Nonidentical Quantum Wells Research Articles

Comprehensive Modeling of Superluminescent Light-Emitting Diodes

We present a self-consistent electric and optic model for superluminescent light-emitting diodes (SLED) using 3D finite-element method. The carrier transport is calculated by the drift-diffusion method, which is coupled with the radiative recombination obtained from the solution of Shrodinger-Poison equations self-consistently. The spontaneous emission noise is described by the fundamental theory using the Green's function method. Our model allows 2D treatment of the carrier dynamics and optical confinement on the transverse plane, along with the electronic and optical variation on the longitudinal axis. The theoretical model has been benchmarked with an InP-based edge-emitting SLED. The device has nonidentical quantum wells with broad bandwidth from 1300 to 1600 nm. The results show the importance of 3D effects and demonstrate the validity of the model.

Optical excitation of nonidentical quantum wells in the active region of a vertical-external-cavity laser

Optical excitation of a semiconductor structure comprising two nonidentical quantum wells (QWs) separated by barriers absorbing the pump radiation has been numerically simulated. It is shown that the equalization of populations in the QWs can be achieved in two ways: (i) shift of the deeper QW to a region of weak carrier generation and (ii) introduction of a blocking layer preventing the transport of carriers.

Multidimensional Electro-Opto-Thermal Modeling of Broad-Band Optical Devices

This paper investigates the self-consistent modeling of broad-band optical devices such as super-luminescent light-emitting diodes (SLEDs) and semiconductor optical amplifiers. A multidimensional electro-opto-thermal approach using many-body gain theory, and temperature-dependent microscopic transport equations is presented. In addition, a Green's function based model for amplified spontaneous emission is derived from Maxwell's equations in a consistent way. To illustrate the model's validity it is implemented into an existing simulation tool and benchmarked with two InP-based edge-emitting SLEDs operating around 1310 nm, featuring nonidentical quantum wells as active region. A comparison between simulated and measured characteristics (both electro-thermal and spectral) proves the applicability of the novel model.

Novel effects in extremely broadband semiconductor optical amplifiers with non-identical quantum wells

An extremely broad emission spectrum is obtained for semiconductor optical amplifiers with multiple quantum wells fabricated on the substrate. The spectral width is nearly 400 nm (1200–1600 nm), which covers the entire usable bandwidth of an optical fiber. Broadband characteristics allow observing three novel effects: (i) the bi-directional guided effect of lasing mode in a bent waveguide of semiconductor optical amplifiers, (ii) the optical switching effect in one semiconductor optical amplifier for optical communication band, and (iii) the effect of separate confinement heterostructure layer thickness.

Simultaneous Dual-Wavelength Emission From Vertical External-Cavity Surface-Emitting Laser: A Numerical Modeling

The analysis of novel vertical external-cavity surface-emitting laser (VECSEL) designed for simultaneous dual-wavelength emission is presented. Inhomogeneous optical pumping of the nonidentical quantum wells of the active region has been studied. The novel rate equations description of our VECSEL is presented taking into account a strong time-delayed feedback. Steady-state stability conditions and the dynamics of dual-wavelength lasing have been investigated. It appears that tendency to self-pulsation due to Q-switching at high pump power is avoidable by accurate modeling and epitaxial growth of the active region of the laser

Dual-Wavelength Distributed Feedback Laser for CWDM Based onNon-Identical Quantum Well

Using non-identical quantum wells as the active material, a newdistributed-feedback laser is fabricated with period varied Bragggrating. The full width at half maximum of 115 nm is observed in theamplified spontaneous emission spectrum of this material, which isflatter and wider than that of the identical quantum wells. Twowavelengths of 1.51 μm and 1.53 μm are realized underdifferent work conditions. The side-mode suppression ratios of bothwavelengths reach 40 dB. This device can be used as the light source ofcoarse wavelength division multiplexer communication systems.

External-cavity semiconductor laser tunable from 1.3 to 1.54 μm for optical communication

Using semiconductor optical amplifiers with properly designed nonidentical quantum wells made of InGaAsP-InP materials in the external-cavity configuration, the semiconductor laser is broadly tunable. The tuning range covers from 1.3 /spl mu/m to 1.54 /spl mu/m. Without additional filtering techniques, the laser beam emitted from the linear external cavity has the sidemode suppression ratio better than 30 dB. Also, the power ratio of the lasing mode to the total output power is 90%-99%, indicating the dominance of the lasing mode in the amplification process due to the broad gain spectrum.

Sequence influence of nonidentical InGaAsP quantum wells on broadband characteristics of semiconductor optical amplifiers–superluminescent diodes

Extremely broadband emission is obtained from semiconductor optical amplifiers-superluminescent diodes with nonidentical quantum wells made of InGaAsP/InP materials. The well sequence is experimentally shown to have a significant influence on the emission spectra. With the three In(0.67) Ga(0.33) As(0.72) P(0.28) quantum wells near the n -cladding layer and the two In(0.53) Ga(0.47) As quantum wells near the p -cladding layer, all bounded by In(0.86) Ga(0.14) As(0.3)P(0.7) barriers, the emission spectrum could cover from less than 1.3 to nearly 1.55 microm, and the FWHM could be near 300 nm.

Carrier distribution, spontaneous emission and gain engineering in lasers with nonidentical quantum wells

Novel quantum-well lasers with a 100-/spl Aring/ GaAs quantum-well (QW) (/spl lambda//spl sim/840 nm) and a higher energy 40-/spl Aring/ AlGaInAs QW (/spl lambda//spl sim/810 nm) in a graded Al/sub x/Ga/sub 1-x/As separate confinement heterostructure (SCH) with the bandgap increasing from the p- to the n-side are characterized. A sizeable variation in the QW carrier densities can be achieved as a function of well composition and placement due to the built-in electric field that forces carriers toward the p-side of the SCH and the different densities of states and carrier capture rates of the QW's. Transversely emitted spontaneous emission (SE) is measured through a windowed contact to determine the relative contribution from each QW to the total SE. Information from these measurements is incorporated into a detailed device model to determine the carrier density and evaluate the gain characteristics in a new way. Since the nonidentical wells emit different photon energies, it is shown for the first time that the carrier density can be determined at a specific location within the SCH of a semiconductor laser. By changing the placement of dissimilar QW's and the grading of the SCH, it is found that the gain spectrum can be substantially engineered.