Arūnas Krotkus

Investigations of the preparation process for efficient second-harmonic generation in optical fibers

Experiments were carried out to elucidate aspects of the preparation process, which enables glass fibers to efficiently frequency‐double infrared laser light. A picture is described which is consistent with most of the observations.

Simulations and experiments of mode-locking of semiconductor lasers: pulse evolution, frequency detuning, and bias dependence

Simulations of a mode-locked diode laser based on a travelling-wave rate-equation model have been compared with experiments. The pulse measurement technique involved a conventional intensity autocorrelator together with an internally generated second-harmonic emission measurement set-up. The latter is ideal for systematic relative measurements. For the first time, pulse evolution as a function of the number of round-trips was measured. Short optical pulses were obtained after approximately 40 round-trips. The experimental and simulated detuning range was about 1 MHz and the d.c. bias dependence was investigated.

Influence of laser irradiation on optical properties of GaAsBi/GaAs quantum wells

This paper is focused on investigation of the impact of laser irradiation on the structural and optical properties of bismide-based multiple quantum wells (MQWs). The MQW structures, composed of 5 GaAsBi quantum wells, 7 nm thick, separated by 10 nm-thick GaAs barriers, were grown by molecular beam epitaxy on GaAs (100)-plane oriented semi-insulating substrates at 330°C temperature. The bismuth content in as-grown GaAsBi wells evaluated from the measurements of HR-XRD rocking curves was about 6%. HR-TEM and AFM studies of the MQWs evidenced sharp interfaces between the wells and barriers, and a smooth, droplet-free surface, respectively. HR-TEM images also evidenced a homogeneous bismuth distribution in the wells. The spatially-resolved photoluminescence study of GaAsBi/GaAs MQWs revealed the enhancement of PL emission efficiency of up to 80% with no shift of the spectral position after intense laser irradiation. The obtained results were explained by improvement of the GaAsBi crystal quality.