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.     

Low threshold current CW operation of GaInAsP/InP buried heterostructure distributed Bragg-reflector integrated-twin-guide laser emitting at 1.5?1.6 ?m

Low threshold current CW operation of a 1.5?1.6 ?m-wavelength GaInAsP/InP buried heterostructure distributed Bragg reflector integrated twin guide (BH-DBR-ITG) laser was obtained up to 12°C. Single wavelength operation was obtained at a temperature range of 25 deg. The temperature dependence of lasing wavelength was 0.10 nm/deg. At 248 K, the threshold current, the differential quantum efficiency and the maximum output power were 37 mA, 16.3%/facet and 6 mW, respectively.     

A high-efficiency vertical-cavity surface-emitting switching laserfabricated with post-growth cavity mode positioning

The first room-temperature continuous-wave (CW) operation of the double heterostructure optoelectronic switching laser implemented as a vertical-cavity laser is described. A deposited dielectric top reflector of SiO₂/TiO₂ allowed the use of a cavity etch back technique after the sample was grown, to position the cavity mode at the desired wavelength. Room temperature CW threshold currents as low as 4.8 mA for a 14-μm-diameter device were obtained with slope efficiencies of 0.45 mW/mA. The maximum CW output power was 2.5 mW and the resistivity was 4×10^-4 Ωcm²     

A Four‐Channel Laser Array with Four 10 Gbps Monolithic EAMs Each Integrated with a DBR Laser

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non‐return to zero operation with 12 dB extinction ratio is obtained. A four‐channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.     

Analysis of a 1060-nm Nd:SiO2 superfluorescent fiberlaser

This CW source is made of a single-mode Nd-doped silica fiber end-pumped near 830 nm by a dye laser, with a thin high reflector placed against its input end for enhanced conversion. At the maximum output power of 13 mW, obtained with a pump power of 75 mW, the emission linewidth is still as broad as 16 nm, and the pump-to-signal conversion efficiency approaches the quantum limit of 78%. A simple model of superfluorescence in fibers, which relates the source emission characteristics to the fiber single-pass gain, is also presented. The single-pass gain, measured to be 0.27 dB/mW, was used to fit the model to the data. A good agreement is found for the nonlinear output versus input power curves of the sources, but it appears that the emission linewidth does not narrow with increasing pump power as fast as expected. Based on these results and an existing model of gain in single-mode fibers, it is suggested that simple improvements in the fiber design may reduce the pump requirement of this source and make laser-diode pumping possible     

Long-wavelength monolithic GaInNAs vertical-cavity optical amplifiers

We report on the continuous-wave amplification characteristics of an optically pumped 1.3-/spl mu/m multiple-quantum-well GaInNAs-GaAs vertical-cavity semiconductor optical amplifier (VCSOA). The VCSOA structure was monolithically grown by molecular beam epitaxy and operated in reflection mode in a fiber-coupled system. The maximum on-chip gain attained, limited by the onset of laser action, was 15.6 dB at 196 mW of 980-nm pump power. For a chip gain of 10.4 dB, the optical bandwidth was 10.8 GHz and the saturation output power was -9 dBm. By varying the pump laser power, a maximum extinction ratio of 22.3 dB was obtained. Temperature-controlled tuneable operation of the device is also presented and demonstration of 9 dB of chip gain obtained over 9.5 nm with an optical bandwidth of 12 GHz is reported.     

Widely tunable high-power external cavity quantum cascade laser operating in continuous-wave at room temperature

A grating-coupled external cavity quantum cascade laser operating in continuous-wave at room temperature is reported. Single-frequency operation tunable over more than 160 cm^-1 around the centre wavelength of 4.6 mum has been observed at a chip temperature of 300 K. The maximum optical power at the gain peak was 300 mW, corresponding to a wall-plug efficiency of 6 %. Observed power output at the gain bandwidth edges was in excess of 125 mW.     

CW operation of 1.5 ~ 1.6 ?m wavelength GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector

A 1.5 ~ 1.6 ?m GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was realised, for the first time, and CW operation was achieved up to 255 K. Single-wavelength operation was obtained at temperatures between 228 K and 245 K with the temperature dependence of lasing wavelength of 10 ?/deg. At 233 K, the threshold current, the output power and the differential quantum efficiency were 110 mA, 2.2 mW and 4.8%/facet, respectively.     

