Single axial-mode selection in a far-infrared p-Ge laser

Abstract

Single axial-mode operation of the pulsed far-infrared p-Ge laser with an intracavity Fabry–Perot type frequency selector has been observed by means of Fourier-transform spectroscopy. A spectral resolution better than 1 GHz has been achieved on an ordinary continuous-scan spectrometer using the event-locked technique for pulsed emission sources. A laser active-cavity finesse of at least unity has been directly confirmed from the measured emission spectral width. Analysis of the envelope of the corresponding interferogram suggests that the finesse exceeds 10.

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

“…Tunable intracavity frequency selectors used by all investigators to date [3]- [7] have incorporated a silicon or pure germanium spacer in their design. Although such selectors are capable of selecting a single longitudinal mode at certain frequencies [5], they experience difficulties with fine continuous tunability [6]. These problems are due to preferred amplification of those longitudinal modes which fall close to spacer resonances.…”

“…The output is generally weaker by 1-2 orders of magnitude than that for the p-Ge intersubband laser mechanism. In contrast, the intersubband p-Ge laser with a tunable intracavity frequency selector can generate emission of a single longitudinal mode [5], which has megahertz line width. Moreover, such tuning elements can be electrically controlled [6], and this mode of operation allows the use of uncooled permanent magnet assemblies [19].…”

Far-infrared p-Ge laser with variable length cavity

“…The laser normally generates a 20-30 cm À1 wide spectrum with up to a thousand longitudinal modes. Single mode generation [4] can be achieved using an intracavity frequency selector, which has the form of a tunable Fabry-Perot etalon coupled with the main laser cavity [2][3][4][5]. Because the selective element is placed inside the laser cavity, remarkable spectral power density is concentrated in a single longitudinal mode [4] having a width of several MHz [6].…”

“…The p-Ge laser mechanism is based on intersubband transitions of hot holes [1], where an inversion population is built up between light and heavy hole subbands in crossed electric and magnetic fields at cryogenic temperatures. The laser has a wide gain spectrum, which allows tuning over the spectral range 50-140 cm À1 (70-200 lm or 1.5-4.2 THz) [2][3][4][5]. The laser normally generates a 20-30 cm À1 wide spectrum with up to a thousand longitudinal modes.…”

Operation of THz p-Ge laser in a closed-cycle refrigerator

“…Fig. 1 presents a characteristic laser spectrum when intracavity wavelength selection is used [2]. The laser mechanism is based on population inversion between light-and heavy-hole valence sub-bands in crossed electric and magnetic fields at cryogenic temperatures.…”