With the technology development, it is highly desirable to enhance the power and brightness of a 1550 pulsed laser in order to increase the detectable distance and improve the spatial resolution. In this paper, a 1550 tunnel junction high peak power semiconductor laser based on AlGaInAs/InP material system for lidar detection is designed, which peak output power is approximately three times that of a individual emitter.The adjacent individual emitter of the tunnel junction laser is connected by the tunnel junction, and each tunnel junction is formed by a highly doped p-type InGaAs layer and a highly doped n-type InGaAs layer. Crosslight Software's PICS3D module is used to simulate the epitaxial structure of an individual emitter, simulating its photoelectric characteristics and through the simulation and optimization of a individual emitter with a strip width of 100 μm and different cavity length, it is found that when the cavity length is 1000 μm, the slope efficiency of the single-junction laser can reach 0.37 W/A; when the cavity length is 800 μm, the slope efficiency of the individual emitter can reach 0.45 W/A. Therefore, shortening the cavity length of the laser can improve the slope efficiency of the laser, and it is expected to increase the slope efficiency of the three-tunnel junction laser to more than 1 W/A. It is expected to achieve a 1550 high-power tunnel junction semiconductor laser.
KEYWORDS: Waveguides, Semiconductor lasers, Beam divergence, High power lasers, Quantum wells, Near field optics, Optical simulations, Refractive index, Laser therapeutics
High power 1470 nm semiconductor lasers are widely used in microtissue repair, white polymer plastic welding, and turbulence detection in front of defense aircraft. Most of the current 1470 nm lasers mostly suffer from low slop efficiency and large divergence angle. In order to reduce the divergence angle and increase the output power of the 1470 nm lasers, a mode expansion layer (MEL) is introduced to narrow the far-field divergence angle, and an electron blocking layer (EBL) is introduced to minimize the carrier leakage. Based on the strain quantum well theory, the active region material was optimized with a thickness of 5 nm quantum well layer and 11 nm barrier layer. Simulation results show that the slope efficiency is increased from 0.086W/A to 0.466 W/A, and the full width at half maximum (FWHM) of the vertical farfield divergence angle is reduced from 38.6° to 27.0°, which is of great significance for the study of 1470 nm lasers.
Quantum-well intermixing (QWI) technology is considered as an effective methodology to tune the post-growth bandgap energy of semiconductor compound materials, and is widely used in diode lasers and photonic integrated devices, and other fields. In order to improve the resistance to the catastrophic optical damage for 8XX semiconductor lasers based on AlGaInAs/AlGaAs quantum wells, we adopt a method of impurity-free vacancy disordering. Plasma enhanced chemical vapor deposition is used to grow SiO2 layer on the surface of the epi-wafer in the experiment. The influence of dielectric layer thickness, heat treatment temperature and heat treatment time on the QWI effect is explored through the control variable method, and the inhibition effect of oxygen ion bombardment on QWI is also investigated. The Photo-luminescence wavelength blue shift of the sample is 30-40 nm when the sample is covered by 450 nm SiO2 and subjected to rapid heat treatment under 900°C for 270 s, which can be used as the non-absorbing region of the laser. In addition, in the experiment of suppressing QWI, the laser epitaxy is first bombarded by oxygen ions from 10 s to150s, and then is deposited with 450 nm SiO2 dielectric layer, and finally underwent rapid heat treatment under 875°C for 270s. It’s found that the sample blue shift is 5nm after 150 s bombardment, and the blue shift inhibition effect is good. Therefore, the combination of SiO2 dielectric layer and plasma bombardment can be applied to the preparation of laser transparent window
High-power single-mode laser diodes around 795 nm are widely used in applications such as Rb atomic clocks and nuclear magnetic resonance imaging. We simulate a high-power single-mode semiconductor laser around 795 nm based on a supersymmetric structure. In the lateral direction, the mode stability characteristics are investigated by varying the three waveguides widths and the distances between the middle main waveguide and the two sub-waveguides. Since the left and right waveguides have different widths, the optimal distance from them to the main waveguide is also different. In order to ensure the single-mode operating of the laser, there is a pair of optimized distances from the left and right waveguides to the main waveguide. The distances from the left and right waveguides to the main waveguide are 1 μm and 1.2 μm, respectively, when the widths of the left waveguide, right waveguide and main waveguide are set as 2.3 μm, 3.5 μm and 6 μm, respectively. In the longitudinal direction, a laterally-coupled grating structure is used to achieve longitudinal mode selection. Such lasers are expected to be the next generation of high-power, narrow-linewidth, singlemode laser diodes.
Microdisks and micro-rings are commonly used micro-optical devices that greatly enhance the interaction between light and matter within a cavity due to their high-quality factor and small mode volume, making them widely used in microcavity optical sensing. By introducing parity-time (PT) symmetric structures into the microcavity, the coupling efficiency of the optical field inside the cavity can be improved, which is conducive to obtaining higher sensing sensitivity. We theoretically verify the feasibility of using a PT-symmetric micro-ring coupled microdisk composite cavity as an active sensor based on the characteristics of exceptional point (EP) enhanced sensing in PT-symmetric systems. Gain is introduced to the microdisk cavity by injecting current until the system undergoes PT symmetry breaking, i.e., when the sensor is at the EP, the transmission of light will exhibit a nonlinear enhancement effect due to the degeneracy of eigenvalues and corresponding eigenvectors of the system, making the signal more sensitive to changes in the sensing medium. The results obtained through the finite difference time domain method show that the intensity sensitivity of the PT-symmetric microcavity at the EP is improved by about 11.8 times compared with the conventional microcavity when the working wavelength is in the range of communication band and different concentrations of the same gas are injected into the air, which is expected to provide reference and insight for the further development of microcavities for refractive index sensing.
The beam quality of the semiconductor laser is influenced by the structure of the laser's own waveguide as well as the beam shaping system. The cylindrical lens is used to compress the laser beam in the fast-axis direction in optically pumped source applications. Significant spectral deterioration occurs during the shaping of the laser beam. The spectrum of the laser split into some small peaks and misaligned with the absorption peaks of the crystal, resulting in a decrease in the overall absorption efficiency. In this paper, the reasons of spectral deterioration are investigated, and the spectral characteristics are optimized by varying the the output facet coating film’s reflectivity of the semiconductor laser chip. An improvement scheme for spectral deterioration of high power semiconductor lasers after beam shaping is proposed. The experiment results shows that the deterioration of the spectrum is significantly eliminated when the coating film’s reflectivity is adjusted from 0.88% to nearly 15%. A 976nm high power semiconductor laser chip with 7.16% reflectivity coating film has the highest slope efficiency. Due to a trade-off between spectral quality and the slope efficiency, it is necessary to choose an appropriate coating film’s reflectivity on the output facet surface to achieve both high output power and good spectra. This has important application prospects in future solid-state laser pump source applications.
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