We report room temperature injection lasing in the yellow-orange spectral range (599-605 nm) in (Al
Ga
)
In
P-GaAs diodes with 4 layers of tensile-strained In
Ga
P quantum dot-like insertions. The ...wafers were grown by metal-organic vapor phase epitaxy side-by-side on (811), (211) and (322) GaAs substrates tilted towards the direction with respect to the (100) surface. Four sheets of GaP-rich quantum barrier insertions were applied to suppress leakage of non-equilibrium electrons from the gain medium. Laser diodes having a threshold current densities of ~7-10 kA/cm
at room temperature were realized for both (211) and (322) surface orientations at cavity lengths of ~1mm. Emission wavelength at room temperature ~600 nm is shorter by ~8 nm than previously reported. As an opposite example, the devices grown on (811) GaAs substrates did not show lasing at room temperature.
Virtual cavity in distributed Bragg reflectors Shchukin, V A; Ledentsov, N N; Kalosha, V P ...
Optics express,
2018-Sep-17, 2018-09-17, 20180917, Letnik:
26, Številka:
19
Journal Article
Recenzirano
Odprti dostop
We show theoretically and experimentally that distributed Bragg reflector (DBR) supports a surface electromagnetic wave exhibiting evanescent decay in the air and oscillatory decay in the DBR. The ...wave exists in TM polarization only. The field extension in the air may reach several wavelengths of light. Once gain medium is introduced into the DBR a novel class of diode lasers, semiconductor optical amplifiers, light-emitting diodes, etc. can be developed allowing a new type of in-plane or near-field light outcoupling. To improve the wavelength stability of the laser diode, a resonant cavity structure can be coupled to the DBR, allowing a coupled state of the cavity mode and the near-field mode. A GaAlAs-based epitaxial structure of a vertical-cavity surface-emitting laser (VCSEL) having an antiwaveguiding cavity and multiple GaInAs quantum wells as an active region was grown and processed as an in-plane Fabry-Pérot resonator with cleaved facets. Windows in the top stripe contact were made to facilitate monitoring of the optical modes. Three types of the optical modes were observed in electroluminescence (EL) studies under high current densities > 1 kA/cm
. Mode A with the longest wavelength is a VCSEL-like mode emitting normal to the surface. Mode B has a shorter wavelength, emitting light at two symmetric lobes tilted with respect to the normal to the surface in the direction parallel to the stripe. Mode C has the shortest wavelength and shifts with a temperature at a rate 0.06 nm/K. Polarization studies reveal predominantly TE emission for modes A and B and purely TM for mode C in agreement with the theory. Spectral position, thermal shift and polarization of mode C confirm it to be a coupled state of the cavity mode and near-field DBR surface-trapped mode.
Results are given for a kinetic study of the synthesis of a new fullerene derivative containing a diterpene fragment obtained using HPLC and subsequent mathematical modelling. Kinetic and activation ...parameters were found for the cyclopropanation of fullerene using the Bingel procedure and a reaction mechanism was proposed. The optimal synthesis conditions were found to entail a slight excess of a chlorine‑containing cyclopropanation agent and carrying out the reaction at room temperature.
Results are presented on a comparative study of InGaAs/GaAs/AlGaAs coupled large optical cavity (CLOC) laser heterostructures emitting at either 1.03 or 0.98 μm. The smaller energy of carrier ...localization in the active region of the latter structure leads to stronger carrier leakage out of the quantum well that in its turn results in a higher internal optical loss, higher threshold current density and more pronounced temperature sensitivity. In continuous wave regime, the maximal output power of 8 W in the 0.98-μm lasers is found to be limited by the thermal rollover, whereas in the longer wavelength laser it is 10.8 W being limited by the catastrophic optical mirror damage.
We present a systematic study of basic characteristics of edge-emitting lasers based on a new type of quantum-sized InGaAs active medium grown on GaAs substrates. The active region referred to as ...quantum-well-dots (QWDs) comprises properties of quantum wells (QWs) and quantum dots (QDs). We have fabricated and investigated lasers with the active regions consisted of 1, 2, 5 and 10 layers of the QWDs. The low internal loss has allowed us to obtain maximal optical power as high as 8.8 W in the continuous wave (CW) regime. We have shown that QWD-based active media are very promising for devices requiring high gain, stacking a large number of layers in the active region, and suppressing of lateral carrier transport.
The influence of waveguide parameters (thicknesses and contrasts in both transverse and lateral directions) on optical mode compositions in narrow-ridge lasers is numerically investigated. The ...proposed numerical model explains our experimental results on the drastic difference in optical mode compositions in broad-area and narrow-ridge lasers processed from the same wafer based on a broadened GaAs/AlGaAs transverse-waveguide heterostructure. It is shown that in the broadened transverse waveguides the fundamental mode tends to have a much lower 2D optical confinement factor than high-order modes. We suppose that waveguides possessing no more than two transverse eigenmodes would provide more opportunities for designing narrow-ridge lasers with robust single-mode emission.
Having investigated narrow-ridge lasers based on a single layer of InGaAs quantum well-dots emitting at the wavelength of 1.06 μm we have shown anomalous transverse multimode lasing not observed in ...the broad-area lasers. The effect is shown to be caused by the wavelength shift triggered by the ground state gain saturation.
We present a study of high-power characteristics of edge-emitting lasers based on quantum well-dots (QWD) in a pulsed regime. QWD-based lasers with 2 and 5 active layers emitting at ∼1.1 μm provided ...maximal optical power of 39 W limited by the pulse current source available. We have investigated the lasing spectra and shown that under the injection current above 20 kA/cm2 the active region overheats approximately by 0.5°C per 1 kA/cm2 during 100 ns current pulse. The active region overheating correlates well with the reducing of the differential efficiency of our devices. We believe that maximal pulse optical power of the QWD-based lasers is limited mainly by our laser wafer design rather than by the QWD active media properties.
We present a study of diode lasers with two identical optically coupled ridges. Two coupled ridges were made gradually divergent to a distance of 50 μm which allowed creating three electrically ...isolated sections within a single laser. We carried out numerical simulations of the electromagnetic modes in the coupled ridge waveguide and calculated far-field patterns for each mode. The results are in good agreement with the experimental data. We have found that current spreading provided unwanted optical gain in the active region in between ridges and dramatically changed the structure of the lasing modes. The obtained numerical and experimental results can be used to design twin-ridge diode lasers able to operate in mode-locking regimes.
Abstract
Epi-side down bonding on a silicon substrate of AlGaAs/GaAs microdisk lasers is presented. A heterostructure with coupled large optical cavities enables location of an InGaAs quantum dot ...active region at a distance of ∼1
µ
m from the heterostructure surface. The thermal resistance was reduced to 0.2 and 0.1 K mW
−1
for disks of 30 and 50
µ
m in diameter, respectively. The maximum continuous-wave power limited by the thermal rollover is more than doubled after bonding.
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