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A brief overview is presented of results obtained at the Rzhanov Institute of Semiconductor Physics in the development of photon detectors and emitters promising for use in quantum cryptography systems, along with miniature quantum frequency standards based on the effect of coherent population trapping. [ABSTRACT FROM AUTHOR]

The results of investigation of the gain properties of 1300 nm vertical-cavity surface-emitting lasers active regions based on In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattices and threshold characteristics comparison of superlattices and highly lattice mismatched In0.74Al0.16Ga0.10As quantum wells are presented. The heterostructure of injection lasers with an In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattice was grown by molecular beam epitaxy. Mesa structure of injection lasers was obtained by selective liquid etching followed by the application of ohmic contacts. The formation of injection lasers with various cavity lengths is performed using the method of manually cleaving mirrors. The output characteristics were measured in a pulsed mode using a large area calibrated germanium photodiode. Spectral characteristics were measured using a spectrophotometer based on monochromator. The achieved threshold characteristics (modal gain about 40 cm–1, transparency current density about 650 A/cm2, internal optical losses about 8 cm–1) of injection lasers based on In0.60Ga0.40As/In0.53Al0.20Ga0.27As superlattices with low lattice mismatch InGaAs layers are comparable to previously presented lasers based on active regions with strongly strained In0.74Al0.16Ga0.10As quantum wells. The characteristic temperatures T0 and T1 were 60 K and 87 K for injection lasers with a cavity length of 1 mm. An increase in the frequency of small-signal modulation of vertical-cavity surface-emitting lasers and their temperature stability is associated with the use of highly strained In0.74Ga0.26As/In0.53Al0.25Ga0.21As superlattices. The proposed active regions based on InGaAs-InP superlattices have the potential to be used in the development of vertical-cavity surface-emitting lasers in the 1300 nm spectral range. The findings of this work can be applied in the realization of experimental species and optimization of modulation parameters for vertical-cavity lasers operating in the 1300 nm wavelength range.

Based on the chaotic polarization system of optically injected cascaded vertical-cavity surface-emitting lasers (VCSELs), we propose a novel implementation scheme for high-speed optical chaotic data selection logic operations. Under the condition where the slave VCSEL (S-VCSEL) outputs a chaotic laser signal, we calculate the range of the applied electric field and the optical injection amplitude. We also investigate the evolution of the correlation characteristics between the polarized light output from the periodic poled LiNbO3 (PPLN) and the S-VCSEL as a function of the optical injection amplitude under different applied electric fields. Furthermore, we analyze the polarization bistability of the polarized light from the PPLN and S-VCSEL. Based on these results, we modulate the optical injection amplitude as the logic input and the applied electric field as the control logic signal. Using a mean comparison mechanism, we demodulate the polarized light from the PPLN and S-VCSEL to obtain two identical logic outputs, achieving optical chaotic data selection logic operations with an operation speed of approximately 114 Gb/s. Finally, we investigate the influence of noise on the logic outputs and find that both logic outputs do not show any error symbols under the noise strength as high as 180 dBw. The anti-noise performance of logic output O1 is superior to that of optical chaotic logic output O2. For noise strengths up to 185 dBw, error symbols in O2 can be detected and corrected by comparison with O1. [ABSTRACT FROM AUTHOR]

In this paper, we propose and demonstrate experimentally and numerically a hierarchical time-delay optical reservoir computing (RC) system based on cascaded vertical-cavity surface-emitting lasers (VCSELs) with feedback and multiple injections. The prediction performance characteristics of the hierarchical time-delay RC system based on cascaded VCSELs under different reservoir layers are compared. Evidently, the prediction performance of the hierarchical time-delay RC system is first improved and saturates as the number of reservoir layers increases. Besides, the impacts of key factors on predicting the hierarchical time-delay RC system are also analyzed in detail experimentally and numerically. This proposed hierarchical time-delay RC system based on VCSELs is useful for the further development of RC systems and may be beneficial to improve the ability of RC systems to solve more complex problems. [ABSTRACT FROM AUTHOR]

We propose a highly polarized vertical-cavity surface-emitting laser (VCSEL) consisting of staggered InGaN multiple quantum wells (MQWs), with the resonance cavity and polarization enabled by a bottom nanoporous (NP) n-GaN distributed Bragg reflectors (DBRs), and top TiO2 high-index contrast gratings (HCGs). Optoelectronic simulations of the 612 nm VCSEL were systematically and numerically investigated. First, we investigated the influences of the NP DBR and HCG geometries on the optical reflectivity. Our results indicate that when there are more than 17 pairs of NP GaN DBRs with 60% air voids, the reflectance can be higher than 99.7%. Furthermore, the zeroth-order reflectivity decreases rapidly when the HCG's period exceeds 518 nm. The optimal ratios of width-to-period (52.86 ± 1.5%) and height-to-period (35.35 ± 0.14%) were identified. The staggered MQW design also resulted in a relatively small blue shift of 5.44 nm in the emission wavelength under a high driving current. Lastly, we investigated the cavity mode wavelength and optical threshold gain of the VCSEL with a finite size of HCG. A large threshold gain difference of approximately 67.4–74% between the 0th and 1st order transverse modes can be obtained. The simulation results in this work provide a guideline for designing red VCSELs with high brightness and efficiency. [ABSTRACT FROM AUTHOR]

