The shape of couped oxide-confined apertures governs the selective losses and dynamics of main optical supermodes in VCSELs and their polarization. (i) For the case of coupled apertures with broader (similar to 1.5 mu m) and shorter (similar to 2 mu m) bridge connecting the non-oxidized regions the VCSELs can demonstrate both co-polarized and cross-polarized lasing despite of the significant shape anisotropy of the coupled aperture. The loss discrimination among the polarized modes is weak. Strong antiphase intensity oscillations exist in the coupled apertures for symmetric (S) and antisymmetric (AS) supermodes are observed in streak camera studies in this case. Polarization switching and polarization hysteresises confirm low scattering losses in the coupled aperture system resulting in quasi-equal threshold currents and gains for the supermodes at different polarizations. The dephasing time is long, exceeding tens of nanoseconds. Upon current increase the splitting of the modes and the intensity oscillation frequency increase linearly with current reaching 50-70GHz. Once the device switches to self-injection locked (SIL) regime characterized by a single AS mode, the oscillation frequency decreases by similar to 25GHz and both apertures oscillate in phase. Upon further current increase the same linear slope of the frequency vs current is reestablished up to 60- 70GHz. Cross-polarized modes revealed below the onset of SIL regime may be responsible for the resonance frequency feature in the modulation response observed in circular polarized studies, even when the intensity of the cross-polarized mode is weak. (ii) For the coupled apertures connected by a longer (similar to 4 mu m) and narrower (similar to 1 mu m) bridge only co-polarized along the coupling axis S and AS modes are observed, indicating that scattering loss mechanisms become important and significantly and selectively affect threshold gains for differently polarized modes. No antiphase oscillations are observed for such chips below SIL threshold, and the mode splitting is reducing with current. In the SIL regime defined by the AS mode, in-phase oscillations evolve in both cavities at a frequency matching the reduced mode splitting similar to 20GHz at currents in the very vicinity of the onset of the SIL regime. The frequency of the first post-excitation oscillation rapidly increases above SIL threshold linearly with current reaching effective bandwidths similar to 100GHz. The following two oscillations proceed at lower frequencies. Further oscillations demonstrate further reduced frequencies and decay rapidly with time. Our data indicates that shape engineering can effectively control the mode scattering mechanisms. Consequently, one can design the intrinsic modulation response either by making it suitable for ultrahigh data transmission rates in digital format, or, as opposite, for generation of stable frequencies controlled by drive current. Cavity engineering becomes, however, challenging once ultimate control over the shape is required. Avoidance of oxide-confined apertures by applying purely metal apertures for optical confinement enables drastic extension of shape and loss engineering options while keeping low threshold, high differential efficiency and controlled S and AS mode splitting. We show that coupled apertures can be also generated by introducing etch pattern in the top dielectric cap layer, which effectively confines optical emission within similar to 1 mu m-scale areas and generates specific multispot near filed patterns for high order modes.

Coupled-cavity mini-array vertical-cavity surface-emitting lasers (VCSELs) are promising laser sources for high-speed data transmission due to their extended intensity modulation frequencies. Here, it is demonstrated for the first time how to use such a 2 x 1 mini-array VCSEL for the photonic generation of CW THz radiation. The emission frequencies of the cavities are tuned via current and provide the beat frequency for the photoconductive antennae. With coherent lock-in detection we measured frequencies up to 300 GHz, making the mini-array VCSEL an extremely simple and low-cost alternative laser source for frequency-modulated continuous-wave radar or spectroscopy systems.

Substantial improvements in the performance of optical interconnects based on multi-mode fibers are required to support emerging single-channel data transmission rates of 200 Gb/s and 400 Gb/s. Future optical components must combine very high modulation bandwidths—supporting signaling at 100 Gbaud and 200 Gbaud—with reduced spectral width to mitigate chromatic-dispersion-induced pulse broadening and increased brightness to further restrict flux-confining area in multi-mode fibers and thereby increase the effective modal bandwidth (EMB). A particularly promising route to improved performance within standard oxide-confined VCSEL technology is the introduction of multiple isolated or optically coupled oxide-confined apertures, which we refer to collectively as multi-aperture (MA) VCSEL arrays. We show that properly designed MA VCSELs exhibit narrow emission spectra, narrow far-field profiles and extended intrinsic modulation bandwidths, enabling longer-reach data transmission over both multi-mode (MMF) and single-mode fibers (SMF). One approach uses optically isolated apertures with lateral dimensions of approximately 2–3 µm arranged with a pitch of 10–12 µm or less. Such devices demonstrate relaxation oscillation frequencies of around 30 GHz in continuous-wave operation and intrinsic modulation bandwidths approaching 50 GHz. Compared with a conventional single-aperture VCSELs of equivalent oxide-confined area, MA designs can reduce the spectral width (root mean square values < 0.15 nm), lower series resistance (≈50 Ω) and limit junction overheating through more efficient multi-spot heat dissipation at the same total current. As each aperture lases in a single transverse mode, these devices exhibit narrow far-field patterns. In combination with well-defined spacing between emitting spots, they permit tailored restricted launch conditions in MMFs, enhancing effective modal bandwidth. In another MA approach, the apertures are optically coupled such that self-injection locking (SIL) leads to lasing in a single supermode. One may regard one of the supermodes as acting as a master mode controlling the other one. Streak-camera studies reveal post-pulse oscillations in the SIL regime at frequencies up to 100 GHz. MA VCSELs enable a favorable combination of wavelength chirp and chromatic dispersion, extending transmission distances over MMFs beyond those expected for zero-chirp sources and supporting transfer bandwidths up to 60 GHz over kilometer-length SMF links.

