Evidence for self-mode-locking in p-Ge laser emission

Abstract

Investigations of the dynamics of the far-infrared p-Ge laser emission reveal strong periodic soliton-like intensity spikes with less than 100 ps duration. We interpret these spikes as self-mode-locking of p-Ge laser modes. The effect becomes more pronounced when a GaAs/ AlGaAs/InGaAs quantum well structure on a semi-insulating GaAs substrate is inserted into the laser cavity.

High-resolution study of composite cavity effects for p-Ge lasers

“…4 and 5 because of beating between different pairs among the ensemble of evenly spaced [14] axial modes. These modes are defined by frequencies , where the mode index is an integer.…”

“…Examples include transparent, electrically isolating silicon spacers, which have been used as part of tunable intra- cavity wavelength selectors ( Fig. 1) [3]- [7] and intracavity electrooptic modulators or passive saturable intracavity absorbers [14], which might be used for active or passive mode locking, respectively. However, use of passive intracavity optical elements in p-Ge laser cavities can introduce undesirable effects because of intrinsic reflections and loss at interfaces between optical components.…”

“…Such a laser operates on a wide spectrum of active intersubband transitions and normally generates microsecond pulses of far-infrared radiation in a broad spectrum, which consists of many longitudinal modes. To generate spectrally pure single-mode emission or ultrashort pulses, the laser design may require composite cavities that include passive intracavity optical elements [3]- [7], [14]. Examples include transparent, electrically isolating silicon spacers, which have been used as part of tunable intra- cavity wavelength selectors ( Fig.…”

“…T HE far-infrared p-Ge laser [1], based on intersubband transitions of hot holes, has a wide homogeneous gain spectrum [2], which allows tuning over the spectral range 50-140 cm (70-200 m or 1.5-4.2 THz) [3]- [7] or generation of picosecond pulses of far-infrared radiation [8]- [14]. The traditional electrodynamic cavity of a p-Ge laser consists of a bulk p-Ge rod with external mirrors attached to its ends.…”

Narrow linewidth intervalence-band emission from germanium terahertz lasers

“…The electrical contacts were placed on the 4x20 mm 2 In contrast, figure 1(b) shows the emission of a 10 times smaller laser with dimensions 3.8x3.8x2 mm 3 . In this laser the electrical contacts were placed on the 3.8x3.8 mm The emission of the laser after the etch procedure is shown in figure 2(b).…”