Ho:YAG laser pumped by 1.9-μm diode lasers

A 21-μm Ho:YAG laser end pumped by 1.9-μm diode lasers has generated nearly 0.7-W CW output power. Laser operation was maintained even with Ho:YAG heat sink temperatures in excess of 60°C     

Effects of internal loss on power efficiency of mid-infraredInAs-GaInSb-AlSb quantum-well lasers and comparison with InAsSb lasers

Experimental studies of the lasing efficiency of optically pumped 4-μm GaInSb-InAs-AlSb multiple-quantum-well (MQW) lasers that emitted >1-W peak power/facet at 80 K indicated that internal loss is the main factor that limits the power output. The internal loss coefficient and internal quantum efficiency were determined by measuring the lasing efficiency versus temperature for devices of different facet reflectivities and lengths. The internal loss coefficient was found to increase from ~18 cm^-1 near 70 K to ~60-100 cm^-1 near 180 K, while the internal quantum efficiency remained constant at ~47% (or ~67% with the correction for the finite absorption of the active region) from 70 to 130 K. The increase of internal loss and the decrease of external quantum efficiency versus temperature were found very similar to those of double-heterostructure InAsSb-GaSb lasers and were similarly interpreted in terms of intervalence band carrier absorption. Extrapolation of power performance for improved devices with lower internal loss indicated that high-efficiency multi-watt quasi-CW output with a broad-area brightness of ~1 MW/cm².sterad is possible     

High-power 2.0 μm InGaAsP laser diodes

Data detailing the performance of strained-layer InGaAs/InGaAsP double-quantum-well laser diodes operating at 2.0 μm are presented. The total external efficiency and maximum power achieved are 55% and 1.6-W continuous wave (CW), respectively, from a 200-μm gain-guided laser diode. Measurements on gain-guided broad area devices yield an internal efficiency of 0.73 with a distributed loss coefficient, α, of 7.5 cm^-1. The measured threshold current density is 300 A/cm² for a 2-mm-long broad area device operated CW at 25°C     

Picosecond laser diode pulse amplification up to 12 W by laserdiode pumped erbium-doped fiber

Intense picosecond optical pulse generation from a gain-switched laser diode (LD) was demonstrated using a 1.48-μm LD-pumped Er³⁺ -doped fiber laser amplifier. Saturation characteristics of the amplifier output power were also measured as a function of input repetition frequency. An amplified peak power of 12 W and 105-pJ pulse energy were obtained for 9-ps pulses at a 33-GHz repetition frequency. This is the highest peak power yet demonstrated in pulse generation employing all-laser diodes as active devices     

The route toward a diode-pumped 1-W erbium 3-μm fiber laser

A rate-equation analysis of the erbium 3-μm ZBLAN fiber laser is performed. The computer calculation includes the longitudinal spatial resolution of the host material. It considers ground-state bleaching, excited-state absorption (ESA), interionic processes, lifetime quenching by co-doping, and stimulated emission at 2.7 μm and 850 mn. State-of-the-art technology including double-clad diode pumping is assumed in the calculation. Pump ESA is identified as the major problem of this laser. With high Er³⁺ concentration, suitable Pr³⁺ co-doping, and low pump density, ESA is avoided and a diode-pumped erbium 3-μm ZBLAN laser is predicted which is capable of emitting a transversely single-mode output power of 1.0 W when pumped with 7-W incident power at 800 nm. The corresponding output intensity which is relevant for surgical applications will be in the range of 1.8 MW/cm². Compared to Ti:sapphire-pumped cascade-lasing regimes, the proposed approach represents a strong decrease of the requirements on mirror coatings, cavity alignment, and especially pump intensity. Of the possible drawbacks investigated in the simulation, only insufficient lifetime quenching is found to have a significant influence on laser performance     

Efficient Nd:YAG slab longitudinally pumped by diode lasers

An efficient scalable 1.06-μm continuous-wave (CW) Nd:YAG slab laser longitudinally pumped by diode lasers is discussed. The 809-nm diode radiation is focused into every laser channel emerging from the reflection points of the 1.06-μm beam on the coated slab surfaces. A maximum CW TEM₀₀ output power of 675 mW has been obtained at a diode pump power of 2 W resulting in a slope efficiency of 40%     

Diode-array pumping of Er3+/Yb3+ Co-dopedfiber lasers and amplifiers

Single-mode double-clad Er³⁺/Yb³⁺ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 μm and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported     

Time-resolved spectroscopic study of high-pressure self-sustaineddischarge-pumped atomic xenon lasers

