Vertical Cavity Surface Emitting Laser Research Papers (original) (raw)

- by and +1
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- Power Electronics, Driver, Vertical Cavity Surface Emitting Laser, Power Control

Vertical-Cavity Surface-Emitting Laser (VCSEL) diodes are among the youngest members of the semiconductor laser diode family. The main aim of our work focuses on the measurement of the basic properties (the spectral range of the laser emission, temperature and current tunability) of experimental VCSEL diode lasers based on GaSb operating in the infrared region around 4250 cm −1. A high-resolution FTIR Bruker IFS 120 HR spectrometer with a maximum resolution of 0.0035 cm −1 was used in the emission setup for the laser diagnostic research. The absorption spectra of atmospheric pollutants like methane, carbon monoxide and ammonia have been measured using these VCSELs for the first time.

- by S. Civiš
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- Mechanical Engineering, Physics, Materials Science, Organic Semiconductor Laser

We report an ultracompact label-free biosensor that uses a vertical-cavity surface-emitting laser (VCSEL)-based measurement system for the characterization of biomolecular interactions. It consists of a VCSEL, a plastic guided-mode resonant filter, and two p-in detectors. The system has demonstrated very high sensitivity to molecules on top of the sensor.

- by Carlos Mateus
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- Biosensors, Photonics, Molecular Biophysics, Photodetectors

Novel, two-dimensional MEMS-controllable microlens array has been integrated with a vertical cavity surface emitting laser (VCSEL) array using¯ip-chip assembly. The MEMS/VCSEL hybrid system is built as an ef®cient and reliable smart pixel array for board-to-board or chip-to-chip optical interconnects in digital systems. Theory including geometrical and Fourier transform analysis and beam steering experimental results are presented. By translating polymer microlens, fabricated on a MEMS X±Y movable plate, using electro-thermal actuators, a beam steering angle of 70 mrad is achieved. VCSEL beam steering was successfully demonstrated in our MEMS/VCSEL hybrid system to collimate and steer laser beam for a precision alignment in a two-dimensional free-space optical interconnect. #

Based on design guidelines from a three-dimensional, fully vectorial model, we have fabricated vertical-cavity surface-emitting lasers (VCSELs) with a monolithically integrated dielectric surface grating for polarization control. For VCSELs with emission wavelengths of 850 and 980 nm we have achieved orthogonal polarization suppression ratios (OPSRs) above 15 dB for all modes up to thermal rollover, which very well agrees with theory. It is shown both theoretically and experimentally that the grating has no influence on the emission far-field. The surface grating has also been combined with a surface relief to stabilize the polarization and to increase the fundamental mode output power at the same time.

In this letter, we present the first experimental results of frequency doubling the output of vertically stacked grating coupled surface-emitting laser/dual-grating reflector devices with different emitting wavelengths. We used a multigrating 5% magnesium-oxide-doped periodically poled lithium niobate (MgO : PPLN) crystal as the nonlinear conversion medium. In pulse operation, 0.6 W of multiwavelength total second-harmonic peak power was obtained. The individual emitter output is focused into each channel of the crystal by diffractive beam shaping optical element array to minimize the footprint area of the whole setup.

Tactile shear stresses play an important role in the medical field and robotics. To monitor these stresses in situ, there is a need for unobtrusive flexible sensors that can be wrapped around curved surfaces or moving body parts. The presented sensor is based on changing coupling of optical power between a verticalcavity surface-emitting laser (VCSEL) and a photodiode facing each other and separated by a deformable transducer layer. The required optoelectronic components were embedded in a polymer foil of only 40 m thick, yielding a very thin and flexible total sensor stack of 250 m thick. In the linear part of the range (between 2 and 5.5 N), the sensitivity of the prototype was 350 A/N; the maximum measurable force was 5.5 N. However, by selecting the appropriate deformable sensor transducer material, the sensitivity and range can be tuned for a specific application.

- by Jan Vanfleteren and +2
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- Photonics, Optical Sensor, Vertical Cavity Surface Emitting Laser, Shear Stress

The thermal resistance of vertical-cavity surfaceemitting lasers (VCSEL's) flip chip bonded to GaAs substrates and CMOS integrated circuits has been measured. The measurements on GaAs show that if the bonding is done properly, the bonding does not add significantly to the thermal resistance. However, the SiO 2 under the CMOS bonding pad can double the thermal resistance unless measures are taken to improve the thermal conductance of these layers. Finite element simulations indicate that the thermal resistance of bonded VCSEL's increases rapidly as the solder bond size and the aperture size decrease below 10 m.

