InGaAs Multiple Quantum Research Articles

Room‐Temperature Lasing of Dual‐Metal Nanoparticle Surface Lattice Resonance with Monolithic InGaAs Multiple Quantum Wells on GaAs Substrates

This study demonstrates the surface lattice resonance (SLR) laser utilizing asymmetric dual‐metallic nanoparticle arrays, incorporating a high‐refractive‐index material, which exhibits a confinement factor of 16%, enhancing the coupling between metal and dielectric materials. Multiple quantum wells (MQWs) are integrated with plasmonic SLR in the proposed structure. Through theoretical design and experimental validation, the MQW plasmonic SLR laser exhibits excellent high Q‐factor and stable operation at room temperature. This demonstration enhances laser performance and achieves low‐threshold operation with a laser threshold as low as ≈2.39 MW cm−2. This study's design of plasmonic SLR lasers further advances the realization of optoelectronic device applications.

45 nm broadband continuously tunable semiconductor disk laser

A broadband continuously tunable semiconductor disk laser is reported in this paper. The active region of gain chip is composed of InGaAs multiple quantum wells with resonant periodic gain structure, and its fluorescence peak wavelength is around 965 nm. Using the wideband characteristics of the quantum wells in gain chip, along with the simple linear cavity that is formed by a high reflectivity external mirror, the laser has a low cavity loss and a wide tuning range. The continuously tunable laser wavelength can be obtained by inserting birefringent filters with different thickness into the cavity. When the thickness of the birefringent filter is 2 mm, the wavelength tuning range of the laser is 45 nm, the maximum output power is 122 mW, and the beam quality <i>M</i><sup>2</sup> factors in the <i>X-</i> and the <i>Y-</i>directions are 1.00 and 1.02, respectively. The temperature characteristics of the surface-emitting spectra of gain chip and the narrowing effect of birefringent filter on laser linewidth h are also discussed.

Room-temperature two-color lasing by current injection into a GaAs/AlGaAs coupled multilayer cavity fabricated by wafer bonding

Room-temperature two-color lasing was demonstrated by current injection into a GaAs/AlGaAs coupled multilayer cavity for terahertz emitting devices utilizing its difference-frequency generation (DFG) inside the structure. We prepared two epitaxial wafers with (001) and (113)B orientations and they were directly bonded to form the coupled multilayer cavity. The (001) side cavity contains two types of InGaAs multiple quantum wells to realize optical gain for two-color lasing while a single GaAs layer of the (113)B side cavity is a nonlinear medium for efficient DFG. Lasing behavior was clearly observed for two modes under pulsed current conditions at room temperature. We found that the intensity relation between two-color lasings was dependent on the pulse duration because of the different temporal profiles of emission intensity. Simultaneous two-color lasing in the device was also confirmed by measuring the sum-frequency generation signal using a beta barium borate crystal.

Frequency doubling of an InGaAs multiple quantum wells semiconductor disk laser

We demonstrate a good beam quality 483 nm blue coherent radiation from a frequency doubled InGaAs multiple quantum wells semiconductor disk laser. The gain chip is consisted of 6 repeats of strain uncompensated InGaAs/GaAs quantum wells and 25 pairs of GaAs/AlAs distributed Bragg reflector. A 4 × 4 × 7 mm3 type I phase-matched BBO nonlinear crystal is used in a V-shaped laser cavity for the second harmonic generation, and 210 mW blue output power is obtained when the absorbed pump power is 3.5 W. The M2 factors of the laser beam in x and y directions are about 1.04 and 1.01, respectively. The output power of the blue laser is limited by the relatively small number of the multiple quantum wells, and higher power can be expected by increasing the number of the multiple quantum wells and improving the heat management of the laser.

