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Dependence of a) threshold gain for the fundamental transverse LP01-E⊥ mode and b) transverse and polarization mode discrimination (threshold gain differences) on grating fill-factor. The grating pitch and depth is 120 and 59 nm, respectively, and the oxide aperture and mode filter diameters are 5 and 3 µm, respectively.
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We demonstrate a 6.5 mW single transverse and polarization mode GaAs-based oxide-confined VCSEL at 850 nm. High power is enabled by a relatively large oxide aperture and an epitaxial design for low resistance, low optical loss, and high slope efficiency VCSELs. With the oxide aperture supporting multiple polarization unrestrained transverse modes,...
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Citations
... To overcome this limitation, researches investigate a number of indirect approaches, like use of graphene-bubble dielectric distributed Bragg reflectors (DBRs) [16], double cavities [15], [17], shallow relief [18], zinc-diffusion with oxide-relief [19], [20], grating couplers [21]- [23], or application of antiresonant reflecting optical waveguides (ARROWs) [24]- [27]. This simplest form of such antiresonant structure (S-ARROW) is a low-index core surrounded by a single high-index ring. ...
This article focuses on the optimization of 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.
... Moreover, the integration potential of this ITO-based metasurface with other key optical components, such as Vertical-Cavity Surface-Emitting Lasers (VCSELs) and Photonic Integrated Circuits (PICs), opens up exciting new possibilities for compact and efficient optical systems. [60][61][62][63][64][65][66] VCSELs are a type of semiconductor laser that emits light perpendicular to the surface of the chip, making them ideal for high-density integration. By combining the metasurface with VCSELs, it becomes possible to create highly integrated, electrically controlled laser sources with enhanced frequency response. ...
... Therefore, the appearance of higher-order modes leads to expansion of spectrum, blue-shift of peak position and larger divergence angle in VCSEL array. These thermal accumulative effects significantly restrict the utilization of VCSEL array in the next-generation wireless communication systems [5][6][7], silicon photonic integrated circuits [11,12] and time-of-flight (ToF) radar [3,4]. A way to address the issue of higher-order modes is to suppress the current crowding effect, but methods like double oxide apertures [13] have complex manufacturing processes, distributed-ring contacts [14] are challenging to apply to small-aperture VCSEL. ...
Thermal crosstalk and current crowding effects are pressing issues that significantly impact the beam quality and efficiency of vertical-cavity surface-emitting laser (VCSEL) arrays. In this paper, by taking advantage of the excellent current transmission characteristics of graphene, what we believe to be a novel VCSEL array based on graphene electrode is designed to realize vertical current injections. The series resistance and self-heating of arrays are reduced by controlling the transport direction of the current, effectively suppressing the thermal crosstalk effect. Furthermore, high array beam quality is obtained by optimizing the current density distribution in active regions. Ultimately, the high-power quasi-single mode emission of VCSEL arrays is achieved by introducing graphene electrodes (Gr-VCSEL array) designs. Compared to traditional VCSEL arrays, the 10 × 10 Gr-VCSEL array demonstrates a 41% reduction in series resistance, a side mode suppression ratio of 32 dB, and a divergence angle around 12 °. This structure simultaneously achieves quasi-single mode emission and effectively suppresses the thermal crosstalk effect, providing a new method for the development of high-beam quality VCSEL arrays.
... Furthermore, VCSELs are prone to unstable polarization due to their cylindrical symmetry of resonators and isotropic gain of quantum wells (QWs). The major approaches to achieve polarization-stable VCSELs including introducing asymmetric resonators and polarization-dependent gain or mirror loss [11][12][13]. While these methods have shown effectiveness in controlling the transverse mode and polarization state of VCSELs, they typically require additional structural complexity and stringent fabrication control. ...
We demonstrate a polarization-stable and single-mode grating-coupled surface-emitting laser (GCSEL) with high side-mode suppression ratio (SMSR) of ∼40 dB and orthogonal polarization suppression ratio (OPSR) of ∼25 dB around 795 nm. The fabricated devices have low threshold current of ∼4.8 mA and low electrical resistance of 53 Ω at 25 °C. Meanwhile, a low thermal resistance of ∼1 K/mW is achieved, which is comparable with that of the record of ever reported for vertical-cavity surface-emitting lasers (VCSELs). The far-field divergence angle of surface-emitting beam is ∼14.5°x14.7° at an injection current of 12 mA indicating a relatively good beam quality. Our results open what we believe is a new way to produce polarization-stable single-mode surface-emitting lasers with simple fabrication process. While the GCSEL is specifically designed for quantum sensing applications such as atomic clocks, magnetometers, and gyroscope, its performance in terms of low-power consumption, low thermal resistance, good beam qualities, and wafer-level testing are of particular interest for a wide range of applications.
