Monolithic integration of microlensed resonant photodetectors andvertical cavity lasers

Monolithic integration of high performance microlensed resonant photodetectors and vertical cavity lasers (VCLs) from a single epitaxial growth is presented. The VCLs have sub-200 μA threshold currents. Adjacent detectors have the same operating wavelength and responsivities of ~0.4 A/W with ~6 nm optical bandwidths     

Flip-chip bonded arrays of monolithically integrated, microlensedvertical-cavity lasers and resonant photodetectors

We present flip-chip bonded arrays of monolithically integrated vertical-cavity lasers (VCLs) and resonant photodetectors. The VCLs and photodetectors are integrated using a novel structure that allows through-the-substrate emission and detection without compromising device performance. Substrate-side microlenses have been integrated to take advantage of the through-the-substrate architecture. Flip-chip bonded VCLs exhibit threshold currents as low as 135 μA with differential efficiencies of ~53%. The detectors have the same operating wavelength as the VCLs and responsivities of 0.48 A/W, corresponding to 60% absorption, with optical bandwidths of 7 nm     

Small electrically pumped index-guided vertical-cavity lasers

High-yield, reliable electrically pumped index-guided vertical cavity lasers with diameters less than 4 microns have been fabricated using low resistance, alloyed, ring contact metallization. Existing metallization schemes used for bottom emitting vertical cavity lasers (VCLs) tend to be highly resistive, since the top metallization layer serves the dual purpose of mirror and electrical contact. This results in acceptable performance for large diameter devices, but poor performance for smaller devices that operate at higher current densities. Low resistance alloyed ring contacts have been developed for small bottom emitting VCLs that maintain the required optical properties while dramatically improving the electrical properties     

Monolithic integration of substrate input/output resonantphotodetectors and vertical-cavity lasers

We present theoretical and experimental results on monolithically integrated through-the-substrate input/output vertical-cavity lasers (VCLs) and resonant photodetectors that are compatible with substrate-side micro optics and flip-chip bonding. The required difference in bottom mirror reflectivity between the VCL and the detector is achieved by selective oxidation of a few high Al-content AlGaAs layers in the bottom mirror for the VCL. The modeling shows that using this approach makes it possible to individually design VCLs and resonant detectors from the same epitaxial structure without compromising performance of either device. Furthermore, since the oxidized layers are placed far enough from the active region, the VCL design is very robust with respect to uncertainties in the oxidized layers. For the detectors, we expect about 60% quantum efficiency, a 6-nm full-width at half-maximum optical bandwidth, and less than 1 nm difference in operating wavelength from the VCLs. Experimentally, VCLs and adjacent detectors with integrated microlenses have a difference of less than 0.5 nm in operating wavelength. The detectors have responsivities of 0.48 A/W, corresponding to 60% quantum efficiency and 7-nm optical bandwidths. Single-mode VCL's exhibit threshold currents as low as 135 μA while maintaining differential efficiencies above 50%. Larger multimode VCLs have differential efficiencies exceeding 70% with threshold currents of 0.5 mA     

Low-threshold 840-nm laterally oxidized vertical-cavity lasers using AlInGaAs-AlGaAs strained active layers

We explore the use of a novel strained AlInGaAs-AlGaAs material system to achieve low-threshold current in oxide-apertured vertical-cavity lasers (VCLs) emitting near 850 nm. We report a low continuous-wave (CW) room-temperature threshold current of 290 /spl mu/A from top-emitting, 840-nm VCLs with a 5-/spl mu/m-wide thin-oxide aperture. The low-threshold current has been attributed to the use of strained active layers, which increase the gain and reduce the transparency current. We also studied the effects of post-growth rapid thermal annealing (RTA) on the characteristics of AlInGaAs-AlGaAs VCLs and found that RTA improves the material quality and significantly enhances VCL performance.     

