Room-temperature Laser Diodes Research Articles

High-Brightness Blue Polariton Organic Light-Emitting Diodes.

Polariton organic light-emitting diodes (POLEDs) use strong light-matter coupling as an additional degree of freedom to tailor device characteristics, thus making them ideal candidates for many applications, such as room temperature laser diodes and high-color purity displays. However, achieving efficient formation of and emission from exciton-polaritons in an electrically driven device remains challenging due to the need for strong absorption, which often induces significant nonradiative recombination. Here, we investigate a novel POLED architecture to achieve polariton formation and high-brightness light emission. We utilize the blue-fluorescent emitter material 4,4'-Bis(4-(9H-carbazol-9-yl)styryl)biphenyl (BSBCz), which exhibits strong absorption and a highly horizontal transition-dipole orientation as well as a high photoluminescence quantum efficiency, even at high doping concentrations. We achieve a peak luminance of over 20,000 cd/m2 and external quantum efficiencies of more than 2%. To the best of our knowledge, these values represent the highest reported so far for electrically driven polariton emission from an organic semiconductor emitting in the blue region of the spectrum. Our work therefore paves the way for a new generation of efficient and powerful optoelectronic devices based on POLEDs.

Novel materials GaInAsPSb/GaSb and GaInAsPSb/InAs for room-temperature optoelectronic devices for a 3–5 µm wavelength range (GaInAsPSb/GaSb and GaInAsPSb/InAs for 3–5 µm)

A novel class of narrow-bandgap semiconductor materials is proposed as well as heterostructures based on these materials and suitable for the fabrication of mid-infrared optoelectronic devices, such as room-temperature laser diodes and thermo-photovoltaic converters. Our experimental data on infrared emission of such materials demonstrate high effectiveness of photoluminescence in a wavelength range 3–3.4 µm at room temperature. Simulations of the operating characteristics of room-temperature laser diodes, based on suggested heterostructures, show that their threshold current does not exceed 1 kA cm−2 due to suppression of the CHHS Auger-recombination process.

High-Power 2.3-<tex>$mu$</tex>m GaSb-Based Linear Laser Array

High-power 2.3-μm In(Al)GaAsSb-GaSb type-I double quantum-well diode laser arrays were fabricated and characterized. Linear laser arrays with 19 100-μm-wide elements on a 1-cm-long bar generated 10 W in continuous-wave (CW) mode and 18.5 W in quasi-CW mode (30 μs/300 Hz) at a heatsink temperature of 18/spl deg/C. Array power conversion efficiency peaked at 30 A and was about 9%. Device internal efficiency was about 50%. Individual laser differential gain with respect to current was about twice as high as in InP-based laser heterostructures, demonstrating the potential of GaSb-based material system for high-power CW room-temperature laser diode arrays.

Low threshold, room temperature laser diode pumped Sb-based VECSEL emitting around 2.1 [micro sign

The operation of a diode-pumped AlGaAsSb/GaInAsSb type-I quantum-well vertical cavity surface emitting laser emitting near 2.1µm is reported. The epitaxial structure, grown on GaSb by molecular beam epitaxy consists of a GaSb/AlAsSb Bragg reflector and a GaInAsSb/AlGaAsSb active region. A TEM00 low-divergence laser operation is demonstrated in quasi-CW (10 µs pulses, 10% duty cycle) from 250 up to 350K. A threshold as low as 390W/cm2 at 250K combined with a T0 around 33K has been measured.

On the growth and doping of blue-green emitting ZnSe laser diodes

Structural, optical and electrical properties of green and blue emitting room temperature laser diodes grown by molecular beam epitaxy are presented. The influence of the growth start at the GaAsZnSe heterointerface is discussed based on cross sectional and plan view transmission electron microscopy studies. GaAs buffer layers are necessary for reproducible layer growth and stable room temperature lasing. Doping problems like the ratio of the net acceptor concentration to the overall nitrogen incorporation for binary, ternary and quaternary layers and laser diodes are discussed as well as the problem of ohmic contacts.

Bleaching of excitons in a (Zn,Cd)Se/Zn(S,Se)/(Zn,Mg)(S,Se) laser diode under lasing conditions.

We performed a pump-and-probe photoluminescence excitation spectroscopy of the stimulated emission of a ${\mathrm{Zn}}_{0.7}$${\mathrm{Cd}}_{0.3}$Se single-quantum-well (SQW) struture proven to act as an efficient room-temperature laser diode under current injection. Excitonic absorption features in the excitation spectra of stimulated emission are completely bleached if the sample is simultaneously pumped by a second laser of fixed wavelength and an intensity of only 40 kW/${\mathrm{cm}}^{2}$. The stability of excitons under lasing conditions, thus, is seriously called into question in ZnSe-based SQW laser structures even at low temperatures.

Efficient modulation and coupling of CW junction laser light using electrooptic waveguides

The use of an electrooptical-waveguide modulator to achieve over 80-percent modulation of 7980-Å light from a room temperature laser diode operating at 10 mW CW is reported. The insertion loss of the modulator including couplers is 8.5 dB, and the output beam has high coherence.

Room-temperature laser operation of InxGa1−xAs p-n junctions

Room-temperature laser diodes which emit coherent infrared radiation near 1.1 μm have been prepared from InxGa1−xAs (x [inverted lazy s]0.23) vapor-grown p-n junction structures. At 77°K, laser threshold current densities as low as 1210 A/cm2 and external differential quantum efficiencies as high as 50% have been obtained at 1.08 μm. At 300°K, the threshold current densities are between 70 000 and 98 000 A/cm2 for emission at 1.145 μm.

Recent trends in room temperature laser diodes

Recent trends in room temperature laser diodes