To explore the lasing kinetics of UV-preionized, self-sustained discharge-pumped atomic xenon (5d→6p) lasers, the time-resolved spectroscopy of the laser output from the multiline laser resonator is reported. The dilutents used were Ar and He. Increasing Xe concentration shortened the 1.73-μm laser pulse duration and decreased the total (multiline) laser output energy, because increased Xe metastable state population contributes to the increase of the 6p state population (lower laser level) by electron-impact excitation and radiation trapping during discharge pumping. High-excitation-rate pumping resulted in the decrease of the laser output power of 1.73- and 2.63-μm lines. Increasing the total gas pressure leads to high-efficiency operation due to modest-excitation-rate pumping at high pressures     

Output characteristics of Nd:GdVO4 crystals laser with dual c-axis orthogonal gains end-pumped by two fiber- coupled diode lasers

The output characteristics of neodymium-doped gadolinium vanadate (Nd:GdVO4) crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers are investigated. With two 1 W semiconductor diode lasers pumping, the output power of TEM00 laser is 920 mW, and the optical conversion efficiency is close to 46%. By changing the relative orientations of both Nd:GdVO4 crystals, the polarization characteristics of laser are varied. In particular, by keeping the c-axes of two Nd:GdVO4 crystals orthogonal to each other and adjusting two diode pump lasers to operate at the same power level, the completely unpolarized light is obtained.     

500 kHz波长锁定878.6 nm LD双端泵浦Nd:YVO4声光调Q激光器

报道了一种由波长锁定878.6 nm LD双端抽运Nd:YVO4声光调Q激光器,重复频率在500 kHz时具有稳定的1 064 nm脉冲激光输出。在重频为100 kHz,晶体吸收功率58 W时,获得18.2 W的1 064 nm激光输出,光-光转换效率为31.3%,脉宽为15.2 ns;在重频为500 kHz、晶体吸收功率58 W时,获得26.1 W的1 064 nm激光输出,光-光转换效率为45%,脉宽为44.2 ns,重频在100~500 kHz下具有稳定的脉冲输出,光束质量较传统模式下有明显提高,并且转换效率也有提升。实验表明:利用波长锁定878.6 nm激光二极管直接泵浦的方式,有利于降低晶体热效应、提高光束质量,提高光-光转换效率,获得窄脉宽的脉冲激光输出,并且在一定的温度变化范围内具有极好的温度稳定性。     

激光二极管千赫兹级Nd:YVO4皮秒脉冲激光再生放大器

采用光纤耦合激光二极管端面抽运Nd:YVO4激光晶体,抽运光平均功率为20W,脉冲宽度为100μs,获得了重复频率为1 kHz、平均功率为1.5 W的再生皮秒脉冲激光输出,脉冲宽度约为15 ps,两个方向上的光束质量因子均小于1.4。     

激光二极管抽运Tm:YAP晶体实验研究

简要阐述2 μm激光光源的广泛应用需求,分析掺铥铝酸钇(Tm:YAP)晶体的能级结构和吸收光谱特性,报道了采用激光二极管(LD)端面抽运Tm:YAP晶体的方式,实现室温下2 μm激光的高效输出。在激光二极管输出功率为19 W时, 2 μm连续激光输出功率为6.5 W,光光转换效率达34％,斜率效率为47.5％。经过声光(AO)Q开关进行调制后,在重复频率10 kHz下,获得5.4 W的动态激光输出,激光单脉冲宽度为70 ns,激光二极管输出功率到2 μm激光动态输出功率的转换效率为28％,斜率效率为42％。通过实验验证了激光二极管端面抽运Tm:YAP晶体在室温下高效输出的特性。     

2μmTm,Ho∶YLF激光抽运ZnGeP_2光参量振荡技术研究

ZnGeP2晶体具有宽的透明范围(0.7～12μm),较大的非线性系数(d36=75pm/V),最高损伤阈值能量密 度为10J/cm2,较高的热导率(0.18W/(m·K)),因而非常适合作为高功率中红外光参量振荡器(OPO)晶体。理 论上分析了ZnGeP2光参量振荡器相位匹配特性,实现3～5μm连续调谐范围输出的Ⅰ类相位匹配角在52.5～ 55.2°之间。实验上,以15W光纤耦合激光二极管(LD)抽运的2.05μm高重复频率声光调QTm,Ho∶YLF激光 器作为抽运源,其最大平均功率4W,脉冲宽度小于40ns,脉冲重复频率100Hz～10kHz可调。为降低准三能级 系统激光器阈值,提高激光脉冲能量抽取效率,Tm,Ho∶YLF晶体采用液氮制冷方式,工作在77K温度条件下。 非线性频率转换晶体ZnGeP2长15mm,55.7°切割,光参量振荡器谐振腔为平平腔,腔长约20mm。在3.6W的抽 运功率下,脉冲重复频率10kHz,实现了4.1μm附近中红外激光输出,参量光脉冲宽度为20ns,平均输出功率为 0.7W,光 光转换效率为20%,抽运光阈值功率为0.65W。     

High-power high-efficiency 0.98-μm wavelengthInGaAs-(In)GaAs(P)-InGaP broadened waveguide lasers grown by gas-sourcemolecular beam epitaxy

