Semiconductor Laser Structures Research Articles

Optimization of high power AlGaInP laser diodes at 626 nm

The rapid advancement of 9Be+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{9}\\hbox {Be}^{+}$$\\end{document} ion-based quantum computing is creating a high demand for scalable and specialized laser sources. For this purpose, laser radiation at 313 nm is necessary which is generated by frequency doubling of 626 nm laser emission. Laser sources in this spectral region lack simplicity and need to be miniaturized. We carry out a systematic improvement of room temperature semiconductor laser structures emitting at 626 nm. They are based on a GaInP single quantum well embedded in AlGaInP grown on GaAs. We first investigate the structure theoretically and determine its limits and optima. We select the three most promising quantum well combinations, which are grown by metal-organic vapor-phase epitaxy. Furthermore, we fabricate broad-area lasers with dimensions of 1600 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m. All structures show laser operation around 626 nm. We are able to achieve a threshold current density of 721 A/cm2, a slope of 0.384 mW/mA and total maximum output power of 708 mW under pulsed excitation. Based on these results, we believe that quantum computing focusing on beryllium ions will highly benefit from these results.

Design of Mode-Locked Semiconductor Laser Comb-Based Analog Coherent Links

Multi-wavelength analog coherent links using mode-locked laser (MLL) frequency combs as transmitter and local oscillator (LO) sources are proposed. Carrier recovery (CR) in all wavelength channels is achieved using only two optical phase-locked loops (PLLs), while polarization demultiplexing and static phase offset removal are performed using cascaded optical phase shifters. A three-section Fabry-Perot semiconductor laser structure is proposed for the comb sources. Phase-error performance in a 2.6 Tb/s system using 56-Gbaud dual-polarization quadrature phase-shift keying on 13 channels is studied. For optical and microwave beat linewidths of 2 MHz and 1 kHz, respectively, achieving phase-error penalties below 1.5 dB requires PLL delays below 400 ps. A symmetric CR scheme is shown to achieve better phase-error performance than an asymmetric CR scheme. In 13-channel analog coherent links, the MLL comb-based design is projected to consume 38 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> less power than a resonator-enhanced electro-optic comb-based design and 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> less power than a design using arrays of single-wavelength lasers as transmitter and LO sources, excluding modulator driver power, which is identical for the three designs.

Study on the influence of variable temperature growth on the properties of highly strained InGaAs/GaAs MQWs grown by MOCVD

The InGaAs/GaAs multiple quantum wells (MQWs) have played an important role in the epitaxial structure of semiconductor laser, solar cell, detector and so on. However, the preparation of high-quality InGaAs/GaAs MQWs with high indium content has always been a research problem. In this paper, five periods InGaAs/GaAs MQWs were obtained with two methods by metal-organic chemical vapor deposition (MOCVD): constant and variable temperature growth methods, respectively. Our systematic theoretical and experimental studies indicated that there were wedding cake-like stacked steps on the surface of constant temperature sample, revealing an inhomogeneous distribution of layer thickness and indium content. Such interface fluctuations were manifested as two peaks in the photoluminescence (PL) spectra at low temperature, which were confirmed by theoretical fitting as the localized states emission (LE) peak and the free-carrier emission (FE) peak, respectively. For variable temperature sample, the change in the growth temperature of the barrier and well layers in each period could transform the morphology to a step-flow-mode surface, thus eliminating the localized states in MQWs. It could be seen that the variable temperature growth method was superior to the constant temperature method, the surface morphology, optical characteristics and crystal quality were all improved. This study will provide technical support for optimizing the device performance of InGaAs/GaAs MQWs with high indium content.

Long-Distance High-Power Wireless Optical Energy Transmission Based on VECSELs

Wireless charging systems are critical for safely and efficiently recharging mobile electronic devices. Current wireless charging technologies involving inductive coupling, magnetic resonance coupling, and microwave transmission are bulky, require complicated systems, expose users to harmful radiation, and have very short energy transmission distances. Herein, we report on a long-distance optical power transmission system by optimizing the external cavity structure of semiconductor lasers for laser charging applications. An ultra-long stable oscillating laser cavity with a transmission distance of 10 m is designed. The optimal laser cavity design is determined by simulating the structural parameters for stable operation, and an improved laser cavity that produces an output of 2.589 W at a transmission distance of 150 cm is fabricated. The peak power attenuation when the transmission distance increases from 50 to 150 cm is only approximately 6.4%, which proves that this wireless power transfer scheme based on a vertical external cavity surface-emitting laser can be used to realize ultra-long-distance power transmission. The proposed wireless energy transmission scheme based on a VECSEL laser is the first of its kind to report a 1.5 m transmission distance output power that exceeds 2.5 W. Compared with other wireless energy transmission technologies, this simple, compact, and safe long-distance wireless laser energy transmission system is more suitable for indoor charging applications.

