Linewidth enhancement factor and modulation bandwidth of lattice-matched 1.5 micron InGaAsN/GaAs quantum well lasers
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The linewidth enhancement factors of lattice-matched 1.5 µm wavelength InGaNAs/GaAs and InGaAs/InP singlequantum-well structures have been calculated using microscopic theory including many-body effects and a 10x10 effective-mass Hamiltonian.For applications which require high gain and carrier densities, InGaNAs/GaAs quantum wells have a much lower linewidth enhancement factor over a temperature range 300-400 K than InGaAs.The linewidth enhancement factor of InGaNAs is almost independent of both carrier density and temperature compared with InGaAs.The small-signal modulation characteristics of these 1.5µm lattice-matched structures and their temperature dependence have also been calculated.It is found that the maximum bandwidth of the InGaNAs/GaAs quantum well lasers is about 2.3 times larger than that of the InGaAs/InP quantum well lasers due to the high differential gain.The slope efficiency for the 3dB bandwidth as a function of optical density is twice as large for InGaNAs/GaAs as for InGaAs/InP quantum well lasers.Keywords:
Laser linewidth
Differential gain
Indium gallium arsenide
Asymmetric tunnel coupled quantum wells with built-in resonant second order nonlinearity were designed and fabricated within the antimonide material system. The quantum wells demonstrated intensive photo- and electroluminescence responses associated with optical transitions between two tunnel-split conduction band subbands and one valence band subband. The thickness of the tunnel barrier defined the optical gain bandwidth and resonance energy for the difference frequency generation. The test diode lasers based on asymmetric quantum wells with a conduction subband splitting of about 25 meV operated near 2.1 μm at room temperature and demonstrated high differential gain and excellent performance parameters. The experimental modal gain spectra showed relatively flat top and an extended bandwidth at high pumping levels.
Antimonide
Differential gain
Tunnel diode
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The differential gain of an InGaAs/GaAs vertical cavity surface emitting laser (VCSEL) has been obtained through measurement of the subthreshold spectral linewidth. The results are in close agreement with a theoretical model for a VCSEL operating at the peak of the gain spectrum. The linewidth enhancement factor has been measured to be ~0.7 at low bias currents again in agreement with theory.
Laser linewidth
Vertical-cavity surface-emitting laser
Differential gain
Subthreshold conduction
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In this paper we report a new THz Schottky detector based on vertically contacted high doped (1 × 10 18 cm-3) indium gallium arsenide (InGaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact. Compared to Schottky diodes based on gallium arsenide (GaAs) it has better zero-bias operation of 100 μA @ 0.05 V raising to more than 1 mA @ 0.27 V for lower noise application.
Indium gallium arsenide
Indium arsenide
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Indium Gallium Arsenide (InGaAs) photodetectors have been fabricated which exhibit dark current as low as 10 picoamps (−5V), quantum efficiencies as high as 35% at 850nm, 90% at 1300nm, 93% at 1550nm and failure rates below 1 in 109 hours (1 Failure unIT = 1 FIT). The devices have 75 micron diameter active regions with InP "cap" layers. Pulse response times below 35 picoseconds have also been measured.
Indium gallium arsenide
Indium arsenide
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Indium phosphide
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Quantum well (QW) lasers have been predicted to have enhanced differential gain compared to their bulk counterparts—double heterostructure (DH) Quantum well (QW) lasers have been predicted to have enhanced differential gain compared to their bulk counterparts—double heterostructure (DH) lasers.' Thus, higher modulation bandwidth is expected for QW lasers due to the higher differential gain. However, the modulation bandvvidths of QW lasers do not show too much improvement over the DH lasers in experiments, especially for the case of SQW lasers. Enhanced photon density dependent gain compression,^ which leads to anomalously high damp;; ing, and carrier transport mechanism’ have been proposed to explain modulation dynamics of QW lasers. To fully understand the modulation dynamics of QW lasers it is necessary to carefully investigate the differential gain of QW lasers. The separate confinement heterostructure (SCH) QW structure is usually employed in QW lasers to support the quantum confinement of the injected carriers and confinement of the optical field. At finite temperature, due to the Fermi-Djrac statistics, the injected carriers populate not only the energy states of the QW(s) but also the large density of states in the SCH structures. The carriers populating the SCH states contribute little to the peak gain because of their nonresonance with the optical transition at the peak gain. The carrier population of SCH states makes the quasi-Fermi energy levels change slovvly with the change of injected carrier density. These lead to lower differential gain. Figure 1 shows the calculated differential gain for a typical GaAs/ AlGaAs DH laser and typical GaAs/ AlGaAs QW lasers with various number of wells. The differential gain in SQW structure is lower than that of the DH structure. There is a differential gain enhancement as the number of wells CWR5 Fig, 1. Differential gain as a function of modal gain for a typical GaAs/AlGaAs DH laser and typical GaAs/AlGaAs QW lasers with different quantum well number. increases in MQW structures. The differential gain enhancement in MQW structures is attributed to the fact that the effect of carrier population in SCH structure is distributed among the QWs and the quasi-Fetmi level is lower in MQW structures than that in a SQW structure for the same value of modal gain. These results, combined with considerations of damping effects and operating conditions, are consistent with the experimental observations. Figure 2 shows the maximum modulation bandwidth for DH laser and QW lasers with different well number. We find that some of the previous conclusions about QW lasers need to be changed by considering the unavoidable thermal population of injected carriers in the optica] SCH region. CWR5 Fig. 2. Maximum modulation bandwidth as a function of cavity length for a typical CaAs DH laser and typical GaAs QW laser.s with different well number.
