Search

Vertical-cavity surface emitting lasers in UVA band (UVA VCSELs) operating at a central wavelength of 395 nm are designed by employing PICS3D(2021) software. The simulation results indicate that the thickness of the InGaN quantum well and GaN barrier layers affect the emission efficiency of UVA VCSELs greatly, suggesting an optimal thicknesses of 2.2 nm for the well layer and 2.7 nm for the barrier layer. Additionally, an overall consideration of threshold current, series resistance, photoelectric conversion efficiency, and optical output power results in the optimized thickness of the ITO current spreading layer, ~20 nm. Furthermore, by employing a five-pair Al0.15Ga0.85N/GaN multi-quantum barrier electron blocking layer (EBL) instead of a single Al0.2Ga0.8N EBL, the device shows a ~51% enhancement in the optical output power and a ~48% reduction in the threshold current. The number of distributed Bragg reflector (DBR) pairs also plays crucial roles in the device's photoelectric performance. The device designed in this study demonstrates a minimum lasing threshold of 1.16 mA and achieves a maximum wall plug efficiency of approximately 5%, outperforming other similar studies. [ABSTRACT FROM AUTHOR]

Vertical-cavity surface-emitting lasers (VCSELs) are essential for exhibiting single-transverse-mode output characteristics, which are critical for applications in quantum sensing, optical interconnection, and laser printing. In this study, we achieved stable single-transverse-mode lasing using extended-2λ-cavity with an oxide aperture diameter of 7.08 μm. The device demonstrated a high output power of 6.8 mW and a narrow linewidth of 49.8 MHz at room temperature. Additionally, it maintained stable single-mode emission at 794.8 nm and achieved a side-mode suppression ratio (SMSR) exceeding 40 dB within the temperature range of 25 °C~85 °C, thereby meeting the requirements of 87Rb atom quantum sensors. The fabricated device obtained high-power and narrow linewidth single-transverse-mode operation by a monolithic extended cavity without introducing additional processing procedures, which is expected to promote the commercial viability of VCSELs in quantum sensing. [ABSTRACT FROM AUTHOR]

Optical wireless communication (OWC) is recognized as a promising technology for future fifth generation (5G) networks. However, limited research efforts have been dedicated to the development of symmetric and bidirectional OWC systems using vertical cavity surface emitting lasers (VCSELs). In this study, we design and investigate a bidirectional 4 × 10 Gbps VCSEL-incorporated OWC system with an extensive reach, taking into account channel impairments. VCSELs offer high operating power and high reliability, making them suitable for this application. Simulation analyses have been conducted to evaluate the system performance in both the downlink and uplink directions, considering various factors such as noise, geometric losses, and attenuation losses. The results indicate that a maximum OWC range of over 130 km in the downlink direction and 128 km in the uplink direction can be achieved with a link loss of 0.001 dB. The system can tolerate a maximum link attenuation of 2.25 dB/km in the downlink direction and 2.2 dB/km in the uplink direction while maintaining a bit error rate (BER) within the acceptable limit of 10^-9. Additionally, the system demonstrates robust performance at a maximum operating temperature of 348 K for VCSELs over a 10 km range at a data rate of 40/40 Gbps. The results further indicate that the maximum values of signal, noise, gain, noise figure, and optical signal-to-noise ratio (OSNR) are − 69.68 dBm, − 87.65 dBm, − 21.14 dB, 21.14 dB, and 82.13 dB, respectively, at a total input power of − 69.61 dBm. Comparative analysis with existing studies highlights the superiority of this work over previous efforts, demonstrating significant improvements in system performance and range. This research underscores the potential of bidirectional OWC systems using VCSELs for enhancing future 5G networks. [ABSTRACT FROM AUTHOR]

This paper presents a modified current-mode vertical-cavity surface-emitting laser (VCSEL) driver as a transmitter for short-range light detection and ranging (LiDAR) sensors, where a stable bias generator is suggested with a regulated cascode current mirror circuit to provide the bias current of 1 mA with a trivial deviation of 5.4%, even at the worst-case process–voltage–temperature (PVT) variations. Also, a modified current-steering logic circuit is exploited with N-type MOSFET (NMOS) switches to deliver the modulation currents of 0.1~10 mApp to the VCSEL diode simultaneously, with no overshoot distortions. Post-layout simulations of the modified current-mode VCSEL driver (m-CMVD), using 180 nm CMOS technology, demonstrate very large and clean output pulses with significantly reduced signal distortions. Hereby, the VCSEL diode is transformed into an equivalent circuit with a 1.6 V DC voltage and a 50 Ω resistor for circuit simulations. The proposed m-CMVD consumes a maximum of 11 mW from a 3.3 V supply voltage and the chip core occupies an area of 0.196 mm2. [ABSTRACT FROM AUTHOR]