... Generally, VCSELs have two orthogonal polarization modes because of isotropic gain, which coexist and align primarily along the [011] and [0-11] crystal axes. [5] There have been a number of efforts to achieve polarization control in VCSELs, including utilizing an asymmetrical mesa structure, [6] growing VCSELs on misoriented substrate, [7] mode and polarization selecting gratings, [8] etc. There is also a method using rhomboidal aperture to realize polarization control. ...
Vertical Cavity Surface Emitting Laser (VCSELs) as the ideal light source for rubidium (Rb) and cesium (Cs) atomic clocks is analyzed for its mode and polarization control. We fabricated three kinds of shapes: triangular, elliptic and circular oxidation aperture which also has different sizes. We formed 3 different shape oxide apertures by wet-oxidation with 36-39μm circular mesa. Our results show that triangular oxidized-VCSELs has the advantages of mode and polarization selection over elliptic and circular oxide aperture. When triangular oxide-confined VCSELs emit in single mode, the measured Side Mode Suppression Ratio (SMSR) is larger than 20 dB and Orthogonal Polarization Suppression Ratio achieves 10 dB. Resonant blueshift of VCSELs with triangular and elliptic aperture is observed with the decrease of aperture size.
... Finally, its transparency extends to the visible range, where absorption from water and gas is negligible. Wavelengths near 850 nm are a good compromise with low waveguide scattering loss and commercially available lasers and CMOS imagers, thus attracting a lot of interest from the biosensing community [32][33][34][35]. ...
Silicon photonics can address a variety of applications, from datacom and biosensing to lidars. Recently, this technology has been explored for gas sensing. Detection and identification of odors remains a critical challenge in diverse areas such as air quality, food spoilage, or personal well-being. In this work, we present an olfactory sensor based on an array of 64 biofunctionalized Mach-Zehnder interferometers integrated on a silicon nitride platform. The ability to analyze odors at ppm level is demonstrated for several volatile organic compounds.
... Vertical-cavity surface-emitting lasers (VCSELs) offer many advantages in comparison to edge-emitters, including high coupling efficiency to optical fibers, low threshold current, singlemode operation, compactness, high energy efficiency, low fabrication costs, ease of 2D array packaging, and on-wafer testing capability [25]. Recent work also shows integration of VCSELs on a silicon photonic integrated circuit [26]. VCSELs usually show two linear orthogonally polarized modes, and polarization switching (PS) between these two orthogonal modes can be observed with temperature or bias current changes [25,27]. ...
In this paper, we report an experimental and theoretical study of the random excitation of the linearly polarized modes of a gain-switched VCSEL characterized by having polarization switching under continuous wave operation. We show that equal probability of excitation of both linearly polarized modes can be achieved by adjusting the modulation conditions and the sampling time. Our VCSEL is such that the bistable region associated to the polarization switching is very narrow, indicating that the random process of excitation of the polarizations works independently of the existence of those bistable regions. A characterization of the random polarization switching is performed by analyzing the dependence of the probability of excitation, autocorrelation, and histograms of both polarized signals on the modulation conditions and sampling times. We finally present preliminar results on random number generation using the analyzed system.
... Also, polarization modes of a VCSEL under a rotated polarization angle of optical feedback are not considerably affected for relatively low levels of feedback, while polarization switching has Research Article been observed for rotated polarization angles larger than a certain value [14]. Single longitudinal mode operation originated from a short cavity length and single transverse and polarization mode operation stemming from oxide aperture confinement [15] have been reported as mode characteristics of VCSELs, while multimode operation can also be attained for data transmission at short distances using multimode optical fibers [16]. In addition, high contrast grating buried tunnel junction (HCG-BTJ)-based VCSELs are highly polarization stable, single mode at large apertures, and solve the VCSEL-mirror problem at long wavelengths due to polarization-sensitive reflectivity [17]. ...
Quantum cascade lasers with quantum dot (QD) active regions have been developed to overcome the drawbacks of quantum-well-based cascade lasers. Low threshold current and enhanced bandwidth characteristics of QD lasers can be combined with promising energy-efficient features of vertical cavity surface emitting lasers (VCSELs) through introducing the novel, to the best of our knowledge, concept of a QD cascade VCSEL (QDC-VCSEL). Design steps and predicted features of a QDC-VCSEL operating at 4.5 µm wavelength are discussed in this paper, where the cavity and active region are optimized for TE mode using a high contrast grating design. Laser characteristics are investigated by developing rate equations for the cascade scheme. Threshold and L-I characteristics are obtained at different temperatures. Also, the dependency of threshold current, slope efficiency, and modulation bandwidth on design parameters, mainly the carrier tunneling time, is studied. Results exhibit output peak powers of ${\sim}{{2}}$ ∼ 2 and ${\sim}{0.5}\;{\rm{mW}}$ ∼ 0.5 m W at 150 and 273 K, respectively. In addition, threshold current increment and modulation bandwidth reduction are observed with the increase in tunneling time.