Optical pulses with duration below 60 ps were generated by gain switching a Vertical Cavity Surface Emitting Laser (VCSEL) at 1535 nm. We used a radio frequency (RF) sinusoidal signal to modulate the device near threshold. Relaxation oscillations or pulse train generation were observed depending on the gain switching conditions. Repetition rates between 100 MHz and 2 GHz were tested. The dependence of the pulse width and amplitude was investigated in relation with the bias current and excitation frequency and amplitude. The optimal configuration of the current bias and RF modulating signal provided the shortest pulse duration of 57 ps at repetition rate of 800 MHz.

We present a comprehensive noise model for verticalcavity surface-emitting lasers (VCSELs). The time-domain model accounts for the stochastic fluctuations in the local carrier density in the separate confinement heterostructure and quantum wells, and in the modal intensity and phase of both the internal and the out-coupled optical field. In this work, we consider these fluctuations to be caused by the temporal uncertainty of the processes that supply or consume carriers and photons, such as carrier diffusion and photons escaping the cavity, and the processes that create or annihilate carriers and photons, such as stimulated emission and absorption. The noise model is based on a deterministic quasithree-dimensional dynamic model that treats the carrier transport, heat generation and dissipation, and optical fields in the device. Langevin noise terms are derived and added to the rate equations in the numerical solution. The noise model is applied to simulate the noise characteristics of fundamental-mode stabilized VCSELs with a shallow, mode discriminating, surface relief. The relative intensity noise and frequency noise of the output are calculated. From the latter, the linewidth of the VCSEL can be estimated. The results are compared with those of conventional multimode VCSELs. and is currently working toward the Ph.D. degree. His research is focused on characterizing and modeling the dynamics of vertical-cavity surface-emitting lasers.

1.3-and 1.55-µm vertical-cavity surface-emitting lasers (VCSELs) on InP have been realized. High-reflectivity AlGaInAs-InP lattice matched distributed Bragg reflectors (DBRs) were grown on InP substrates. 1.7 (for 1.3 µm) and 2.0 (for 1.55 µm) mW single mode power at 25 • C, 0.6 mW single mode power at 85 • C and lasing operation at >100 • C have been achieved. 10 Gbit/s error free transmissions through 10 km standard single mode fiber for 1.3-µm VCSELs, and through 15 km nonzero dispersion shift fiber for 1.55-µm VCSELs, have been demonstrated. With the addition of an SOA, 100 km error free transmission at 10 Gbit/s also has been demonstrated through a negative dispersion fiber. No degradation has been observed after over 2500-h aging test.

- by Rajaram Bhat
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- Engineering, Quantum Physics, Organic Semiconductor Laser, IEEE

Quantum cascade (QC) lasers and vertical-cavity surface-emitting lasers (VCSELs) are of great interest due to their potential importance for a variety of device applications. Both kinds of lasers call for very highly reflective mirrors. Usually distributed Bragg reflector (DBR) mirrors, which consist of periodic quarter wavelength stacks of high and low refractive index compound semiconductors are used. These stacks are superlattices containing more than 40 individual layers. To obtain very high reflectivity DBRs alternating GaAs and AlAs layers are used for both the high and low index mirrors. GaAs/AlAs DBR structures containing 15 periods were characterized by the complementary use of RBS/ channeling, TEM and HRXRD. Since the total thickness of a DBR exceeds 2 mm the RBS analysis was performed at two He-ion energies: 1.7 MeV and 3.82 MeV. After some stopping power corrections TEM and RBS provided similar results. Discrepancies with HRXRD data were attributed to the lateral inhomogeneity of produced superlattice. Virtues and pitfalls of complementary use of these techniques were discussed.

