Marcin Gębski

Monolithic high-index contrast grating: a material independent high-reflectance VCSEL mirror

In this paper we present an extensive theoretical and numerical analysis of monolithic high-index contrast grating, facilitating simple manufacture of compact mirrors for very broad spectrum of vertical-cavity surface-emitting lasers (VCSELs) emitting from ultraviolet to mid-infrared. We provide the theoretical background explaining the phenomenon of high reflectance in monolithic subwavelength gratings. In addition, by using a three-dimensional, fully vectorial optical model, verified by comparison with the experiment, we investigate the optimal parameters of high-index contrast grating enabling more than 99.99% reflectance in the diversity of photonic materials and in the broad range of wavelengths.

Double-diamond high-contrast-gratings vertical external cavity surface emitting laser

A new design of vertical external cavity surface emitting laser (VECSEL) with diamond-based high contrast gratings is proposed. The self-consistent model of laser operation has been calibrated based on experimental results and used to optimize the new proposed device and to perform comparative thermal and optical analysis of conventional and double-diamond high-contrast-grating VECSELs. The proposed design considerably reduces the dimensions and complexity of the device and provides up to 80% increase of the maximum emitted power as compared with the conventional design.

Transverse mode control in high-contrast grating VCSELs

This paper presents an extensive numerical analysis of a high-contrast grating VCSEL emitting at 0.98 μm. Using a three-dimensional, fully vectorial optical model, we investigate the influence of a non-uniform grating with a broad range of geometrical parameters on the modal behavior of the VCSEL. Properly designed and optimized, the high-contrast grating confines the fundamental mode selectively in all three dimensions and discriminates all higher order modes by expelling them from its central region. This mechanism makes single mode operation possible under a broad range of currents and could potentially enhance the single-mode output power of such devices. The high-contrast grating design proposed here is the only design for a VCSEL with three-dimensional, selective, optical confinement that requires relatively simple fabrication.

Monolithic Subwavelength High-Index-Contrast Grating VCSEL

In this letter, we propose and numerically investigate a new vertical-cavity surface-emitting laser (VCSEL) structure consisting of a nearly lambda-thick active optical cavity sandwiched between two planar monolithic subwavelength high-index-contrast gratings (MHCGs) etched directly into the semiconductor layers surrounding the optical cavity. The structure allows the reduction of the vertical thickness of the subsequent MHCG VCSEL to roughly 0.6 μm for emission at 980 nm. Compared with a conventional all-semiconductor VCSEL with distributed Bragg reflector mirrors, the MHCG VCSEL has a shorter effective cavity length and thus a shorter roundtrip cavity time. Our proposed design enables the fabrication of VCSELs with lattice-matched mirror layers in all common semiconductor optoelectronic material systems, or alternatively VCSELs with hybrid HCGs.

Optimal parameters of monolithic high-contrast grating mirrors.

In this Letter a fully vectorial numerical model is used to search for the construction parameters of monolithic high-contrast grating (MHCG) mirrors providing maximal power reflectance. We determine the design parameters of highly reflecting MHCG mirrors where the etching depth of the stripes is less than two wavelengths in free space. We analyze MHCGs in a broad range of real refractive index values corresponding to most of the common optoelectronic materials in use today. Our results comprise a complete image of possible highly reflecting MHCG mirror constructions for potential use in optoelectronic devices and systems. We support the numerical analysis by experimental verification of the high reflectance via a GaAs MHCG designed for a wavelength of 980 nm.

The Influence of Imperfections and Absorption on the Performance of a GaAs/AlO

This paper discusses the influence of fabrication imperfections and absorption on high contrast grating (HCG) reflectivity and reveals that HCGs show considerable tolerance to both factors. A fully vectorial optical numerical model was used to design an HCG for use as the top mirror of a 980 nm GaAs-based vertical-cavity surface-emitting laser. Parameters providing a high degree of reflectivity were determined with special attention to optimizing the low refractive index layer.

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A 3-D, fully vectorial optical numerical model is used to design a high contrast grating for use as the top mirror of a 980-nm arsenide-based vertical-cavity surface-emitting laser. We study the parameters of two high contrast gratings made from GaAs/AlOx and Si/SiOx, respectively. Parameters providing high degrees of reflectivity, high levels of polarization discrimination, and fine tuning of the reflectivity of the high contrast grating are determined. The results demonstrate that both configurations if carefully designed by advanced numerical models can offer better performance in comparison to conventional distributed Bragg reflectors.

High-Contrast Grating for Monolithic Integration With 980 nm GaAs-Based VCSELs

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.

Optical Properties of GaAs/AlO

In the talk a new automated and self-consistent approach to modeling photonic devices is presented. Is is based on a new software being developed at Lodz University of Technology and its main idea is automated consideration of mutual interactions between various physical phenomena taking place in photonic devices. The software consists of several solvers that can model temperature distribution within the investigated structure, the electric current flow and carriers diffusion, the optical eigenmodes of the analyzed cavity or waveguide and the light-matter interaction. Results of the modeling performed with one solver are automatically provided as the input state of another one, and the calculations are performed in a user-controlled self-consistent loop. In the talk the basic idea of the approach is presented and it is supported by examples of simulation results of semiconductor lasers.

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Semiconductor-metal subwavelength grating (SMSG) can serve a dual purpose in vertical-cavity surface-emitting lasers (VCSELs), as both optical coupler and current injector. SMSGs provide optical as well as lateral current confinement, eliminating the need for ring contacts and lateral build-in optical and current confinement, allowing their implementation on arbitrarily large surfaces. Using an SMSG as the top mirror enables fabrication of monolithic VCSELs from any type of semiconductor crystal. The construction of VCSELs with SMSGs requires significantly less p-type material, in comparison to conventional VCSELs. In this paper, using a three-dimensional, fully vectorial optical model, we analyse the properties of the stand-alone SMSG in a number of semiconductor materials for a broad range of wavelengths. Integrating the optical model with thermal and electrical numerical models, we then simulate the threshold operation of an exemplary SMSG VCSEL.