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

Abstract

Abstract-The temporal dynamics, spectrum, and gain of the far-infrared p-Ge laser for composite cavities consisting of an active crystal and passive transparent elements have been studied with high temporal and spectral resolution. Results are relevant to improving the performance of mode-locked or tunable p-Ge lasers using intracavity modulators or wavelength selectors, respectively. It is shown that an interface between the active p-Ge crystal and a passive intracavity spacer causes partial frequency selection of the laser modes, characterized by a modulation of their relative intensities. Nevertheless, the longitudinal mode frequencies are determined by the entire optical length of the cavity and not by resonance frequencies of intracavity sub-components. Operation of the p-Ge laser with multiple interfaces between Ge, Si, and semi-insulating GaAs elements, or a gap, is demonstrated as a first step toward a p-Ge laser with an external quasioptical cavity and distributed active media.Index Terms-Laser modes, laser tuning, submillimeter wave lasers, submillimeter wave resonators, submillimeter wave spectroscopy, submillimeter wave technology.

Far-infrared p-Ge laser with variable length cavity

“…Reflections caused by the substantial index mismatch between Ge and vacuum can create unwanted spectral resonances [10], which could interfere with continuous tunability of the laser. Such effects might be minimized by orienting the active crystal at Brewster's angle.…”

Intracavity modulation of THz p-Ge laser gain by interband optical excitation

“…Both materials have been tested in the p-Ge laser cavity and have been shown to have a high transparency [6]. …”

Wavelength selection for the far-infrared p-Ge laser using etched silicon lamellar gratings

“…In the tunable lamellar-gratings used to date, a silicon spacer has supported aluminum stripes and isolated the high-voltage laser-excitation pulse from the metal tuner parts [5][6][7][8]. A disadvantage of this design is the appearance of unwanted wavelength-selective resonances introduced by the silicon spacer itself [8,10]. The pattern of evaporated stripes is di cult to experimentally optimize for highest selector Q.…”