High speed intracavity-contacted vertical cavity surface emitting lasers with separated quantum wells

In this work, the simulation of the 980 nm InGaAs intra-cavity-contacted oxide-confined vertical-cavity surface-emitting lasers (ICOC VCSELs) with separated triplets of quantum wells (STQW) is presented. We analyze the thermal, electrical and optical properties of such devices. Results of simulations show the larger optical power efficiency and higher modulation bandwidth for devices with included STQW.     

Watt-level red-emitting diode lasers and modules for display applications

Red-emitting lasers for display applications require high output powers and a high visibility. We demonstrate diode lasers and modules in the red spectral range based on AlGaInP with optical output powers up to 1 W and a nearly diffraction limited beam. These high-luminance light sources based on tapered lasers are well suited for laser TVs and projectors for virtual reality simulators based on the flying spot technology. Additionally, we developed diode lasers with internal distributed Bragg reflector (DBR) surface gratings. These DBR tapered lasers and master-oscillator power-amplifiers based on DBR ridge-waveguide lasers and tapered amplifiers feature high power, single mode emission with coherence lengths up to several meters, which are suitable for the next-generation 3D displays based on holography.     

Mode-locked all-fiber ring laser based on broad bandwidth in-fiber acousto-optic modulator

Active mode-locking of long-cavity all-fiber ring laser based on broad bandwidth in-fiber acousto-optic modulator (AOM) is reported. The proposed AOM combines the advantages of intermodal coupling induced by standing flexural acoustic waves in a double-ended tapered fiber. We focus our attention on the effects of large tapered transitions to improve the bandwidth modulation. Our approach permits the implementation of broad modulation bandwidth (13 nm), high modulation depth (50 %), and low optical loss (1.1 dB) in an 80-μm configuration. The effects of the AOM in the laser performance are also investigated. Transform-limit optical pulses of 25 ps temporal width and 2.7 W peak power were obtained at 2.46 MHz repetition rate.     

气源MBE外延自组装GeSi量子点光致荧光研究

利用气源分子束外延设备（MBE）制作了GeSi自组装量子点样品。利用原子力显微镜（AFM）和光致荧光（PL）光谱研究了量子点的形貌和光学性质。气源MBE在较低温度下生长的量子点材料具有较高的量子点覆盖度。200K以下载流子以局域激子形式束缚在量子点中,激子束缚能约为17meV。升温至200K,载流子的输运过程发生变化。对量子点PL积分强度与温度关系曲线进行拟合得到量子点中空穴跃迁至浸润层的热激活能为129meV。     

High-power passively mode-locked tapered InAs/GaAs quantum-dot lasers

We report picosecond pulse generation with high peak power in the range of 3.6 W from monolithic passively mode-locked tapered quantum-dot laser diodes, exhibiting low divergence and good beam quality. These results were achieved using a gain-guided tapered laser geometry. The generation of picosecond pulses with high average power up to 209 mW directly from such tapered lasers is also demonstrated, corresponding to 14.2 pJ pulse energy (14.65 GHz repetition rate). A comparison between the mode-locking performance of these tapered lasers incorporating either five or ten layers of InAs/GaAs self-organized quantum dots in their active layer is also presented.     

High-efficiency, high-power, diode-pumped continuous-wave Tm:YAlO3 slab lasers

We report diode end-pumped continuous-wave Tm:YAlO₃ slab lasers with high power and high efficiency. At room temperature, b-cut Tm:YAlO₃ slabs with doping concentrations of 1, 4 and 5 at.% pumped by fiber-coupled and fast-axis collimated laser diodes with different wavelengths are compared. Tm:YAlO₃ slab lasers of 4 at.% doping concentrations have the highest optical-to-optical efficiency. When pumped with fiber-coupled and fast-axis collimated laser diodes, the maximum output powers are 11 W and 15 W, corresponding to a slope efficiency of 52% and 40%, respectively.     

High efficient Tm3+ doped double cladding silica fiber laser with an intracavity biconical taper

A high efficient LD (laser diode) pumped Tm³⁺ doped double clad silica fiber laser with an intravacity biconical taper was reported. A biconical taper located ～3 cm from the output end of the fiber laser was fabricated by heating and stretching method with a length 1.5 cm and waist diameter ～20 µm. The slope efficiency was 49.8% with respected to the launched pump power, and the maximum output power was 1.97 W. Pre and post output laser power ratio was ～10. This fiber laser was compared with other three biconical tapered fiber lasers (the same fiber with different tapers) and a uniform geometry fiber laser. With intracavity biconical tapers, fiber lasers’ thresholds were ～1 W higher than the fiber laser without the taper (1.97 W). The pump end’s slope efficiencies of fiber lasers with tapers were 3–5% in contrast with 37.6% of the uniform one. After tapered, the pre and post laser power ratios were much higher than the un-tapered one’s, but not changed much with the launched pump power.     

