The periodical pulse bundles were presented in a Yb-doped double-clad distributed Bragg reflector all-fiber configuration. With a pumped power of 529.2 mW, the periodical pulse bundles is obtained. Furthermore, a single pulse bundle composes of one main pulse and two sub-pulses. The pulse width of the main pulse and the sub-pulse are 2.2 μs and 7.7 μs, respectively. The separations of between main pulse, right sub-pulse and left are 22.70 μs and 22.15 μs, respectively. The average period of the pulse bundle is approximately 75 μs with repetition rate of 13.3 kHz. The number of sub-pulses between adjacent main pulses decreases to one when the pumped power does to 450.2mW. When the pumped power increases to 594.4 mW, the number goes to three.
An external cavity wavelength-locked red semiconductor laser with a narrow-linewidth was designed and fabricated. The AlGaInP strained quantum wells were meticulously designed and grown,while the epitaxial layer of a high-power red semiconductor laser was synthesized using metal-organic chemical vapor deposition (MOCVD).The chips were fabricated by photolithography, metal electrode fabrication, cavity surface coating and other processes. The prepared laser chip with the cavity length of 1.5 mm has a strip width of 100 μm. The chip was made into a laser device through packaging technique, and an external resonant cavity was constructed using a Volume Bragg Grating. A series of oexperiments were conducted to optimize the performance of laser devices, and the characteristics of spectrum, power and other parameters in the condition of free running spectrum and wavelength-locked spectrum at different temperatures. A narrow-linewidth red semiconductor laser with the central wavelength of 640 nm, the linewidth of 0.11 nm, and the power of 2.7 W was obtained by means of the continuous drive current measurement at room temperature with the drive current of 3 A and fiber parameters of 50/125. In addition, the output power of 5.02 W was achieved with the method of the quasi-continuous drive current of 5 A.The power loss of the external cavity mode-locked using VBG is controlled within 3%.
Germanene (Ge) has a Dirac-type electronic structure similar to that of graphene and has excellent nonlinear saturable absorption properties, which has attracted extensive research. In this paper, few-layer Ge nanosheets were prepared and characterized in detail. Its nonlinear modulation depth was measured to be 8.5%, and the saturation intensity was 0.12 GW/cm2. Ge nanosheets are used as a saturable absorber (SA) in an Er-doped fiber laser (EDFL) to obtain a stable Q-switched mode-locking (QML) pulse. As the pump power (Ppump) increases from 64.2 mW to 204 mW, the repetition frequency (RF) and pulse width of the Q-switched (QS) envelope increase from 46.2 KHz to 109 KHz and decrease from 4.4 μs to 2.25 μs, respectively. The mode-locked pulse has a RF of 30.2 MHz with a center wavelength of 1559.6 nm. The QML pulses obtain a maximum output power of 2.278 mW and a maximum pulse energy of 20.9 nJ when the Ppump is 204 mW. Our study proves that Ge, as a high-energy light pulse absorbing material, can be used in the field of ultrafast laser.
MoSe2 thin films have excellent catalytic, electrical, and optical properties and have potential applications in the fields of catalytic hydrogen precipitation, field effect transistors, sensor devices, and optoelectronic devices. In this paper, MoSe2 thin films were synthesized based on the solid-phase reaction at the interface between Se and Mo film at high temperatures, which are deposited on sapphire substrates sequentially. The structure and morphology were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The synthesis temperature and saturable absorption (SA) properties of the MoSe2 films were investigated. The results show that 400°C is close to the optimal temperature for synthesizing MoSe2 films, and the synthesized MoSe2 films exhibit multilayer structure. When it is applied as a saturable absorber in a 1064 nm solid-state laser, the maximum repetition frequency of the Q-modulated laser pulse is obtained to be 428.1kHz, which corresponds to a pulse width of 67.6 ns and a maximum modulation depth of 27.4%.
Semiconductor laser devices have the characteristic of small size, high integration and stable requirements, and TO package red semiconductor laser are widely used in laser display application market. Due to the limitations of the electro-optical conversion efficiency of laser devices, the active region will generate over 55% of Joule waste heat under normal operation, and the traditional TO9 packaging form with Aluminum Nitride heat sink is not conducive to the heat dissipation for high power laser application. Therefore, this has become a key factor restricting the stable operation of short wavelength red semiconductor laser devices. In order to improve the heat dissipation problems, this paper developed an upgraded TO packaging type of red wavelength laser device using single-crystal Silicon Carbide (SiC) heat-sink under constant temperature condition. The experimental results show that the output power of TO packaged red laser with self-developed single-crystal SiC heat-sink is significantly higher than that of AlN heat-sink packaged device at high temperatures. The maximum electro-optical conversion efficiency of TO devices contained SiC heat sink is also improved, and the thermal resistance of the package dissipation is effectively reduced.
In recent years, layered transition metal sulfides (TMDCs) exhibit excellent nonlinear saturable absorption properties in laser modulations. Nevertheless, few of them are applied to the optimization of optical parametric oscillators (OPOs). In this work, we prepared a 12.5 nm-thickness platinum disulfide (PtS2) saturable absorber (SA) by a combination of electron beam evaporation (EBE) and post-vulcanization method. The nonlinear transmittance is measured, which exhibits the SA characteristic of PtS2 film. The acousto-optic (AO) Q-switch and the prepared PtS2 SA are used to realize the operation of active and passive Q-switched OPO, and the mid-infrared idler pulse with nanosecond width is obtained. By measuring the experimental output results, the optimizations of PtS2 SA to OPO’s operation are analyzed, including the stabilization of pulse train by 240%, the compression of idler-light pulse by 59.7%, the improvement of peak power by 198%. As a result, the improvement of nonlinear conversion is attained by 16.9%. The phenomenon may be due to the excellent saturable absorption effect of PtS2 SA to the fundamental light. This paper shows the optimization effect of the prepared layered transition metal sulfide for laser intracavity modulation on the nonlinear frequency conversion process, especially for the improve of nonlinear conversion effect.
