I. L. Krestnikov

InAs/InGaAs quantum dot structures on GaAs substrates emitting at 1.3 μm

InAs self-organized quantum dots inserted in InGaAs quantum well have been grown on GaAs substrates by molecular beam epitaxy. The lateral size of the InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases. The quantum dot emission wavelength can be controllably changed from 1.1 to 1.3 μm by varying the composition of the InGaAs quantum well matrix. Photoluminescence at 1.33 μm from vertical optical microcavities containing the InAs/InGaAs quantum dot array was demonstrated.

Subpicosecond high-power mode locking using flared waveguide monolithic quantum-dot lasers

Ultrashort pulse, high-power mode locking is demonstrated in InGaAs quantum dot lasers using a flared waveguide laser incorporating a narrow waveguide sections acting as both a mode filter and saturable absorber. 24GHz mode locking with 780fs pulses and 500mW peak powers are demonstrated at an emissions wavelength of 1.3μm.

Room-temperature photopumped InGaN/GaN/AlGaN vertical-cavity surface-emitting laser

We report photopumped room-temperature surface-mode lasing at 401 nm in a InGaAlN vertical-cavity surface-emitting laser grown on a sapphire substrate using metal–organic vapor-phase epitaxy. A 2λ cavity was formed by a quarter-wave Al0.15Ga0.85N/GaN distributed Bragg reflector on the one side of the active layer and a GaN–air interface on the other. A multilayer structure composed of 12-fold-stacked ultrathin InGaN insertions in a GaN matrix served as an active layer providing ultrahigh material gain and making possible vertical lasing without use of the upper Bragg reflector.

Ultrafast gain dynamics in 1.3 μm InAs/GaAs quantum-dot optical amplifiers: the effect of p doping

Ultrafast gain dynamics of the ground-state transition are measured in electrically pumped InAs∕GaAs quantum-dot amplifiers emitting near 1.3μm at room temperature. Gain recovery on a subpicosecond time scale occurs at high electrical injection. However, when comparing p-doped and undoped devices fabricated under identical conditions and operating at the same gain, faster absorption recovery but slower gain dynamics are observed in p-doped amplifiers. The slower gain dynamics is attributed to a reduced reservoir of excited-state electrons in p-doped quantum-dot devices, which limits the recovery of the electron ground-state occupation mediated by intradot carrier-carrier scattering.

Characterization and Modeling of Broad Spectrum InAs–GaAs Quantum-Dot Superluminescent Diodes Emitting at 1.2–1.3

High-power broadband superluminescent diodes (SLDs) emitting in the 1.2-1.3-mum region are demonstrated using InAs-GaAs quantum dots (QDs). The highest output powers of ~30-50 mW are achieved using 18 QD layers with p-doped GaAs spacers. At these high powers the device operates in a regime of broad bandwidth (~100 nm) with a spectral dip of ~5 dB between two separate peaks originated by the QD ground and excited states. Spectral calculations performed with a traveling-wave rate equation model show excellent agreement with the experimental data and provide design rules for optimizing the output spectrum. SLD characteristics are presented for two different device structures consisting of tilted and bent waveguides. The latter allows the achievement of higher output powers at lower currents. The coherence properties and the temperature characteristics are also discussed in detail.

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A detailed study of harmonic mode-locking in a quantum-dot laser diode is presented. Mode-locking of the 1^st, 2^nd, 3^rd and 6^th harmonics are demonstrated, corresponding to repetition rates ranging from 39 GHz to 238 GHz

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The photoluminescent properties of quantum dots formed in the deposition of an InSb thin film (1–3 monolayers) on GaAs(100) and GaSb(100) surface are investigated. The results indicate the importance of As-Sb substitution reactions in the formation of quantum dots on a GaAs surface.

Harmonic Mode-Locking of a Quantum-Dot Laser Diode

Through absorber length optimisation, sub-picosecond pulse generation and ultra-low timing jitter are demonstrated in a 20 GHz passive mode-locked quantum-dot laser diode. Pulsewidths as low as 796 fs and timing jitter performance of 390 fs (20 kHz-50 MHz) are achieved

Photoluminescence of InSb quantum dots in GaAs and GaSb matrices

Room temperature operation in the wavelength range of 401 to 415 nm has been successfully realized in InGaN/GaN/AlGaN vertical cavity surface emitting lasers (VCSELs) under photoexcitation. The VCSELs are grown by metal-organic vapor phase deposition and composed of a 2l vertical cavity including twelvefold stacked multiple InGaN insertions in a GaN matrix grown on top of a quarter-wave strain-compensated Al0.15Ga0.85N/GaN distributed Bragg reflector.

Absorber length optimisation for sub-picosecond pulse generation and ultra-low jitter performance in passively mode-locked 1.3 /spl mu/m quantum-dot laser diodes

A method is proposed for growing stacked InAs/InGaAs self-organized quantum dots on GaAs substrates. The technique allows fabrication of structures exhibiting intense and narrow-line photoluminescence in the 1.3 µm wavelength region. The influence of growth conditions on structural and optical characteristics was studied. The proposed structures show promise in developing vertical-cavity surface-emitting devices.