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 optically pumped VECSEL using a double-well resonant periodic gain structure

We present the design and fabrication of an optically pumped vertical-external-cavity surface-emitting lasers with double-well resonant periodic gain structure. Each double-well consists of two 4-nm-thick InGaAs strained quantum wells. The double-well provides optimum overlap between the quantum wells and the antinodes of the standing wave of laser signal at high-power and high-temperature operation. The structure is more tolerant to variation of the growth, processing, and operating temperature for maintaining high modal gain. For a 230-/spl mu/m diameter pump spot, over 4-W continuous-wave output with a slope efficiency of 39% is demonstrated at 30/spl deg/C without thermal rollover.     

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.     

Transient gain behavior in 1050/1550-nm dual-wavelength pumped TDFAs

We present an experimental study on transient events in 1050/1550-nm dual-wavelength pumped thulium-doped fiber amplifiers (TDFAs)-a promising candidate for S-band telecommunication applications. For appropriate power ratios of the two pump wavelengths, transient excursions due to signal add-drop are comparable to those in single-wavelength pumped TDFAs. Pump modulation effects, however, more severely impact the signal gain. With our experimental results, it should be possible to develop transient gain suppression control loops for this TDFA type.     

Improved spectral properties of an optically pumped semiconductor disk laser using a thin diamond heat spreader as an intracavity filter

This letter describes an optically pumped high-power InP-based semiconductor disk laser with a thin (50 /spl mu/m) diamond heat spreader bonded to the surface of the gain chip. The diamond heat spreader performs the multiple functions of heat removal, spectral filtering, and wavelength stabilization by utilizing the high thermal conductivity and the low thermooptic coefficient of diamond, along with the large free-spectral range of a thin intracavity etalon. A pump-power-limited output power of 680 mW at 1.55 /spl mu/m is demonstrated at a heat sink temperature of -30/spl deg/C, and 140 mW at room temperature. The spectral width was measured to be less than 0.08 nm and the spectral drift with temperature and pump power as low as 0.03 nm//spl deg/C and 0.14 nm/W, respectively.     

High-power operation and scaling behavior of CW optically pumped FIR waveguide lasers

High-power far infrared (FIR) laser operation at the 10- 100 mW level is described for wavelengths throughout the 40 μm-1.22 mm spectral region. These data correspond to order of magnitude improvements in converting CO2laser energy into FIR laser output. This improved FIR laser performance is attributed to a waveguide laser geometry with reduced losses for the CO2pump and also to a new method of output coupling. The basic design concept of the efficient laser resonator is discussed as well as the prospect for further increases in laser performance through improved efficiency and sealing.     

0.8 W optically pumped vertical external cavity surface emitting laser operating CW at 1550 nm

An InP based optically pumped vertical external cavity surface emitting laser has been designed and optimised for emission at 1550 nm. To overcome thermal limitations an intra-cavity synthetic diamond heatspreader is bonded to the gain structure. The laser produces 780 mW at -30/spl deg/C and 100 mW at 20/spl deg/C in a near Gaussian beam (M/sup 2/<1.2).     

Wavelength conversion in a 1550-nm multifrequency laser

Wavelength conversion of input signals at data rates of 622 and to 1250 Mb/s was as demonstrated using an integrated multifrequency laser having 8 channels with 1.6-nm channel spacing.     

A 1550-nm millimeter-wave photodetector with a bandwidth-efficiencyproduct of 2.4 THz

The monolithic integration of an optical preamplifier and a waveguide p-i-n photodiode has resulted in a 1550-nm photodetector having an external quantum efficiency of 72 (a responsivity of 89 A/W) and an electrical bandwidth of 33.5 GHz. These figures combine to give a bandwidth efficiency product of 2.4 THz, which is approximately one hundred times higher than for any other type of millimeter-wave photodetector published to date. In addition, the preamplifier performance is supplemented by wide optical bandwidth (60 nm), low polarization sensitivity (1 dB), near traveling wave amplification (1-dB maximum gain ripple), and high saturated output power (+11 dBm). The principal advance over work reported earlier is the traveling wave operation of the monolithic optical preamplifier     

1.55-/spl mu/m optically pumped wafer-fused tunable VCSELs with 32-nm tuning range

We demonstrate widely tunable InAlGaAs-InP-AlGaAs-GaAs optically pumped vertical-cavity surface-emitting lasers operating in the 1.55-/spl mu/m waveband. The tuning range of 32 nm is achieved by applying a low tuning voltage of 4 V. Maximum single-mode output power of 2 mW with less than 1.5-dB power variation over the whole tuning range and side-mode suppression ratio in excess of 30 dB have been obtained.     

High-power 1320-nm wafer-bonded VCSELs with tunnel junctions

A new long-wavelength vertical-cavity surface-emitting laser structure is described that utilizes AlGaAs-GaAs mirrors bonded to AlInGaAs-InP quantum wells with an intracavity buried tunnel junction. This structure offers complete wavelength flexibility in the 1250-1650 nm fiber communication bands and reduces the high free-carrier losses and bonded junction voltage drops in previous devices. The intracavity contacts electrically bypass the bonded junctions to reduce threshold voltage. N-type current spreading layers and undoped AlGaAs mirrors minimize optical losses. This has enabled 134/spl deg/C maximum continuous-wave lasing temperature, 2-mW room-temperature continuous-wave single-mode power, and 1-mW single-mode power at 80/spl deg/C, in various devices in the 1310-1340 nm wavelength range.     