Power scaling of a side-pumped Nd:YLF laser based on DBMC technology

This work demonstrates the power scalability of double-beam-mode controlling, a technique that has generated the highest optical efficiency reported so far for Nd:YLF lasers. We analyze two types of power scaling possibilities by numerical simulations: multiplication of intracavity pump modules and MOPA configuration. About 44 W of TEM₀₀ output power at 1053 nm was experimentally demonstrated with a beam-parameter product of 1.07 × 1.15. The results show great ease of power scaling without sacrificing beam quality.     

Wavelength stabilization of extended-cavity tapered lasers with volume Bragg gratings

The wavelength stabilization of high-brightness extended-cavity lasers at 810-nm by the use of volume Bragg gratings is described. Narrow linewidth (<?20 pm), high power (2.5 W) and good beam quality (M²<4) operation has been obtained in a robust and simple design. The impact of the beam focusing into the Bragg grating on the external cavity performance has been theoretically and experimentally investigated. Finally, second-harmonic generation of the infrared beam has been obtained in a ppKTP crystal, demonstrating a non-linear conversion efficiency of 0.8%/W and up to 8 mW at 405 nm.     

850nm高亮度锥形半导体激光器的光电特性

采用激射波长为850 rm的AlGaInAs/AlGaAs梯度折射率波导分别限制增益量子阱结构的外延片,设计并制备了具有条形结构和锥形结构的半导体激光器.在输出功率同为1 W时,锥形激光器的发散角、光束传播因子和亮度分别为4°、2.8和9.9 MW·cm-2·sr-1,远好于条形激光器的6°、9.2和3.0 MW·cm...     

Si homojunction structured near-infrared laser based on a phonon-assisted process

We fabricated several near-infrared Si laser devices (wavelength ～1300 nm) showing continuous-wave oscillation at room temperature by using a phonon-assisted process induced by dressed photons. Their optical resonators were formed of ridge waveguides with a width of 10 μm and a thickness of 2 μm, with two cleaved facets, and the resonator lengths were 250–1000 μm. The oscillation threshold currents of these Si lasers were 50–60 mA. From near-field and far-field images of the optical radiation pattern, we observed the high directivity which is characteristic of a laser beam. Typical values of the threshold current density for laser oscillation, the ratio of powers in the TE polarization and TM polarization during oscillation, the optical output power at a current of 60 mA, and the external differential quantum efficiency were 1.1–2.0 kA/cm², 8:1, 50 μW, and 1 %, respectively.     

High power single-sided Bragg reflection waveguide lasers with dual-lobed far field

We report on 980-nm InGaAs/GaAs lasers with dual-lobed far field based on a single-sided Bragg reflection waveguide (BRW). The high slope efficiency ～0.92 W/A and a continuous wave (CW) output power >1.5 W (3.2 W pulsed) have been obtained. The threshold current density is as low as 253 A/cm² for a 1.5-mm-long device and the transparency current density is only 140 A/cm². The further analysis shows the intrinsic reason for the single-lobed or the dual-lobed far-field distribution is determined by the mode shape in the cavity, not the single-sided or dual-sided BRW structure. The condition to achieve a narrow single-lobed far-field distribution is discussed.     

High Performance AlGaAs Quantum Well Lasers with Low Beam Divergence Grown by Molecular Beam Epitaxy

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Diode-end-pumped passively mode-locked Nd:LuVO4 laser with a semiconductor saturable-absorber mirror

A diode pumped passively mode-locked Nd:LuVO₄ laser with a semiconductor saturable-absorber mirror (SESAM) is demonstrated. The mode-locked pulses have a pulse duration of about 8.8 ps and a repetition rate of 157 MHz. Under an absorbed pump power of 12 W a maximum output power of 3.71 W is obtained, which gives an optical conversion efficiency of 31%. Our results show that Nd:LuVO₄ is a promising gain medium for the high power mode-locked solid-state lasers.     

