dynamic testing. From optical output power-current-voltage characteristics we extract and compare threshold currents, differential series resistances, and wall plug efficiencies. We measure the dynamic 2-port scattering parameters (S11 and S21) to determine the small signal modulation frequency response of the VCSEL and the combined VCSEL and photodetector optical link. By extracting and comparing the D-factor, modulation current efficiency factor, -3 dB bandwidth, and resistanceinductance- capacitance (RLC) circuit elements we find only a small difference in the static and dynamic performance characteristics of the five VCSEL designs, with slightly higher bandwidth for the half-lambda cavity VCSELs with two top oxide apertures.
High contrast gratings (HCGs) are an attractive alternative to distributed Bragg reflectors (DBRs) as highly reflective mirrors for VCSELs. In our previous work we proposed the use of monolithic HCGs (MHCGs) to reduce the vertical thickness and simplify the epitaxial structure of VCSELs. In this work we discuss the optimization and fabrication of MHCGs. We also analyze the impact of processing imperfections on the power reflectance of MHCGs.
Since the very first demonstration of a vertical-cavity surface-emitting laser (VCSEL) incorporating subwavelength high refractive index contrast grating (HCG) membrane mirror in 2007 by the group of Prof. Chang-Hasnain, numerous research groups around the world have presented devices based on the same concept emitting at wavelengths from ~400 to 1550 nm manufactured in gallium nitride (GaN), gallium arsenide (GaAs) and indium phosphide (InP) material systems. On one hand, an open access to a VCSEL cavity through an air gap combined with a very low inertia of an HCG mirror opened a way for a large range of emission wavelengths in MEMS tunable VCSELs. On the other hand, an air gap in a cavity generally hinders heat and current flow, while the potentially rather fragile HCG membrane is prone to mechanical instability. We present electrically-injected VCSELs incorporating monolithic HCG (MHCG) mirrors. An MHCG mirror being a special case of an HCG mirror, keeps the extraordinary features of an HCG such as scalability with wavelength, ultra-low thickness and very large power reflectance, but doesn't have to be surrounded by a low refractive index material and hence can be monolithically integrated with an all-semiconductor VCSEL cavity. We present an extensive analysis of the impact of the MHCG parameters on the modal properties and thermal stability of single- and double-mode devices, with various oxide apertures. We additionally compare MHCG VCSELs and generic distributed Bragg reflector VCSELs in terms of modal properties and temperature stability based on measured data and the results of computer simulations.
A physical structure constructed from stripes of a material with high refractive index that are separated with a low refractive index medium is called a high contrast grating (HCG). Here we present the simulations of long focal-length GaAs-based planar focusing monolithic HCG reflectors designed for 980 nm. We discuss how the focal spot size depends on the reflector size and how it is possible to improve the maximum value of the electric field intensity distribution.
Monolithically grown, electrically-injected VCSELs of a generic design - a short cavity, sandwiched between two distributed Bragg reflectors (DBRs) - can only be realized easily in a gallium arsenide (GaAs) material system which restricts the emission wavelength to ~600 - 1100 nm range. The smartphones market and emerging applications such as LIDAR (light detection and ranging), free space communication and face recognition create a demand for VCSELs emitting outside of this range. We demonstrate electrically-injected VCSELs incorporating a monolithic high contrast grating (MHCG) - a special case of a subwavelength high contrast grating mirror (HCG). MHCG can be made of most of the common materials used in optoelectronics and provides reflectivity close to 100% at a wavelength of interest in range from ultraviolet to infrared. In contrast to the HCG, the MHCG doesn't have to be surrounded by a low refractive index material and hence, can be monolithically integrated with the rest of the VCSEL cavity. In our design the greater part of the top DBR is substituted by an MHCG mirror which reduces the amount of required material and growth time by about 20%. We show continuous wave emission around 980 nm up to 75 °C ambient temperature. Our devices are quasi-single- and double-mode from threshold to rollover for 13.5 μm and 16.5 μm oxide aperture diameters respectively. Our MHCG VCSEL concept can be produced using material systems where lattice-matched and high reflectivity DBRs are not available to create devices emitting at wavelengths from ultraviolet to infrared.