... Great effort has been devoted to controlling the polarization state of VCSELs by introducing polarization-dependent gain, reflectivity, and external optical injection or feedback to the cavity or by fabricating an on-facet metasurface-based polarizer outside the cavity [11][12][13][14][15][16][17]. Among the reported methods, surface gratings with polarization-dependent reflectivity can generate stable but fixed polarized light without significantly deteriorating the original characteristics of VCSELs, such as low threshold and monolithic integration [18]. ...
We report a method for flexibly switching the dominant polarization of a vertical-cavity surface-emitting laser (VCSEL) by introducing polarization-resolved resonant optical feedback from a whispering-gallery-mode (WGM) cavity to the lasing cavity. Switching between the originally dominant mode and a side mode is experimentally demonstrated under different bias currents once one of them is locked to the resonance mode of the WGM cavity. In addition to a controllable polarization state, the reported VCSEL also demonstrates a linewidth as narrow as tens of kilohertz, which is highly desirable for many applications, including high-speed data communication, light detection and ranging (lidar), and absorption spectroscopy.
... Here, the area of the light emission aperture (S) is determined by Wz. The brightness can be as high as 2.9 MW cm sr the highest brightness ever reported in the electrical pumping SM VCSELs, including for an 850 nm VCSEL with a linear grating [31] (1.7 MWcm sr at a 6.5 mW output with a 9 o divergence angle) and long-wavelength VCSEL [19] with buried tunnel junctions (1.36 MWcm -2 sr -1 at an 8 mW output with a 8 o divergence angle). The singlepolarized output from the VCSEL is also an important feature for the process of light coupling into different components [31]. ...
... The brightness can be as high as 2.9 MW cm sr the highest brightness ever reported in the electrical pumping SM VCSELs, including for an 850 nm VCSEL with a linear grating [31] (1.7 MWcm sr at a 6.5 mW output with a 9 o divergence angle) and long-wavelength VCSEL [19] with buried tunnel junctions (1.36 MWcm -2 sr -1 at an 8 mW output with a 8 o divergence angle). The singlepolarized output from the VCSEL is also an important feature for the process of light coupling into different components [31]. The polarization states of most of the reported VCSELs hop between two orthogonal orientations (<011> and <011 >) with a change of bias current [28,29]. ...
... Figure 3 (b) shows the measured bias dependent OPSR, which can be as high as around 20 dB over a wide range of bias currents. This OPSR performance is comparable with that of the 850 nm VCSEL integrated with a linear grating on the top DBR mirror [31]. However, as discussed above, the cost of such high brightness output is the SHB induced lowfrequency roll-off in its E-O response and the significant degradation in the eye pattern quality under large signal modulation [17,18]. ...
The development of high-speed and high-brightness vertical-cavity surface-emitting lasers (VCSELs), which can serve as an efficient light source for optical wireless communication (OWC), play a crucial role in growth of the next generation of wireless communication networks, e.g., 6 G and satellite communications. In this work, by optimizing the size of the Zn-diffusion and oxide-relief apertures in a high-speed 850 nm VCSEL, we obtain record-high brightness (2.9 MWcm-2sr-1at 10 mW output) with single polarized and (quasi-) single-mode (SM) outputs under continuous wave (CW) operation. However, such high brightness output comes at the cost of spatial hole burning (SHB) effect and degraded quality of 25 Gbit/sec eye patterns. In addition, an SM VSCEL array structure is usually needed to further boost the total available optical power for long-reach OWC. Here, a novel (quasi-) SM VCSEL array structure is demonstrated which releases the trade-off between the performances of brightness and eye-pattern quality. Our demonstrated array has a special crisscross mesa connecting neighboring VCSEL units and an extra electroplated copper substrate integrated on the backside of the chip. Compared to the reference array without the copper substrate and connected active mesas, the demonstrated array exhibits a higher (quasi-) SM output power, narrower divergence angle, larger orthogonal polarization mode suppression ratio (OPSR), and flatter E-O response. This in turn leads to smaller jitter and less noise in the measured 12.5 Gbit/sec eye-patterns. The demonstrated 7x7 array exhibits a maximum SM power of around 90 mW with a 1/e2 divergence angle as narrow as 7° (FWHM: 5°), single polarized output (10 dB OPSR), decent relative intensity noise performance (< -130 dB/Hz) and clear 12.5 Gbit/sec eye-opening. Such new device with remarkable static/dynamic performances has strong potential to further improve the product of the linking distance and data rate in the next generation of OWC channels.
