Showing papers on "Semiconductor optical gain published in 2000"
TL;DR: It is demonstrated that light amplification is possible using silicon itself, in the form of quantum dots dispersed in a silicon dioxide matrix, which opens a route to the fabrication of a silicon laser.
Abstract: Adding optical functionality to a silicon microelectronic chip is one of the most challenging problems of materials research. Silicon is an indirect-bandgap semiconductor and so is an inefficient emitter of light. For this reason, integration of optically functional elements with silicon microelectronic circuitry has largely been achieved through the use of direct-bandgap compound semiconductors. For optoelectronic applications, the key device is the light source--a laser. Compound semiconductor lasers exploit low-dimensional electronic systems, such as quantum wells and quantum dots, as the active optical amplifying medium. Here we demonstrate that light amplification is possible using silicon itself, in the form of quantum dots dispersed in a silicon dioxide matrix. Net optical gain is seen in both waveguide and transmission configurations, with the material gain being of the same order as that of direct-bandgap quantum dots. We explain the observations using a model based on population inversion of radiative states associated with the Si/SiO2 interface. These findings open a route to the fabrication of a silicon laser.
2,204 citations
TL;DR: In this article, the authors presented experimental evidence for the synchronization of two semiconductor lasers exhibiting chaotic emission on sub-nanosecond time scales, where the receiver acts as a chaos pass filter, which reproduces the chaotic fluctuations of the transmitter, but suppresses additionally encoded signals.
Abstract: We present experimental evidence for the synchronization of two semiconductor lasers exhibiting chaotic emission on subnanosecond time scales. The transmitter system consists of a semiconductor laser with weak to moderate coherent optical feedback and therefore exhibits chaotic oscillations. The receiver system is realized by a solitary semiconductor laser in which a fraction of the transmitter signal is coherently injected. We find that for a considerably large parameter range, synchronized receiver output can be achieved. We discuss the physical mechanism and demonstrate that the receiver acts as a chaos pass filter, which reproduces the chaotic fluctuations of the transmitter laser, but suppresses additionally encoded signals. Signal extraction at frequencies of up to 1 GHz has been achieved. Thus we provide a simple and robust optical chaos synchronization system that is promising for the realization of communication by sending signals with chaotic carriers.
312 citations
TL;DR: In this paper, a surface-emitting semiconductor laser has been passively mode-locked in an external cavity incorporating a semiconductor saturable absorber mirror, with a repetition rate variable around 4.4 GHz.
Abstract: A surface-emitting semiconductor laser has been passively mode locked in an external cavity incorporating a semiconductor saturable absorber mirror. The gain medium consists of a stack of 12 InGaAs-GaAs strained quantum wells, grown above a Bragg mirror structure, and pumped optically by a high-brightness diode laser. The mode-locked laser emits pulses of 22-ps full-width at half maximum duration at 1030 nm, with a repetition rate variable around 4.4 GHz.
223 citations
TL;DR: In this paper, surface-plasmon modes confined at the interface between a metal and a semiconductor are exploited in place of conventional dielectric waveguides for the realization of a λ∼17μm semiconductor laser.
Abstract: Surface-plasmon modes confined at the interface between a metal and a semiconductor are exploited in place of conventional dielectric waveguides for the realization of a λ∼17 μm semiconductor laser. The device is based on the quantum cascade concept and outperforms with its 38 mW of peak output power and 240 K of maximum operating temperature any previous semiconductor laser of comparable wavelength. Pure single-wavelength emission with a tuning rate of ∼1 nm/K is achieved using Bragg reflection from a two-metal grating that modulates the skin depth of the surface plasmons.
134 citations
TL;DR: In this article, the presence of switching between two fundamental modes with orthogonal linear polarization in vertical-cavity surface-emitting lasers and the current at which this phenomenon occurs depend on both the magnitude and the orientation of an externally induced in-plane anisotropic strain.
Abstract: We experimentally demonstrate that the presence of switching between two fundamental modes with orthogonal linear polarization in vertical-cavity surface-emitting lasers and the current at which this phenomenon occurs depend on both the magnitude and the orientation of an externally induced in-plane anisotropic strain. We interpret this behavior by considering the anisotropy in gain and in refractive index, both induced by the in-plane strain, and by accounting for a redshift of the two gain curves as a result of current-induced heating.