Speckles are inherent in structured laser-based light projection using diffractive optics such as metasurfaces or diffractive optical elements (DOEs). One application of structured light is to provide illumination for machine vision and depth sensing. This is particularly attractive for mobile or low-power applications, where metasurfaces provide a compact, customizable solution, which can furthermore reach extreme field of illuminations. However, the speckles might limit detection capabilities by, e.g., lowering the detection range or providing false results. In this work, we present a series of measurements with matching simulations on a 70 × 50 degrees diffractive diffuser using different light sources (varying divergence angles + VCSEL array) to quantify the impact of speckles. We observe a qualitative agreement in speckle correlation between the measurements and the simulations and explain, in part using cross-correlation for analysis, why we do not observe the same speckle pattern between the measurements and the simulations. By performing extra simulations, we conclude that by only changing the light source, there is a limit to the reduction of the speckle contrast which, we can achieve, and, to reduce it further, alternative approaches such as changing the design method of the diffractive diffuser must be harnessed. [ABSTRACT FROM AUTHOR]

In this study, a novel metal-dielectric film mode filter structure that can flexibly regulate the transverse mode inside vertical-cavity surface-emitting lasers (VCSELs) is proposed. The number, volume, and stability of transverse modes inside the VCSEL can be adjusted according to three key parameters—the oxide aperture, the metal aperture, and the distance between the oxide aperture and the metal aperture—to form a flexible window, and a new parameter is defined to describe the mode identification. This study provides a complete simulation theory basis and calculation method, which is of great significance for the optical mode control in VCSELs. [ABSTRACT FROM AUTHOR]

This study involves a simulation-based optimization of a wavelength division multiplexing (WDM) in a passive optical network system, and an RZ modulator, with incorporating a vertical cavity surface emitting laser (VCSEL) and an edge-emitting (CW) laser alternately. Two scenarios have been proposed. First, 8 VCSEL/CW lasers, having distinctive frequency, are assigned for each user in the WDM PON. In the second scenario, only one optical source (193.1 THz) is employed to share among the eight users of the PON. The first scenario supports 5 Gbps up to 150 km fiber length, and comparably, the VCSEL-based system provides a better Q-factor performance comparable with the CW laser-based system. The second scenario confirmed the transmission of 20 Gbps up to 150 km by the VCSEL-based system, while the CW laser system allowed 20 Gbps up to only 100 km, while demonstrating a lower Q-factor. [ABSTRACT FROM AUTHOR]

This paper presents a current-mode VCSEL driver (CMVD) implemented using 180 nm CMOS technology for application in short-range LiDAR sensors, in which current-steering logic is suggested to deliver modulation currents from 0.1 to 10 mApp and a bias current of 0.1 mA simultaneously to the VCSEL diode. For the simulations, the VCSEL diode is modeled with a 1.6 V forward-bias voltage and a 50 Ω series resistor. The post-layout simulations of the proposed CMVD clearly demonstrate large output pulses and eye-diagrams. Measurements of the CMVD demonstrate large output pulses, confirming the simulation results. The chip consumes a maximum of 11 mW from a 3.3 V supply, and the core occupies an area of 0.1 mm2. [ABSTRACT FROM AUTHOR]

Eye tracking as an important human‐machine interface plays avital role in immersive displays such as augmented reality (AR) and virtual reality (VR). Different from near infrared (NIR) camerabased methods, the proposed corneal reflection method based on principle of eyeball co‐vision takes advantage of using eye‐safe 940‐ nm vertical cavity surface emitting laser (VCSEL) and dual‐column linear array sensor (DCLAS) to obtain coordinates of the eyeball's moving positions through detecting its reflected light. The DCLAS not only delivers high sensitivity at eye‐safe NIR wavelength, but also has high spatial resolution for position accuracy and wide dynamic range to suppress ambient light influence. Together with low power consumption, good wearability, low data redundancy and simple computing algorism, a great promise can be made to enable smart eye tracking for AR/VR. [ABSTRACT FROM AUTHOR]

The rapid evolution of passive optical network (PON) technologies has been driven by the necessity to accommodate 5th-generation system requirements. This research introduces a PON wavelength division multiplexing-based optical transmitter that is improved in both fiber link and bit rate. The transmitter is designed to connect many clients to a single-mode optical fiber. The optical transmitter under consideration is designed to provide an optimum data rate up to 20 Gbps per user. The data is modulated using a 2-bit per symbol Quadrature Phase Shift Keying (QPSK), and an M-array pulse coder. The R.F. signal is optically modulated during the optical system stage using a Mach–Zehnder external modulator supplied with an optical carrier generated by a vertical cavity surface emitting laser (VCSEL). Two PON configurations are devised in this context: initially, 16 VCSELs spanning 193.1–194.6 THz with a 10 GHz separation are utilized to modulate 16 data sources with 16 MZM. In contrast, in the second configuration, to reduce input laser power and system complexity, 16 data consumers share a single 193.1 THz VCSEL. Simulations of the performance measurements were conducted by Optisystem 19 for both configurations. The initial system configuration permits 20 Gbps transmission to 120 km with a Q-factor of at least 6. The power penalty of this configuration was reduced from − 970 to − 930 dB. The second configuration guarantees the dependability of data transmission over a distance of 100 km. The maximal Q-factors for the first and second configurations are 12 and 10, respectively, at a distance of 20 km. It has been established that the ideal input bias current for a VCSEL is 2 mA. The effects of the quadrature phase shift keying modulation QPSK is clearly appeared, as the current results are surpassed the peer publications regarding the utmost achievable fiber link length, Q-factor and supported data rate. [ABSTRACT FROM AUTHOR]

