Design of wide-emitter single-mode laser diodes

An accurate laser simulator is developed to investigate the influences of various device parameters on modal discrimination and beam quality to optimize the brightness of semiconductor lasers. Previous work using the Prony method is extended, both by using a more robust laser simulator to solve for the optical fields and by extending the Prony method to operating conditions above threshold. The semiconductor laser model is used to investigate the effects of various device parameters on the characteristics of a gain-guided 980-nm Al-free stripe geometry laser. The device parameters investigated are the device geometry, the thickness and doping level of the waveguiding layer and the front facet reflectivity. Together with practical and economic considerations, the device parameters of a wide emitter gain-guided laser are optimized. The optimized gain-guided laser is predicted to operate in the fundamental mode up to 1.15 W. At this maximum fundamental mode power, the slow axis beam divergence at 1/e/sup 2/ points is 5.4/spl deg/, the beam quality factor M/sup 2/ is 1.62, the astigmatism is 27 /spl mu/m, and the brightness is 61 MW/cm/sup 2/sr.     

利用GaAs作为饱和吸收体的被动调Q光子晶体光纤激光器

利用GaAs晶体作为可饱和吸收体, 实现了掺镱光子晶体光纤激光器的被动调Q输出。实验用掺杂光子晶体光纤的芯径为21 μm, 数值孔径为0.04, 在实现了大模场面积的同时, 保证了激光器的单模运转, 从而得到高光束质量的激光输出。实验使用高功率半导体激光器作为抽运源, 采用自行研制的耦合系统将抽运光耦合进入光子晶体光纤的包层中。在激光器平均输出功率为5.8 W时, 实验得到的最短输出激光脉冲为80 ns, 重复频率为6.7 kHz。     

High-power, high-brightness, mJ Q-switched ytterbium-doped fibre laser

A simple diode-pumped, Q-switched fibre laser is reported based on large mode area ytterbium-doped fibre capable of producing pulses with a high beam quality (M/sup 2/=1.1), a duration of /spl sim/40 ns and energies as high as 1.2 mJ at a repetition rate of 10 kHz. This combination of desirable beam qualities makes the source attractive for a range of industrial applications currently serviced by conventional bulk crystal/glass based Q-switched laser systems.     

InP-based optically pumped VECSEL operating CW at 1550 nm

We present a vertical external-cavity surface-emitting laser operating at 1550 nm. The laser comprises an InGaAsP-based gain element, with a resonant periodic gain structure on top of a distributed Bragg reflector, and a high reflectivity spherical mirror as the external reflector. Optical pumping is achieved using a 1250-nm fiber Raman laser. A maximum continuous output power of 70 mW was obtained under multitransverse mode operation at 233 K. Under single-mode operation, we obtained a maximum power of 60 mW with a beam quality factor M/sup 2/ less than 1.1.     

High-power nearly diffraction-limited AlGaAs-InGaAs semiconductor slab-coupled optical waveguide laser

Beam-quality measurements on the output of a 915-nm AlGaAs-InGaAs-GaAs slab-coupled optical waveguide laser (SCOWL) are reported. This device had a nearly circular mode (3.8 /spl mu/m by 3.4 /spl mu/m 1/e/sup 2/ widths in the near-field) and was capable of a single-ended continuous-wave output power of greater than 1 W. Measurements of M/sup 2/ indicate that the SCOWL output beam is nearly diffraction-limited in both directions with M/sub x//sup 2/ /spl sim/ M/sub y//sup 2/ /spl sim/ 1.1 over the entire range of output powers measured.     

Compact hybrid master oscillator power amplifier with 3.1-W CW output power at wavelengths around 1061 nm

A hybrid master oscillator power amplifier (MOPA) laser source has been realized by coupling a single-mode three-section distributed Bragg reflector (DBR) laser as master oscillator and a tapered power amplifier with a single lens only. A maximum continuous-wave optical output power of 3.1 W was achieved. The emission spectrum was completely determined by the DBR laser. Single longitudinal mode operation at a wavelength of /spl lambda/=1061 nm was maintained over the whole power range. Up to an output power of 1.8 W, the beam propagation factor M/sup 2/was less than 1.6.     

