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.

In this paper we discuss performance and limitations of 850nm single mode multiaperture vertical cavity surface emitting laser and compare it to the single aperture design. This design is not meant to be coupled cavity but focuses on single drive multiaperture devices. Both the static and dynamic parameters are shown and equivalent circuit model of the multiaperture device is proposed and validated. The static characteristic show high output power exceeding 6mW with very narrow spectrum and Gaussian beam in far-field. Based on the equivalent circuit model the parasitic limitation of the device is established to be of 26.8GHz. Further the intrinsic response is modeled where thermal and damping bandwidth limitations are derived at 37.6GHz and 49.2GHz respectively. The data transmission experiments present error-free performance for NRZ rates of 50Gbit/s which altogether with a low RIN level opens a way to a 100Gbit/s with PAM-4. Almost no penalty in the available bandwidth is observed even after 800m of OM4 fiber.

In this work we investigate the ultrabroadband dynamics of transverse coupled cavity VCSELs. This study is based on a multimode rate equation model, whose parameters are directly provided by a full-wave vectorial electromagnetic solver. This approach sets a step towards the comprehensive physics-based modeling of transverse-coupled cavity VCSELs, providing a relation between the features of the optical supermodes and the enhancements of the intensity modulation response. The approach emphasizes how the bandwidth enhancement, ascribable to a photon-photon resonance picture, can be triggered by forcing asymmetries in the bias and modulation contacting scheme of the device, and the importance of collecting the fields from each single cavity, providing an interpretation of recent experimental observations and paving the way towards more systematic design strategies.

Vertical-cavity surface-emitting lasers ( VCSELs) are of utmost importance as key components for high-speed datacom, sensor and free-space applications. Therefore, for a successful further optimization of their performance understanding their behavior during operation is of crucial importance. A set of 850 nm VCSEL samples employing different doping of the active cavity zone are studied during operation by means of reverse current-voltage (IV) characteristics as well as photocurrent spectroscopy (PCS) under reverse bias. Reverse IV characteristics exhibits avalanche breakdown which enables an estimation of the electric field in the active region as a function of applied bias. Photocurrent spectroscopy is a powerful, nondestructive technique which measures essentially the convolution of the top mirror and intrinsic region absorption spectra and reveals quantum well transitions which redshift with reverse bias due to quantum-confined Stark effect (QCSE). The VCSELs are characterised before and after high current operation. VCSELs with a controlled doping of the active cavity region do not alter neither avalanche breakdown nor the QCSE shift of the quantum well transitions during operation. However, VCSELs without doping of the active cavity region show a systematic shift in breakdown voltage towards lower values, which is accompanied by an operation-induced redshift of quantum well transitions observed by PCS. These results indicate an increase of the built-in electric field in the active cavity zone after high current operation which is discussed in terms of conceivable processes such as dopant diffusion, impurity electromigration, burn-in of contacts and/or the activation of dopants during operation.

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.

A DC-coupled single supply NRZ voltage-mode VCSEL driver is demonstrated in 22 nm CMOS SOI eliminating the need for energy-inefficient equalization techniques for data rates up to 60 Gbit/s. The highly digitized driver architecture inherently features an impedance (voltage-level) calibration scheme to handle both driver and VCSEL-based process variations. While maintaining error free (BER < le-12) electro-optical transmission, an efficiency of <0.37pJ/bit is reached, improving the SOTA by almost 2x.

Herein, it is shown how the novel layout and arrangement of electrodes of a vertical‐cavity surface‐emitting laser (VCSEL) array can simultaneously improve its high‐speed data transmission performance and the brightness of the output beam. In contrast to the layout of the traditional VCSEL array with its isolated mesas and a single electrode to electrical parallel arrangement of all active elements, the new inverse design can effectively reduce the pitch size between neighboring light emission apertures thereby allowing significant downscaling of the whole active area of the array and high brightness output. Moreover, there are two separate electrodes in demonstrated compact 7 × 7 VCSEL array, one for pure dc current injection and the other for large ac signal modulation. Compared with the single electrode reference device, the demonstrated array shows heavier dampening of the electrical–optical (E–O) frequency response, a wider maximum 3‐dB E–O bandwidth (17 vs 13 GHz), and a Gaussian‐like optical far‐field pattern with a higher brightness output (65.95 vs 40.8 kW cm −2 sr −1 ), under the same high output power (≈145 mW). The advantages of this novel VCSEL array lead to a much better quality of 32 Gbps eye‐opening with a higher brightness output.

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.

We present the first true voltage-mode VCSEL driver achieving 60Gbit/s at peak efficiency of 0.36pJ/bit with BER < 1e-12 improving the state-of-the-art by a factor of 2. Transmission experiments showcase error-free 56Gbit/s transmission up to 100m fiber. Advanced demonstration enables even 224Gbit/s when using SWDM at a total efficiency of 0.4pJ/bit.