Current-injection two-color lasing in a wafer-bonded coupled multilayer cavity with InGaAs multiple quantum wells

Current-injection two-color lasing has been demonstrated using a GaAs/AlGaAs coupled multilayer cavity that is a good candidate for novel terahertz-emitting devices based on difference-frequency generation (DFG) inside the structure. The coupled cavity structure was fabricated by the direct wafer bonding of (001)- and (113)B-oriented epitaxial wafers for the efficient DFG of two modes in the (113)B side cavity, and two types of InGaAs multiple quantum wells (MQWs) were introduced only in the (001) side cavity as optical gain materials. The threshold behavior was clearly observed in the current–light output curve even at room temperature. Two-color lasing was successfully observed when the gain peaks of MQWs were considerably tuned to the cavity modes by the operating temperature.

Two-color surface-emitting lasers using a semiconductor coupled multilayer cavity

Two-color surface-emitting lasers were demonstrated, employing a GaAs/AlGaAs coupled multilayer cavity composed of two cavity layers and three distributed Bragg reflector (DBR) multilayers. InGaAs multiple quantum wells (MQWs) with two different well widths were introduced only in the upper cavity, and sandwiched between p- and n-type DBRs. This current-injection type device exhibited two-color lasing in the near-infrared region under room temperature pulsed conditions. Two-color lasing was achieved when the lower cavity had an optimal thickness relative to the upper cavity thickness and the MQW emission properties.

Si and InGaAs Spatial Wavefunction-Switched (SWS) FETs with II–VI Gate Insulators: An Approach to the Design and Integration of Two-Bit SRAMs and Binary CMOS Logic

Electron wavefunctions are switched spatially from one quantum well to another by varying the gate voltage Vg in spatial wavefunction-switched (SWS) field-effect transistors (FETs), which comprise two or more coupled quantum wells serving as the transport channel. This is shown for Si/SiGe and InGaAs/AlInAs quantum well systems. The presence of charge in a particular well or channel is used to encode four states 00, 01, 10, 11. This unique property is used for two-bit processing, resulting in compact two-bit static random-access memory devices. Experimental data including capacitance–voltage peaks in Si and InGaAs multiple quantum well SWS-FETs has verified the SWS phenomenon. Replacing quantum wells by an array of cladded quantum dots, forming a quantum dot superlattice (QDSL) layer, enhances the contrast and noise margin in SWS-FETs. This paper reports I–V and C–V characteristics for a fabricated twin-drain SWS-quantum dot channel (QDC) FET comprising four layers of self-assembled SiOx-Si quantum dots. SWS-QDC-FETs are shown to be scalable to ∼9 nm, and comprise four layers of cladded quantum dots with an array of 3 × 3 forming the channel.

Ultrafast spin-polarized lasing in a highly photoexcited semiconductor microcavity at room temperature

We demonstrate room-temperature spin-polarized ultrafast ($\sim$10 ps) lasing in a highly optically excited GaAs microcavity. This microcavity is embedded with InGaAs multiple quantum wells in which the spin relaxation time is less than 10 ps. The laser radiation remains highly circularly polarized even when excited by nonresonant elliptically polarized light. The lasing energy is not locked to the bare cavity resonance, and shifts $\sim$10 meV as a function of the photoexcited density. Such spin-polarized lasing is attributed to a spin-dependent stimulated process of correlated electron-hole pairs. These pairs are formed near the Fermi edge in a high-density electron-hole plasma coupled to the cavity light field.

Research on the high indium content InGaAs multiple quantum wells wafers for λ > 1.55 μm laser diodes

The effects of TMIn flow rate and AsH3 flow rate on the photoluminescence spectra of the high indium content InGaAs multiple quantum wells for λ>1.55μm laser diodes have been investigated both experimentally and theoretically. The wavelength peak red-shifted about 4.8nm for increasing 1sccm H2 flow rate through TMIn under a AsH3 flow rate of 150sccm, while the wavelength shift increases to 6.5nm at a higher AsH3 flow rate of 300sccm. Results show that more AsH3 flow rate will promote much TMGa pyrolysis than TMIn in the high indium content InGaAs growth. Considering the influence of growth parameters, the longest wavelength of 1.889μm among the InGaAs/InGaAsP strained MQWs samples was obtained with high crystal quality.