Differential gain
Gain compression
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Indium arsenide
Indium gallium arsenide
Arsenide
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The differential gain which is an important parameter for modulation dynamics in semiconductor lasers is evaluated experimentally by measuring the gain coefficient and the carrier lifetime in GaAs/AlGaAs double-heterostructure (DH) lasers, quantum well (QW) lasers, and p-modulation-doped quantum well (p-MDQW) lasers. The results indicate that the differential gain of the QW laser is 2.4 times as high as that of the DH laser, which is consistent with the theory. In addition, it is found that improvement of the differential gain using the p-MDQW structure is not so large as that expected by the theory. This result suggests that enhanced energy broadening due to the reduction of the equivalent dephasing time τeqin, which includes both the dephasing time τin due to the intraband relaxation and the band tailing effects, significantly affects the gain spectra in the p-MDQW lasers, which is confirmed by the measurement of the spontaneous emission spectra.
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Dephasing
Semiconductor optical gain
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This contribution deals with the investigation and characterisation of fully integrated broadband Terahertz (THz) Schottky diodes using silver (Ag) metallic nanowires (NWs) with 120 nm diameter as bridge contacts for zero-bias operating THz detectors based on highly doped Gallium Arsenide (GaAs) and Indium Gallium Arsenide (InGaAs) layers. The combination of InGaAs and metallic NWs shows almost 7 times higher forward current than the metallic NW with GaAs at 0.27 V with a capacitance of 0.5 fF and a series resistance of 29 Ω. The highest calculated cut-off frequency of 10.7 THz was obtained for a NW contacted vertical InGaAs diode.
Indium gallium arsenide
Equivalent series resistance
Indium arsenide
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Higher speed short-wavelength (850 nm) VCSELs are required for future high-capacity, short-reach data communication links. The modulation bandwidth of such devices is intrinsically limited by the differential gain of the quantum wells (QWs) used in the active region. We present gain calculations using an 8-band k·p Hamiltonian which show that the incorporation of 10% In in an InGaAs/AlGaAs QW structure can approximately double the differential gain compared to a GaAs/AlGaAs QW structure, with little additional improvement achieved by further increasing the In composition in the QW. This improvement is confirmed by extracting the differential gain value from measurements of the modulation response of VCSELs with optimized InGaAs/AlGaAs QW and conventional GaAs/AlGaAs QW active regions. Excellent agreement is obtained between the theoretically and experimentally determined values of the differential gain, confirming the benefits of strained InGaAs QW structures for high-speed 850-nm VCSEL applications.
Differential gain
Modulation (music)
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The conventional response band of Indium Gallium Arsenide (InGaAs) detectors ranges from 0.9 to 1.7μm. The J atmospheric window (1.25μm) in infrared astronomy falls at the center of the response band of InGaAs detectors, making them widely used in this spectral region for infrared astronomy. Three representative Chinese-made Indium Gallium Arsenide focal plane arrays (InGaAs FPAs) were selected, and corresponding interface circuits were designed to match the testing system. Key performance indicators such as dark current, gain, and readout noise were tested.
Indium gallium arsenide
Indium arsenide
Semiconductor detector
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