- by Anna Stonert
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- Materials Engineering, Quantum Cascade Lasers, Structural Analysis, TEM
- by Toni Laurila
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- Analytical Chemistry, Water, Lasers, Vertical Cavity Surface Emitting Laser

Motivated by the need for affordable, high-performance fiber-optic microwave links in fiber-fed microcellular networks and radar systems, we have performed a comprehensive experimental evaluation of the microwave modulation characteristics of high-speed oxide-confined vertical cavity surface emitting lasers (VCSELs) emitting at 840 nm. VCSELs with different oxide aperture diameters, including both single-and multimode lasers, have been used to track the dependence on modal behavior. The study includes both static and dynamic characteristics, with an emphasis on those of major importance for analog modulation. This includes the small-signal modulation response ( 11 and 21 ), the relative intensity noise (RIN), and the intermodulation distortion. From this, we determine the spurious free dynamic range, the impedance characteristics, and the speed limitations.

- by Richard Schatz
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- Optics, Medical Imaging, Fiber Optics, Telecommunications

- by Rajaram Bhat
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- Engineering, Quantum Physics, Organic Semiconductor Laser, IEEE

We review recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 980nm. Selectively oxidized, bottom-emitting single VCSEL emitters with 51% power conversion efficiency were developed as the basic building block of these arrays. More than 230W of continuous-wave (CW) power is demonstrated from a ~5mm x 5mm array chip. In quasi-CW mode, smaller array chips exhibit 100W output power, corresponding to more than 3.5kW/cm 2 of power density. High-brightness arrays have also been developed for pumping fiber lasers, delivering a fiber output power of 40W. We show that many of the advantages of low-power single VCSEL devices such as reliability, wavelength stability, low-divergence circular beam, and low-cost manufacturing are preserved for these high-power arrays. VCSELs thus offer an attractive alternative to the dominant edge-emitter technology for many applications requiring compact high-power laser sources.

High-speed fiber-optic transceiver modules using parallel optics require that oxide-confined vertical-cavity surface-emitting lasers (VCSELs) be moisture resistant in a nonhermetic package. We have found that the conventional storage 85/85 (85 C/85% relative humidity) test does not adequately characterize oxide VCSELs moisture resistance. We have identified three failure modes in the oxide VCSELs under operating conditions in high humidity. In this paper, we discuss the failure mechanisms including dislocation growth, semiconductor cracks, and aperture surface degradation, all associated with operation under high relative humidity. Understanding of these failure modes has led to more appropriate qualification standards and environmentally robust oxide VCSELs.

- by D. Chamberlin and +1
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- Vertical Cavity Surface Emitting Laser, Dislocations, High Temperature, Relative Humidity

Next generation integrated photonic circuits will be dominated by small footprint devices with lower power consumption, low threshold currents and high efficiencies. Vertical Cavity Surface Emitting Lasers (VCSELs) having those attractive qualities has shown results to meet the next generation demands for optical communication sources. VCSELs applications are sensors, data com, optical communication, spectroscopy, printers, optical storage, laser displays, atomic optical clocks, laser radar, optical signal processing to name a few. This review centres around on the basic operation of semiconductor lasers, structure analysis of the devices and parameter optimisation for optical communication systems. This paper will provide comparisons on growth techniques and material selection and intends to give the best material realisation for nano optical sources that are up to date as used in optical communication systems. It also provides summarised improvements by other research groups in realisation of VCSELs looking at speeds, efficiency, temperature dependence and the device physical dimensions. Different semiconductor device growth methods, light emitting materials and VCSELs state of art are reviewed. Discussions and a comparisons on different methods used for realising VCSELs are also looked into in this paper.

- by Nonofo Ditshego and +1
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- Nanotechnology, Vertical Cavity Surface Emitting Laser, Semiconducting Indium Phosphide, Semiconducting Gallium Compounds

High speed fiber optic transceiver modules using parallel optics require that oxide-confined vertical-cavity surfaceemitting lasers (VCSELs) be moisture resistant in non-hermetic environments. Conventional storage 85/85 (85°C and 85% relative humidity) testing without a bias does not adequately characterize oxide VCSEL's moisture resistance. Oxide VCSELs do not fail or degrade significantly under such conditions. With a bias, however, we have found that moisture can cause failure modes not seen in dry reliability testing. Without proper device design and fabrication, these failure modes lead to high failure rates in oxide VCSELs. In this paper, we first discuss the failure mechanisms we have identified, including dense dislocation network growth, semiconductor cracking and aperture surface degradation, all in high humidity and high temperature under operating conditions. We then report the results of environmental reliability tests on Agilent's oxide VCSELs developed for the parallel optics modules. The results from a large number of wafers produced over an extended period of time have shown consistent, robust environmental reliability.