X-ray structural analysis and photoluminescence spectroscopy techniques were used to study heterostructures based on InGaAs/InAlGaAs superlattice for active regions of 1300 nm range lasers grown by molecular beam epitaxy. It is shown that the grown heterostructures have a high crystal quality. The perpendicular lattice mismatch of the average crystal lattice constant of the InGaAs/InAlGaAs superlattice with respect to the crystal lattice constant of the InP substrate is estimated at ~ +0.01%. An analysis of the photoluminescence spectra made it possible to conclude that the contribution of Auger recombination is insignificant in the studied range of excitation power density. Studies of vertical-cavity surface-emitting lasers with an active region based on the InGaAs/InAlGaAs superlattice made it possible to estimate the gain coefficient at a level of 650 cm–1 for the standard logarithmic approximation of the dependence of the gain on the current density. The transparency current density of the laser was 400–630 A/cm2, which is comparable to the record low values for the case of highly strained InGaAs–GaAs and InGaAsN–GaAs quantum wells in the spectral ranges of 1300 nm, respectively. [ABSTRACT FROM AUTHOR]

Based on the chaotic polarization system of optically injected cascaded vertical-cavity surface-emitting lasers (VCSELs), we propose a novel implementation scheme for high-speed optical chaotic data selection logic operations. Under the condition where the slave VCSEL (S-VCSEL) outputs a chaotic laser signal, we calculate the range of the applied electric field and the optical injection amplitude. We also investigate the evolution of the correlation characteristics between the polarized light output from the periodic poled LiNbO3 (PPLN) and the S-VCSEL as a function of the optical injection amplitude under different applied electric fields. Furthermore, we analyze the polarization bistability of the polarized light from the PPLN and S-VCSEL. Based on these results, we modulate the optical injection amplitude as the logic input and the applied electric field as the control logic signal. Using a mean comparison mechanism, we demodulate the polarized light from the PPLN and S-VCSEL to obtain two identical logic outputs, achieving optical chaotic data selection logic operations with an operation speed of approximately 114 Gb/s. Finally, we investigate the influence of noise on the logic outputs and find that both logic outputs do not show any error symbols under the noise strength as high as 180 dBw. The anti-noise performance of logic output O1 is superior to that of optical chaotic logic output O2. For noise strengths up to 185 dBw, error symbols in O2 can be detected and corrected by comparison with O1.

All-inorganic lead halide perovskite nanocrystals (NCs) have been widely investigated as highly promising optical gain materials due to their compelling electrical and optical properties. Although many efforts have been carried out, a deep understanding of perovskite NC vertical-cavity surface-emitting lasers (VCSELs) is elusive, which is very important in the development of photoelectronic integrated circuits. Along these lines, in this work, a low lasing threshold (22 μJ/cm2) single-mode VCSEL consisting of CsPbBr3 NCs film and two distributed Bragg reflectors was successfully constructed. The CsPbBr3 NCs were synthesized by using the supersaturated recrystallization method. Interestingly, benefiting from the strong coupling between the active layer and the optical field in the cavity, a single-mode lasing at 527 nm was demonstrated under femtosecond optical pumping. The carrier dynamics of the perovskite NC VCSEL was also thoroughly investigated by performing pump intensity-dependent time-resolved photoluminescence measurements. The typical gain-switching phenomenon was observed with an ultrafast decay of the laser pulse of ∼10 ps. Our work provides valuable insights for the implementation of the CsPbBr3 NC VCSEL for various optoelectronic applications.

The results of studies of the characteristics of vertical-cavity surface-emitting lasers of 1550-nm spectral range with active region based on quantum InGaAs wells implemented within wafer fusion technology. Current and optical confinements are provided by buried tunnel junction n+/p+-InAlGaAs. In a wide range of temperatures, lasers with a mesa diameter of the buried tunnel junction of 7 μm demonstrated a threshold current ~1.5 mA, differential efficiency of ~0.49 W/A, the maximum output optical power of more than 4 mW, and the –3dB modulation bandwidth of approximately 9 GHz. It is revealed that, as the length of the optical link increases, the chromatic dispersion of the SMF-28 fiber and the parasitic frequency modulation of laser cause considerable distortions of the shape of output optical pulses, as well as the strengthening of intersymbol interference, which finally leads to disappearance of opening of the eye diagram. The maximum data rate using direct current modulation by the amplitude NRZ format reaches 30 Gb/s at 20°C for a short communication link (BTB configuration), and for a communication link of 2 km the maximum data rate is no more than 25 Gb/s. [ABSTRACT FROM AUTHOR]