This paper demonstrates why VCSEL-based transmitter systems are not able to capitalize on higher-order PAM modulation formats (such as PAM-4) to push the link data rate towards 100 Gbit/s with BER of better than 10−5. First, the non-linear and biasing-dependent VCSEL behavior is analyzed in great detail to prove why state-of-the-art VCSELs with linear equalization are not able to reach these bandwidth targets. Consequently, based on an enhanced VCSEL model, a digital non-linear transmit equalizer is proposed to overcome voltage-dependent relaxation frequency shifts as well as data-dependent VCSEL bandwidth variations. The proposed digital non-linear equalizer is compared with a standard linear FFE structure using PAM-4 transmission experiments of 100 Gbit/s and beyond. This way, the proposed non-linear equalizer reveals a BER improvement of more than 30-fold compared to a linear FFE at a data rate of 80 Gbit/s. Finally, at 112 Gbit/s PAM-4 the non-linear equalizer was successfully demonstrated at a BER of 1.5·10−7.

Bragg effect technol-sensors as interrogation 2. Sensor The main sensing principle of the proposed sensor is based on multipath Mach-Zehnder interferometer build upon 6 core single mode optical fiber (core diameter 5.16 um, the core-to-core distance 39.5 um,

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.

In this work, a novel design for the electrodes in a near quasi-single-mode (QSM) vertical-cavity surface-emitting laser (VCSEL) array with Zn-diffusion apertures inside is demonstrated to produce an effective improvement in the high-speed data transmission performance. By separating the electrodes in a compact 2×2 coupled VCSEL array into two parts, one for pure dc current injection and the other for large ac signal modulation, a significant enhancement in the high-speed data transmission performance can be observed. Compared with the single electrode reference, which parallels 4 VCSEL units in the array, the demonstrated array with its separated electrode design exhibits greater dampening of electrical-optical (E-O) frequency response and a larger 3-dB E-O bandwidth (19 vs. 15 GHz) under the same amount of total bias current (20 mA). Moreover, this significant improvement in dynamic performance does not come at the cost of any degradation in the static performance in terms of the maximum near QSM optical output power (17 mW @ 20 mA) and the Gaussian-like optical far-field pattern which has a narrow divergence angle (full-width half maximum (FWHM): 10° at 20 mA). The advantages of the separated electrode design lead to a much better quality of 32 Gbit/sec eye-opening as compared to that of the reference device (jitter: 1.5 vs. 2.8 ps) and error-free 32 Gbit/sec transmissions over a 500 m multi-mode fiber has been achieved under a moderate total bias current of 20 mA.

High power single mode wafer-fused 1300-nm VCSELs with a gain region based on InGaAs/InAlGaAs short period superlattice are fabricated. An InP-based optical cavity and two AlGaAs/GaAs distributed Bragg reflector heterostructures were grown by molecular beam epitaõy. The current and optical confinement is provided by a lateral-structured buried tunnel junction with etching depth of $\sim 25$ nm. It is shown that optimal diameter of the buried tunnel junction for high-power single mode emission is $\sim 5$ - $6~\mu \text{m}$ . The VCSEL demonstrates more than 6 mW single mode continuous-wave power and a threshold current less than 1.5 mA at 20 °C. The output optical power exceeds 1 mW at 85 °C. A -3dB modulation bandwidth up to 8 GHz and 6 GHz is obtained at 20 °C and 85 °C, respectively. The gain coefficient of $\sim 650$ cm −1 and the transparency current density of $\sim 630$ A/cm 2 are estimated at zero gain-to-cavity detuning (\sim 60 °C). The ultimate low internal optical losses about 0.08 % per round-trip (distributed losses ~3.2 cm −1 ) at 20 °C and 0.13 % per round-trip (distributed losses ~5.5 cm −1 ) at 100 °C were obtained.

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.

Vertical-cavity surface-emitting lasers (VCSELs) are of utmost importance as key components for high-speed datacom, sensor and free-space applications. Therefore, for a successful further optimization of their performance, understanding their aging behavior is of crucial importance. Photocurrent spectroscopy (PCS) is a powerful, nondestructive technique which can be used to analyze semiconductor materials. Applying it on VCSELs makes it a powerful tool to investigate these tiny devices. In this work, we present room temperature high-resolution PCS analyses of fresh vs. aged 850 nm VCSELs. These VCSELs are characterized before and after aging by means of PCS, which measures essentially the convolution of the top mirror and intrinsic region absorption spectra. Heavy hole and light hole quantum well transitions are revealed and the related quantum-confined Stark effect is studied. The VCSELs used in this study are mounted on a standard V-connector and were intentionally aged at extreme conditions to accelerate their degradation till reaching optical damage. It was found that in these VCSELs, a reduced PCS current is observed, which is possibly caused by nonradiative recombination centers generated by the aging-related processes. Moreover, we observe that aging of the devices at very high current densities results in the evolution of defect related states, which modify the IV-curve under reverse bias. Degraded devices also show a systematic shift in breakdown voltage towards lower values, indicating a possible shrinkage of the undoped region by impurity electromigration and diffusion. Interestingly, these changes are minimal in stable devices that were aged under normal conditions.