- by Seongsin Kim
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- Proceedings, Vertical Cavity Surface Emitting Laser, Dislocations, High Temperature

This paper describes a new optical link system which consists of a metal optical bench, a module printed circuit board, a driver/receiver integrated circuit, a vertical-cavity surface-emitting laser/photo diode (VCSEL/PD) array, and an optical link block with plastic optical fibers for reducing electromagnetic interference (EMI) noise. For the optical interconnection between the light-sources and detectors, an optical wiring method whose distinctive features include the absence of EMI noise and easy assembly is proposed. The results clearly demonstrate that the use of an optical wiring method can provide robust, cost-effective assembly and easy-repair. We successfully achieved a 4.5 Gb/s data transmission rate without EMI problems.

An efficient model scheme that combines the nonlinear behaviour of the input parasitics with the intrinsic fundamental device rate equations of the Vertical Cavity Surface Emitting Lasers (VCSELs) is proposed. The model parameter values are extracted using a fully defined systematic technique from dc current-optical power-voltage (I-L-V) and ac S 11 -S 21 response measurements. Extraction and simulation procedures are implemented in commercial integrated circuit design tools. Investigation on their accuracy and efficiency is performed by comparing simulation results with the experimental measurements.

- by Lawrence Shacklette
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- Packaging, Optoelectronics, Printed Circuit Board, Photodetectors

We present recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 808nm. Selectively oxidized, top-emitting single VCSEL emitters with 49% power conversion efficiency were developed as the basic building block of these arrays. Because of the strong GaAs absorption at the 808nm wavelength, the traditional bottom-emitting, substrate-emission configuration is not possible for large arrays that require efficient heat dissipation. The processing and packaging challenges are discussed. We demonstrate 3mm x 3mm arrays and 5mm x 5mm arrays with the GaAs substrate completely removed and mounted on diamond submounts. These arrays emit more than 50W and 120W, respectively, and exhibit a maximum powerconversion efficiency of 42%.

- by Emanuel Haglund and +1
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- Vertical Cavity Surface Emitting Laser, VCSEL

High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture radars, high-resolution cameras, and fast image-compression processors that produce data beyond gigabits per second. We have developed a fiberoptic link, named SpaceFibre, which operates up to 3.125 Gb/s and is compatible with the existing SpaceWire network. The link provides symmetrical, bidirectional, full-duplex, and point-topoint communication. It employs 850-nm vertical-cavity surface emitting lasers, radiation-hardened laser-optimized 50/125 µm graded-index fibers, and GaAs p-i-n photo diodes. The transceiver electronics is realized using a multilayer-ceramic-substrate technology that enables the passive alignment of optical fibers to active devices. The SpaceFibre link demonstrator was tested to transfer data at 2.5 Gb/s over 100 m with a bit error rate of less than 1.3 · 10 −14 . Fiber-pigtailed modules were stressed with temperature variations from −40 • C to +85 • C, vibrations up to 30 g, and mechanical shocks up to 3900 g. The test results of 20 modules show that the SpaceFibre link is a promising candidate for the upcoming high-speed intrasatellite networks.

This paper deals with the design and implementation of a self-consistent electrothermooptical device simulator for vertical-cavity surface-emitting lasers (VCSELs). The model is based on the photon rate equation approach. For the bulk electrothermal transport, a thermodynamic model is employed in a rotationally symmetric body. Heterojunctions are modeled using a thermionic emission model and quantum wells are treated as scattering centers for carriers. The optical field is expanded into modes that are eigensolutions of the vectorial electromagnetic wave equation with an arbitrary, complex dielectric function. The open nature of the VCSEL cavity is treated by employing perfectly matched layers. The optical gain and absorption model in the quantum-well active region is based on Fermi's Golden Rule. The subbands in the quantum well are determined by solving the stationary Schrödinger equation and using a parabolic band approximation for the electrons, light and heavy holes. The photon rate equation is fully integrated into the Newton-Raphson scheme used to solve the system of nonlinear device equations. An efficient numerical optical mode solver is used, that is based on a Jacobi-Davidson type iterative eigensolver. The latter combines a continuation scheme with preconditioner recycling. The practical relevance of the implementation is demonstrated with the simulation of a realistic etched-mesa VCSEL device.