High-power 980-nm DFB RW lasers with a narrow vertical far field

We compare 980-nm distributed-feedback ridge-waveguide lasers having cavity lengths of 1.5 and 3 mm. The maximum single-mode output powers are 500 and 700 mW, respectively. The full-width at half-maximum of the vertical far-field profile is only 22/spl deg/ due to a superlarge optical cavity.     

All-optical 1300-nm to 1550-nm wavelength conversion using cross-phase modulation in a semiconductor optical amplifier

All-optical 1300-nm to 1550-nm wavelength converters may be important components in lightwave networks which use both the 1300-nm and the 1550-nm low-loss transmission windows of silica optical fiber. We describe a new all-optical 1300-nm to 1550-nm wavelength converter, based on cross-phase modulation in a 1300-nm semiconductor optical amplifier. We demonstrate operation of the wavelength converter at 1.25 Gb/s, and present bit-error rate measurements. The wavelength converter demonstrated here potentially operates at high speed, with low input power and low polarization-sensitivity.     

Gain of a CW optically pumped far-infrared laser with sandwich resonator

The FIR laser gain of CW optically pumped HCOOH was measured and compared to theoretical calculations. Since the laser has a transversely pumped parallel-plate (or “sandwich”) waveguide, the pump field is the same for oscillating and amplifying operation. Therefore, “true” FIR-gains were measured. The theory takes into account several phenomena, that are frequently simplified when considering FIR lasers, such as the pump and the FIR beam's spatial distribution, power broadening of the pump absorption, as well as heat and molecular diffusion. As a result, good quantitative agreement between theory and measurement was achieved.     

基于平板热管的大功率LED散热系统模拟及优化

为解决大功率LED的散热问题,设计了平板热管散热器来实现LED芯片的高效散热。通过Flotherm模拟软件,对大功率LED在自然对流条件下的散热情况进行了三维数值模拟。通过平板热管与常规铜、铝散热基板对比,发现平板热管有效降低了大功率功率LED的结温和热阻,使得LED温度分布更为均匀。此外,还研究了平板热管LED散热系统在不同芯片功率下的热性能,并对四种不同排布方式的LED平板热管散热系统进行了优化,发现阵列分布其温度分布最为均匀,结温最低,是较优的排布方式。     

196W功率输出的高功率包层泵浦光纤激光器

文章首先阐述了包层泵浦技术以及基于包层泵浦技术的包层泵浦激光器,同时还介绍了一种新型泵浦技术,即从大面积激光二极管向小截面的单模光纤芯层传输能量的侧面泵浦技术。然后介绍了我们试验中的大功率包层泵浦光纤激光器,该激光器采用的是端面泵浦技术。当泵浦功率为240W时,光纤激光器在1．09μm处产生了高质量的196W连续波长输出,获得了85％的斜坡效率。     

Prediction of gap in QFP with unattached heat spreader

Due to cost and process considerations, sometimes the heat spreader of a quad flat package (QFP) is not attached to the die pad. Consequently, due to mismatch of thermal expansions of the components, gapping is inevitable on the unattached interface during temperature change. Presence of the gap would potentially decrease the reliability and thermal performance of QFP. In this paper, contact methodologies were incorporated into finite element models to calculate the distribution of gap on the unattached interface. Both plane two-dimensional and general three-dimensional models were built up and compared for a multi-chip module QFP with a drop-in heat spreader.     

Effect of surface roughness of silicon die and copper heat spreader on thermal performance of HFCBGA

From the available mass production devices of HFCBGAs, there can be a range of surface roughness with different surface finished of silicon dies and heat spreader. An aluminum filled gel is used to examine the surfaces clamping with both identical substrates at both sides whether compatible to the thermal conduction. Their thermal contact resistances are measured by laser flash technology and therefore modeling HFCBGAs with those measured roughnesses and resistances for characterizing thermal performances.     

产生超短脉冲的光泵浦垂直外腔面发射激光器的研究进展

光泵浦半导体垂直外腔面发射激光器（OPS-WCSEL）在产生超短脉冲方面显示了优越的特性,在脉冲宽度、平均输出功率和脉冲重复频率等方面都得到了与传统超短脉冲激光器可比的结果．显出巨大的发展潜力。本文综合分析了用于产生超短脉冲的OPS-VECSE的基本原理和最趣研究进展,并探讨了该领域的发展方向和应用前景。     

High-power 660-nm GaInP-AlGaInP laser diodes with low vertical beam divergence angles

We present 660-nm GaInP-AlGaInP ridge multiple-quantum-well laser diodes (LDs) reliably operating at high output power over 200 mW at 70/spl deg/C not showing unstable higher order lateral modes owing to an adoption of a dry etching method instead of a conventional chemical wet etching for realizing steep ridge sidewalls. Employing an optimized two-step n-cladding layer LDs produced very narrow horizontal and vertical beam divergence angles of 8.6/spl deg/ and 15.3/spl deg/, respectively. To the best of our knowledge, this vertical beam divergence angle is the lowest value ever reported in high-power 660-nm LDs operating over 200 mW and is expected to play an important role in minimizing the coupling loss between LD and passive optical components in digital versatile disc system.