4 W single-transverse mode VECSEL utilising intra-cavity diamond heat spreader

An optically pumped semiconductor vertical external cavity surface emitting laser, with high output power and excellent beam quality operating at a wavelength near 1.05 /spl mu/m, is reported. A transparent diamond heat spreader was used for thermal management of the laser. The gain structure grown by molecular beam epitaxy includes 13 compressively strained InGaAs quantum wells. Maximum output power of 4 W with diffraction-limited beam (M/sup 2//spl les/1.15) was achieved using a 2% output coupler and incident pump power of 20 W. It is shown that power scalability is feasible with the presented laser geometry.     

A single transverse-mode monolithically integrated long vertical-cavity surface-emitting laser

We present a fully monolithic long vertical-cavity surface-emitting laser operating in the fundamental TEM/sub 00/ transverse mode with output powers up to 7.8 mW. The lasing wavelength is 980 nm and the threshold is 9.1 mA. Pump currents from threshold to rollover produce an output beam with an M/sup 2/<1.08. The laser consists of an InGaAs-GaAs-AlGaAs gain region/semiconductor mirror bonded to a 0.5-mm-thick glass substrate with an integrated curved mirror.     

High-power optically pumped 1550-nm VECSEL with a bonded silicon heat spreader

We present an optically pumped 1550-nm vertical-external-cavity surface-emitting laser with improved output power and operating temperature using a bonded heat spreader. The laser comprises an InGaAsP-based gain element, with a resonant periodic gain structure on top of a distributed Bragg reflector, and a high reflectivity spherical mirror as the external reflector. Heat transport is enhanced by a Si heat spreader bonded to the InGaAsP surface by liquid capillary bonding. Optical pumping is achieved using a 1250-nm fiber Raman laser. A maximum continuous output power of 250 mW was obtained under multitransverse mode operation at 240 K. Under operation in the fundamental near-Gaussian mode, we obtained a maximum power of 230 mW with a beam quality factor (M/sup 2/) of 1.22. At room temperature, the output power was limited to 12 mW.     

Power scaling of 2 /spl mu/m ytterbium-sensitised thulium-doped silica fibre laser diode-pumped at 975 nm

An ytterbium-sensitised thulium-doped silica fibre laser that generates up to 75 W of output power in the 2 /spl mu/m wavelength range when cladding-pumped by a 975 nm diode stack is reported. The slope efficiency is 32% with respect to the launched pump power and the beam quality factor (M/sup 2/) is 1.3.     

High-power 808-nm tapered diode lasers with nearly diffraction-limited beam quality of M/sup 2/=1.9 at P=4.4 W

High-power 808-nm tapered diode lasers mounted as single emitters with very good brightness were manufactured and analyzed. The beam propagation ratio M/sup 2/ is 1.9 at 4.4 W; a very low beam propagation ratio M/sup 2/ of 1.3 is achieved at 3.9 W. At 808 nm, the high brightness of 460 MW/spl middot/cm/sup -2/ sr/sup -1/ never reported before is a step forward toward new applications of tapered diode lasers.     

High-performance singlemode InGaNAs/GaAs laser

Performance characteristics of an InGaNAs/GaAs ridge-waveguide in-plane laser diode, which is grown by molecular beam epitaxy, are reported. The laser emits at a wavelength of 1.262 /spl mu/m in a single lateral mode, launching an output up to 240 mW at 20/spl deg/C and 20 mW at 120/spl deg/C. The threshold is 15 mA at 20/spl deg/C, corresponding to a threshold current density of 313 A/cm/sup 2/.     

Ytterbium-doped large-core fibre laser with 610 W of near diffraction-limited output power

A cladding-pumped ytterbium-doped fibre laser, generating up to 610 W of continuous-wave output power at 1.1 /spl mu/m with slope efficiency of 80% and near diffraction-limited beam quality (M/sup 2/=1.3) is reported. No undesirable roll-over was observed in output power with increasing pump power.     

