Measurements Of Gain Spectra Research Articles

A simple apparatus for the direct measurement of optical gain spectra

A simple apparatus which allows direct recording of optical gain and induced absorption spectra is presented. It makes use of the very sensitive method based on the modulation of the length of the illuminated sample surface. It can easily be assembled with elements usually present in any spectroscopy laboratory and does not need calibration. The sensitivity of the system and the main sources of error are analysed in detail.

Luminescence and generation in zinc telluride under laser excitation

Light generation in single crystals of ZnTe has been achieved through two-photon excitation by picosecond pulses of ruby laser radiation at liquid nitrogen temperature [I]. The occurrence of stimulated emission in zinc telluride in the temperature range 4.2-80~ has been reported in several publications [2-7], and photoluminescence in zinc telluride single ~3, crystals under two-photon excitation has been studied 8] In the literature there are no reports of generation in ZnTe under two-photon excitation by nanosecond pulses of laser radiation, or of the measurement of gain spectra at liquid nitrogen temperature.

Measurement of gain and absorption spectra in AlGaAs buried heterostructure lasers

A new method for measuring absorption and gain spectra of lasers is presented. These spectra are deduced from measurements of spontaneous emission spectra at different laser currents supplemented by measurements of the laser line energy and the differential quantum efficiency. The spontaneous emission emerged from the side of the laser after traveling through a transparent cladding layer. At each current, the bias energy eV is determined. A simple theoretical model is used to convert eV to minority carrier density. The method is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption. A new general proof of these relations is presented. The gain versus carrier density relation at the laser line energy is measured for four samples having different active layer doping or Al composition. Gain increased superlinearly with carrier density in undoped and n-type samples and increased slightly sublinearly in a p-type sample. The losses at low carrier densities ranged from 100–200 cm−1. For one undoped sample, the changes in the absorption edge caused by the electron and hole densities increasing from 5×1016 to 1.1×1018 cm−3 were deduced by comparing the measured changes with a model calculation. It was found that the exponential broadening increased 20%, that the energy gap decreased 12–16 meV, and that the strength of optical absorption at low energies decreased by about a factor of 1.4.

Study of excitation transfer in dye mixtures by measurements of gain spectra

The laser behavior of the Cresyl Violet-Rhodamine 6G dye system is studied by measurements of the small-signal gain spectra for various dye mixtures and pump powers. It is found that most of the pump power absorbed by the Rhodamine 6G is transferred to the Cresyl Violet as useful pump power. The experimental results are in good agreement with a simple theoretical model.