Internally folded Nd:YAG and Nd:YVO4 lasers pumped bylaser diodes

An efficient, scalable, diode-pumped Nd laser design is reported. The gain element can be longitudinally pumped along five separate axes and is relatively simple to fabricate. Both Nd:YAG and Nd:YVO₄ gain media were evaluated. Using five single-stripe laser diodes to pump the Nd:YAG, 3.94 W of absorbed power produced 2.1 W CW at 1.06 μm. The slope efficiency was 54 percent and the output was TEM₀₀. The threshold power was 40 mW. No evidence of thermal saturation was observed up to the maximum pump power. Repetitively Q-switched operation is also reported. The maximum output power for Nd:YVO₄ obtained with 2.9 W of pump power was 1.3 W. The slope efficiency was 47 percent     

Fabrication of wavelength-tunable butt-coupled sampled grating DBR lasers using planar buried heterostructure

Planar buried heterostructure (PBH) was adopted to fabricate a sampled grating distributed Bragg reflector laser diode (SGDBR-LD) having a low threshold current and a stable fundamental transverse mode. The etching process for butt-coupling was optimized to improve the reproducibility and the uniformity of the butt-coupled waveguide. The maximum output power of the fabricated SGDBR-LD was 20 mW at 200-mA continuous-wave operation at 25/spl deg/C. The output power was measured 10 and 9 mW higher than those of ridged waveguide (RWG) structure and buried ridge stripe (BRS), and the threshold current was slightly higher than those of RWG and BRS. The spectra of 25 channels spaced 50 GHz within the tuning range of 44.4 nm was obtained by a precise control of SG and phase control currents. The side-mode suppression ratio of more than 35 dB was obtained in the whole tuning range. The output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structure.     

Tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback laser

The fabrication of the first 1.55-/spl mu/m wavelength tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback laser is reported. A low-threshold and stable single-mode operation is obtained when the devices were uniformly pumped. A single-mode output power close to 10 mW from a single-mode fiber (40 mW in free space) is obtained with a 0 V bias to the modulator and an extinction ratio of up to 15 dB at 2.5 V. This single mode stability is due to the continuously distributed phase shift implemented in the structure. With a nonuniform injection, it was possible to select one particular mode out of the three neighboring modes inside the broad-reflection band of the reflector. A tuning range of 3.5 mm was obtained while maintaining an output power of more than 2 dBm from each mode.     

Analysis of gain improvements through a pump reflector in Er/sup 3+/-doped optical amplifiers in the presence of concentration quenching

We numerically examine the small-signal gain improvements possible when the pump light is reflected in erbium-doped amplifiers suffering from concentration quenching caused by homogeneous and inhomogeneous energy-transfer upconversion. For an unquenched amplifier, the improvement is larger for a pump power of 20 mW than it is at 100 mW. On the other hand, at a pump power of 100 mW, the reflector is found to be efficient for a quenched amplifier, with a maximum improvement of 6.5 dB. We also find that the reflector is more efficient at 1.535 /spl mu/m than it Is at 1.550 /spl mu/m, under all examined operating conditions.     

Laser-diode-pumped Cr:LiSrGaF6 laser

Diode-pumped operation of a Cr:LiSrGaF₆ laser is described. Efficient performance was obtained between 810 and 855 nm. The maximum output power was 130 mW at 810 nm, and the slope efficiency was 26%. The sample was pumped with a total incident power of 560 mW using two polarization-combined high-power visible laser diodes. These results represent the CW power reported for a diode-pumped Cr-doped laser     

High-Power Single Transverse Mode Vertical-Cavity Surface-Emitting Lasers With Monolithically Integrated Curved Dielectric Mirrors

We report the monolithic integration of vertical-cavity surface-emitting lasers (VCSELs) with curved dielectric mirrors. The laser structure has an InGaAs/GaAs gain region and incorporates a photoresist pattern fabricated on the substrate side. A dielectric distributed Bragg reflector is applied on the curved photoresist surface which provides sufficient optical feedback for laser operation. On-wafer measurements at room temperature show single transverse mode output powers up to 15.0 mW under continuous wave operation.      