可用于高功率脉冲激光的面阵CCD模式测量装置

本文介绍了一种用面阵ＣＣＤ摄像机作探测器的激光光束测量装置。整个装置包括光束衰减器、单脉冲选取及脉冲同步、光束直径匹配、ＣＣＤ摄像机、图像卡、计算机及监示器以及系统软件。软件根据激光混合模的二阶矩阵理论［１］编制，可测量高功率、高重复频率脉冲激光的空间能量分布，并可对所测结果进行模拟。由软件给出所测的光束参数，可对光束质量作出正确评价。     

GaInAsN/GaAs quantum dot laser diodes operating in 1.36 /spl mu/m wavelength range

For the first time, a pseudomorphic GaInAsN DWELL laser with laser emission at 1.36 /spl mu/m and a low transparency current density (206 A/cm/sup 2/) grown by molecular beam epitaxy is reported. The GaInAsN DWELL laser shows a redshift in comparison to an N-free GaInAs DWELL laser of about 90 nm and a transparency current density of 35 A/cm/sup 2/ per single QD layer.     

Ytterbium-doped large-core fibre laser with 272 W output power

A highly efficient cladding-pumped Yb-doped large-core fibre laser, generating up to 272 W of continuous-wave output power at 1.08 /spl mu/m with a beam quality (M/sup 2/) of 3.2, is reported. The slope efficiency was 83% with respect to the launched pump power. No saturation (roll-off) was observed in output power with increasing pump power.     

Ytterbium-doped large-core fibre laser with 1 kW of continuous-wave output power

A ytterbium-doped fibre laser with up to 1 kW of continuous-wave output power at 1.09 /spl mu/m with a slope efficiency of 80% and a good beam quality (M/sup 2/=3.4) is reported. The fibre was pumped by two diode-stack sources launched through opposite ends. No undesirable roll-over was observed in output power with increasing pump power.     

光纤弯曲对掺镱光纤激光器光束质量的影响

通过改变F-P腔全光纤激光器中的光纤盘绕半径,对输出激光光束质量进行了研究.搭建了百瓦级全光纤激光器.最大泵浦功率为436 W的条件下,获得了300 W波长1 080 nm的激光输出.光束质量M2=1.13.光-光转换效率为69%.理论分析并计算了20/400 m大模场面积双包层光纤中的两种导波模式LP01模和LP11模沿光纤径向的功率分布和弯曲损耗;利用光纤弯曲选模方法,实验上探究了光纤弯曲半径对输出激光模式及光束质量的影响.实验发现,通过光纤弯曲方式可以有效地消除高阶模式,再经过包层光剥除可以获得更好的光束质量M2=1.06.     

1 W high brightness index guided tapered laser at 980 nm using Al-free active region materials

Index guided tapered laser diodes at 0.98 /spl mu/m have been optimised for high brightness. We demonstrate an index guided tapered laser using an Al-free active region with an optical power of 1 W at 20/spl deg/C under continuous-wave operation. The parallel beam quality parameter M/sup 2/ of these devices has been measured to be less than 3 at 1 W at 980 nm.     

Performance of Ar/sup +/-milled Ti:sapphire rib waveguides as single transverse-mode broadband fluorescence sources

Rib waveguides have been fabricated in pulsed-laser-deposited Ti:sapphire layers using photolithographic patterning and subsequent Ar/sup +/-beam milling. Fluorescence output powers up to 300 /spl mu/W have been observed from the ribs following excitation by a 3-W multiline argon laser. Mode intensity profiles show high optical confinement and the measured beam propagation factors M/sub x//sup 2/ and M/sub y//sup 2/ of 1.12 and 1.16, respectively, indicate single transverse-mode fluorescence emission. Loss measurements using the self-pumped phase conjugation technique have yielded comparable values (1.7 dB/cm) for the ribs and the unstructured planar waveguide counterparts. The combination of optimum modal properties and strong optical confinement, together with sufficient levels of fluorescence output, make the single-moded Ti:sapphire rib waveguides a very interesting candidate as a fluorescence source for optical coherence tomography applications.