Dark line resonances, narrowed with a buffer gas to less than 100 Hz width, are observed in a Cs vapor cell using a directly modulated vertical-cavity surface-emitting laser (VCSEL). An external oscillator locked to one of these resonances exhibits a short-term stability of ( ) = 9 3 10 12 , which drops to 1 6 10 12 at 100 s. A physics package for a frequency-reference based on this design could be compact, low-power, and simple to implement.

- by J. Kitching
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- Thermal Environment, Vertical Cavity Surface Emitting Laser, Oscillations, Low Power

This Thesis describes the research work that has been carried out on the generation of optical pulses, with duration of tens of picoseconds, from semiconductor lasers. The work is focused on 1550 nm Vertical Cavity Surface Emitting Lasers (VCSEL), which are promising optical transmitters due to their advantageous characteristics in the context of fiber optical communications with directly modulated sources. The high bandwidth expected for future optical networks requires the accurate knowledge of the transmitter electrical properties and of the laser generated optical pulses which carry the binary information. This Thesis describes the various achievements obtained in the characterization of these devices and the generated pulses, as well as their applications to an optical communication environment. VCSELs emitting at 1550 nm, based on quantum wells and tunnel junction, have been characterized by static and dynamic impedance measurements and modulation response up to 10 GHz. The electrical parasitics and the equivalent circuit of the device have been modeled, taking into account the effects of capture and escape of carriers in quantum wells, and the laser intrinsic parameters have been extracted from the measurements. The VCSELs have been used for pulse generation at different repetition rates using the gain switching technique and the duration, peak amplitude, jitter and spectral width of the pulses have been measured as a function of the gain switching conditions. The shortest duration achieved has been 55 ps. The effect of optical injection on the pulses generated by gain switched VCSELs has been investigated, obtaining a jitter reduction over a wide range of injection parameters. An Optical Code Division Multiple Access (OCDMA) encoder based on optical delay lines has been designed and implemented, using the optical pulses generated by the gain switched devices. Finally, a novel implementation of the Phase Reconstruction using Optical Ultrafast Differentiation (PROUD) technique has been proposed and demonstrated for optical pulse characterization in amplitude and phase. The optical differentiator required in the PROUD technique has been realized with a birefringent interferometer based on a polarization maintaining fiber and PROUD has been applied to the measurement of the instantaneous frequency of pulses generated from a gain switched semiconductor laser. The linewidth enhancement factor of the laser has been extracted from the time resolved chirp and intensity measurements. The accuracy of the proposed method has been validated by the comparison between the independently measured and recovered (from temporal amplitude and phase) pulse spectra.

- by Antonio Consoli
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- Optical Fiber Communications, Optical Communication, Ocdma, Semiconductor Lasers

This volume contains the extended abstracts of 12 Doctoral Dissertations conducted in the Department of Informatics and Telecommunications, National and Kapodistrian University of Athens and completed in the time period 12/2006 to 12/2007. The goal of this volume is to demonstrate the breadth and quality of the original research conducted by our Ph.D. students and to facilitate the dissemination of their research results. We are happy to present the third collection of this kind and expect this initiative to continue in the coming years. The submission of an extended abstract in English is required by all graduating Ph.D. students. We would like to thank all Ph.D. students who contributed to this volume and hope that this has been a positive experience for them. Finally, we would like to thank Mr. Demetris Manatakis for his help in putting together the material included in this publication. The image in the cover is a painting "Amatory" by Yannis Moralis. The Committee of Research and Development Ioannis Emiris (Chair) Dimitris Gunopulos Elias Manolakos Panos Rondogiannis Athens, December 2008 3 4

- by K Minoglou and +1
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- Vertical Cavity Surface Emitting Laser, Rare Earth Element Mineralization, High Speed, Parameter Extraction