High average power generation in barium nitrate Raman laser

The generation of low divergent (M ²≤1.5) first and third Stokes radiation in a barium nitrate Raman laser with average powers of 11 W and 5 W, respectively, was demonstrated. The quantum conversion efficiency was up to 21%. The possibility of thermal lens compensation in such Raman lasers was shown.     

Highly efficient continuous-wave composite Nd:YAG laser at 1,112 nm under diode pumping directly into the emitting level

We present an efficient, high-brightness laser at 1,112 nm by combining the direct pumping technique with an 885 nm laser diode and the composite crystal. Output power as high as 12.8 W at 1,112 nm is achieved under 22.2 W of absorbed pump power and it yields an optical-to-optical efficiency of 57.7 % and a slope efficiency of 64.0 % with respect to the absorbed pump power. To the best of our knowledge, both of these optical-to-optical and slope efficiencies with respect to the absorbed pump power are the highest values ever reported for 1,112 nm Nd:YAG lasers. Modeling of the temperature rise and stress induced in the laser crystals, with and without the undoped cap, and employing the pump at 808 and 885 nm are performed, respectively. Contributions of the composite crystal geometry and of the pump at 885 nm to lowering the threshold power, enhancing the optical-to-optical and the slope efficiencies with respect to the absorbed pump power are discussed, respectively.     

Tapered diode lasers and laser modules near 635nm with efficient fiber coupling for flying-spot display applications

Flying-spot displays require light sources in the red, green and blue with a high optical output power and nearly diffraction limited beams. In this paper we present experimental results of red-emitting, AlGaInP based, tapered diode lasers and their integration into diode laser modules. The laser modules emit a collimated, almost diffraction limited beam with an optical output power as high as 1W at a wavelength close to 635 nm. The tapered laser chips were designed with emphasis on achieving a good beam quality in vertical and lateral directions of a collimated beam. To test the suitability for flying-spot display applications, we performed fiber coupling experiments with a low mode number optical fiber with an etendue as low as 6 × 10^?6 mm² sr. A maximum transmission of 70% of the launched power behind the uncoated fiber as well as a usable power in excess of 580mW were measured.     

An Ho:YAG Laser with Double-Pass Pumping and the ZnGeP2 OPO Pumped by the Ho:YAG Laser

We report an efficient Ho:YAG laser end pumped by Tm:YLF lasers with double-pass pumping. We achieve the maximum continuous wave (CW) output power of 46.0 W with a single-pass pumping and 50.2 W with a double-pass pumping, corresponding to a slope efficiency of 58.0% and 62.8%, respectively. In addition, we use the Ho:YAG laser as a pumping source of the ZnGeP₃ optical parametric oscillator (OPO) and obtain the maximum average output power of 14.2 W with a linear cavity and 17.0 W with a ring resonator, respectively.     

Stable MHz-repetition-rate passively Q-switched microchip laser frequency doubled by MgO:PPLN

We present an Nd³⁺:YVO₄ microchip laser that is passively Q-switched by a semiconductor saturable absorber mirror. The system generates 520 ps pulses at 1064 nm with 340 mW average output power at up to 2.3 MHz repetition rate. Single longitudinal and transverse mode operation with a peak-to-peak timing jitter less than 1 % is achieved. We discuss the influence of different setup parameters by using numerical simulations of the coupled rate equations and FEM simulations of the thermal management. The infrared light was frequency doubled in an MgO:PPLN crystal with up to 75 % conversion efficiency, which to our knowledge is the highest conversion efficiency that was ever achieved with passively Q-switched microchip lasers.     

Efficiency improvement of multimode Tm3+ doped double cladding silica fiber laser by in-line biconical tapers

Efficiencies improvement of LD (laser diode) pumped multimode large mode area (LMA) Tm³⁺ doped double cladding silica fiber lasers with different in-line biconial tapers were reported. Two types of multimode Tm³⁺ doped fiber were used in this experiment. Each type of fiber was made into three fiber lasers, a uniform geometry fiber laser and two tapered fiber lasers with different taper parameters. Biconical tapers located several centimeters from the output end of the multimode fiber lasers were made by heating and stretching method. Although the threshold of the best tapered fiber laser was added 200 mW, the slope efficiency (25.3%) and the maximum output power (1.31 W) of the fiber laser increased by 10.3% and 350 mW respectively, in comparison with the un-tapered one. Pre and post output laser power ratio was 6.3–15.6. Simultaneously, the laser spectrum moved to shorter wavelengths. The same trends of these characteristics were also observed in the other three tapered fiber lasers.