All-inorganic lead halide perovskite nanocrystals (NCs) have been widely investigated as highly promising optical gain materials due to their compelling electrical and optical properties. Although many efforts have been carried out, a deep understanding of perovskite NC vertical-cavity surface-emitting lasers (VCSELs) is elusive, which is very important in the development of photoelectronic integrated circuits. Along these lines, in this work, a low lasing threshold (22 μJ/cm2) single-mode VCSEL consisting of CsPbBr3 NCs film and two distributed Bragg reflectors was successfully constructed. The CsPbBr3 NCs were synthesized by using the supersaturated recrystallization method. Interestingly, benefiting from the strong coupling between the active layer and the optical field in the cavity, a single-mode lasing at 527 nm was demonstrated under femtosecond optical pumping. The carrier dynamics of the perovskite NC VCSEL was also thoroughly investigated by performing pump intensity-dependent time-resolved photoluminescence measurements. The typical gain-switching phenomenon was observed with an ultrafast decay of the laser pulse of ∼10 ps. Our work provides valuable insights for the implementation of the CsPbBr3 NC VCSEL for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

We present the design, fabrication, and performance of high-speed oxide-confined 1030 nm vertical-cavity surface-emitting lasers (VCSELs) with a short anti–waveguiding optical cavity. By using a half-wavelength cavity to enhance the limit of the optical field, the anti-waveguide design increases the oscillator strength, thus promoting high-speed modulation. We carefully optimized the multiple quantum wells and the doping profile in order to achieve high-speed operation. The developed VCSELs exhibit a modulation bandwidth exceeding 25.1 GHz at 25 °C, supporting back-to-back data rates up to 40 Gb/s under binary non-return-to-zero (NRZ) modulation.

Three-junction 905 nm vertical-cavity surface-emitting laser (VCSEL) was designed and fabricated for medium and long range sensing applications such as lidar. Through simulations using PICS3D software, the optimal adjacent active region spacing and number of P-type distributed Bragg reflectors (DBR) in the multi-junction VCSEL were determined, resulting in a design featuring a 2λ adjacent active region spacing and 14 pairs of P-type DBR. Using this design, a 100-element threejunction VCSEL array was grown and fabricated with an oxide aperture of 15 μm. The resulting array achieves a maximum peak power of 24. 7 W and a peak power density of 182 W/ mm 2 under narrow pulse conditions (with a pulse width of 100 ns and a duty cycle of 0. 05% ). [ABSTRACT FROM AUTHOR]

Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in consumer electronics, light detection and ranging, optical interconnects, atomic sensors, and so on. In this paper, a VCSEL with the surface metastructure like one-dimensional high-contrast grating (HCG), based on the HCG-DBR vertical cavity, was first designed and fabricated. The polarization characteristic of the HCG-VCSEL were experimentally studied. The p-doped top 4-pair DBR for the current spreading and the direction shift between the HCG and the elliptical oxide aperture may result in a low orthogonal polarization suppression ratio in the HCG-VCSEL. Then, the Bloch surface wave surface-emitting laser (BSW-SEL), based on the HCG-DBR metastructure, is proposed for single-mode, high-efficiency, and high-power output with a low divergence angle. The mode field and the far field profile of the BSW-SEL are calculated for verification. The surface-emitting lasers with surface metastructures are useful for the sensing applications and optical interconnects. [ABSTRACT FROM AUTHOR]

We propose a highly polarized vertical-cavity surface-emitting laser (VCSEL) consisting of staggered InGaN multiple quantum wells (MQWs), with the resonance cavity and polarization enabled by a bottom nanoporous (NP) n-GaN distributed Bragg reflectors (DBRs), and top TiO2 high-index contrast gratings (HCGs). Optoelectronic simulations of the 612 nm VCSEL were systematically and numerically investigated. First, we investigated the influences of the NP DBR and HCG geometries on the optical reflectivity. Our results indicate that when there are more than 17 pairs of NP GaN DBRs with 60% air voids, the reflectance can be higher than 99.7%. Furthermore, the zeroth-order reflectivity decreases rapidly when the HCG’s period exceeds 518 nm. The optimal ratios of width-to-period (52.86 ± 1.5%) and height-to-period (35.35 ± 0.14%) were identified. The staggered MQW design also resulted in a relatively small blue shift of 5.44 nm in the emission wavelength under a high driving current. Lastly, we investigated the cavity mode wavelength and optical threshold gain of the VCSEL with a finite size of HCG. A large threshold gain difference of approximately 67.4–74% between the 0th and 1st order transverse modes can be obtained. The simulation results in this work provide a guideline for designing red VCSELs with high brightness and efficiency.

We propose a simple method to generate broadband polarization chaos using two mutually coupled free-running vertical-cavity surface-emitting lasers (VCSELs). Specifically, we quantitatively investigate the effect of critical external parameters (bias current, frequency detuning and coupling coefficient) on the polarization chaos bandwidth in the scenarios of parallel injection and orthogonal injection, and reveal the physical mechanism of bandwidth enhancement in two scenarios. Final simulation results show that the bandwidth of chaotic signals obtained from parallel and orthogonal injection can reach 35.15 GHz and 32.96 GHz, respectively. [ABSTRACT FROM AUTHOR]

