We present magnetooptical and transport properties of metamorphic periodic structures containing InAsSb layers with controllable modulated Sb composition [1]. The modulation period is determined by the thicknesses of the strain compensated InAsSbx/InAsSby pairs grown on a virtual AlGaInSb substrate with a lattice constant of 6.25 A. We demonstrate that the bandgap energy of ordered InAsSb0.3/InAsSb0.75 alloy varies from 100mev to a few meV as a result of the well-regulated variation of the modulation period from ∼3 to ∼7.5 nm. The material effective masses and the specific character of the energy spectra will be discussed.
1. G. Belenky, Y. Lin, L. Shterengas, D. Donetsky, G. Kipshidze and S. Suchalkin, Electron. Lett. 51 (19), 1521, (2015)
Cascade GaSb-based type-I quantum well diode lasers were designed and fabricated. Cascade pumping was achieved utilizing efficient interband tunneling through "leaky" window in band alignment at GaSb/InAs heterointerface. The 100% efficient carrier recycling between stages was confirmed by twofold increase lightcurrent characteristics slope of two-stage 2.4 – 3.3 μm cascade lasers as compared to reference single-stage devices. Moderate internal optical loss increase was observed in cascade lasers with interband injector located near the optical mode peak. Cascade pumping scheme increased the continuous wave output power of room temperature operated 2.4 - 3 μm semiconductor lasers and led to improved power conversion efficiency.
An interband cascade laser design has been grown by molecular beam epitaxy using uncracked arsenic and antimony
sources. Lasers were fabricated into both broad-area and narrow-ridge devices, with cavity lengths ranging between 1
mm and 4 mm. At 300K, under low-duty-cycle pulsed conditions, threshold current densities for lasers with 2-mm cavity
lengths are as low as 395 A/cm2, with optical emission centered at a wavelength of ~3.82 μm at 300 K. Continuous-wave
(cw) performance of the narrow-ridge devices has been achieved for temperatures up to almost 60°C. We present results
of both pulsed (broad-area and ridge) and cw (ridge only) measurements on these lasers, including L-I-V, spectral,
cavity-length, and Hakki-Paoli analyses.
In our talk we will report on our progress toward the development of a mid-infrared interband cascade LED array. Our goal is to develop a 256 x 256 array of vertical LED emitters operating at 3.5 microns with each pixel emitting up to approximately 1mW of mid-infrared optical power.
The first part of our development plan was to determine the best interband cascade LED structure for efficient generation of light. To this end we first investigated the tradeoff between operating current and voltage that is obtained when the number of cascades within the LED is varied. More cascades leads to a higher LED power versus current slope efficiency; however, this increase in slope efficiency is obtained at the cost of higher operating voltage and dissipated power.
We will present the LED performance of interband cascade structures containing 18, 12, 6 and 3 cascades. We will exhibit mid-infrared output power performance versus the number of cascades, input power, the diameter of the LED mesas, and temperature. We will also present the LED output divergence properties. Our results to date indicate a significant drop in the efficiency of the emitted power for LED diameters near 50 microns and a nearly Lambertian power distribution. Our approach toward mitigating these issues will be to fabricate LED structures employing a surface passivation step to inhibit surface recombination on the LED mesa walls and to deep etch the mesa profile to create an index-guided output distribution. We intend to present these new results in our talk.
We propose a novel design of an electrically tunable type II mid-IR light source based on a InAs/AlSb/GaInAsSb/GaInSb heterostructure. The design combines the advantages of strong wavelength tuning due to the linear Stark effect and the presence of separate charge accumulation layers, which enables laser wavelength tuning without a change of the optical loss. Experiment shows a blue shift of the electroluminescence (EL) line at increasing bias current, commensurate with that expected form the linear Stark effect. The laser generation was observed at higher currents. The EL wavelength shifts from 2.79um to 2.38um ( ~ 80meV) at T=80K as the bias current increases from 97mA to 418mA, which provides the record combination of the wide tuning range and low relative change of the bias current.
Laser sources operating in spectral region 2 - 4 μm are in demand for ultra-sensitive laser spectroscopy, medical diagnostics, home security, industrial process monitoring, infrared countermeasures, optical wireless communications, etc. Currently, solid state lasers and optical parametric oscillators and amplifiers are used as coherent light sources in this spectral region. Solid state and parametric sources are being optically pumped by near infrared diode lasers. This intermediate energy transfer step from near infrared pumping diode to mid infrared emitting device reduces power-conversion system efficiency. Development of the highly efficient semiconductor diode lasers operating in 2 - 4 μm spectral region will significantly improve the performance of the many existing systems and enable new applications. In this work we will describe major breakthrough in the development of the high power room temperature operated mid-IR semiconductor lasers. The performance limitations of the devices based on type-I and type-II quantum well (QW) active region design will be analyzed. Future directions in device performance optimization and enhancement of the wavelength for high power room temperature operation will be discussed.
Gain in broad area mid-infrared diode W lasers ((lambda) =3- 3.1micrometers ) has been measured using lateral mode spatial filtering combined with the Hakki-Paoli approach. The internal optical loss of approximately equals 19cm-1 determined from the gain spectra was the same for devices with either 10- or 5-period active regions and nearly constant in the temperature range between 80 and 160K. Analysis of the differential gain and spontaneous emission spectra shows that the main contribution to the temperature dependence of the threshold current is Auger recombination, which dominates within almost the entire temperature range studied (80-160K).
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