Pulse separation control for mode-locked far-infrared p-Ge lasers

Abstract

Active mode locking of the far-infrared p-Ge laser giving a train of 200 ps pulses is achieved via gain modulation by applying an rf electric field together with an additional bias at one end of the crystal parallel to the Voigt-configured magnetic field. Harmonic mode locking yields a train of pulse pairs with variable time separation from zero to half the roundtrip period, where pulse separation is electrically controlled by the external bias to the rf field.

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

“…The pulse train of a harmonically mode-locked p-Ge laser can be electrically modulated (Fig. 1b) [5]. However, active mode-locking of p-Ge lasers has required large rf power because of the low impedance of the active crystal.…”

Inter-Valence-Band Hot Hole Laser in Two-Dimensional Delta-Doped Homoepitaxial Semiconductor Structures

“…The authors have worked for many years to advance the technology of inter-valence-band hot hole lasers based on bulk rods of p-Ge having ∼cubic centimeter active volume. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] One of us (AVM) has been involved in this research since its beginnings more than two decades ago. 20 Features of this laser are broad tunability (1.5-4.2 THz) with high spectral density in a single device ( Fig.…”

Actively mode-locked p-Ge laser in Faraday configuration

“…In previous papers, [2][3][4][5] generation of 200 ps far-infrared pulses by the p-Ge laser was obtained by active mode locking in Voigt geometry of applied fields with gain modulation at one end of the laser crystal. The modulation field E rf was applied at a frequency rf equal to the half of the cavity roundtrip frequency rf .…”

“…The rf circuit is described in Ref. 5. Figure 2 shows the intensity contours of the laser operation as a function of the bias voltages U 1 and U 2 on the additional contacts.…”

“…In Voigt configuration, the impedance between rf contacts was estimated to be only ϳ1-5 ⍀. [2][3][4][5] In Faraday geometry, the contribution of magnetoresistance increases this value to ϳ50 ⍀, which is the ideal load for most commercial electronics. Hence the required rf modulating-field power is lower in Faraday than in Voigt geometry.…”