In the latest generation of optical fiber systems, broadband telecommunication network access with ultrahigh speed services is almost realized by passive optical network (PON) radio over fiber system. In this study, a least complex and cost-effective downstream radio over fiber system (RoF)-based direct modulation vertical cavity surface emitting laser (VCSEL) optical source is designed. Different simulations are presented, including the VCSEL output power dependence on the temperature. For the selected VCSEL, the maximum output power of 4mW at bias current of 13 mA and 20 °C, whereas the least power of 1.5mW at 9.5 mA and 60 °C was recorded. For a single user, the proposed system driving the VCSEL at 20 °C enabled 5Gbps data transmission up to 100 km with the significant signal performance. The RoF system is further expanded to include a 16-channel WDM system to design a passive optical network system to enhance the data rate and rout more independent subscribers to share the same optical fiber. Without externally modulating optical signal, the various simulations of Q-factor, bit error rate, and eye diagram conformed that the presented PON-based WDM and VCSEL support fiber span up to 100 km. [ABSTRACT FROM AUTHOR]

Many failures of semiconductor-based oxide confined vertical cavity surface emitting lasers (VCSELs) are closely related to the generation and expansion of defects in the device structure. However, existing research has predominantly focused on the static study of defect morphology, with little attention given to analyzing the dynamic process of defect expansion, which limited our ability to predict device random failures due to lack of understandings on defect generation and expansion. To address this issue, we present a macroscopic phenomenological evolution model that describes the dynamic expansion of defects in VCSELs, in which the expansion of defects is treated as an anisotropic lattice strain diffusion process. We further exploit a diffusion-limited aggregation (DLA) method in solving the diffusion equation, which describes the random propagation and aggregation of strain in the vicinity of highly strained areas, resulting in defect formation when the stress from accumulated strain surpasses the bonding force of the atoms in the lattice. Our simulation result manages to replicate the dendritic expansion morphology of defects, aligning with experimental observations very well. Our model also predicts an accelerated defect expansion process, which is again consistent with the experimental result. This model finds relevance in applications such as random failure prediction through device aging, burn-in condition setting in device screening, and device structural and/or material design improvement for mitigating defect expansion.

This article focuses on increasing the single-mode power in Vertical Cavity Surface Emitting Lasers (VCSELs) through the strategic integration of an antiresonant oxide islands. Using a gallium arsenide-based VCSEL as a case study, we explore the influence of oxide island parameters on lateral mode discrimination in term of threshold currents and emitted powers. The analysis confirms non-uniform variations in threshold currents, with varying oxide island position and size. Leveraging the spatial hole burning effect, we compute the output power and identify optimal island configurations for maximizing single-mode power. The results showcase the efficacy of antiresonant oxide islands in significantly enhancing single-mode power output in VCSELs.

This work reports a multiscale physics-based approach aimed at investigating the benefits of introducing a single tunnel junction (TJ) within conventional AlGaAs Vertical-Cavity Surface-Emitting Lasers (VCSELs). Our comprehensive VCSEL solver VENUS is augmented with a non-equilibrium Green's function (NEGF) approach to extract the band-to-band tunneling rate across the TJ. To showcase the NEGF-VENUS features, we apply it to the commercial pin oxide confined AlGaAs VCSEL previously investigated by VENUS, by inserting a TJ with minimal variations to the optical resonator. Besides finding the optimal position of TJ and oxide aperture, we can also compare the different hole injection schemes in the active region. Our results show the potential of doubling the maximum output power with the same threshold current, with perspectives of further enhancement by stacking more tunnel junctions.