Battery‐Operated Mid‐Infrared Diode Laser Frequency Combs

AbstractMid‐wave infrared (MIR, 3–5 µm) optical frequency combs (OFC) are of critical importance for spectroscopy of fundamental molecular transitions in space and terrestrial applications. Although in this band OFCs can be obtained via supercontinuum or difference frequency generation using optical pumping schemes, unprecedented source miniaturization, and monolithic design are unique to electrically‐pumped semiconductor laser structures. To date, high‐brightness OFC generation in this region has been demonstrated in quantum‐ and interband cascade lasers (QCL/ICL), yet with sub‐optimal spectral properties. Here, an MIR quantum well diode laser (QWDL) OFC is shown, whose excellent spectral uniformity, narrow optical linewidths, and milliwatt optical power are obtained at a fraction of a watt of power consumption. The continuously tunable source offers ≈1 THz of optical span centered at 3.04 µm, and a repetition rate of 10 GHz. As a proof‐of‐principle, a directly‐battery‐operated MIR dual‐comb source is shown with almost 0.5 THz of optical coverage accessible in the electrical domain in microseconds. These results indicate the high suitability of QWDL OFCs for future chip‐based real‐time sensing systems in the mid‐infrared.

Research on Silicon-Substrate-Integrated Widely Tunable, Narrow Linewidth External Cavity Lasers

Widely tunable, narrow linewidth external cavity lasers on silicon substrates have many important applications, such as white-light interferometry, wavelength division multiplexing systems, coherent optical communication, and optical fiber sensor technology. Wide tuning range, high laser output power, single mode, stable spectral output, and high side-mode suppression ratio external cavity lasers have attracted much attention for their merits. In this paper, two main device-integrated structures for achieving widely tunable, narrow linewidth external cavity lasers on silicon substrates are reviewed and compared in detail, such as MRR-integrated structure and MRR-and-MZI-integrated structure of external cavity semiconductor lasers. Then, the chip-integrated structures are briefly introduced from the integration mode, such as monolithic integrated, heterogeneous integrated, and hybrid integrated. Results show that the silicon-substrate-integrated external cavity lasers are a potential way to realize a wide tuning range, high power, single mode, stable spectral output, and high side-mode suppression ratio laser output.

Calculation of threshold current density and efficiency for multiple quantum wire of 〖Hg〗_(0.5) 〖Cd〗_(0.5) Te/〖Hg〗_(0.8) 〖Cd〗_(0.2) Te/CdTe laser

This study of semiconductor laser structure works on reducing the value of the threshold current density to improve the working conditions of the laser device. In this paper shown that the threshold current density and Optical confinement factor Г depends on Barrier width (B), and Number of well (Nw). We found any increase in Barrier width and Number of well is enhanced important parameters of diode laser such as threshold current density and confinement factor that's clearly for (Nw=2, B=40 nm) then (Г=0.175, ), while for (Nw=2, B=60 nm), that give results are (Г=0.195, ). On the other hand when changing Nw=3, the results become for (B=40 nm and B=60 nm), as follows (Г=0.275, and (Г=0.295, respectively. This investigated contributed to calculating the efficiency and work of the laser device. We found the value of slope efficiency equal (45 %) and the external quantum efficiency (50%).

Threshold current density calculation for quantum wire of 〖Hg〗_(0.5) 〖Cd〗_(0.5) Te/〖Hg〗_(0.8) 〖Cd〗_(0.2) Te/CdTe laser

This study of semiconductor laser structure works on reducing the value of the threshold current density to improve the working conditions of the laser device. In this paper shown that the threshold current density and Optical confinement factor Г depends on Barrier width (B), and Number of well (Nw). We found any increase in Barrier width and Number of well is enhanced important parameters of diode laser such as threshold current density and confinement factor that's clearly for (Nw=2, B=40 nm) then (Г=0.175, ), while for (Nw=2, B=60 nm), that give results are (Г=0.195, ). On the other hand, when changing Nw=3, the results become for (B=40 nm and B=60 nm), as follows (Г=0.275, and (Г=0.295, respectively. This investigated contributed to calculating the efficiency and work of the laser device. We found the value of slope efficiency equal (45 %) and the external quantum efficiency ( 50 %).