High power AlGaInP laser diodes (LDs) and bars emitting at about 685 nm have been fabricated. The epitaxial structures, including the AlInP cladding layer, asymmetric waveguide and single compressive-strained quantum well, were designed to optimize the thermal performance. The transparent window structure formed by Zn diffusion was employed to increase the output power of AlGaInP LDs. A maximum power of 4.9 W was realized for the single emitter LDs without catastrophic optical damage. Using micro-channel heat sinks, an array stacked with six 1-cm bars showed an output power of more than 300 W with 40% conversion efficiency.
In this paper, we present a theoretical model to describe the passively-Q output characteristics of quasi-three level Ho3+-doped Fluorotellurite fiber lasers. According to the model, we have studied the factors impacting on the output characteristics of the laser through numerical simulation method. The calculating program of the theoretical model is written using the Matlab language. We obtain the passively-Q output laser with the pulse repetition rate of 13.1 kHz, pulse width of 28.63ns, peak power of 25W, and pulse energy of 0.34 μJ at the pump power of 0.1W. When the pump power increases, the pulse width of the laser decreases, the pulse repetition rate linearly increases, both the pulse energy and the peak power also increases. The pulse width of the laser linearly increases and the pulse energy increases when the length L does. When the output coupler transmission T increases, both the pulse width and the peak power of the laser decrease. The pulse energy of the laser firstly increases and then decreases when the output coupler transmission T does. We qualitatively analyze what causes the change laws of the outputlaser characteristics, such as the pulse width and the pulse energy.
16-core photonic crystal fiber (PCF) was designed. In order to obtain spatially flat in-phase modes, the super-mode near- field properties were studied through method of numerical simulation calculation and according to coupled mode theory. On the based of the scalar Fraunhofer Diffraction, a far- field in-phase super-mode theoretical modeling was presented. According to the modeling, one discussed the influence of the random phase perturbation, the random amplitude perturbation and the polarization direction perturbation on the far-filed intensity distribution, in detail. The results show that both phase perturbation and amplitude perturbation sharply impact the far-filed distribution of interference intensity and contrast. However, the influence of the polarization direction perturbation is not obvious. When the parameterδ, μ and ▵ increases, the field center intensity decreases and the power of the central spot also does, which means the profile of the spot will blur and the beam quality drop.
An intracavity optical parametric oscillator (IOPO) pumped by a continuous-wave (CW) mode-locked laser is experimentally realized. The fundamental cavity and optical parametric oscillator cavity are designed to satisfy synchronous pumping. The output characteristics of signal and idle light are measured. Because of higher fundamental photon intensity in IOPO, the threshold of IOPO is lower than that of an extra-cavity optical parametric oscillator. The spectroscopy of signal light is obtained and the wavelength of idle light can be estimated to be 3.298 μm from noncritical phase matching. Based on the intensity fluctuation mechanism of fundamental locking, the dynamical model for IOPO pumped by a CW mode-locked laser is developed. The simulated results for the temporal shape of three lights are calculated from the derived rate equations. Because of dispersion, the signal pulse width of the theory is smaller than that of the experiment with the same pump energy.
A laser-diode-pumped actively Q-switched Yb:NaY(WO4)2 laser operating at around 1040 nm is presented for the first time with acoustic-optic modulator. The dependence of pulse width on incident pump power for different pulse repetition rates is measured. By considering the Guassian spatial distribution of the intracavity photon density and the initial population-inversion density as well as the longitudinal distribution of the photon density along the cavity axis and the turn off time of the acoustic-optic Q-switch, the coupled equations of the actively Q-switched Yb:NaY(WO4)2 laser are given. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.
Highly uniform solid-phase Zn-diffusion technique was developed to fabricate transparent windows for 650 nm red laser diodes (LDs). The maximum output power was up to 120 mW, which is three times higher than that for LDs without window structure. The LDs showed excellent thermal characteristics and aging reliability with TO-can package. The characteristic temperature was estimated to be 85 K in the temperature range of 25~65 °C. The LDs showed stable operation of 10 mW at a high temperature of 75 °C. After aging test of 2000 h, the elevated operation current was less than 3%, compared to the initial value. The predicted life time was over 10000 h for 10 mW operation at 75 °C.
KEYWORDS: Semiconductor lasers, Quantum wells, High power lasers, Waveguides, Near field optics, Reliability, Laser development, Absorption, Cladding, Laser optics
In this paper, we present a high power TM Polarized GaAsP laser diode of 808nm wavelength. For high power and narrow beam divergence, an asymmetry broad waveguide structure and a tensile strained GaAsP quantum well were used and the epilayers were grown by low-pressure metalorganic chemical vapor deposition. We have obtained an optical power of 20.86W at 20A without COMD and the vertical farfield of 27°. It is expected that Al-free GaAsP quantum well laser diodes will have good reliability
without any facet treatment.
With the support of state key project, Shandong Huaguang Optoelectronics Co. Ltd. realizes the mass production of low threshold current 650nm GaInP/AlGaInP semiconductor laser chips, rapidly. At present, six million 650nm LD chips can be produced per month. The lowest threshold current at 25°C is 7.4mA. The slope efficiency reaches 1.1mW/mA and the output power is 34mW at 40mA CW operation.
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