Gallium Nitride (GaN)-based vertical-cavity surface-emitting lasers (VCSELs) in green spectral region face the difficulty of the “green gap”. One of the main obstacles is the strong polarization electric field in GaN-based materials, which leads to a strong quantum confinement Stark effect (QCSE) and reduces the efficiency of radiative recombination. In this study, we systemically simulated and compared the optical and electrical performance of GaN-based green VCSELs based on Ga-polar and N-polar InGaN quantum wells (QWs) by using the software of PICS3D. The results show that the light-output power of N-polar VCSEL is greatly improved by 183% compared to Ga-polar VCSEL at an injection current of 20 mA, while the threshold current is reduced by 49%. The improved performance is mainly attributed to: 1) the decreased QCSE; 2) the more efficient carrier injection, and 3) the reduced carrier leakage in N-polar devices. The results of this study suggest that N-polar based GaN is promising for the realization of high-performance green VCSELs, which can provide a guidance for the fabrication of high-power green VCSELs.

Vertical-cavity surface emitting lasers in UVA band (UVA VCSELs) operating at a central wavelength of 395 nm are designed by employing PICS3D(2021) software. The simulation results indicate that the thickness of the InGaN quantum well and GaN barrier layers affect the emission efficiency of UVA VCSELs greatly, suggesting an optimal thicknesses of 2.2 nm for the well layer and 2.7 nm for the barrier layer. Additionally, an overall consideration of threshold current, series resistance, photoelectric conversion efficiency, and optical output power results in the optimized thickness of the ITO current spreading layer, ~20 nm. Furthermore, by employing a five-pair Al0.15Ga0.85N/GaN multi-quantum barrier electron blocking layer (EBL) instead of a single Al0.2Ga0.8N EBL, the device shows a ~51% enhancement in the optical output power and a ~48% reduction in the threshold current. The number of distributed Bragg reflector (DBR) pairs also plays crucial roles in the device’s photoelectric performance. The device designed in this study demonstrates a minimum lasing threshold of 1.16 mA and achieves a maximum wall plug efficiency of approximately 5%, outperforming other similar studies.

A highly strained InGaAs quantum well (QW) vertical-cavity surface-emitting laser (VCSEL) with low threshold current density, high efficiency and output power emissions around 1130 nm was grown by MOCVD. Its static characteristics at room temperature and high operation temperature were studied in detail. The 7 μm oxide aperture device exhibits a threshold current of 0.68 mA, corresponding to a threshold current density of 1.7 kA/cm2. The slope efficiency is 0.43 W/A and the maximum output power is 3.3 mW. Continuous-wave (CW) operation in the 10–80 °C temperature range is observed. The slope efficiency is almost constant at 10–80 °C. The threshold current becomes lower at high temperatures thanks to the alignment between gain peak and cavity mode. The 3 μm oxide aperture device's lasing in single mode with the RMS spectral width of 0.163 nm and orthogonal polarization suppression ratio (OPSR) is ~15 dB at 25 °C. The small-signal response analysis indicates that reducing the parasitics of the device and refining the fabrication process will improve the dynamics response characteristics. These results indicate that the 1130 nm GaAs-based VCSEL with highly strained InGaAs QWs is expected to be used as source for silicon photonics. [ABSTRACT FROM AUTHOR]

The emission linewidth of single-mode vertical-cavity surface-emitting lasers with an active region based on strained InGaAs/InGaAlAs quantum wells in the spectral range of 1.55 μm was studied. The removal of degeneracy in polarization of the fundamental mode (splitting of the resonance wavelength) and polarization switching (type I) associated with the transition from lasing via the short-wavelength mode to lasing via the long-wavelength one were observed. As the output optical power increased, the emission linewidth dropped to ~30 MHz for both orthogonally polarized modes and was limited by the residual linewidth. The value of the α-factor was estimated: for the short-wavelength mode it reached 5, while for the long-wavelength mode it increased to ~9. At an output optical power of more than 1 mW, the emission line broadening is observed, which can be associated with a gain saturation and the increased α-factor caused by a strong self-heating of the investigated laser. [ABSTRACT FROM AUTHOR]

A step-index standard single-mode fiber as a two-mode fiber at 1060 nm can have a high modal bandwidth. In the current work, we conducted a detailed study and found that the LP11 mode of such a fiber is bending-sensitive and that the light excited to LP11 mode can be stripped out due to bending. The transmission experiments were conducted using offset launch with both LP01 and LP11 modes excited and center launch with only LP01 mode excited to show transmission performance in different conditions. We demonstrated the feasibility of 25 Gb/s NRZ transmission over 1 km of the fiber when both LP01 and LP11 modes were excited. We further explored the feasibility of a trench-assisted bending-insensitive step-index standard single-mode fiber with good bending properties for both LP01 and LP11 modes for two-mode transmission at 1060 nm. We found a fiber that has high modal bandwidth at 1060 nm and can sustain bending down to at least a 20 mm diameter. The high-bandwidth two-mode fiber can be potentially useful for future 1060 nm-based VCSEL transmission. [ABSTRACT FROM AUTHOR]

Experimental methods are presented for determining the thermal resistance of vertical-cavity surfaceemitting lasers (VCSELs) and the lateral electrical conductivity of their p-type semiconductor layers. A VCSEL structure was manufactured from III-As compounds on a gallium arsenide substrate. Conductivity was determined using transmission line measurement (TLM). Electrical and thermal parameters were determined for various ambient temperatures. The results could be used for computer analysis of VCSELs. Keywords: TLM, thermal resistance, VCSEL, AlGaAs.

