Theoretical investigation of anti-index guiding inactively Q-switched two-section diode lasers

Abstract

We present a new theoretical design for diode lasers which should be capable of generating sub-100-ps pulses with pulse energies of more than 10 nJ per 100-μm-contact width by active Q-switching. We show that the carrier-induced reduction of the refractive index in the active layer, i.e. the vertical anti-index guiding effect, results in a dependence of the optical confinement factor on the carrier density which can be exploited for a further enhancement of the pulse energy and a reduction of the pulse length.

Theoretical studies of the generation of picoseconds pulses with two-section blue-violet semiconductor lasers

“…The principle of pulse generation is active Q-switching as in [5]. If the switch section is unbiased, it prevents lasing even if a large current I g (gain current) is injected into the gain section.…”

“…For the simulations we use a rate equation model as already presented in [5,18,19] consisting of coupled ordinary differential equations for the excess carrier densities N g and N s in the gain and switch sections, respectively, and the optical power P uniformly distributed along the whole cavity…”

“…However, diode lasers compete with other lasers such as solid state and fibre lasers regarding pulse energy and peak power. Therefore, during the last years experimental and theoretical efforts have been undertaken by several groups to improve the performance of pulsed diode lasers in the red and near-infrared spectral region [1][2][3][4][5].…”

“…In this paper we apply the approach for the generation of sub 100 ps pulses with high peak power by active Q-switching proposed in [5] to an InGaN laser emitting at 405nm. The cavity consists of two sections along the cavity axis-a gain section and a saturable absorber section, called switch section.…”

“…The cavity consists of two sections along the cavity axis-a gain section and a saturable absorber section, called switch section. The layer structure underlying the numerical simulations in this paper, identical for both sections, originates from a continuous-wave emitting laser and is not particular optimized for pulsed operation, in contrast to [5]. Firstly we investigate the impact of the emission wavelength relative to the gain peak wavelength on the properties of the pulses.…”