A vertical-cavity surface-emitting laser (VCSEL) is easily made into a two-dimensional array to improve its output power. However, if the near-field complex amplitude output cannot be stabilized in the lowest supermode generated by the fundamental transverse mode, the spot cannot converge on the center normal of the far-field array geometry, and the energy will be diverged. The external cavity is prepared for the VCSEL array, and the output of the array can be stabilized in the lowest order supermode generated by the fundamental transverse mode by supermode control through diffraction coupling. In this study, the parallel-coupled model for the 2-dimensional VCSEL array based on Fresnel diffraction integration was established and used to numerically calculate and analyze the influence on the supermodes' thresholds of different array distributions, array elements' transverse modes and duty ratios versus the length of the external cavity. The simulation results show that the square array provides a wider range of external cavity control length ( 0.2 d 2 / λ and approximately 0.9   to   1.0 d 2 / λ ). The lowest supermode of the fundamental transverse mode can be outputted. For the regular hexagonal array with the length of the external cavity of 0.15 d 2 / λ and 0.6 d 2 / λ . The results have important reference significance for the design of an external cavity VCSEL array, which can control the supermode and obtain VCSEL coherent array beams with high power and near diffraction limits. [ABSTRACT FROM AUTHOR]

The research deals with the topical problem of stabilizing the optical parameters of a single-mode vertical-cavity surfaceemitting laser. A solution to the problem is proposed by forming an external cavity based on a Bragg grating induced into an optical polarization-maintaining fiber. In this experimental research, the authors estimated the contribution of an external cavity to the relative intensity noise of a vertical-cavity surface-emitting laser. The stability of the laser generation with a varying phase of back reflections at various pump currents is investigated. The relative intensity noise of laser radiation in the pump current range of 1.1–6.3 mA is estimated using a photodetector with a bandwidth of 8.5 MHz. The phase change of the back reflections was carried out by shifting the optical fiber end with a 100 nm step. As a result of the research, it was obtained that the vertical-cavity surface-emitting laser with such an external cavity shows a stable emission in the current range of 1.8–3.2 mA. However, one can observe instability with constant switching between adjacent longitudinal modes outside this range. The most stable laser operation mode with an external cavity against a change in the phase of back reflections is registered at a pump current of 2.78 mA. Utilizing an external cavity with the fiber Bragg grating made it possible to reduce the relative intensity noise from 7.2∙10–10 1/Hz to 1.5∙10–11 1/Hz in the currents range 1.86–3.2 mA. The study can be useful in applications that require an optical radiation coherent source with a low relative intensity noise level (such as coherent optical communication or fiber-optic sensors).

The degradation process of Vertical-cavity Surface-emitting lasers with high speed and a central wavelength at 850 nm is investigated via constant-current accelerated aging experiments. Degradation of the photoelectric performances under different operating conditions are characterized by optical output power, and forward and reverse bias current–voltage. The 1/f noise characteristics and formation mechanism are discussed in terms of the experimental results of low frequency noise below threshold current. The main composition of low frequency noise before and after aging, the bias current dependence and the origin of the noise are analyzed emphatically. The correlation between the degradation suggests that the loss of photoelectric performance and the fluctuation of low frequency noise characteristic can be attributed to the contagion of defects towards the active region of Vertical-cavity Surface-emitting lasers. Furthermore, the results of failure analysis confirmed the conclusion that the contagion of defects occurred towards the active region of the samples after aging. [ABSTRACT FROM AUTHOR]

The impact of diffusion profile shaping through the use of tensilely and compressively strained diffusion masks on the modulation response of single-mode vertical-cavity surface-emitting lasers (VCSELs) using disorder-defined apertures is investigated. VCSELs designed for high-power single-fundamental-mode emission through the use apertures defined via impurity-induced disordering (IID) in conjunction with a standard oxide-confinement process are characterized to extract high-frequency optical cavity parameters across oxide aperture and diffusion mask strain variations. The 3-dB small-signal bandwidth is maintained for a 7.68 mW single-mode 850 nm VCSEL with an oxide aperture of 13 $\mu \text{m}$ using a tensilely strained diffusion mask relative to a non-disordered multimode device of the same oxide aperture. A large K-factor reduction is also observed, from 0.248 ns to 0.045 ns, indicating that damping and photon lifetimes within the cavity of VCSELs employing disorder-defined apertures are substantially reduced. Performance implications to data communication applications are discussed. [ABSTRACT FROM AUTHOR]

In this work, the architecture of a high-power InAlGaP/InGaP vertical-cavity surface-emitting laser (VCSEL) with an emission wavelength of 680 nm was studied. The design of quantum well, including the well thickness, indium composition, and barrier aluminum composition targeting the emission wavelength, was elaborately optimized. Moreover, the influences of leakage current, temperature dependence of optical gain, and resonance mode gain to threshold current under different barrier aluminum compositions were investigated. Lastly, the temperature characteristics of InAlGaP/InGaP VCSEL with substrate removal have also been calculated with 24% and 40.6% improvement in thermal resistance and operating current range, respectively. It holds great promise for high-power red VCSEL application. [ABSTRACT FROM AUTHOR]