1.9 µm hybrid silicon/III‐V semiconductor laser

A 1.9 µm hybrid silicon/III-V laser based on a wafer bonding technique is reported. The gain materials are InGaAs multiple quantum wells grown on InP substrate, with strain compensation between barriers and wells. The III-V wafer is bonded to a silicon-on-insulator wafer with processed silicon waveguides and transition tapers. Laser emission with a threshold current of 95 mA at room temperature and 45 mA at 5 °C is demonstrated.

Rapidly swept, ultra-widely-tunable 1060 nm MEMS-VCSELs

Demonstrated are 1060 nm microelectromechanical-systems-based tunable vertical-cavity surface-emitting lasers (MEMS-VCSELs) with a 100 nm continuous tuning range under repetitively scanned operation at rates beyond 500 kHz and a 90 nm continuous tuning range under static operation. These devices employ a thin strained InGaAs multiple quantum well active region integrated with a fully oxidised GaAs/AlxOy bottom mirror and a suspended dielectric top mirror. The devices are optically pumped via 850 nm light. These ultra-widely tunable lasers represent the first MEMS-VCSELs reported in this wavelength range, and are ideally suited for application in ophthalmic swept-source optical coherence tomography.

Selecting detection wavelength of resonant cavity-enhanced photodetectors by guided-mode resonance reflectors

We propose and demonstrate a novel device structure of resonant cavity-enhanced photodetector (RCE-PD). The new RCE-PD structure consists of a bottom distributed Bragg reflector (DBR), a cavity with InGaAs multiple quantum wells (MQWs) for light absorption and a top mirror of sub-wavelength grating. By changing the fill factor of the 2-D grating, the effective cavity length of RCE-PDs can be varied so the resonant wavelength can be selected post growth. Accordingly, we can fabricate an array of PDs on a single chip, on which every PD aims for a specific wavelength.

InGaAlAs∕InGaAs strain-balanced multi-quantum-well laser/semiconductor optical amplifiers operating at excited transitions

We report the design, growth, and fabrication of strain-balanced n-type modulation-doped InGaAlAs∕InGaAs multiple quantum well laser/semiconductor optical amplifiers on InP. The quantum well contains a lattice-matched InGaAs core, a compressive-strained InGaAs padding, and a tensile-strained InGaAlAs spacer. Electroluminescence spectra show higher optical gain for the quantum well e1-hh2 transition at λ=1460nm than the e1-hh1 transition at λ=1550nm. Ridge-waveguide lasers of Fabry-Pérot (FP) type and tilted-end-facet (TEF) type were fabricated. The FP laser shows a lasing peak of λ=1514nm at threshold. Additional lasing wavelengths at λ=1528 and 1545nm were observed sequentially as the injection current increased. For the TEF laser, only the emission at λ=1511nm was observed. These TE-polarized lasing wavelengths are consistent with the δ-like absorption peaks in photocurrent spectra. The lasing performance is attributed to optical transitions within quantum dots/wires which are formed by the strain-field profile and alloy segregation/migration.

High-energy saturable absorber mode-locked fiber laser system

We demonstrate a mode-locked erbium-doped fiber laser with a 1-microm InGaAs saturable absorber that produces 84-ps, 1-nJ transform-limited pulses. Measurements of the InGaAs multiple quantum well revealed a slow saturable absorber that is useful for passive mode locking. Optical fiber was added to extend the cavity and vary the repetition rate from 51 kHz to 5.4 MHz. The narrow spectral width of the laser output (<0.04 nm) permits amplification to 0.2 microJ/pulse with minimal pulse broadening. Pulse energies as large as 1.7 microJ can be achieved with pulse widths of <330 ps. Average powers of 0.5 W at megahertz repetition rates are demonstrated.

