Internal parameters and optical properties of green II‐VI heterostructure lasers with active region composed of multi‐sheet electronically‐coupled CdSe quantum dots

Abstract

Optically pumped green‐emitting ZnSe‐based laser heterostructures of optimized design have been grown by molecular‐beam epitaxy and studied. The structures containing five electronically‐coupled stacked CdSe quantum dot (QD) sheets demonstrate the minimum threshold power density of 2.2 kW/cm2 and the maximum external quantum efficiency of ∼ 50%. Internal laser characteristics were determined by measuring the differential laser efficiency and laser threshold of a series of samples with different cavity lengths. The characteristic gain and internal quantum efficiency of the structures have been shown to reach the values as high as ΓG0 = 114 cm‐1 and ηi = 65.4%, while the transparency threshold and internal losses are evaluated as low as IT = 1.22 kW/cm2 and αi = 2.55 cm‐1, respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Internal laser characteristics of optically pumped yellow-orange lasers

“…Estimated ΓG 0 exhibited values of 54 and 81 cm −1 , I T was 0.6 and 1.2 kW cm −2 for structures A and B , correspondingly. The ΓG 0 value for structure B having the optimized GIW design exceeds the respective value for green lasers of the same GIW design . This is despite a decrease in the optical confinement factor (defined as part of the radiation intensity localized in the active region) with wavelength increase, which occurs due to reduction of the difference in the refractive index between the heterostructure layers.…”

“…Figure shows reciprocal differential quantum efficiency 1/ η Q D of structures A and B as a function of L cav . Internal quantum efficiency and internal optical loss were estimated from these data by a linear approximation using the well‐known expression …”

“…As the figure shows, the experimental data are well approximated by a linear dependence. Using the relation, in which I thr is expressed in an exponential form one can estimate the magnitudes of transparency intensity I T and characteristic gain ΓG 0 for the structures using the experimental values of the threshold excitation intensity for a set of lasers with different L cav . Estimated ΓG 0 exhibited values of 54 and 81 cm −1 , I T was 0.6 and 1.2 kW cm −2 for structures A and B , correspondingly.…”

Violet–green laser converter based on MBE grown II–VI green lasers with multiple CdSe quantum dot sheets, pumped by InGaN laser diode

“…The proposed design of CdSe QDS laser allows reduction of the laser threshold by raising both the internal efficiency and the characteristic gain. The following results were obtained at the N 2 laser excitation [6]: characteristic gain -GG 0 ¼ 114 cm À1 ; internal quantum efficiency -h i ¼ 65.4%; transparency threshold -I T ¼ 1.22 kW/cm 2 and internal loss -a i ¼ 2.55 cm À1 . It is well known that the threshold current (I thr ) versus cavity length (L cav ) dependence has a minimum at a fixed value of the exciting stripe width d [7].…”