We investigate the impact of reduced photon lifetime on the static and dynamic performance of high-speed, oxideconfined 850-nm vertical-cavity surface-emitting lasers (VCSELs). The photon lifetime is reduced by a shallow-surface etch that lowers the reflectivity of the top mirror. From an analysis of the dependence of slope efficiency on mirror loss (etch depth) and temperature, we deduce values for the internal quantum efficiency and the internal optical loss and their dependencies on temperature. From an analysis of the dependence of the small-signal-modulation response on photon lifetime (etch depth) and temperature, we deduce values for differential gain and gain compression, and their dependencies on photon lifetime and temperature. We find a tradeoff between high resonance frequency and low damping for speed enhancement, leading to an optimum photon lifetime close to 3 ps for this particular VCSEL design that enables a modulation bandwidth of 23 GHz and error-free transmission at 40 Gb/s.

Vertical-cavity surface-emitting lasers (VCSELs) have become leading light sources in plenty of applications due to their good characteristics and low costs. There are, however, some features that need improvements; therefore, optimized or new designs ideas are necessary. To this aim, an electromagnetic simulation tool, which is fast and precise at the same time, is desirable; to cover all the possible requirements, it should be fully three-dimensional 3-D) and vectorial. A model with such features was first proposed by Bava et al. ("Three-Dimensional Model for Vectorial Fields in Vertical-Cavity Surface-Emitting Lasers," Phys. Rev. A, vol. 63, p. 23816, 2001), based on coupled-mode theory.

We report on the design, fabrication, and evaluation of large-aperture, oxide-confined 850 nm vertical cavity surface emitting lasers (VCSELs) with high modulation bandwidth at low current densities. We also compare the use of InGaAs and GaAs quantum wells (QWs) in the active region. Both VCSELs reach an output power of 9 mW at room temperature, with a thermal resistance of 1.9 • C/mW. The use of InGaAs QWs improves the high-speed performance and enables a small-signal modulation bandwidth of 20 GHz at 25 • C and 15 GHz at 85 • C. At a constant bias current density of only 11 kA/cm 2 , we generate open eyes under large-signal modulation at bit rates up to 25 Gbit/s at 85 • C and 30 Gbit/s at 55 • C.

The dynamic performance including chirp measurements of 1.27 mm single-mode InGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) with a large gain-cavity offset is presented. The VCSELs are based on a novel p -n confinement structure with selective area epitaxial regrowth. A resonance frequency of 9.11 GHz, a slope efficiency of 0.25 W/A and an a-factor of 5.7 were measured. The modulation bandwidth is limited by electrical parasitics. Eye diagrams at 5 Gb/s with 7 dB extinction ratio and Q-factor around 5 were obtained. The results are compared with the performance of oxide-confined VCSELs with similar active layer and negative gain-cavity detuning.

We report the continuous-wave operation of an optically pumped mid-infrared (mid-IR) vertical-cavity surfaceemitting laser (VCSEL). The active region consisting of type-II antimonide quantum wells with a "W" configuration occupies a cavity formed by a semiconductor bottom mirror and dielectric top mirror. The emission wavelength of 2.9 m is nearly independent of temperature (d=dT 0.09 nm/K) compared to type-II edge-emitters and the multimode linewidth is narrow (2.9 nm). At T = 78 K, the threshold pump intensity is 940 W/cm 2 , the peak output power from a 50-m spot is 45 mW, and the differential power conversion efficiency is 4.5%. Lasing is observed up to T = 160 K.

We demonstrate a novel oxide confined GaAs-based photonic crystal vertical cavity surface emitting laser (PC-VCSEL) operating at a wavelength of 850 nm based on coherent coupling. A ring-shaped light-emitting aperture is added to the conventional PC-VCSEL, and coherent coupling is achieved between the central defect aperture and the ring-shaped light-emitting aperture. Measurements show that under the continuous-wave (CW) injected current of 20 mA, a high power of 2 mW is obtained, and the side mode suppression ratio (SMSR) is larger than 20 dB. The average divergence angle is 4.2° at the current level of 20 mA. Compared with the results ever reported, the divergence angle is reduced. photonic crystal, vertical cavity surface emitting laser, coherent coupling, divergence angle, single mode Citation: Liu A J, Qu H W, Xing M X, et al. A novel photonic crystal vertical cavity surface emitting laser based on coherent coupling.