The photonic device market has a need for low‐cost, high‐resolution periodic patterning that scales with product maturity to large substrate sizes. Eulitha's DTL (Displacement Talbot Lithography) technology was limited to only a single exposure field per substrate on preexisting platforms which can fully pattern 100 and 150mm substrates. The new 'PhableS' is Eulitha's step‐and‐repeat solution to bring all the advantages of the DTL patterning to larger substrates. The PhableS tool builds on Eulitha's patented displacement Talbot lithography technology to open the way for customers to fully scale to high volume production. This tool retains the strong technical performance; including 60nm half pitch resolution (DUV version), 140x140mm2 single shot exposure field, large depth of focus (hundreds of microns), high throughput (+40wph), non‐contact, mask‐based patterning. Automated wafer and mask handling support industry expected repeatability and defect‐free patterning. [ABSTRACT FROM AUTHOR]

Speckles are inherent in structured laser-based light projection using diffractive optics such as metasurfaces or diffractive optical elements (DOEs). One application of structured light is to provide illumination for machine vision and depth sensing. This is particularly attractive for mobile or low-power applications, where metasurfaces provide a compact, customizable solution, which can furthermore reach extreme field of illuminations. However, the speckles might limit detection capabilities by, e.g., lowering the detection range or providing false results. In this work, we present a series of measurements with matching simulations on a 70 × 50 degrees diffractive diffuser using different light sources (varying divergence angles + VCSEL array) to quantify the impact of speckles. We observe a qualitative agreement in speckle correlation between the measurements and the simulations and explain, in part using cross-correlation for analysis, why we do not observe the same speckle pattern between the measurements and the simulations. By performing extra simulations, we conclude that by only changing the light source, there is a limit to the reduction of the speckle contrast which, we can achieve, and, to reduce it further, alternative approaches such as changing the design method of the diffractive diffuser must be harnessed.

This paper presents a modified current-mode vertical-cavity surface-emitting laser (VCSEL) driver as a transmitter for short-range light detection and ranging (LiDAR) sensors, where a stable bias generator is suggested with a regulated cascode current mirror circuit to provide the bias current of 1 mA with a trivial deviation of 5.4%, even at the worst-case process–voltage–temperature (PVT) variations. Also, a modified current-steering logic circuit is exploited with N-type MOSFET (NMOS) switches to deliver the modulation currents of 0.1~10 mApp to the VCSEL diode simultaneously, with no overshoot distortions. Post-layout simulations of the modified current-mode VCSEL driver (m-CMVD), using 180 nm CMOS technology, demonstrate very large and clean output pulses with significantly reduced signal distortions. Hereby, the VCSEL diode is transformed into an equivalent circuit with a 1.6 V DC voltage and a 50 Ω resistor for circuit simulations. The proposed m-CMVD consumes a maximum of 11 mW from a 3.3 V supply voltage and the chip core occupies an area of 0.196 mm2.

In this study, a novel metal-dielectric film mode filter structure that can flexibly regulate the transverse mode inside vertical-cavity surface-emitting lasers (VCSELs) is proposed. The number, volume, and stability of transverse modes inside the VCSEL can be adjusted according to three key parameters—the oxide aperture, the metal aperture, and the distance between the oxide aperture and the metal aperture—to form a flexible window, and a new parameter is defined to describe the mode identification. This study provides a complete simulation theory basis and calculation method, which is of great significance for the optical mode control in VCSELs.

The results of the experimental study of the effect of optical feedback (OF) on intensity fluctuations at a selected polarization in a single-mode vertical-cavity surface-emitting laser (VCSEL) are presented. The aim of this study is to look for conditions of enhancement of the level of polarization noise for possible use as a source of randomness for fast random bit generation. It is shown for several VCSEL examples that strong optical feedback can lead to an increase polarization noise, the amplitude and frequency band of which is sufficient for the efficient generation of random bits at a speed of several Gbit/s. This approach makes it possible to implement a fairly compact and structurally simple high-speed random bit generator. [ABSTRACT FROM AUTHOR]

Transverse dynamics of a broad-area semiconductor surface-emitting laser with a vertical resonator (VCSEL) with еxternal optical injection was investigated above threshold. It is obtained that two types of instabilities can develop in system: Turing and Hopf instabilities. Turing instability in turn can be subdivided into plane-wave instability (PWI) and modulation instability (MI). We found some sets of system parameters where the steady-state curve of the homogeneous solution can be bistable or monostable. Modulation instability can lead to the development of spatial patterns, which was obtained. [ABSTRACT FROM AUTHOR]