113 citations
TL;DR: In this article, a diode-pumped broadband multiple-quantum-well vertical-external-cavity surface-emitting semiconductor laser has been developed for high-sensitivity intracavity laser-absorption spectroscopy.
Abstract: A diode-pumped broadband multiple-quantum-well vertical-external-cavity surface-emitting semiconductor laser has been developed for high-sensitivity intracavity laser-absorption spectroscopy. The semiconductor structure design has been optimized so as to provide maximum laser-emission bandwidth and wavelength tunability. The laser has a 100-mW threshold of continuous room-temperature operation, and it can be tuned within 25 nm around its design wavelength (980 nm). A detection limit lower than 10-10 per centimeter of absorption path has been achieved, given ∼3×10-11 cm-1 Hz-1/2. Its spectro-temporal dynamics has been studied in the time range from a few microseconds to ∼1 s. No evidence of nonlinear mode interactions, which in many cases limit the sensitivity, has been observed. We have also shown that with a cavity length reduced to 2.5 cm, the laser is very attractive as a tunable single-frequency source owing to its stable operation in a single TEM00 mode at a pump power of up to 1 W.
111 citations
TL;DR: In this paper, a computer simulator of semiconductor optical amplifiers is presented, where the nonlinear input-output response of the device is characterized in terms of a complex gain, representing the accumulated gain and wavevector change of the propagating field across the active waveguide.
Abstract: We present a computer simulator of semiconductor optical amplifiers. The nonlinear input-output response of the device is characterized in terms of a complex gain, representing the accumulated gain and wavevector change of the propagating field across the active waveguide. We account for the gain saturation induced by stimulated recombination and by the perturbation of the carrier quasi-equilibrium distribution within the bands. A rigorous elimination of the spatial coordinate allows us to reduce the description of the amplifier dynamics to the solution of a set of ordinary differential equation for the complex gain. If the waveguide internal loss is negligible, the spatial inhomogeneity of the complex gain is implicitly yet exactly taken into account by the reduced model. The accuracy of the reduced model is the same for models based on the direct solution of the set of partial differential equations describing the interaction between the optical field and the active semiconductor waveguide, but the model is computationally much simpler. To preserve the input-output characteristics of the model, we include the amplified spontaneous emission noise in the device description by an equivalent signal applied to the device input and amplified by the saturated gain. At the expense of a minor increase of the program complexity, the waveguide internal loss may also be included. We report on the comparison between the output of the simulator and the results of four-wave mixing experiments in various pump-signal configurations. Good agreement is obtained.
89 citations
TL;DR: In this article, the authors report on advances in vertical-cavity surface-emitting lasers (VCSELs) and VCSOAs operating at 1.3 and 1.55 /spl mu/m.
Abstract: We report on advances in vertical-cavity surface-emitting lasers (VCSELs) and vertical-cavity semiconductor optical amplifiers (VCSOAs) operating at 1.3 and 1.55 /spl mu/m. These devices have the potential to dramatically reduce manufacturing costs compared to traditional in-plane devices, while allowing for the possibility of producing integrated modules and arrays on wafer. A number of different technologies have been proposed and demonstrated for these devices. We discuss the different materials systems used for distributed Bragg reflectors (DBRs) and active regions. Recent designs and results are summarized. Wafer bonded VCSELs and VCSOAs are examined in detail.
84 citations
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TL;DR: The recent achievement of compact blue-emitting gallium nitride semiconductor lasers is likely to have far-reaching technological and commercial effects as discussed by the authors, and the high photon energy will open up new applications for these inexpensive, compact light sources.