High-power single-mode triple-ridge waveguide semiconductor laser based on supersymmetry

To achieve a high-power single-transverse mode laser, we here propose a supersymmetry-based triple-ridge waveguide semiconductor laser structure, which is composed of an electrically pumped main broad-ridge waveguide located in the middle and a pair of lossy auxiliary partner waveguides. The auxiliary partner waveguides are designed to provide dissipative modes that can phase match and couple with the higher-order modes in the main waveguide. By appropriately manipulating the gain–loss discrimination of the modes in the laser cavity, one can effectively suppress all the undesired higher-order transverse modes while keeping the fundamental one almost unaffected, thereby ensuring stable single-mode operation with a larger emitting aperture and accordingly a higher output power than a conventional single-transverse-mode ridge waveguide diode laser.

Automated system for surface photovoltage spectroscopy.

This paper details the development of a lab-made experimental setup for surface photovoltage spectroscopy (SPS) measurements using an open-source and Arduino® microcontroller to control a monochromator and some off-the-shelf electronic components. The experimental setup is interfaced to a computer, where LabVIEW® based software manages system control and data acquisition. We also report the design of a compact sample holder, simple and easy to manufacture and handle. Results of the application of SPS to the characterization of MoO3 thin films and semiconductor laser structures are presented to validate the performance of the setup, highlighting the effectiveness of SPS for the characterization of semiconductor materials and devices.

Research on Mirror Coupling Process in Array Semiconductor Laser

In order to improve the coupling efficiency of the array semiconductor laser and the multimode fiber, this paper establishes an ideal coupling model for the general structure of the array semiconductor laser. Combined with experiments and Zemax simulation, the relationship between the size error of the mirror package and the coupling efficiency is studied. The results show that : in the displacement error, the coupling efficiency is most sensitive to the X-axis displacement; in the angle error, the coupling efficiency is more sensitive to the Y-axis rotation angle than the Z-axis rotation angle error; the coupling efficiency curve has obvious peaks and is sensitive to changes, and the tolerance is small, which puts forward higher requirements on the stability of the coupling device.

The Leap from Organic Light-Emitting Diodes to Organic Semiconductor Laser Diodes

In recent years, organic light-emitting device technology has expanded from organic light-emitting diodes (OLEDs) to organic semiconductor laser diodes (OSLDs) with the progress of sophisticated mo...

Structure and properties of current-injection organic semiconductor lasers

Structure and properties of current-injection organic semiconductor lasers

Investigation of photoelectric performance of laser diode by regulation of p-waveguide layer thickness

It is important to design semiconductor laser diode with a broad waveguide layer structure by simulation in theory for achieving high output power and high power conversion efficiency. The influence of p-waveguide layer thickness on the optical and electrical properties was studied by theoretical calculation and experimental results. Optical field distribution results indicated that transverse electric (TE) modes of the optical field mainly distribute in waveguide layer and fractional photons leaked into the cladding layer which result in increasing the optical loss. The maximum value of internal quantum efficiency was obtained when the p-waveguide layer thickness was 550 nm and its physical mechanism was revealed by boundary current density of quantum well and sheet electron and hole concentration in the active region. Moreover, the increasing band offset of p-waveguide layer could result in a decrease of the leakage current which can be explained by energy band theory. Finally, the optimal output power and photo-electronic conversion efficiency were obtained with 550 nm p-waveguide layer. The relationship among these photo-electronic parameters was analyzed, which will be favorable for designing semiconductor laser structure and providing a theoretical basis for growing high power semiconductor laser. Experimentally, a single chip with 2000 μm cavity length and 20% fill factor was fabricated, realizing a high power laser that agrees well with the theoretical results.

Nonlinear optical effects during femtosecond superradiant emission generation in semiconductor laser structures.

This paper presents theoretical and experimental studies of ultrabright internal second harmonic during femtosecond superradiant emission generation in multiple sections GaAs/AlGaAs laser structures at room temperature. Experimentally measured conversion efficiencies are by 1-2 orders of magnitude greater than expected. To explain this fact, a model based on one-dimensional nonlinear Maxwell curl equations without taking into consideration the slowly-varying envelope approximation has been developed. It has been demonstrated that strong transient periodic modulation of e-h density and refraction index dramatically affects the process of superradiance in semiconductor media and can explain the ultrastrong internal second harmonic generation.