A cavity-resonator-integrated guided-mode resonance mirror (CRIGM) consisting of a small-aperture grating coupler integrated in a waveguide cavity on a high-reflection substrate reflects an incident free-space wave with reflection-phase variation of 2 π in a resonance condition. CRIGM has been investigated as a key component in surface mount packaging of VCSEL for future optical interconnects but the reflectance of a fabricated CRIGM was not sufficient. Matching of electric field distribution between an incident Gaussian beam and the reflected beam from the CRIGM is discussed for improving the reflectance. A new apodization method of grating-tooth shift is proposed for the field-distribution matching. CRIGMs with the new and a well-known fill-factor apodization methods are characterized by numerical simulation. It is predicted that the previously measured reflectance will be improved by more than 1.2 dB by introducing either of the apodization methods. [ABSTRACT FROM AUTHOR]

An investigation of angled flip-chip integration of a singlemode 850 nm vertical-cavity surface-emitting laser (VCSEL) on a silicon nitride photonic integrated circuit (PIC) is presented. Using numerical FDTD simulations, we consider the conditions under which the VCSEL can be integrated at an angle over a grating coupler with high coupling efficiency and low optical feedback. With both coupling efficiency and feedback decreasing with increasing angle, there is a trade-off. With co-directional coupling, first-order diffraction loss sets in at a critical angle, which further reduces the coupling efficiency. No such critical angle exists for contra-directional coupling. We also experimentally demonstrate angled flip-chip integration of GaAs-based 850 nm single transverse and polarization mode VCSELs over grating couplers on a silicon-nitride PIC. At the output grating coupler, light is either collected by an optical fiber or converted to a photocurrent using a flip-chip integrated GaAs-based photodetector. The latter forms an on-PIC optical link. We measured an insertion loss of 21.9, 17.6 and 20.1 dB with a singlemode fiber, multimode fiber and photodetector over the output grating coupler, respectively. [ABSTRACT FROM AUTHOR]

In this simulation study, the dynamics of a twin vertical-cavity surface-emitting laser (VCSEL) subjected to optical injection are studied. A special novel configuration includes two laser devices, of which one is considered as the injector, while the other is considered as the transmitter. The signal for the first laser, LD1, is directed towards the second, LD2, which is responsible for chaotic transmission. During the signal trip from LD1 to LD2, the signal is separated into two parts by fibre Bragg grating (FBG). This is to change some signal properties. Results indicated that moderate bandwidth chaotic emission is available outside the laser device cavity. Contrary to conventional edge-emitting lasers, it is found that VCSELs operate with fewer modes and higher amplitudes. The selected properties for the simulated signal are: LD SEED, polarisation, FBG applied stress and temperature. The resulting lasing modes range from chaotic to enhanced modes. To ensure independent dynamics, cross-correlation (CC) between LD1 (which is responsible for perturbation) and LD2 antisynchronisation is approved. The CC for these two lasers ranged from - 0.0028 to - 6.5 E - 05 . [ABSTRACT FROM AUTHOR]

Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in consumer electronics, light detection and ranging, optical interconnects, atomic sensors, and so on. In this paper, a VCSEL with the surface metastructure like one-dimensional high-contrast grating (HCG), based on the HCG-DBR vertical cavity, was first designed and fabricated. The polarization characteristic of the HCG-VCSEL were experimentally studied. The p-doped top 4-pair DBR for the current spreading and the direction shift between the HCG and the elliptical oxide aperture may result in a low orthogonal polarization suppression ratio in the HCG-VCSEL. Then, the Bloch surface wave surface-emitting laser (BSW-SEL), based on the HCG-DBR metastructure, is proposed for single-mode, high-efficiency, and high-power output with a low divergence angle. The mode field and the far field profile of the BSW-SEL are calculated for verification. The surface-emitting lasers with surface metastructures are useful for the sensing applications and optical interconnects.

We propose a simple method to generate broadband polarization chaos using two mutually coupled free-running vertical-cavity surface-emitting lasers (VCSELs). Specifically, we quantitatively investigate the effect of critical external parameters (bias current, frequency detuning and coupling coefficient) on the polarization chaos bandwidth in the scenarios of parallel injection and orthogonal injection, and reveal the physical mechanism of bandwidth enhancement in two scenarios. Final simulation results show that the bandwidth of chaotic signals obtained from parallel and orthogonal injection can reach 35.15 GHz and 32.96 GHz, respectively.

A vertical-cavity surface-emitting laser (VCSEL) is easily made into a two-dimensional array to improve its output power. However, if the near-field complex amplitude output cannot be stabilized in the lowest supermode generated by the fundamental transverse mode, the spot cannot converge on the center normal of the far-field array geometry, and the energy will be diverged. The external cavity is prepared for the VCSEL array, and the output of the array can be stabilized in the lowest order supermode generated by the fundamental transverse mode by supermode control through diffraction coupling. In this study, the parallel-coupled model for the 2-dimensional VCSEL array based on Fresnel diffraction integration was established and used to numerically calculate and analyze the influence on the supermodes’ thresholds of different array distributions, array elements’ transverse modes and duty ratios versus the length of the external cavity. The simulation results show that the square array provides a wider range of external cavity control length (0.2d2/λ and approximately 0.9 to 1.0d2/λ). The lowest supermode of the fundamental transverse mode can be outputted. For the regular hexagonal array with the length of the external cavity of 0.15d2/λ and 0.6d2/λ. The results have important reference significance for the design of an external cavity VCSEL array, which can control the supermode and obtain VCSEL coherent array beams with high power and near diffraction limits.