In this paper, we present a novel design of a nitride-based VCSEL emitting at 414 nm and perform numerical analysis of optical, electrical and thermal phenomena. The bottom mirror of the laser is a Al(In)N/GaN DBR (Distributed Bragg Reflector), whereas the top mirror is realized as a semiconductor-metal subwavelength-grating, etched in GaN with silver stripes deposited between the stripes of the semiconductor grating. In this monolithic structure simulations show a uniform active-region current density on the level of 5.5 kA/cm2 for the apertures as large as 10 μm. In the case of a broader apertures, e.g. 40 μm, we showed that, assuming a homogeneous current injection at the level of 5.5 kA/cm2 , the temperature inside the laser should not exceed 360 K, which gives promise to improve thermal management by uniformisation of the current injection.
This paper presents results of numerical simulations of a GaAs-based vertical-cavity surface-emitting laser, emitting at 980 nm. These simulations concern the influence of the number of top DBR pairs on the laser’s threshold parameters, as well as the optical loses in the cavity. Moreover, electrical parameters such as the device’s resistance and its capacitance-related temporal characteristics are analyzed as functions of the thickness of the top DBR. The simulations suggest that there is a possibility of a significant reduction in the number of pairs in the top DBR that can be beneficial in certain applications.
We propose a novel optical sensing system based on one device that both emits and detects light consisting of a verticalcavity surface-emitting laser (VCSEL) incorporating an high contrast grating (HCG) as a top mirror. Since HCGs can be very sensitive to the optical properties of surrounding media, they can be used to detect gases and liquid. The presence of a gas or a liquid around an HCG mirror causes changes of the power reflectance of the mirror, which corresponds to changes of the VCSEL’s cavity quality factor and current-voltage characteristic. By observation of the current-voltage characteristic we can collect information about the medium around the HCG. In this paper we investigate how the properties of the HCG mirror depend on the refractive index of the HCG surroundings. We present results of a computer simulation performed with a three-dimensional fully vectorial model. We consider silicon HCGs on silica and designed for a 1300 nm VCSEL emission wavelength. We demonstrate that our approach can be applied to other wavelengths and material systems.
Here we investigate the influence of the p- and n-oxide-aperture radii in all-semiconductor GaAs-based verticalcavity surface-emitting lasers (VCSELs), designed for 980 nm, on the modulation time constant (τ). Our analysis shows that the minimum value of τ is obtained if the oxide layers on both sides of the junction have identical depths. The simulations of the number of oxide layers on both p- and n-type sides reveal that double p- and n-oxidations are the most effective in the reduction of the modulation time constant as compared to single oxide layers.
We reduce the epitaxial design complexity of our conventional single-cavity oxide-aperture vertical-cavity surfaceemitting lasers (VCSELs) to reduce manufacturing costs while still meeting our internal 980 nanometer VCSEL performance goals via simplicity-in-design principles. We achieve maximum static single-mode optical output powers exceeding 4 milliwatts with small-signal modulation bandwidths exceeding 30 gigahertz at an ambient temperature of about 25 degrees Celsius for VCSELs with an oxide-aperture diameter of about 4 micrometers. Neighbor VCSELs with oxide-aperture diameters above 15 micrometers have maximum room temperature multiple-mode optical output powers of about 20 milliwatts with small-signal modulation bandwidths exceeding 20 gigahertz. The performance of our conventional oxide-confined 980 nanometer simplicity VCSELs exceeds the performance of our previously-reported and more complex 980 nanometer VCSEL epitaxial designs where we previously achieved maximum small-signal modulation bandwidths of about 26 gigahertz with oxide-aperture diameters of about 4 to 6 micrometers.
Record-large modulation bandwidths of 30 GHz and larger have been achieved with state-of-the art directly and indirectly modulated VCSELs and VCSEL arrays. One next big challenge is to make VCSELs viable for integration onto silicon while maintaining large bandwidth values. Various integration schemes of VCSELs might require process variations potentially detrimental for large modulation bandwidths. We present and compare directly modulated oxide-confined top-emitting 980-nm VCSELs processed from one single epitaxial wafer design into four different extracavity and intracavity contact variations.
In this paper, using our model of capacitance in vertical-cavity surface-emitting lasers (VCSELs), we analyze certain differences between an oxide-confined arsenide VCSEL emitting in the NIR region, and a nitride VCSEL emitting violet radiation. In the nitride laser its high differential resistance, caused partially by the low conductivity of p-type GaN material and the bottom contact configuration, is one of the main reasons why the nitride VCSEL has much worse modulation properties than the arsenide VCSEL. Using the complicated arsenide structure, we also analyze different possible ways of constructing the laser’s equivalent circuit.