Butt-coupling efficiency of VCSELs into multimode fibers

We report a detailed study on butt coupling efficiencies of vertical-cavity surface-emitting lasers (VCSELs) to standard graded index multimode silica fibers. Coupling efficiency strongly depends on active laser diameter as well as index guiding and transverse mode spectrum of the laser. For typical active laser diameters of 16-20-/spl mu/m coupling efficiencies of about 90% are obtained with weakly index guided proton-implanted vertical-cavity lasers (VCLs) whereas stronger index guided oxidized lasers show considerably lower coupling efficiencies between 75% and 55%, depending on driving currents.     

光纤激光器的发展现状

由于在光通信、光数据存储、传感技术、医学等领域的广泛应用,近几年来光纤激光器发展十分迅速.本文简要介绍了光纤激光器的工作原理及特性,并对目前多种光纤激光器作了较为详细的分类;同时介绍了近几年国内外对于光纤激光器的研究方向及其目前的热点是高功率光纤激光器、窄线宽可调谐光纤激光器和超短脉冲光纤激光器;最后指出光纤激光器向高功率、多波长、窄线宽发展的趋势。     

光子晶体光纤激光器

光子晶体光纤激光器可标定kW级的输出功率,可使高功率工作的掺稀土光纤激光器产生变革。介绍了光子晶体光纤激光器的基本概念、特性及其典型器件。     

光纤激光器

近年来光纤激光器得到了迅速发展。本文简要介绍了光纤激光器的基本原理和特点，并对其进行了较为详细的分类。最后指出了光纤激光器在光通信、工业加工、医疗等领域的应用及其未来的发展方向。     

RIN transfer measurement and modeling in dual-order Raman fiber amplifiers

A numerical analysis is presented that models the transfer of relative intensity noise (RIN) from the first- and second-order pump lasers to the signal radiation in dual-order Raman fiber amplifiers. Measurements are presented of the first- and second-order RIN transfer functions for co- and counter-propagating fiber amplifiers. The second-order RIN transfer function is similar to that found in single-order Raman fiber amplifiers and the first-order transfer function is approximately 15 dB less than the second-order transfer function. The impact of the RIN transfer from the first- and second-order pump lasers to the signal radiation on the system performance is examined and estimates for the required pump laser RIN levels are presented.     

Novel performance of fiber lasers: tunable operation in visible range

A review of the main physical processes important for frequency doubling of fiber lasers and the results of development by the Novosibirsk group of the fiber lasers operating from blue-green to yellow-red spectral ranges with a potential of the broad continuous tuning are presented. These lasers with ～100 mW power are treated to be attractive light sources for applications in medicine, especially in confocal microscopy and flow cytometry.     

掺镱光纤激光器中的自脉冲效应

高功率光纤激光器多选用掺镱双包层光纤作为增益介质。掺镱双包层光纤与普通非掺杂光纤相似,由于纤芯尺寸非常小,一般为几微米至几十微米量级,极容易产生自脉冲效应。进行了大功率条件下掺镱光纤激光器自脉冲效应的研究,观察到不同的自脉冲现象。 研究结果表明,在大功率激光作用下,尽管镱离子不存在浓度淬灭,但是对于大芯径掺镱双包层光纤,与其他三能级系统相同,均存在弛豫振荡引发的饱和吸收自脉冲效应。掺镱光纤激光器中的饱和吸收效应、受激布里渊散射、受激拉曼散射等自脉冲效应不容忽视。     

大功率双包层光纤激光器

归纳了新型双包层光纤激光器的各种结构、工作原理和泵浦方法,并从各个角度对这种激光器的特点进行了详细的分类介绍。分析表明选择适当的双包层光纤、腔体结构和泵浦方法对提高光纤激光器的性能具有重要作用。同时展望了这种新型激光器的应用前景。     

Modeling of short, single-frequency, fiber lasers in high-gainfiber

Grating gain must be accounted for when designing single-frequency fiber lasers which utilize intracore, erbium-doped, Bragg reflectors for cavity feedback, and mode selectivity. A closed-form solution, derived through coupled mode theory for the spectral reflectivity of an intracore Bragg phase grating in an amplifying fiber is derived and applied to the design of single-mode fiber lasers. Both analytical and experimental results are presented     