Laser diode-pumped internally folded Nd:YAG laser

A diode-pumped Nd:YAG laser in which the gain element is fabricated in the shape of an isosceles right-angle prism is described. An orthogonal face forms the highly reflective end of the resonator, while the hypotenuse serves as an internal fold mirror. Scaling was demonstrated by pumping the gain element along three axes simultaneously. The maximum power obtained was 1.3 W at 1.06 μm and 128 mW at 532 nm. Repetitive Q-switched operation is also reported     

High-Performance Continuous-Wave Operation of $lambda sim {hbox {4.6}}~mu{hbox {m}}$ Quantum-Cascade Lasers Above Room Temperature

We report the high-performance continuous-wave (CW) operation of 10-mum-wide quantum-cascade lasers (QCLs) emitting at lambda ~ 4.6mum, based on the GaInAs-AlInAs material without regrowth, in epilayer-up and -down bonding configurations. The operational characteristics of QCLs such as the maximum average power, peak output power, CW output power, and maximum CW operating temperature are investigated, depending on cavity length. Also, important device parameters, i.e., the waveguide loss, the transparency current density, the modal gain, and the internal quantum efficiency, are calculated from length-dependent results. For a high-reflectivity (HR) coated 4-mm-long cavity with epilayer-up bonding, the highest maximum average output power of 633 mW is measured at 65% duty cycle, with 469 mW still observed at 100%. The laser exhibits the maximum wall-plug efficiencies of 8.6% and 3.1% at 298 K, in pulsed and CW operatons, respectively. From 298 to 393 K, the temperature dependent threshold current density in pulsed operation shows a high characteristic temperature of 200 K. The use of an epilayer-down bonding further improves the device performance. A CW output power of 685 mW at 288 K is achieved for the 4-mm-long cavity. At 298 K, the output power of 590 mW, threshold current density of 1.52 kA/cm², and maximum wall-plug efficiency of 3.73% are obtained under CW mode, operating up to 363 K (90degC). For HR coated 3-mm-long cavities, laser characteristics across the same processed wafer show a good uniformity across the area of 21 cm², giving similar output powers, threshold current densities, and emission wavelengths. The CW beam full-width at half-maximum of far-field patterns are 25deg and 46deg for the parallel and the perpendicular directions, respectively.     

A Distributed Bragg Reflector Silicon Evanescent Laser

We report a distributed Bragg reflector silicon evanescent laser operating continuous wave at 1596 nm. The lasing threshold and maximum output power are 65 mA and 11 mW, respectively. The device generates open eye-diagrams under direct modulation at data rates up to 4 Gb/s.      

蓝光激光二极管抽运Pr:YLF绿光激光器

报道了蓝光激光二极管抽运的掺镨氟化钇锂(Pr:YLF)固体绿光激光器。采用长度5mm、掺杂离子数分数为0.5%的Pr:YLF晶体作为激光增益介质,在中心波长444nm的蓝光激光二极管抽运下,获得波长522.4nm的连续绿光激光输出。应用不同透射率的输出耦合镜研究了激光器的输入输出特性。在吸收抽运光功率530mW,输出镜透射率为1.9%时获得最大输出功率为90.1mW,斜率效率达到65.3%。     

Room-temperature, continuous-wave operation for mode-stabilisedAlGaInP visible-light semiconductor laser with a multiquantum-wellactive layer

646 nm continuous-wave operation at room temperature (25°C) has been achieved by a transverse mode stabilised AlGaInP laser diode with a (multi-)quantum-well structure. The laser structure was grown by metalorganic vapour phase epitaxy. The threshold current (density) is 55 mA (4.4 kA/cm²) and maximum light output power is 19 mW. Stable fundamental transverse-mode operation was obtained, at least up to 15 mW     

Efficient, scalable, internally folded Nd:YAG laser end-pumped bylaser diodes

A scalable diode-pumped Nd:YAG laser is described in which the gain element resembles a penta-prism. This design allows longitudinal pumping along five separate axes. Using five high-power single stripe laser diodes, 4.16 W of absorbed power produced 2.3 W CW at 1.06 μm. The slope efficiency was 56%, the output was plane polarized, and the laser operated in the TEM₀₀ mode. The threshold power, was 48 mW. No evidence of thermal saturation was observed up to the maximum pump power. With an intracavity KTP crystal, 431 mW of CW amplitude-stable output at 532 nm was generated. Repetitive Q-switched operation is also reported