Small aperture (similar to 2 mu m) oxide-confined single-mode (SM) Vertical-Cavity Surface-Emitting Lasers (VCSELs) are capable of intrinsic optical modulation bandwidth above 42 GHz at low currents (similar to 2 mA). The measured optical bandwidth is limited to similar to 36-38 GHz by the VCSEL resistance and capacitance (RC parasitics). To match requirements for industrial VCSELs, we applied a single mesa multi-aperture (MA) single-mode (SM) VCSEL design. The design is based on 4 diamond-shaped apertures at similar to 10 mu m pitch and an effective diameter of a single aperture of similar to 1.7-2 mu m. Higher capacitance of the large VCSEL mesa is compensated by a reduced resistance (50 Omega) of the device, allowing optical bandwidth f-3dBo similar to 32 GHz. The intrinsic optical bandwidth f-3dBo of similar to 45 GHz is extracted. MA SM VCSEL allows narrow spectral width and error-free 50-Gbaud data transmission over 200 m OM5 multimode fibre (MMF).

Leading-edge machine learning algorithms require large amounts of matrix multiplications, which absorb significant computational resources in modern digital electronic systems. Analogue optical computing systems consisting of light sources, modulators and receivers may perform these operations with much higher efficiency. We introduce an integrated device based on electro-optically modulated (EOM) vertical-cavity surface-emitting lasers (VCSELs) that can perform analog multiplication at >28 GHz and at <20 mW power consumption. Due to its monolithic integration, the EOM VCSEL may be used as a building block for integrated optical computing devices. Development of such devices can help create 3-dimensionally integrated computing and communication systems.

We report high frequency (20-100 GHz range) optical field intensity oscillations in laterally-coupled-cavity vertical-cavity surface-emitting lasers with several different techniques. The oscillation frequency is defined by the photon energy splitting of the coupled states. The resonance effect is stable in an extended current range and can enable modulation frequency resonances at higher frequencies as compared to the conventional relaxation oscillation frequency of the laser. This paves a way towards high-speed data transmission solutions at data rates beyond similar to 200 Gb/s with the advantage of better laser stability, as the resonance observed can reach high frequencies even at low current densities. A similar to 75 GHz intensity modulation between optical modes of a coupled-cavity VCSEL array was first reported by the authors in a two-aperture configuration in 2023 applying optical excitation [1]. Studies of 4- and 10-element coupled VCSEL arrays give further insight into the effects observed. New 3D numerical simulations and electrical modulation techniques have been applied to address the specific nature of the photon-photon resonance studies.

We investigate photon-photon resonances in laterally coupled mini-arrays of vertical-cavity surface-emitting lasers under electrical excitation. We observe resonance peaks in the frequency response of the optical signal, which we investigate for each array element and spectral modes. Furthermore, we show self-injection locking with modulation bandwidth enhancement.

Applying coherent arrays of muti-aperture lasers was proposed to improve data transmission over multimode fiber. We propose a novel compact a coherent and incoherent multi-aperture VCSEL array design in which multiple single-mode VCSEL apertures are electrically driven in parallel. Such approach allows a high output power as in standard multimode devices but shows significantly reduced spectral width not exceeding 0.2nm as well as high speed performance exceeding 25GHz with current density ~20kA/cm2 and beam divergence of 22O (1/e2). Moreover, we study the application of such devices for IM/DD 100Gbit/s PAM-4 and 50Gbit/s OOK.

In this paper we report high frequency (50 – 100GHz range) optical field intensity oscillations in a laterally-coupled-cavity vertical cavity surface-emitting laser. The oscillating frequency is defined by the photon energy splitting of the coupled states, each oscillating at a frequency defined by the related photon energy. As a result of constructive or destructive interference the optical field intensity reaches maximum either in the left or in the right aperture. As the frequency difference is small as compared to the averaged photon frequency, the cavities are quasi-resonant and the interference effect is strong, causing an intense resonance frequency with integrated intensity of at least 3-fold higher as compared to the resonance oscillation frequency feature. The effect is observed at low and at high current destinies. With proper design of the cavities, one should enable a simple and reliable solution for high-speed data transmission at data rates ~200 Gb/s and beyond. The effect coexists with spin-related frequency resonances allowing its combination with novel concepts in data transmission.