In this work, we focused on investigating the eigen frequency and internal standing wave characteristics of a vertical surface cavity emitting laser operating at a wavelength of 1.55 µm. The design of the cavity involved determining the cavity length, selecting the material for the cavity spacer, and carefully placing the quantum wells within the cavity to achieve maximum overlap with the electric field. In our case, the choice of the dielectric Bragg mirror with SiO2/TiO2 layers helps in achieving high reflectivity and low optical losses. The quantum wells are strategically placed within the cavity to ensure maximum overlap with the electric field. This allows for efficient carrier injection and recombination, leading to laser emission. The specific composition of the quantum wells, In0.54Ga0.46As0.99P0.01 / In0.75Ga0.25As0.55P0.45, indicates the proportions of indium (In), gallium (Ga), arsenic (As), and phosphorus (P) in the material. These compositions are chosen to achieve the desired electronic band structure and emission wavelength. By studying the eigen frequency and internal standing waves in our designed laser cavity, our aim is to understand the resonant modes and behavior of light within the device. This knowledge is crucial for optimizing the laser's performance and improving its efficiency for various applications. [ABSTRACT FROM AUTHOR]

The study seeks to design a communication system for a power grid, that will ensure real-time and low-latency communication and automation between the utility and the end users. The performance characterization of the VCSEL in G.655 non-zero dispersion shifted fibre transmitting at 1550 nm is experimentally and theoretically analysed. The experiment reported the various evaluations of BER and eye diagrams using a VCSEL and a DFB laser as light sources. There was the successful achievement of 10 Gbps in 25 and 50 km for VCSEL and DFB respectively. In simultaneous data and clock transmission, 0.4 GHz and 10 Gbps over 25 km was successfully achieved using a VCSEL. The study is significant in the establishment of a pervasive communication system as the backbone of smart power grid design technology. [ABSTRACT FROM AUTHOR]

Laser gas sensors with small volume and light weight are in high demand in the aerospace industry. To address this, a coin-sized oxygen (O2) sensor has been successfully developed based on a small toroidal absorption cell design. The absorption cell integrates a vertical-cavity surface-emitting laser (VCSEL) and photodetector into a compact unit, measuring 90 × 40 × 20 mm and weighing 75.16 g. Tunable diode laser absorption spectroscopy (TDLAS) is used to obtain the O2 spectral line at 763 nm. For further improving the sensitivity and robustness of the sensor, wavelength modulation spectroscopy (WMS) is utilized for the measurement. The obtained linear correlation coefficient is 0.9994. Based on Allen variance analysis, the sensor achieves an impressive minimum detection limit of 0.06% for oxygen concentration at an integration time of 318 s. The pressure-dependent relationship has been validated by accounting for the pressure factor in data processing. To affirm its efficacy, the laser spectrometer underwent continuous atmospheric O2 measurement for 24 h, showcasing its stability and robustness. This development introduces a continuous online laser spectral sensor with potential applications in manned spaceflight scenarios. [ABSTRACT FROM AUTHOR]

This paper presents a current-mode VCSEL driver (CMVD) implemented using 180 nm CMOS technology for application in short-range LiDAR sensors, in which current-steering logic is suggested to deliver modulation currents from 0.1 to 10 mApp and a bias current of 0.1 mA simultaneously to the VCSEL diode. For the simulations, the VCSEL diode is modeled with a 1.6 V forward-bias voltage and a 50 Ω series resistor. The post-layout simulations of the proposed CMVD clearly demonstrate large output pulses and eye-diagrams. Measurements of the CMVD demonstrate large output pulses, confirming the simulation results. The chip consumes a maximum of 11 mW from a 3.3 V supply, and the core occupies an area of 0.1 mm2.

In this study, a new theoretical calculation of metal-mode-filtered vertical-cavity surface-emitting laser (MMF-VCSEL) is proposed. The optimized number of P-DBR and the metal layer thickness are used. The effects of the metal mode filtered structure on the threshold gain of different transverse modes is analyzed. The MMF-VCSEL can operate in fundamental transverse mode under 8 μm oxide aperture compared with the conventional oxide-confined VCSEL. Benefit from the large oxide aperture and small metal aperture, the current crowding effect is effectively avoided and the heat distribution inside the VCSEL is improved.

VCSEL chips with wavelengths in the range of 700 nm–800 nm, the same as the transition spectral lines of alkali atoms, can be used as light sources for novel miniaturized quantum sensors. The conventional temperature control module for VCSEL is based on a thermoelectric cooler (TEC) and temperature sensor. However, the package size is large, and the magnetic field noise is too large for real applications. In this study, we proposed a chip-scale packaging method with an overall dimension of 4 mm × 6 mm for VCSEL with a 795 nm output wavelength. With temperature uniformity and the magnetic field distribution profiles of the package, chips have been carefully evaluated. The generated magnetic field can decay to less than 100 nT within 3 mm. In all, we not only experimentally demonstrated an applicable thermal package structure, but also gave the magnitude and distance effects of the magnetic field caused by this structure. This study can provide an example and reference for the chip-scale temperature control packaging method of VCSELs and their application in quantum sensors.