We propose semiconductor-metal subwavelength grating (SMSG) which can be implemented as VCSEL mirror. Such new type of SMSG plays a double role of the electric contact and mirror simultaneously. It facilitates high optical power reflectance, perfectly vertical current injection. Such construction eliminates the inbuilt current confinement and allows scaling of emitted power by simple variation of SMSG spatial dimensions. To give the credibility to proposed design we perform numerical analysis of VCSEL with SMSG using fully vectorial optical model. We discuss properties of the proposed design realized in arsenide-based material configuration.
We present results of computer simulations of vertical cavity surface emitting lasers (VCSELs) using novel, highreflectivity monolithic high refractive-index contrast grating (MHCG) mirrors and their more advanced version, partially covered by a thin metal layer - metallic MHCG (mMHCG) mirrors. The first experimental realization of this new class of mirrors is presented and discussed. We show that the metal layer does not deteriorate the high reflectivity of an mMHCG mirror, but in contrary, is a crucial element which allows high reflectivity and additionally opens a way for a more efficient electrical pumping of a VCSEL. Comparison of results of thermal-electrical-carrier-gain self-consistent simulations of both MHCG- and mMHCG-based VCSELs is presented and discussed. It is shown that using mHCG mirror as a top mirror of a VCSEL improves electrical characteristics and greatly decreases the differential resistance of the device.
High Contrast Gratings (HCGs) become an attractive alternative for Distributed Bragg Reflectors (DBRs) used as high reflecting mirrors for VCSELs. In this paper we propose to implement HCG or monolithic HCG as a top mirror of the 1650nm InP-based VCSEL intended for use as a methane sensing device. Its unique feature is related to the fact that light taking part in the resonance can be accessed without opening the laser cavity due to the slow light phenomenon which occurs in HCG. Particular designs of HCGs allow to concentrate significant part of the mode between the HCG stripes. In such constructions the presence of the substance in the vicinity of the HCG which interacts with light resonating in the laser will change its emission properties. This enables sensing absorption or change to the refractive index in proximity of the laser based on the emission parameters of the laser. We present a numerical analysis of 1650nm MHCG and HCG mirrors based on fully vectorial optical model. We found optimal parameters of HCGs and MHCGs to detect absorption and refractive index variations in the vicinity of the gratings, based on changes in power reflectance of analysed mirrors. Additionally we consider HCG and MHCG constructions which allow for broad wavelength tuning by the change of the refractive index of substance surrounding mirror.
Different structures of nitride Vertical-Cavity Surface-Emitting Lasers (VCSELs) have been developed in recent years. However there is still many problems with such constructions, especially with electrical and optical confinement, current injection and construction and fabrication of mirrors. In this paper we present novel approach to nitride VCSEL designing. We investigated structure with tunnel junction (TJ) and top and bottom dielectric distributed Bragg reflectors (DBRs). Using our three-dimensional self-consistent model we investigated thermal and electrical properties of such laser. We also proposed replacing bottom DBR by monolithic high contrast grating mirror (MHCG) and presented optical properties of VCSEL with such mirrors.
Monolithic High refractive index Contrast Grating (MHCG) allows several-fold size reduction of epitaxial structure of VCSEL and facilitates VCSEL fabrication in all photonic material systems. MHCGs can be fabricated of material which refractive index is higher than 1.75 without the need of the combination of low and high refractive index materials. MHCGs have a great application potential in optoelectronic devices, especially in phosphide- and nitride-based VCSELs, which suffer from the lack of efficient monolithically integrated DBR mirrors. MHCGs can simplify the construction of VCSELs, reducing their epitaxial design to monolithic wafer with carrier confinement and active region inside and etched stripes on both surfaces in post processing. In this paper we present results of numerical analysis of MHCGs as a high reflective mirrors for broad range of refractive indices that corresponds to plethora of materials typically used in optoelectronics. Our calculations base on a three-dimensional, fully vectorial optical model. We investigate the reflectance of the MHCG mirrors of different design as the function of the refractive index and we show the optimal geometrical parameters of MHCG enabling nearly 100% reflectance and broad reflection stop-band. We show that MHCG can be designed based on most of semiconductors materials and for any incident light wavelength from optical spectrum.