Abstract: The recent achievement of compact blue‐emitting gallium nitride semiconductor lasers is likely to have far‐reaching technological and commercial effects. The lasers' short wavelengths—around 400 nm, half that of gallium arsenide‐based lasers—permit higher spatial resolution in applications such as optical storage and printing. And the high photon energy will open up new applications for these inexpensive, compact light sources. An aesthetic satisfaction with these devices stems from finally extending the existing and mature semiconductor laser technology for the near‐infrared and red to encompass the “new frontier” blue and near‐ultraviolet regions, thereby bridging the entire visible spectrum. At the same time, there are significant research opportunities arising from a plethora of poorly understood microscopic issues in the underlying material system, which include such fundamental properties as charge control, transport, and formation of optical gain for stimulated emission.
79 citations
TL;DR: In this article, the authors compared the performance of gain switching, Q-switching, and mode locking for femtosecond and picosecond pulses with different levels of maximum pulse power and minimum duration.
Abstract: Although diode lasers are almost ideal sources for ultrahigh-speed data communication systems, system performance remains critically dependent on the quality of the optical pulses that they generate. Uniquely among lasers, the output power can be modulated directly by modulating the diode current. However, this leads to relaxation oscillations and a roll-off at high frequencies that is superimposed on the frequency response of the drive circuit. This is limited by parasitics and maximum modulation frequencies range from 1 to 70?GHz, depending on the type of laser and its packaging. The higher values are obtained with short cavity lengths and tight optical confinement, the highest frequencies being achieved in vertical-cavity devices. Modulation bandwidth is usually limited by circuit parasitics, device heating and the maximum power-handling capability of the laser facets. The generation of picosecond and femtosecond pulses demands special techniques and three - gain switching, Q-switching and mode locking - are discussed in detail, with their relative advantages and disadvantages compared. Very short pulses inherently contain a significant spread of wavelengths and their generation requires the optical gain in the laser medium to extend across that wavelength range. While diode lasers satisfy this criterion better than many other types, the effect of gain non-linearities and carrier-transport effects prevent the Fourier-transform limit from being achieved in practice. As a result, external pulse-compression techniques, which exploit the detailed temporal and spectral properties of the laser pulses, such as frequency chirping, self-phase modulation and group velocity dispersion, are becoming more important, and diode lasers are increasingly challenged as primary sources by compact, efficient, diode-pumped solid-state lasers. The paper summarizes the levels of maximum pulse power and minimum duration that have been achieved using the various techniques.
77 citations
TL;DR: In this article, a multiwavelength, fiber ring laser source is demonstrated, which generates 10 wavelength channels, simultaneously mode-locked and synchronized at 30 GHz, each producing 7-ps pulses.
Abstract: A multiwavelength, fiber ring laser source, is demonstrated. It generates 10 wavelength channels, simultaneously mode-locked and synchronized at 30 GHz, each producing 7-ps pulses. The mode-locking technique relies on the gain saturation of the semiconductor amplifier from an external optical pulse train to impose the simultaneous mode-locking of the 10 wavelengths.
TL;DR: In this article, the thickness and position of an oxide layer inside a vertical-cavity surface-emitting laser structure have been optimized for minimum optical scattering loss, and the optical index guiding provided by the oxide aperture is very small.
Abstract: The thickness and position of an oxide layer inside a vertical-cavity surface-emitting laser structure have been optimized for minimum optical scattering loss. In the resulting structure, the index guiding provided by the oxide aperture is very small. Consequently, for an oxide aperture radius <2 μm, the optical mode is only weakly confined. In devices using such small apertures, the formation of a thermal lens has a strong influence on optical guiding. The thermal lens leads to lower threshold currents and increased differential efficiency with continuous wave as compared to pulsed injection operation in devices with small apertures.
TL;DR: An experimental and theoretical study of relative intensity noise (RIN) spectra of side-mode injection-locked Fabry-Perot semiconductor lasers is reported in this paper, where the injection-locking technique effectively increases the relaxation oscillation frequency from 4.5 GHz to 12 GHz and enhances relaxation peaks of the slave laser RIN spectra.
Abstract: An experimental and theoretical study of relative intensity noise (RIN) spectra of side-mode injection-locked Fabry–Perot semiconductor lasers is reported. It is shown that the injection-locking technique effectively increases the relaxation oscillation frequency from 4.5 GHz (free-running mode) to 12 GHz (injection-locked mode) and enhances relaxation peaks of the slave laser RIN spectra. Results from our theoretical model, which include the key parameters for semiconductor quantum-well lasers, such as the linewidth enhancement factor, the nonlinear gain saturation coefficients, and optical confinement factor, show good agreement with our experimental results.