Experimental methods are presented for determining the thermal resistance of vertical-cavity surfaceemitting lasers (VCSELs) and the lateral electrical conductivity of their p-type semiconductor layers. A VCSEL structure was manufactured from III-As compounds on a gallium arsenide substrate. Conductivity was determined using transmission line measurement (TLM). Electrical and thermal parameters were determined for various ambient temperatures. The results could be used for computer analysis of VCSELs. [ABSTRACT FROM AUTHOR]

Recent research results show that great progress has been made in improving the generation rate of physical random numbers. However, there are still some defects such as complex generation process and large volume. To solve these problems, this paper theoretically proposes a scheme for generating random numbers using mode hopping of Vertical Cavity Surface Emitting Laser (VCSEL) with optical feedback. The VCSEL is perturbed by the optical feedback to generate the mode hopping. The square wave signal then modulates the injection current, periodically restarts the VCSEL to switch from the non-emitting state to the mode hopping state, and finally outputs a random pulse sequence to realize the random number generation. The results of this paper show that unbiased random numbers with verified randomness can be generated continuously at a rate of the order of Gbit/s. Our scheme eliminates the need for optoelectronic conversion and post-processing operations, simplifing the current random number generation structure, which has the potential to realize a low-cost photonic integrated random number generator.

We show in simulation and experiment that the coherent coupling of electric fields between elements of a triangular photonic crystal vertical cavity surface emitting laser array can be adjusted into antiguided supermodes with approximately equal injection into each array element. The dominant supermodes are found by a complex waveguide mode simulation and can be identified by the number and arrangement of side-lobes of their Fourier-transformed far-field beam profiles. The supermode with all three elements in-phase is found to possess the minimum central lobe angular divergence. Measurements of the continuous wave coherently coupled properties of photonic crystal triangular arrays, nominally emitting at 850 nm, are compared to our simulations. We show that the array can be adjusted to lase in a desired supermode by varying the injection currents into each element of the array. The optical power confined within the central portion of the in-phase coupled beam is greater than that emitted from a single VCSEL which is advantageous for high-brightness applications.

We numerically investigate the performance of Chinese herbal medicine (CHM) recognition using a time delay reservoir computing (TDRC) system consist of a vertical-cavity surface-emitting laser (VCSEL) subjected to optical feedback. A database of 960 images from 12 CHM categories is used to evaluate the recognition performance, most of which contain many CHM samples and have different backgrounds. The CHM image feature vector is masked and optically injected into the VCSEL, and the VCSEL output in two polarization modes are sampled as the virtual node states for readout. After testing the CHM recognition performance of TDRC under injecting the same information into two polarization modes of the VCSEL, we further test the performance of parallel processing by injecting half of the image information into each of the two polarization modes. By concatenating the virtual node states collected from two modes for readout, the recognition speed is doubled. Meanwhile, the influence of key parameters on recognition performance are investigated and the relationship between system idle state and recognition performance is also examined. The results show that, under parallel processing and orthogonal optical feedback, the TDRC achieves the minimum recognition error of 1.7% at a reservoir processing rate of 2 × 109 images per second.

Excitable optoelectronic devices represent one of the key building blocks for implementation of artificial spiking neurons in neuromorphic (brain-inspired) photonic systems. This work introduces and experimentally investigates an opto-electro-optical (O/E/O) artificial neuron built with a resonant tunnelling diode (RTD) coupled to a photodetector as a receiver and a vertical cavity surface emitting laser as a transmitter. We demonstrate a well-defined excitability threshold, above which the neuron produces optical spiking responses with characteristic neural-like refractory period. We utilise its fan-in capability to perform in-device coincidence detection (logical AND) and exclusive logical OR (XOR) tasks. These results provide first experimental validation of deterministic triggering and tasks in an RTD-based spiking optoelectronic neuron with both input and output optical (I/O) terminals. Furthermore, we also investigate in simulation the prospects of the proposed system for nanophotonic implementation in a monolithic design combining a nanoscale RTD element and a nanolaser; therefore demonstrating the potential of integrated RTD-based excitable nodes for low footprint, high-speed optoelectronic spiking neurons in future neuromorphic photonic hardware.