Absorber Length Optimization of On-Chip Colliding Pulse Mode-Locked Semiconductor Laser

We present theoretical and experimental results regarding the saturable absorber length optimization for the generation of stable mode-locked regimes of a novel on-chip colliding pulse mode-locked semiconductor laser structure. We have been able to apply the design criteria acquired from previous theoretical and experimental reports to define a suitable gain section length for a given saturable absorber section length. The latter is independent from the cavity length and allows obtaining stable mode-locked regimes with the required repetition rate and pulse width in the range of picoseconds for different applications. We have developed four on-chip colliding pulse mode-locked laser structures with saturable absorber lengths ranging from 20 to 50 μm in steps of 10 μm with fundamental repetition rate at 25 GHz and twice this frequency at 50 GHz when operated in the colliding pulse mode-locked regime. The theoretical study was carried out by using the simulation tool called FreeTWM which is a free travelling wave model software designed for the study of the dynamics of multisection semiconductor lasers, while the experimental analysis was executed on the samples fabricated on a generic InP photonic integrated technology through a multi-project wafer run.

Theorical analysis of a monolithic all-active three-section semiconductor laser

We propose a novel semiconductor laser structure. It is composed of three cascaded active sections: a Fabry-Pérot laser section sandwiched between two gain-coupled distributed feedback (DFB) laser sections. We have modeled this multi-section structure. The simulation results show that compared with index- and gain-coupled DFB lasers, a significant reduction in the longitudinal spatial-hole burning can be obtained with the proposed device, and that this leads to a stable single longitudinal mode operation at relatively high optical power with a SMSR exceeding 56dB. Full Text: PDF ReferencesL.A. Coldren, "Monolithic tunable diode lasers", IEEE J. Select. Topics Quant. Electron. 6, 988 (2000) CrossRef O. Kjebon, R. Schatz, S. Lourdudoss, S. Nilsson, B. Stalnacke, L. Backbom, "30 GHz direct modulation bandwidth in detuned loaded InGaAsP DBR lasers at 1.55 [micro sign]m wavelength", Electron. Lett. 33(6), 488 (1997). CrossRef N. Kim, J. Shin, E. Sim, C.W. Lee, D.-S. Yee, M.Y. Jeon, Y. Jang, K.H. Park, "Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation", Opt. Expr. 17(16), 13851 (2009). CrossRef M.J. Wallace, R. ORreilly Meehan, R.R Enright, F. Bello, D. Mccloskey, B. Barabadi, E.N. Wang, J.F. Donegan, "Athermal operation of multi-section slotted tunable lasers", Opt. Expr. 25(13), 14426 (2017). CrossRef J.E. Carroll, J.E.A. Whiteaway, R.G.S. Plumb, "Distributed Feedback Semiconductor Lasers", Distributed feedback semiconductor lasers (IEE and SPIE, 1998). CrossRef H. Ghafour-Shiraz, Distributed Feedback Laser Diodes and Optical Tunable Filters (Wiley, 2003). CrossRef D.D. Marcenac, Ph.D dissertation (University of Cambridge, 1993). DirectLink L.M. Zhang, J.E. Carroll, C. Tsang, "Dynamic response of the gain-coupled DFB laser", IEEE J. Quant. Electr. 29, 1722 (1993). CrossRef W. Li, W.-P. Huang, X. Li, J. Hong, "Multiwavelength gain-coupled DFB laser cascade: design modeling and simulation", IEEE J. Quant. Electro. 36(10), 1110 (2000). CrossRef B.M. Mehdi, H. Rachid, in Proc. 3rd Intern. Conf. on Embedded Systems in Telecomm. and Instrument., Annaba, Algeria (2016). DirectLinkC. Henry, "Theory of the linewidth of semiconductor lasers", IEEE J.Quant. Electr. QE-18, 259 (1982). CrossRef K. Takaki, T. Kise, K. Maruyama, N. Yamanaka, M. Funabashi, A. Kasukawa, "Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes", IEEE J. Quant. Electr. 39, 1060 (2003) CrossRef

Genetically optimized on-chip wideband ultracompact reflectors and Fabry–Perot cavities