Picosecond dynamics of spin-related optical nonlinearities in InxGa1−xAs multiple quantum wells at 1064 nm

Light-induced absorption and diffraction measurements of resonantly excited 10-nm-width InGaAs multiple quantum wells have been carried out, using circularly polarized beams at 1064 nm. Spin relaxation time τs≃280±15 ps has been determined by monitoring dynamics of light absorption bleaching at 0.04 mJ/cm2, while a nonlinearly compressed spin component in diffraction varied from 220±20 ps to 115±15 ps with excitation. The kinetics of carrier grating with randomized spins allowed the determination of the bipolar diffusion coefficient D=11.5 cm2/s, hole mobility of 230 cm2/V s, and carrier lifetime τR=0.73–1 ns.

Picosecond pulse generation from passively modelocked vertical cavity diode laser at up to 15 GHz pulse repetition rate

The generation of ultrashort pulses (∼15 ps) from a passively modelocked InGaAs multiple quantum well (MQW) vertical cavity surface emitting diode laser is reported at a repetition rate up to 15 GHz, utilising a cavity configuration that incorporates a reverse-biased quantum well device as a fast saturable absorber. Pulsing at up to 20 GHz rate has been observed on a continuous-wave background.

Polarization dependence of quantum beats in quantum wells: Raman coherence and two‐exciton correlations

Time-integrated differential detection techniques are used to study quantum beats involving the light-hole and heavy-hole excitons in an optically thin InGaAs multiple quantum well. The contributions of the exciton-exciton correlations are separated from those of the intervalence-band Raman coherence and the interband (population) coherence by monitoring the signal in the probe direction and by taking advantage of the polarization selection rules for the excitonic transitions. Quantum beats are observed for pump and probe pulses with the same circular polarization, providing evidence for two-exciton correlations. A theoretical analysis based on the dynamics-controlled truncation formalism suggests that the beats for the same linear polarization arise from Raman, population, and two-exciton contributions.

Polarization switching in a tensile-strained InGaAs/InGaAsP multiple quantum well distributed feedback laser diode

An inhomogeneously biased distributed feedback (DFB) laser diode (LD) with two electrodes switched its polarization mode by 3 mA change of the bias current, maintaining single longitudinal mode oscillation. In the active layer of the LD, 13 nm thick and 0.6% tensile-strained InGaAs multiple quantum well (MQW) equalized the transverse electric and the transverse magnetic modal optical gain at 1.55 μm. With various grating pitches on the same MQW active layer, polarization switching DFB LDs were realized in the wavelength range as wide as 18 nm. The linewidth characteristics during the polarization switching were confirmed to be narrow due to the small switching current.

Growth of InGaAs multi-quantum wells at 1.3 μm wavelength on GaAs compliant substrates

InGaAs multiple quantum wells at 1.3 μm wavelength have been grown on a twist-bonded GaAs compliant substrate. The GaAs compliant substrate contains a 30 Å GaAs thin layer bonded to a GaAs bulk substrate with a 22-degree angle. Nomarski phase contrast microscopy, transmission electron microscopy (TEM), and photoluminescence were used to characterize the heteroepitaxial layers. The smooth and crosshatch-free surface morphology, dislocation-free cross-sectional TEM, and strong luminescence intensity all provide convincing evidences for substantial improvement of the quality of heteroepitaxial material using the compliant substrate technique. Research is underway to apply the concept and technique of compliant substrate to Si and other materials.

Investigation of Si-doped p-type , quantum well infrared photodetectors and multiquantum wells grown on (3 1 1)A GaAs

We have studied two Si-doped p-type quantum well infrared photodetectors (QWIPs) using AlGaAs GaAs and AlGaAs InGaAs grown on (3 1 1)A GaAs. The Si-doped AlGaAs GaAs p-QWIP exhibits a symmetrical dark I–V characteristic at all the measured temperatures from 40 to 120 K. The strained p-type AlGaAs InGaAs QWIP exhibits a slightly asymmetrical dark I–V characteristic, but is markedly less asymmetrical than that doped with beryllium. The slight asymmetry in dark I–V characteristic and the large blue-shift in responsivity spectra may be due to the thickness modulation observed from TEM and the red-shift of PL peak energy, where PL peak energies from (3 1 1)A AlGaAs InGaAs multiple quantum wells are red-shifts of 7 and 22 meV to the side-by-side grown (1 0 0).