The degradation process of Vertical-cavity Surface-emitting lasers with high speed and a central wavelength at 850 nm is investigated via constant-current accelerated aging experiments. Degradation of the photoelectric performances under different operating conditions are characterized by optical output power, and forward and reverse bias current–voltage. The 1/f noise characteristics and formation mechanism are discussed in terms of the experimental results of low frequency noise below threshold current. The main composition of low frequency noise before and after aging, the bias current dependence and the origin of the noise are analyzed emphatically. The correlation between the degradation suggests that the loss of photoelectric performance and the fluctuation of low frequency noise characteristic can be attributed to the contagion of defects towards the active region of Vertical-cavity Surface-emitting lasers. Furthermore, the results of failure analysis confirmed the conclusion that the contagion of defects occurred towards the active region of the samples after aging.

In this work, the architecture of a high-power InAlGaP/InGaP vertical-cavity surface-emitting laser (VCSEL) with an emission wavelength of 680 nm was studied. The design of quantum well, including the well thickness, indium composition, and barrier aluminum composition targeting the emission wavelength, was elaborately optimized. Moreover, the influences of leakage current, temperature dependence of optical gain, and resonance mode gain to threshold current under different barrier aluminum compositions were investigated. Lastly, the temperature characteristics of InAlGaP/InGaP VCSEL with substrate removal have also been calculated with 24% and 40.6% improvement in thermal resistance and operating current range, respectively. It holds great promise for high-power red VCSEL application.

For the first time up to our knowledge, a centralized-light-source two-way eight-level pulse amplitude modulation (PAM8)/four-level pulse amplitude modulation (PAM4) free-space optical (FSO) communication with parallel optical injection-locked vertical-cavity surface-emitting laser (VCSEL) transmitter is practically demonstrated. With the assistance of parallel optical injection locking, injection locking in the polarization sideband causes a simultaneous generation of the free-running orthogonal polarization sideband to form a centralized-light-source scheme. With the centralized light source, additional light source or wavelength reuse component, such as Fabry-Perot laser diode or reflective semiconductor optical amplifier, is not needed at the receiver side. It is very attractive because it enables the receiver side to share the light source remotely located at the transmitter side. Based on the centralized-light-source scheme and parallel optical injection-locking operation, the injection-locked parallel polarization sideband is used for downlink transmission, and the induced free-running orthogonal polarization sideband is transmitted and used as the optical carrier for uplink transmission. Over a 200-m free-space link, good bit-error-rate (BER) performance, the qualified PAM8, and PAM4 eye diagrams are obtained for two-way FSO communications. This proposed centralized-light-source two-way FSO communication provides a practical choice for two-way high transmission capacities and considerably develops the scenario characterized by parallel optical injection locking.

A face-pumped Nd:YAG slab laser with high-power output and temperature fluctuation adaptability is proposed and demonstrated for the first time. A two-dimensional (2D) vertical-cavity surface-emitting laser (VCSEL) array at 808 nm with a low wavelength shift coefficient is used as the pump source with a total pump power of 1.38 kW. The array is cooled by a double-layer vascularized macro-channel heat sink for effective heat management. A 1064 nm maximum power of 437 W from the slab laser is obtained by optimizing the output coupling, and the power variation is only ±4.9% over the temperature range from 16 °C to 34 °C. The results show that the high-power slab laser pumped by VCSEL has an excellent performance in temperature tolerance and lower requirements for coolant, which is only water cooled by the macro-channel heat sink and no need for deionized water; it also provides a solution for high power lasers used in the complicated environment. Furthermore, it is possible to scale the output power to ~kW-level by further increasing the VCSEL pump power. [ABSTRACT FROM AUTHOR]

The paper presents the results of the experimental study of an application of the phenomenon of vibrational resonance (VR) for enhancement of the response of a bistable vertical-cavity surface-emitting laser (VCSEL) to the effect of optical modulating signals. Specifically, two different cases were investigated: (a) the control of all-optical switching caused by a modulated orthogonal optical injection from another VCSEL and (b) the amplification of autodyne signals from a vibrating diffusely reflecting surface in the self-mixing optical interferometry. It is experimentally demonstrated that an application of the phenomenon of VR in both cases studied leads to a strong amplification of the input optical signals by a factor from 10 to 200 depending on the experimental conditions with respect to the initial values. The effect of the asymmetry of a bistable potential on the amplification factor was also studied. The results obtained can be used to improve alloptical switchings for application in communication systems and enhancement of autodyne signals in self-mixing optical interferometry. [ABSTRACT FROM AUTHOR]