GaN-based 2-D photonic crystal (PC) surfaceemitting lasers (PCSELs) with AlN/GaN distributed Bragg reflectors are fabricated and investigated. A clear threshold characteristic under the optical pumping at room temperature is observed at about 2.7 mJ/cm 2 with PC lattice constant of 234 nm. Above the threshold, only one dominant peak appears at 401.8 nm with a linewidth of 0.16 nm. The laser emission covers whole circular 2-D PC patterns of 50 µm in diameter with a small divergence angle. The lasing wavelength emitted from 2-D PC lasers with different lattice constants occurs at the calculated band edges, showing different polarization angles due to the light diffracted in specific directions, corresponding exactly to Γ-, K-, and M -directions in the K space. The PCSEL also shows a spontaneous emission coupling factor β of 5 × 10 −3 and a characteristic temperature of 148 K. Furthermore, the coupled-wave model in 2-D hexagonal lattice is applied to distinguish the discrepancy in threshold power and the corresponding coupling coefficient. The results show that the lasing actions within Γ, K, and M modes have a substantial relation between the threshold energy density and the coupling coefficient.

This paper summarises the development of the epitaxial growth process for visible vertical-cavity surface-emitting lasers (VCSELs) in metal-organic vapour phase epitaxy (MOVPE). The production of these devices which are of particular interest, e.g. for data communications via plastic optical fibres or for consumer electronics, is a real challenge for MOVPE due to the unfavourable material properties in the AlInGaP/AlGaAs material system necessary for this wavelength range. The following stages of the growth process have been investigated with the intention to reach maximum output power and high temperature stability: distributed Bragg reflector (DBR) doping, interface grading, number of p:DBR pairs, oxide confinement layer, cavity design, number of quantum wells, and wavelength alignment. After optimisation devices with record high output powers of more than 4 mW at 650 nm and 10 mW at 670 nm could be fabricated. Single mode VCSELs show laser emission up to 651C at 650 nm and 871C at 670 nm. Laser operation for more than 1000 h demonstrates the potential of these devices for industrial applications. r

- by M. Weyers
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- Crystal Growth, Epitaxial Growth, Data Communication, Consumer Electronics

This work reports on an optically-pumped vertical external-cavity surfaceemitting laser (VECSEL) emitting around 852 nm for Cesium atomic clocks experiments. We describe in the following our first results on the design and the characterization of a VECSEL's semiconductor structure suitable for these applications. We optimized the parameters of the structure in order to have a low threshold and a high gain structure emitting around 852 nm. With a compact setup, we obtained a 5-mW single frequency emission exhibiting broad and fine tunability around the Cesium D 2 line.

We compare the results of different optical verticalcavity surface-emitting laser models on the position-dependent effects of thin oxide apertures. Both scalar and vectorial models as well as hybrid models are considered. Physical quantities that are compared are resonance wavelength, threshold material gain, and modal stability. For large device diameters and low-order modes, the agreement between the different models is quite good. Larger differences occur when considering smaller devices and higher order modes. It is also observed that the spread in the resonance wavelengths is smaller than that for the threshold material gain.

Many applications require laser pump sources with high output power (tens to hundreds of Watts) in the smallest spot, with the smallest divergence. Such high-brightness pump sources typically use edge-emitting semiconductor lasers. However, it is also possible to use high-power two-dimensional vertical-cavity surfaceemitting laser (VCSEL) arrays for this purpose. Using a single 976nm 2D VCSEL array chip in an external cavity configuration, combined with a matching micro-lens array, we have demonstrated more than 30W output power from a 50μm/0.22NA fiber, corresponding to a brightness of 10MW/cm 2 .sr. This represents a substantial reduction in module complexity compared to edge-emitter based modules with similar brightness. These novel high-brightness pump sources exhibit some well-known intrinsic VCSEL performance features such as wavelength stability and narrow spectrum. Power and brightness can be scaled up using polarization and spectral combining.

