Saturation spectroscopy of thep-Ge far-infrared laser

Deep impurity-center ionization by far-infrared radiation

“…The appearance of high-power pulsed FIR and SBM lasers ͑first of the TEA CO 2 -pumped, molecular-gas type 1,2 and, subsequently, of free-electron lasers 3,4 and p-Ge semiconductor devices [5][6][7][8][9][10] ͒ capable of delivering nanosecond pulses of high intensity, up to a few MW, has opened up totally new vistas in investigation of semiconductors in the FIR range and provided a basis for development of far-infrared spectroscopy of semiconductors at high excitation levels, which was first made use of at the Ioffe Physicotechnical Institute. 11 In this frequency range, the high radiation intensity gives rise to a variety of nonlinear phenomena in semiconductors and semiconductor structures ͑see, e.g., review 12 ͒, such as, for example, multiphoton absorption, [13][14][15][16][17][18][19] absorption saturation ͑bleaching͒, [20][21][22][23][24][25][26][27][28][29][30] nonlinear cyclotron resonance, 31,32 impact ionization, 33,34 nonlinear photoacoustic spectroscopy, 35 high-harmonic generation, 36,37 and the high-frequency Stark effect, 38 whose characteristics differ substantially from their counterparts observed both in the visible and infrared ranges and in the range extending from microwaves to dc electric fields. The reason for this lies in that the FIR-SBM range is actually a domain where the interaction in the electronphoton system undergoes a transition from the quantum to classical limit, thus creating a unique possibility to study the same physical phenomenon in conditions where by...…”

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

“…The wavenumber in the Ge crystal for modes having allowed frequencies for the combined cavity is . The time dependence caused by beating between a pair of modes with mode indices and , where are and are integers, is given by (2) The third term represents beat oscillations with frequencies , which cannot be observed with our detection electronics not beyond about 5-6 GHz. For a given , the amplitude of the beat oscillation depends on the mode number .…”

“…1 The signal was amplified 2 and recorded on a transient digitizer 3 with 4.5-GHz analog bandwidth, oversampled at 200 Gs/s. For spectral measurements, the radiation was directed to a Bomem DA8 Fourier spectrometer with an unapodized instrumental line width of 0.025 cm , equipped with an event-locking accessory (Zaubertek) for low duty sources [16].…”

“…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.…”