TL;DR: In this paper, the pulsed operation of a GaAs/AlGaAs quantum-cascade laser was reported up to 258 K. The maximum peak-collected power at 77 K was 520 mW per facet and still 27 mW at 258 K, and the temperature dependence of the threshold current density was characterized by a T0=128 ǫK.
Abstract: The pulsed operation of a GaAs/AlGaAs quantum-cascade laser is reported up to 258 K. These devices emit at 11.3 μm and are based on a plasmon-confinement waveguide. To optimize the material gain, the active region is designed to diminish electron escape to continuum states. Gain and threshold measurement show evidence of better carrier confinement and improved thermal behavior compared to λ≈9 μm GaAs quantum-cascade lasers. The maximum peak-collected power at 77 K is 520 mW per facet and still 27 mW at 258 K. The temperature dependence of the threshold current density is characterized by a T0=128 K.
TL;DR: In this article, the authors present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting laser (VCSEL) stabilizes the polarization of the emitted light.
Abstract: We present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting lasers (VCSELs) stabilizes the polarization of the emitted light. Anisotropies in the gain and loss mechanisms introduced by asymmetric current injection are considered to explain this effect. The design scheme opens perspectives to obtain actual polarization control in VCSELs.
TL;DR: A review of different mechanisms that have been proposed to explain the excess noise observed in semiconductor lasers, including imperfect anticorrelations in multimode lasers, and Petermann excess noise factor in single-mode lasers, can be found in this article.
Abstract: Single-mode laser theory for semiconductor lasers predicts sub-Poissonian light generation for a laser quietly driven far above threshold. Experiments have shown however that only few laser diodes exhibits such reduced intensity noise. We present a review of different mechanisms that have been proposed to explain the excess noise observed in semiconductor lasers, including imperfect anticorrelations in multimode lasers, and Petermann excess noise factor in single-mode lasers.
TL;DR: In this article, a streak camera was used to measure the three Stokes polarization parameters during a polarization switch of a vertical-cavity semiconductor laser, which takes on average a few nanoseconds; this value agrees with a theoretical treatment based upon the Fokker-Planck equation.
Abstract: Using a streak camera we have measured the three Stokes polarization parameters during a polarization switch of a vertical-cavity semiconductor laser. The switch occurs along a corkscrew path on the Poincare sphere and takes on average a few nanoseconds; this value agrees with a theoretical treatment based upon the Fokker-Planck equation.
TL;DR: A theory of the distribution of trajectories along which a fluctuating system moves over a potential barrier in escape from a metastable state and it is argued that the specific features of this distribution may give an insight into the nature of dropout events in lasers.
Abstract: We report a direct experimental observation and provide a theory of the distribution of trajectories along which a fluctuating system moves over a potential barrier in escape from a metastable state. The experimental results are obtained for a semiconductor laser with optical feedback. The distribution of paths displays a distinct peak, which shows how the escaping system is most likely to move. We argue that the specific features of this distribution may give an insight into the nature of dropout events in lasers.
TL;DR: In this paper, the authors investigated the dependence of the gain and absorption in GaNAs/GaAs quantum well lasers on the valence-band offset and found that the calculated absorption strength, gain amplitudes, and gain bandwidth depend crucially on the value of this offset.
Abstract: The dependence of the gain and absorption in GaNAs/GaAs quantum well lasers on the valence-band offset is investigated. The calculated absorption strength, gain amplitudes, and gain bandwidth are found to depend crucially on the value of this offset. The shift of the peak gain transition energy with carrier density is shown to depend strongly on the magnitude of the offset, providing what should be a useful means to determine the offset experimentally.
TL;DR: In this paper, a distributed feedback (DFB) laser is proposed to achieve a single-wavelength emission (called single-mode operation) as opposed to the usually multiple-mode emission of free-running Fabry-Perot resonators.