Conventional High-index Contrast Gratings (HCG) consist of periodically distributed high refractive index stripes surrounded by low index media. Practically, such low/high index stack can be fabricated in several ways however low refractive index layers are electrical insulators of poor thermal conductivities. Monolithic High-index Contrast Gratings (MHCGs) overcome those limitations since they can be implemented in any material with a real refractive index larger than 1.75 without the need of the combination of low and high refractive index materials. The freedom of use of various materials allows to provide more efficient current injection and better heat flow through the mirror, in contrary to the conventional HCGs. MHCGs can simplify the construction of VCSELs, reducing their epitaxial design to monolithic wafer with carrier confinement and active region inside and etched stripes on both surfaces in post processing. We present numerical analysis of MHCGs using a three-dimensional, fully vectorial optical model. We investigate possible designs of MHCGs using multidimensional optimization of grating parameters for different refractive indices.
In this paper we present optical design and simulation results of vertical-cavity surface-emitting lasers (VCSELs) that
incorporate monolithic subwavelength high refractive-index-contrast grating (MHCG) mirrors - a new variety of HCG
mirror that is composed of high index material surrounded only on one side by low index material. We show the impact
of an MHCG mirror on the performance of 980 nm VCSELs designed for high bit rate and energy-efficient optical data
communications. In our design, all or part of the all-semiconductor top coupling distributed Bragg reflector mirror is
replaced by an undoped gallium-arsenide MHCG. We show how the optical field intensity distribution of the VCSEL’s
fundamental mode is controlled by the combination of the number of residual distributed Bragg reflector (DBR) mirror
periods and the physical design of the topmost gallium-arsenide MHCG. Additionally, we numerically investigate the
confinement factors of our VCSELs and show that this parameter for the MHCG DBR VCSELs may only be properly
determined in two or three dimensions due to the periodic nature of the grating mirror.
Distributed Bragg reflectors (DBRs) are typically used as the highly reflecting mirrors of vertical-cavity surface-emitting lasers (VCSELs). In order to provide optical field confinement, oxide apertures are often incorporated in the process of the selective wet oxidation of high aluminum-content DBR layers. This technology has some potential drawbacks such as difficulty in controlling the uniformity of the oxide aperture diameters across a large-diameter (≥ 6 inch) production wafers, high DBR series resistance especially for small diameters below about 5 μm despite elaborate grading and doping schemes, free carrier absorption at longer emission wavelengths in the p-doped DBRs, reduced reliability for oxide apertures placed close to the quantum wells, and low thermal conductivity for transporting heat away from the active region. A prospective alternative mirror is a high refractive index contrast grating (HCG) monolithically integrated with the VCSEL cavity. Two HCG mirrors potentially offer a very compact and simplified VCSEL design although the problems of resistance, heat dissipation, and reliability are not completely solved. We present an analysis of a double HCG 980 nm GaAs-based ultra-thin VCSEL. We analyze the optical confinement of such a structure with a total optical thickness is ~1.0λ including the optical cavity and the two opposing and parallel HCG mirrors.
In the talk we show the process of modeling complete physical properties of VCSELs and we present a step-by-step development of its complete multi-physics model, gradually improving its accuracy. Then we introduce high contrast gratings to the VCSEL design, which strongly complicates its optical modeling, making the comprehensive multi-physics VCSEL simulation a challenging task. We show, however, that a proper choice of a self-consistent simulation algorithm can still make such a simulation a feasible one, which is necessary for an efficient optimization of the laser prior to its costly manufacturing.
This paper presents results of computer simulation of 1D monolithic high refractive index contrast grating (MHCG) reflector also called surface grating reflector (SGR). We analyzed optical properties of the GaAs reflector designed for 980 nm wavelength with respect to the grating parameters variation. We also determined the electric field patterns after reflection from the structure in several cases of parameters variation. We show that thanks to the scalability and design simplicity, proposed design is a promising candidate for simple, next generation vertical cavity surface emitting lasers emitting from ultra-violet to infrared.
In this paper we present results of computer optical simulations of VCSEL with modified high refractive index contrast grating (HCG) as a top mirror. We consider the HCG of two different designs which determine the lateral aperture. Such HCG mirror provides selective guiding effect. We show that proper design of aperture of HCG results in almost sixfold increase in cavity Q-factor for zero order mode and a discrimination of higher order modes.
In this paper we present results of computer optical simulations of VCSEL with modified high refractive index contrast grating (HCG) as a top mirror. We consider the HCG of two different designs which determine the lateral aperture. Such HCG mirror provides selective guiding effect. We show that proper design of aperture of HCG results in almost sixfold increase in cavity Q-factor for zero order mode and a discrimination of higher order modes.
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