The paper presents multi -aperture single mode 850nm VCSEL with optical modulation bandwidth exceeding 30GHz and narrow optical spectrum width enabling long distance highspeed data transmission exceeding 800m over OM4 multi -mode fiber.

We demonstrate parallel high speed data transmission over single multimode fiber using VCSELs operating in the SWDM wavelength range (850 nm – 940 nm). Total demonstrated throughput of such system reaches 500 Gbit/s with 4-PAM modulation and 600 Gbit/s with DMT modulation.

VCSEL arrays can play an important role in the increasing the data throughput of VCSEL-based optical interconnects both due to the need to increase the channel density and due to new emerging technologies like optical wireless. In this work we show the progress in the development of high-speed VCSEL arrays suitable for multicore fiber transmission leading to an increase of the total throughput through single fiber to 600 Gbps. We also discuss a novel type of compact VCSEL mini-arrays capable of high-speed modulation and coherent emission at the same time. Photon-photon resonance and coherent effects can help increase the resonant frequency and the bandwidth of the VCSELs and enable devices capable of 100 GHz operation.

We present a new hyperchromatic laser-based multifocal display. In the proposed design multiple full-colour virtual image planes can be displayed simultaneously at different depths in front of the observer through wavelength (de-)multiplexing. Each depth plane is displayed through its own combination of red, green and blue lasers at specific wavelengths. Hyperchromatic displays can be useful for augmented (AR) and mixed reality (MR) applications where real and virtual objects are located at different depths in front of the observer because they allow the human eye to focus on virtual objects and reduce the vergence-accommodation conflict (VAC). We present a laboratory demonstrator where the images generated by two red lasers (630 nm and 960 nm) were separated by more than 3 meters. We also discuss the applicability of the technology to the automotive head-up-display (HUD) systems and present an HUD system based on low-cost offthe-shelf components.

Highly efficient electrically–driven single photon sources (SPSs) with a narrow far–field emission pattern suitable for coupling to a single mode fiber are critical components for applications in quantum communication. We address modern concepts of the design of SPSs suitable for such applications: (i) Quantum dot (QD) in a micropillar, where a proper reflectivity balance of top and bottom distributed Bragg reflectors (DBRs) and cavity design allows non–resonant highly directional light source. (ii) Dielectric multilayer structure acting as photon extracting microcavity including a passive cavity design and a deeply etched circular Bragg grating enabling a high efficiency of the light extraction and a narrow far field pattern. The light source is not resonant in wavelength and allows narrow far field distribution at a low series resistance. (iii) Resonant light sources based on broadband high–contrast dielectric DBRs optimized for O–band 1300 nm operation with photon–extraction efficiency above 90% and the coupling efficiency to a single mode fiber of 76%. Resonant tuning of the cavity and QD emission allows Purcell effect–enhancement of the QD photon emission rate.

Strain-induced birefringence in GaAs-based oxide-confined VCSELs (Vertical-Cavity Surface-Emitting Laser) can split the optical modes into orthogonally polarized components. A polarization switching at very high frequencies can occur between these components, which is of great interest for optical communication systems of the future. In this study, we focus our investigation on the frequency characteristics of the polarization switching between the optical modes, which is caused by polarization self-modulation (PSM) in fiber-coupled systems. Moreover, we analyze the PSM that is originating in different optical modes of the VCSEL and compare multi-mode and single-mode VCSELs.

Electrically-pumped optical microcavity single photon sources based on single quantum dots are investigated by numerical modelling techniques. Design of electrically driven 1.3 μm-range single photon source with intra-cavity contacts and multiply oxide aperture layers is proposed. About two times improvement in photon coupling efficiency into the single-mode fiber is demonstrated as compared with single photon source based on cylindrical micropillar.

We propose a hybrid microcavity design of a 1.3 μm range electrically driven single-photon source (SPS) consisting of two high-contrast dielectric distributed Bragg reflectors which surround a 3λ-thick semiconductor cavity with two intra-cavity contact layers and four 40-nm-thick oxide-confined apertures. According to 3D finite-difference time-domain modelling, the overall photon-extraction efficiency of ~74% and the Purcell factor of ~13 can be obtained by properly adjusting the position of oxide-confined apertures relative to the electric field of the fundamental optical mode. The studied SPS design also demonstrates a coupling efficiency of up to 13% within numerical aperture 0.12 in contrast to ~5% reached for a conventional semiconductor micropillar.