Abstract: The quantum cascade (QC) laser does not involve the material bandgap for the generation of light. Therefore, InP- and GaAs-based III-V semiconductor materials can now be used for the generation of long-wavelength, mid-infrared light. These materials are also straightforward to process and pattern. This is essential for the more sophisticated device geometries such as distributed feedback (DFB) lasers. DFB lasers provide a very elegant and reliable method to achieve a well-defined single-wavelength emission (called single-mode operation) as opposed to the usually multiple-mode emission of free-running Fabry-Perot resonators. QC-DFB lasers were first demonstrated in 1996. They have evolved very rapidly and have already shown great promise in many different gas-sensing applications.
TL;DR: In this article, the authors present an explanation of the optical gain and differential gain of two types of self-assembled quantum dots in the laser active region, which shows 1.16 and 1.31 μm spontaneous emission from the ground state at room temperature.
Abstract: This letter presents an explanation of the optical gain and differential gain of two types of self-assembled quantum dots in the laser active region, which shows 1.16 and 1.31 μm spontaneous emission from the ground state at room temperature. The gain spectrum was measured using the Hakki–Paoli method up to the lasing threshold. The maximum optical gain of the ground state was found to be 150–400 cm−1 and the differential gain to be 3×10−15–1×10−16 cm2, which agrees quite well with the calculation, taking into account both homogeneous broadening and inhomogeneous broadening. Our results will be a guide to the design of laser structures.
TL;DR: In this article, a two-step metalorganic chemical vapor deposition growth process is used to fabricate antiguided vertical-cavity surface-emitting lasers (VCSELs) incorporating a simplified-antiresonant reflecting optical waveguide (S-ARROW) design.
Abstract: A two-step metalorganic chemical vapor deposition growth process is used to fabricate antiguided vertical-cavity surface-emitting lasers (VCSELs) incorporating a simplified-antiresonant reflecting optical waveguide (S-ARROW) design. Preliminary results show single-mode cw operation up to 1 mW output power from a 12 μm-diam (λ=930 nm) S-ARROW VCSEL with a large lateral index step (Δn=0.1). Modal discrimination in the S-ARROW-VCSEL is calculated using a fiber-mode approximation and device optimization for high-single-mode powers is discussed.
TL;DR: In this paper, the width of the bistability loop may be enhanced by increasing the injection power of a vertical cavity surface-emitting semiconductor laser subject to optical injection.
Abstract: Pure frequency-polarisation bistability in a vertical cavity surface-emitting semiconductor laser subject to optical injection has been observed. It was found that the width of the bistability loop may be enhanced by increasing the injection power.
Patent•
22 Jun 2000TL;DR: In this article, a cavityless vertical semiconductor optical amplifier is proposed which includes an active region of an intrinsic bulk semiconductor material sandwiched between p-and n-layers of semiconductor materials in which a vertical gain channel of a predetermined confined cross-sectional configuration is formed to constitute an amplification region of the optical amplifier.
Abstract: A cavity-less vertical semiconductor optical amplifier is provided which includes an active region of an intrinsic bulk semiconductor material sandwiched between p- and n-layers of semiconductor materials in which a vertical gain channel of a predetermined confined cross-sectional configuration is formed to constitute an amplification region of the optical amplifier. The amplification region is sandwiched between layers of p- and n-doped layers of linearly graded semiconductor material supplying holes and electrons to the active region upon switching “ON” of the optical amplifier. Several factors contribute to substantial amplification of an optical signal at a relatively low injection current which include a relatively long active region allowing sufficient single pass gain as well as a strictly confined cross-sectional configuration of the vertical gain channel which reduces the active volume of the amplification region resulting in substantially high gain at a relatively low current. Flattening of the conduction band and valence band profiles allows easy access of the holes and electrons into the active region. The cavity-less vertical semiconductor optical amplifier of the present invention is intended for multidimensional architectural structures for high speed communication.
TL;DR: The technology of the high power diode lasers is explained as well as examples for materials processing applications, which are partially even already introduced in industrial manufacturing.