A modified supervised learning rule which is suitable for training photonic spiking neural networks (SNN) is proposed for the first time. The proposed learning rule is independent of the time intervals between actual spike and desired spike or between presynaptic spike and postsynaptic spike. Based on the proposed supervised learning rule, 10 digital images are learned in photonic neural network which consists of 30 presynaptic neurons and 10 postsynaptic neurons. Presynaptic and postsynaptic neurons are photonic neurons based on vertical-cavity surface-emitting lasers with an embedded saturable absorber (VCSEL-SA). The results show that 10 digital images are recognized correctly in photonic SNN after enough training. Additionally, the effects of learning rate, the jitters of learning rate, initial weights distribution of SNN and bias current of postsynaptic neurons (VCSELs-SA) on the recognized error are examined carefully based on the proposed learning rule. To the best of our knowledge, such modified supervised learning rule has not yet been reported, which would contribute to training photonic neural networks, and hence is interesting for neuromorphic photonic systems and pattern recognition. [ABSTRACT FROM AUTHOR]

The thermal and optical properties of a combined (hybrid) metal–dielectric reflector comprising a gold layer and distributed Bragg reflector composed of alternating In0.52Al0.48As/In0.53Ga0.47As bilayers are considered. It is established that a high coefficient of reflection of the hybrid structure can be achieved at low absorption in the metal and relatively small total thickness of the dielectric reflector. [ABSTRACT FROM AUTHOR]

An investigation has been performed of 1.55-μm vertical-cavity surface-emitting lasers based on heterostructures with a buried tunnel junction (BTJ) with a height difference of 15 nm. The devices are obtained by wafer fusion of heterostructures grown by molecular beam epitaxy and provide single-mode lasing at a BTJ diameter of up to 8 μm. A decrease in the BTJ size leads to a sharp increase in the threshold current, the output optical power, and the resonance frequency at the lasing threshold. Stable single-mode lasing takes place due to the smoothed boundary of the buried surface relief, which induces a gradual change in the profile of the effective refractive index in the lateral direction with the effective current confinement retained. This makes it possible to reduce significantly the transverse optical confinement factor for the higher-order modes even at a large BTJ size. However, at a small BTJ size, it leads to the formation of a saturable absorber in unpumped parts of the active region. [ABSTRACT FROM AUTHOR]

A high-speed 84 Gb/s vestigial sideband (VSB)-eight-level pulse amplitude modulation (PAM8) fiber-invisible laser light communication (IVLLC) integration based on vertical-cavity surface-emitting laser (VCSEL) transmitter with injection locking scheme is proposed. To the authors' knowledge, this study is the first to realize a high-speed 84 Gb/s VSB-PAM8 VCSEL transmitter-based fiber-IVLLC integration. It is effectual to adopt an optical VSB-PAM8 signal in fiber-IVLLC integrations to suppress the linewidth of an optical signal so as to reduce the fiber dispersion. An injection locking scheme and a linear equalizer possess enhancements in frequency response, and thereby provide good transmission performances in a high-speed VSB-PAM8 fiber-IVLLC integration. Impressive bit error rate performance and clear eye diagrams are acquired in real time at a 25-km single-mode fiber operation with a 10-m free-space link. Such proposed 84 Gb/s VSB-PAM8 VCSEL transmitter-based fiber-IVLLC integration is a notable option for providing high transmission rates at optical fiber and optical wireless communications.

We experimentally demonstrate multi-channel physical random bits (PRBs) generation by utilizing chaotic outputs from two linear polarization modes in a vertical-cavity surface-emitting laser (VCSEL) under a chaotic optical injection. The polarization-resolved chaotic signal is obtained with a master-VCSEL subject to optical feedback, and then injects into a slave-VCSEL for driving its two linear polarization modes into chaotic state. We analyze the influences of injection parameters on bandwidth, complexity, and the correlation of two-channel chaotic signals. By using the two chaotic signal outputs from the slave-VCSEL under optimized parameters as entropy sources, we have obtained the PRBs at the dual-channel rate of 160 Gbits/s by adopting the m least significant bits extraction with logical exclusive-OR (XOR) post-processing. Further utilizing the n-bit cross-merging method, the PRB at a rate of 320 Gbits/s could be obtained.

We have studied heterostructures based on short-period InGaAs/InGaAlAs superlattices (SLs) manufactured by molecular-beam epitaxy on InP substrates, intended for use as active regions in vertical-cavity surface-emitting lasers operating in a 1.3-μm spectral range. The heterostructures were characterized by measuring photoluminescence (PL) emission and X-ray diffraction. It is established that variation of the ratio of quantum-well and barrier-layer thicknesses in the SL allows controlled shift of the PL peak position for lasing in the 1.3-μm range at almost constant PL efficiency. [ABSTRACT FROM AUTHOR]