The results of complex studies of static and dynamic performance of 1550 nm range VCSELs, which were created by direct bonding (wafer fusion technique) InAlGaAs/InP optical cavity wafers with AlGaAs/GaAs distributed Bragg reflector wafers grown by molecular beam epitaxy, are presented. The VCSELs with a buried tunnel junction diameter less than 7 μm demonstrated a single-mode lasing with a side-mode suppression ratio more than 40 dB; however, at diameters less than 5 μm, a sharp increase in the threshold current is observed. It is associated to the appearance of a saturable absorber due to penetration of optical mode into the non-pumped regions of the active region. The maximum single-mode output optical power and the –3 dB modulation bandwidth reached 4.5 mW and 8 GHz, respectively, at 20°C. The maximum data rate at 20°C under non-return-to-zero on-off keying modulation was 23 Gb/s for a short-reach link based on single-mode fiber SMF-28. As the length of the optical link increased up to 2000 m, the maximum data rate dropped to 18 Gbit/s. The main factors affecting the high-speed operation and data transmission range are defined and discussed, and the further ways to overcome themit are proposed. [ABSTRACT FROM AUTHOR]

We report an experimental study of the effect of the temperature of the VCSEL on the probability of excitation of a linearly polarized mode when gain-switching the device. We consider different modulation frequencies and amplitudes. We show that the probability of excitation of a linearly polarized mode significantly changes with the value of the temperature of the device. We also show that for low values of the temperature the probability of excitation saturates to a constant value as the amplitude of the modulation increases. This extends our previous results obtained at larger temperatures for which that saturation was not observed. We identify situations in which the distributions of the linearly polarized signals at a sampling time are approximately uniform. For these cases we evaluate the quality of the random numbers by using statistical test. [ABSTRACT FROM AUTHOR]

In this paper, we introduce how gallium nitride-based (GaN-based) VCSELs with curved mirrors have evolved. The discussion starts with reviewing the fundamentals of VCSELs and GaN-based materials and then introducing the curved-mirror cavity's principle and history and the latest research where the structure is applied to GaN-based materials to form VCSELs. We prepared these parts so that readers understand how VCSELs with this cavity work and provide excellent characteristics such as efficiency, life, stabilized mode behavior, etc. Finally, we discussed the challenges and prospects of these devices by touching on their potential applications. [ABSTRACT FROM AUTHOR]

VCSEL can be used as the transmitter for optical interconnect applications especially for short reach communication. In this research paper, we proposed a VCSEL structure design which can generate the wavelength of 1160 nm. The VCSEL structure is proposed with the aim of small aperture diameter because for optical interconnects applications the size should reduce. Two distributed Bragg reflectors (DBR), i. e. top DBR and bottom DBR are used to confine the active cavity area and InGaAsP/InP material is used for the formation of active cavity region. Then, the performance of the proposed VCSEL is evaluated at various oxide aperture diameters in the range 2–7 µm for anode voltage, anode current and total power emitted is also calculated to achieve optimized performance. [ABSTRACT FROM AUTHOR]

A highly strained InGaAs quantum well (QW) vertical-cavity surface-emitting laser (VCSEL) with low threshold current density, high efficiency and output power emissions around 1130 nm was grown by MOCVD. Its static characteristics at room temperature and high operation temperature were studied in detail. The 7 μm oxide aperture device exhibits a threshold current of 0.68 mA, corresponding to a threshold current density of 1.7 kA/cm2. The slope efficiency is 0.43 W/A and the maximum output power is 3.3 mW. Continuous-wave (CW) operation in the 10–80 °C temperature range is observed. The slope efficiency is almost constant at 10–80 °C. The threshold current becomes lower at high temperatures thanks to the alignment between gain peak and cavity mode. The 3 μm oxide aperture device’s lasing in single mode with the RMS spectral width of 0.163 nm and orthogonal polarization suppression ratio (OPSR) is ~15 dB at 25 °C. The small-signal response analysis indicates that reducing the parasitics of the device and refining the fabrication process will improve the dynamics response characteristics. These results indicate that the 1130 nm GaAs-based VCSEL with highly strained InGaAs QWs is expected to be used as source for silicon photonics.

Spiking neurons and neural networks constitute a fundamental building block for brain-inspired computing, which is poised to benefit significantly from photonic hardware implementations. In this work, we experimentally investigate an interconnected optical neuromorphic system based on an ultrafast spiking vertical cavity surface emitting laser (VCSEL) neuron and a silicon photonics (SiPh) integrated micro-ring resonator (MRR). We experimentally demonstrate two different functional arrangements of these devices: first, we show that MRR weight banks can be used in conjunction with the spiking VCSEL-neurons to perform amplitude weighting of sub-ns optical spiking signals. Second, we show that a continuously firing VCSEL-neuron can be directly modulated using a locking signal propagated through a single weighting MRR, and we utilise this functionality to perform optical spike firing rate-coding via thermal tuning of the MRR. Given the significant track record of both integrated weight banks and photonic VCSEL-neurons, we believe these results demonstrate the viability of combining these two classes of devices for use in functional neuromorphic photonic systems.