Amplifying metasurface enabled vertical external cavity surface emitting laser

- by Luyao Xu and +2
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- Vertical Cavity Surface Emitting Laser, Terahertz Technology, Metasurface Structure

Measurements of differential carrier lifetimes on gain-guided proton-implanted vertical-cavity surface-emitting lasers with device size as a parameter are reported. The lifetimes were obtained from laser impedance measurements and from small-signal modulation optical response at subthreshold currents. A simple small-signal equivalent circuit was used to correct the optical data and to extract the carrier lifetimes from the impedance data. Carrier lifetimes ranged from 4.2 ns at 0.04 mA, to about 0.6 ns at a bias close to threshold. The measured carrier lifetimes were used to calculate the corresponding threshold carrier density (n th 6 2 10 18 cm 03 ) and recombination parameters.

Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSEL) have profound advantages compared to traditional edge-emitting lasers and its commercialization is gaining momentum as the local and access network in optical communication system expands. In this paper, we present the design parameter variations of multi quantum wells (MQW) in the active region of an InP-based long-wavelength vertical-cavity surface emitting laser (LW-VCSEL) utilizing an air-post design. The MQW and barrier thickness were varied and their effect on the device threshold current, optical power, gain, lattice temperature, peak wavelength and reflectivity were analysed and presented. Quantum well thickness of 5.5 nm and barrier thickness of 8 nm gives the optimum threshold current of 0.579 mA, optical power output of 4.2 mW, modal gain of 27 cm-1 , lattice temperature of 310.6 K and peak wavelength of 1.562 μm.

We describe the design and development of a high-speed 8-channel hybrid integrated optical transceiver package with Clock and Data Recovery (CDR) circuits. The package concept has been developed to be compatible with microprocessor package technology and at the same time allow the integration of low cost, high-performance optical components. A 90nm CMOS optical transceiver chip, 850nm 10Gb/s GaAs based vertical cavity surface emitting laser (VCSEL) array and PIN photodiode array are flip-chip mounted on a standard microprocessor Land Grid Array (LGA) package substrate. The CMOS drivers and receivers on the transceiver chip and the optical components (VCSEL and Photodiode arrays) are electrically coupled using a short transmission line routed on the top surface of the package. VCSEL and photodiode arrays are optically coupled to on-package integrated polymer waveguide arrays with metallized 45 o mirrors. The waveguides, which are terminated with multi-terminal (MT) fiber optic connectors, couple out/in highspeed optical signals to/from the chip. The CMOS transceiver chip fully integrates all analog optical circuits such as VCSEL drivers, transimpedance amplifiers and clock and data recovery (CDR) retiming circuit with a low jitter LC-PLL. Digital circuits for pseudorandom bit-pattern sequence generators (PRBS) and bit-error rate test (BERT) are fully integrated. 20Gb/s electrical and 18Gb/s optical eye diagrams for the transmitter were measured out of the package. A fully packaged transmitter and receiver including clock data recovery at 10Gb/s have also been measured.

This work presents recent results on high-power, high-effi- ciency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 980 nm. More than 230 W of continuous-wave (CW) power is demonstrated from a ~5 mm x 5 mm chip. In quasi-CW mode, smaller chips exhibit 100 W output power, corresponding to more than 3.5 kW/cm 2 of power density. We show that

- by Chuni Ghosh
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- Vertical Cavity Surface Emitting Laser, Refractive Index, Low Power, High Power

We report the onset of wave chaos in a real-world vertical-cavity surface-emitting laser. In a joint experimental and modeling approach we demonstrate that a small deformation in one layer of the complicated laser structure changes the emission properties qualitatively. Based on the analysis of the spatial emission profiles and spectral eigenvalue spacing distributions, we attribute these changes to the transition from regular behavior to wave chaos, and justify the full analogy to two-dimensional billiards by model calculations. Hence, these lasers represent fascinating devices for wave chaos studies.

In this paper, we explore a new signal acquisition method for laser Doppler velocimeter based on the self-mixing technique. The self-mixing technique is applied on commercial multimode transverse Vertical-Cavity Surface-Emitting Lasers (VCSELs) and the signal is acquired by amplification of the junction voltage of the laser diode when it was usually picked-up with an external photodiode. The sensor developed exhibits up to 25dB signal-to-noise ratio for a wide velocity range. We present a study of the sensitivity of such photodiode-free sensors versus the laser static conditions and we compare the results with usual photodetected signals. Finally we expose the advantages of this technique and propose new applications for self-mixing sensors.

- by F. Bony
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- Mixed Effects Models, IEEE, Semiconductor Lasers, Vertical Cavity Surface Emitting Laser