The results are presented of a study and optimization of the conditions under which heterointerfaces of the GaAs–InGaAsP type are formed via the direct intermolecular wafer bonding (fusion) of a heterostructure of an active region on an InP substrate and distributed Bragg reflectors on GaAs substrates upon the fabrication of hybrid heterostructures for long-wavelength vertical-cavity surface-emitting lasers (VCSELs). The heterostructures are grown by solid-source molecular-beam epitaxy. It is shown that, in the case of the incomplete removal of oxide films during preparation of the wafers before fusion and/or in the presence of adsorbed water on the wafer surfaces, the fused interface contains a large number of amorphous inclusions, which are most likely oxides of Group-III elements. Optimization of the conditions in which a buried tunnel junction is formed on the surface of the heterostructure on an InP wafer made it possible to reduce the surface roughness to 1 nm and to ensure that the thickness of the GaAs–InGaAsP fused interface does not exceed 5 nm, with no dislocations or other extended defects found at the fused heterointerfaces. The 1.55-μm VCSELs fabricated from the hybrid heterostructures created using the developed technology demonstrate efficient lasing under continuous-wave pumping in a wide temperature range, which is indicative of the high optical quality of the fused heterointerfaces in the VCSEL structure. [ABSTRACT FROM AUTHOR]

The paper states the operating principles of subminiature semiconductor emitters and offers the research results of the performance for those emitters that were developed and manufactured at the Rzhanov Institute of Semiconductor physics of SB RAS over the last three years. Single photon emitter based on Al In As/Al Ga As quantum dots has been developed. Hanbury Brown and Twiss experiment has been carried out to measure the photon statistics. The photon correlation function demonstrates a clear photon antibunching effect ( (0) 0.04), which is a direct evidence of single photon emission by single Al In As quantum dots. The results of developing single-mode vertical-cavity surface-emitting lasers with a wavelength of 794.8 nm future-oriented for application in chip-scale atomic clock and operating at the transition 5S 5P of Rb are reported. [ABSTRACT FROM AUTHOR]

We evaluate the effects of the external optical feedback on the on-off keying (OOK) and four-level pulse amplitude modulation (PAM4) signals in the single-mode fiber (SMF) link implemented by using a commercial 10G-class 1.55- $\mu \text{m}$ vertical-cavity surface-emitting laser (VCSEL). The results show that the PAM4 signal is much more sensitive to the external optical feedback than the OOK signal. For example, in the back-to-back condition, an error floor is observed at the bit-error rate (BER) of $\sim 8\times 10 ^{\mathbf {-3}}$ for the 10-Gbaud PAM4 signal when we set the optical feedback ratio to be −14 dB. In comparison, the 10-Gbaud OOK signal has a power penalty of only 0.4 dB (@BER $= 5\times 10 ^{-5}$) under the same conditions. The results also show that the PAM4 signal becomes more sensitive to the optical feedback after the SMF transmission due to the shallowed BER curve by the fiber dispersion. In addition, we confirm that the effects of the optical feedback are independent of the baud rate. From these results, we conclude that the error-free transmission of the high-speed PAM4 signal cannot be achieved if there is even one bad fiber connector having >2.5% reflection in the VCSEL-based SMF link. [ABSTRACT FROM AUTHOR]

We demonstrate a high power two-dimensional vertical-cavity surface-emitting laser (VCSEL) array cooled by liquid metal. An output power of 1.1 kW at 808 nm with 39% power conversion efficiency (PCE) is obtained under continuous-wave (CW) operation. To the best of our knowledge, this is the highest output power reported for a laser diode array with liquid metal cooling. Moreover, the wavelength drift is only 1.2 nm from lasing threshold to 1.1 kW output power. Using this laser diode array as pumping module, a solid-state Nd:YAG slab laser at 1064 nm reaches 312 W output power. This verifies that the laser diode array cooled by liquid metal can be used as a pumping source for high power lasers. The higher power scaling can be achieved by two-dimensional geometric extension to the macro-channel heat sink and increasing the flux of the liquid metal. [ABSTRACT FROM AUTHOR]

An active area based on InGaAs/InGaAlAs superlattice for laser diodes operating in the spectral range between 1535 and 1565 nm is proposed and realized practically. It is demonstrated that using a superlattice increases the mode gain at the same values of the pump-diode current density relative to a typical active-area design based on an array of InGaAs quantum wells. [ABSTRACT FROM AUTHOR]

The optimization of the structure of vertical-cavity surface-emitting lasers (VCSELs) is required to produce more efficient devices. The secondary ion mass spectrometry (SIMS) technique can provide information about the structure and the distribution of dopants and contaminants. However, VCSELs are relatively thick, contain hundreds of layers with varying compositions, and consist of very thin layers. Classical SIMS is prone to artifacts which decreases the quality of the results. In this work, modifications of the SIMS measurement procedures are presented: high incident angle bombardment reduces the mixing effect; optimization of the extraction parameters increases the signal-to-noise ratio from 2.1 to 24.3 dB; Ion polishing and beam service preserves the quality of the measurement. Due to impact energy modulations quantum wells and barriers are registered as box-shaped features. The raw data is free of artifacts and reflects the realistic distribution of elements. Such accuracy may prove invaluable for further optimization of VCSELs. [Display omitted] • High incident angle bombardment reduces the mixing effect. • With optimized extraction parameters the signal-to-noise ratio can exceed 24 dB. • Ion polishing and beam service preserves the quality of the measurement. • Quantum wells (3.4 nm thick) are registered as box-shaped features. • Measurements can be performed in depth profiling and 3D imaging modes. [ABSTRACT FROM AUTHOR]