We describe the design and experimental results for high-power, high-efficiency, low threshold current, 0.98-μm wavelength, broadened waveguide (BW) aluminum-free InGaAs-(In)GaAs(P)-InGaP lasers. The decrease in the internal losses with an increase in the width of the waveguide layer for a separate-confinement heterostructure multiple-quantum-well (SCW-MQW) structure is attributed to lower free-carrier absorption due to the reduced overlap of the optical mode with the highly doped cladding regions. The BW lasers grown with both InGaAsP and GaAs waveguides show lower internal losses and similar threshold currents than those designed for an optimum optical confinement factor within the QW region. We report a record-low internal loss of 1.8±0.2 cm^-2 for (In)GaAs(P)-InGaP lasers grown by gas-source molecular beam epitaxy (GSMBE). The temperature dependence of internal loss suggests that optical loss from free-carrier absorption in the waveguide dominates at T>40°C, while near room temperature, the residual loss is attributed to scattering and free-carrier absorption in the QW's. The relative insensitivity of internal loss near room temperature has enabled the use of a simplified InGaAs-GaAs-InGaP BW structure to achieve very high CW and quasi-CW (QCW) power operation. We report the highest CW output power of 6.8 W for a GaAs-InGaP laser, and the highest quasi-continuous output power of 13.3 W measured for a single 100-μm-wide aperture, 0.8-0.98-μm wavelength Al-free laser diode grown by GSMBE     

激光二极管抽运Nd∶GdVO_4微片激光器

报道了一种新型激光二极管(LD)端面抽运Nd∶GdVO4微片激光器,测量了抽运输入功率与激光输出功率的关系,激光阈值功率为83 mW,在2 W的抽运功率下得到860 mW的1.064μm基横模连续激光输出,光-光转换效率为43%,最大斜度效率达到47%。     

LD抽运声光调Q高重复频率短脉宽Nd:YVO4激光器

报道了利用半导体激光器(LD)抽运Nd:YVO4晶体,采用声光调Q,输出1064 nm高重复频率短脉冲的固体激光器.在重复频率为70 kHz时,获得的最大平均输出功率为6.45 W,光-光转换效率为34.9%,斜效率为37.3%;在相同的重复频率下还获得了最短脉冲宽度7.9 ns.在重复频率为10 kHz时获得最大单脉冲能量为213 μJ,峰值功率为11.8 kW.     

1.9-W quasi-CW from a near-diffraction-limited 1.55-μmInGaAsP-InP tapered laser

1.9-W quasi-CW output power with about 80% of the power in the central lobe is obtained from a 1.55-μm wavelength InGaAsP-InP MQW tapered unstable resonator laser. This power is found to be emitted in a near-diffraction-limited beam     

Self-aligned InGaP/GaAs heterojunction bipolar transistors formicrowave power application

As an alternative to AlGaAs/GaAs heterojunction bipolar transistors (HBTs) for microwave applications, InGaP/GaAs HBTs with carbon-doped base layers grown by metal organic molecular beam epitaxy (MOMBE) with excellent DC, RF, and microwave performance are demonstrated. As previously reported, with a 700-Å-thick base layer (135-Ω/sq sheet resistance), a DC current gain of 25, and cutoff frequency and maximum frequency of oscillation above 70 GHz were measured for a 2-μm×5-μm emitter area device. A device with 12 cells, each consisting of a 2-μm×15-μm emitter area device for a total emitter area of 360 μm², was power tested at 4 GHz under continuous-wave (CW) bias condition. The device delivered 0.6-W output power with 13-dB linear gain and a power-added efficiency of 50%     

Noise characteristics of Er3+-doped fiber amplifierspumped by 0.98 and 1.48 μm laser diodes

Measured noise characteristics of Er³⁺-doped optical fiber amplifiers pumped by 0.98- and 1.48-μm laser diodes (LDs) are reported. The noise figures estimated from the beat noise between signal and spontaneous emission are 3.2 dB for pumping by 0.98-μm LD and 4.1 dB for pumping by 1.48-μm LD. The beat noise between spontaneous emission components and the spontaneous shot noise for the 0.98-μm pumping are lower than those for the 1.48-μm pumping     

Highly nondegenerate four-wave mixing among subpicosecond opticalpulses in a semiconductor optical amplifier

We have demonstrated, for the first time, the highly nondegenerate four-wave mixing (FWM) among subpicosecond optical pulses in a 1.3-μm multiple-quantum-well (MQW) semiconductor optical amplifier (SOA). We could directly measure the FWM signal in the output spectrum by current pulse pumping of the device. We achieved a high conversion efficiency of over 10% at a frequency conversion range of less than 1 THz. The limitation of conversion efficiency due to the gain saturation of the SOA was effectively overcome by using the short optical pulses