Reflectors are an essential component for on-chip integrated photonics. Here, we propose a new method for designing reflectors on the prevalent thin-film-on-insulator platform by using genetic-algorithm optimization. In simulation, the designed reflector with a footprint of only 2.16 μm×2.16 μm can achieve ∼97% reflectivity and 1 dB bandwidth as wide as 220 nm. The structure is composed of randomly distributed pixels and is highly robust against the inevitable corner rounding effect in device fabrication. In experiment, we fabricated on-chip Fabry–Perot (FP) cavities constructed from optimized reflectors. Those FP cavities have intrinsic quality factors of >2000 with the highest value beyond 4000 in a spectral width of 200 nm. The reflectivity fitted from the FP cavity resonances is >85% in the entire wavelength range of 1440–1640 nm and is beyond 95% at some wavelengths. The fabrication processes are CMOS compatible and require only one step of lithography and etch. The devices can be used as a standard module in integrated photonic circuitry for wide applications in on-chip semiconductor laser structures and optical signal processing.

Influence of the linewidth enhancement factor on the characteristics of the random number extracted from the optical feedback semiconductor laser

Random numbers play an important role in many fields, including information security, testing and engineering practice. Especially in information security, generation of secure and reliable random numbers, they have a significant influence on national security, financial stability, trade secrets and personal privacy. Generally, random number generators can be classified as two main types: pseudo random number generators and physical random number generators. Pseudo random numbers with high speed are generated by software algorithms, but the inherent periodicity will cause serious hidden dangers when they are used in information security. Random numbers based on physical entropy sources (such as electronic thermal noise, frequency jitter of oscillator, quantum randomness) can produce reliable random numbers. However, due to the limitation of traditional physical source bandwidth, their generation speeds are at a level of Mbit/s typically, which cannot meet the needs of the current high-speed and largecapacity communication. In 2008, Uchida et al. (2008 Nat. Photon. 2 728) realized the physical random number of 1.7 Gbit/s by using a wideband chaotic laser for the first time. The emergence of wideband physical entropy sources such as chaotic laser greatly promote the rapid development of the physical random number generators. As far as we know, a semiconductor laser can generate wideband chaotic signals under external disturbances such as optical feedback, optical injection or photoelectric feedback. However, compared with the structures of other two lasers, the structure of the optical feedback semiconductor laser is simple and easy to integrate. Therefore, chaotic signals have received great attention to produce high-speed physical random number extracted from the optical feedback semiconductor laser. In the reported schemes, a variety of post-processing methods are used to improve the speed and randomness of random numbers. Besides, optimizing the chaotic entropy source can also improve the performance of random number. So far, the influence of internal parameters on the dynamic characteristics of semiconductor lasers has attracted wide attention. The linewidth enhancement factor is one of the key parameters for a semiconductor laser. The values of linewidth enhancement factor are different, depending on the type of semiconductor laser. The existence of linewidth enhancement factor results in a large number of unstable dynamic characteristics of semiconductor lasers. Therefore, it is of great significance for studying the influence of the linewidth enhancement factor on performance of random numbers. In this paper, we focus on the influence of the linewidth enhancement factor on the randomness of the obtained random numbers. The time delay characteristics and complexity are two important parameters to measure the quality of chaotic signals. The simulation results show that with the increase of the linewidth enhancement factor, the time delay characteristic peak of the chaotic signal from an optical feedback semiconductor laser decreases gradually, meanwhile, the maximum Lyapunov exponent of chaotic signal increases gradually. The randomness of random numbers, generated by the chaotic signal from the optical feedback semiconductor laser under different linewidth enhancement factors, is tested by NIST SP 800-22. The test results show that semiconductor laser with larger linewidth enhancement factor is chosen as a physical entropy source to generate random numbers with high quality.

Investigation of Carrier Conduction Mechanism over InAs/InP Quantum Dashes and InAs/GaAs Quantum Dots Based p-i-n Laser Heterostructures

Charge transfer characteristics of the long wavelength semiconductor laser structures, containing quantum dot layers (QDs), were investigated by means of temperature dependent current-voltage and electroluminescence measurements over InAs/InP, and InAs/GaAs based p-i-n structures. In InAs/InP elongated QDs (QDashes) structure, injected carriers were tunneled from the quantum well into QDashes through a thin barrier and subsequently recombined within QDashes. Meanwhile, for InAs/GaAs structure, tunneling kind transport was exhibited in both forward and reverse bias voltage directions. The onset of light took place when the forward bias exceeded 1.3 V (3 V) for InAs/InP (InAs/GaAs) p-i-n structure through electroluminescence measurements. The peak value of emitted laser light for InAs/InP QDashes and InAs/GaAs QDs occurred in 1.55 μm and 1.3 μm, respectively.