SUPER PON-a fiber to the home cable network for CATV andPOTS/ISDN/VOD as economical as a coaxial cable network

A complete super PON fiber to the home cable network as economical as the classic coaxial cable network, designed for application in the local loop is presented. The concept uses high power lasers, remote pumped erbium doped fiber amplifiers (EDFAs) to reduce cost by high splitting ratio, economical receivers for the downstream direction and economical CD player lasers for the upstream direction. Several novel technical solutions for this application (a new method to avoid stimulated Brillouin scattering (SBS), remote pumping of the EDFA and a compensating technique to adapt the CD laser to the normal fiber) are presented     

掺Yb3+双包层光纤激光器的研究进展

光纤激光器以其独特的优势得到快速发展,其应用范围已经扩展到工业加工、国防军事、医疗等领域。综述了连续、脉冲掺Yb3+双包层光纤激光器的国内外研究进展,介绍了利用能承受高功率的合束器、光纤光栅的全光纤激光器,利用种子光主振荡光纤放大技术产生高光束质量、高平均功率、高峰值功率的脉冲光纤激光器。分析了影响光纤激光器功率提高的因素,如光纤的损伤、非线性性效应、热效应。最后,对掺Yb3+双包层光纤激光器的发展前景进行了展望。     

Analytical model for rare-earth-doped fiber amplifiers and lasers

An analytical model for two-, three-, and four-level system rare-earth-doped fiber amplifiers and lasers is presented. The theory is applicable to dopants such as erbium, neodymium, thulium; praseodymium, and ytterbium. Fiber-amplifier gain is expressed in terms of attenuation coefficients, intrinsic saturation powers, and cross-saturation powers at the pump and signal wavelengths. These parameters can be directly determined from one- and two-beam fiber-transmission measurements. System-independent formulas are given for the slopes and thresholds of ring and linear fiber lasers. Good agreement between theory and experiment has been shown for erbium-doped fiber amplifiers and lasers and thulium-doped fiber lasers. Because of the finite-pump-level lifetime, three- and four-level models predict a flattening of the fiber laser slope at higher pumping powers when the fiber is shorter than the optimum length. Approximate system-independent solutions are also given for fiber amplifiers with excited-state absorption at either the pump or signal wavelengths. A novel technique, requiring only one tunable light source, is proposed for finding the best pump wavelength when pump ESA is present. The two-level analytical model recently developed for erbium-doped fibers is a special case of this theory     

双包层掺镱光纤的光谱性能与制备技术

双包层掺镱光纤作为光纤激光器的增益介质受到广泛关注。简要介绍了光纤中Yb＋的光谱性能,用于高功率光纤激光器的光纤结构设计以及双包层掺杂光纤的制备方法。讨论了掺镱光纤的光暗化效应的潜在机理及抑制方法。     

Thermal effects in kilowatt fiber lasers

Thermal effects and their influences on kilowatt ytterbium-doped double-clad (YDDC) fiber lasers are studied through numerical modeling. Solutions to suppress the thermal effects in the YDDC fiber lasers under bidirectional end pump and distributed pump are presented and compared for the first time. It is shown that lower operating temperature and more uniform heat dissipation in fibers can be obtained by optimizing the arrangement of pump powers, pump absorption coefficients, and fiber lengths.     

掺铥光纤激光器研究进展

介绍了掺铥光纤激光器的基本结构以及工作原理;综述和分析了掺铥光纤激光器的研究国内外进展,阐述了掺铥光纤激光器可以采用几种不同的抽运源进行抽运,即LD抽运源、Nd∶YAG激光器抽运源、掺Yb3+光纤激光器抽运源以及色心、掺铒光纤激光器抽运源等。同时也指出了如何提高激光器输出特性的方法,即进一步改善交叉弛豫率、降低上转换以及热处理等。最后展望了掺铥光纤激光器在生物医学领域的应用前景。