Abstract: High Power Diode Lasers with a power from a few ten watts up to several kilowatts are entering the laser materials processing area since a few years now. Because of their construction, based on a high quantity of single semiconductor laser components, which provide a rather low power and which are coupled together by special optical elements, they can provide a high power, but a rather poor beam quality, compared with conventional lasers. Therefore, they are attractive for those applications, where moderate beam quality is acceptable or even advantageous for the process. In this paper we will explain the technology of the high power diode lasers as well as give examples for materials processing applications, which are partially even already introduced in industrial manufacturing.
Patent•
11 Aug 2000
TL;DR: In this paper, a fixed laser of easy maintenance and high durability is used as a laser and further made into linear laser light and throughput is improved so that the production cost is reduced as a whole.
Abstract: PROBLEM TO BE SOLVED: To provide a laser device and a laser annealing method, with which the crystalline semiconductor film of great crystal particle size can be provided and the running cost is reduced. SOLUTION: The fixed laser of easy maintenance and high durability is used as a laser and further made into linear laser light and throughput is improved so that the production cost is reduced as a whole. Further, by irradiating the front and back of an amorphous semiconductor film with such laser light, the crystalline semiconductor film of great crystal particle size is provided.
Patent•
17 Apr 2000TL;DR: In this paper, a thermal sensor is coupled to a diode-laser structure in a place where the temperature gradient across the semiconductor diode laser is close to zero.
Abstract: A semiconductor diode laser with thermal sensor control comprises a heat sink, a diode-laser structure, and a thermal sensor thermally coupled to said diode-laser structure in a place where the temperature gradient across the semiconductor diode laser is close to zero.
TL;DR: In this article, the effects of pump-induced stimulated recombination and cross-gain saturation were derived for the high-speed modulation response of a QW laser in the presence of an external microwave modulated optical pump in the gain region.
Abstract: We present theory and experiment for the high-speed modulation response of a quantum-well (QW) laser in the presence of an external microwave modulated optical pump in the gain region. The model includes the effects of pump-induced stimulated recombination and cross-gain saturation. Expressions for the small-signal modulation response of the test laser under gain modulation are derived. We also present experimental results using a multiple-QW InGaAlAs Fabry-Perot (FP) laser at 1.552 /spl mu/m as the test laser and an external pump by a 1.542 /spl mu/m DFB laser. Comparison between electrical modulation and optical cross-gain modulation (XGM) of the test laser is also presented, which shows improvement of the modulation bandwidth by optical XGM. Our data show a reduction of carrier lifetime with increasing optical pumping, a shift of the test-laser threshold current, a change in the K factor, and a variation of the relaxation frequency with different pump powers. The experimental results agree very well with the theoretical results.
TL;DR: In this article, a review of long-wavelength optical fiber communications, especially for singlemode semiconductor lasers at the longwavelength range of 1.5 /spl mu/m and the dynamics of their lasing wavelength properties, which limit the transmission bandwidth of a single-mode fiber, are reviewed.
Abstract: Research activities devoted to long-wavelength optical fiber communications, especially for single-mode semiconductor lasers at the long-wavelength range of 1.5 /spl mu/m and the dynamics of their lasing wavelength properties, which limit the transmission bandwidth of a single-mode fiber, are reviewed. Advanced semiconductor lasers based on the single-mode operating nature, such as wavelength tunable lasers and photonic integrated circuits are also reviewed.
01 Jun 2000
TL;DR: In this article, the role of charge carriers as well as acoustical and optical phonons in quantum structures in the design and modelling of novel semiconductor lasers such as the tunnel injection laser, quantum well intersubband lasers, and quantum dot lasers is discussed.
Abstract: This volume includes highlights of the theories underlying the essential phenomena occurring in novel semiconductor lasers as well as the principles of operation of selected heterostructure lasers. To understand scattering processes in heterostructure lasers and related optoelectronic devices, it is essential to consider the role of dimensional confinement of charge carriers as well as acoustical and optical phonons in quantum structures. Indeed, it is important to consider the confinement of both phonons and carriers in the design and modelling of novel semiconductor lasers such as the tunnel injection laser, quantum well intersubband lasers, and quantum dot lasers. The full exploitation of dimensional confinement leads to the capability of scattering time engineering in novel semiconductor lasers.