Search Results
Terahertz stimulated emission from silicon doped by hydrogenlike acceptors
2014, Pavlov, S.G., Deßmann, N., Shastin, V.N., Zhukavin, R.K., Redlich, B., van der Meer, A.F.G., Mittendorff, M., Winnerl, S., Abrosimov, N.V., Riemann, H., Hübers, H.-W.
Stimulated emission in the terahertz frequency range has been realized from boron acceptor centers in silicon. Population inversion is achieved at resonant optical excitation on the 1Λ8+ → 1Λ7- , 1Λ6-, 1Λ8- intracenter transitions with a midinfrared free-electron laser. Lasing occurs on two intracenter transitions around 1.75 THz. The upper laser levels are the 1Λ7- , 1Λ6- , and 1Λ8- states, and the lower laser level for both emission lines is the 2Λ8+ state. In contrast to n-type intracenter silicon lasers, boron-doped silicon lasers do not involve the excited states with the longest lifetimes. Instead, the absorption cross section for the pump radiation is the dominating factor. The four-level lasing scheme implies that the deepest even-parity boron state is the 2Λ8+ state and not the 1Λ7+ split-off ground state, as indicated by other experiments. This is confirmed by infrared absorption spectroscopy of Si:B.
Relaxation of Coulomb States in semiconductors probed by FEL radiation
2018, Zhukavin, R.Kh., Kovalevsky, K.A., Tsyplenkov, V.V., Pavlov, S.G., Hübers, H-W., Choporova, Yu.Yu., Knyazev, B.A., Klopf, J.M., Redlich, B., Abrosimov, N.V., Astrov, Yu.A., Shastin, V.N., Silaev, A.A.
This article has no abstract.
Towards a life-time-limited 8-octave-infrared photoconductive germanium detector
2015, Pavlov, S.G., Deßmann, N., Pohl, A., Abrosimov, N.V., Mittendorff, M., Winnerl, S., Zhukavin, R.K, Tsyplenkov, V.V., Shengurov, D.V., Shastin, V.N., Hübers, H.-W.
Ultrafast, ultra-broad-band photoconductive detector based on heavily doped and highly compensated germanium has been demonstrated. Such a material demonstrates optical sensitivity in the more than 8 octaves, in the infrared, from about 2 mm to about 8 μm. The spectral sensitivity peaks up between 2 THz and 2.5 THz and is slowly reduced towards lower and higher frequencies. The life times of free electrons/holes measured by a pump-probe technique approach a few tenths of picoseconds and remain almost independent on the optical input intensity and on the temperature of a detector in the operation range. During operation, a detector is cooled down to liquid helium temperature but has been approved to detect, with a reduced sensitivity, up to liquid nitrogen temperature. The response time is shorter than 200 ps that is significantly faster than previously reported times.
A compact, continuous-wave terahertz source based on a quantum-cascade laser and a miniature cryocooler
2010, Richter, H., Greiner-Bär, M., Pavlov, S.G., Semenov, A.D., Wienold, M., Schrottke, L., Giehler, M., Hey, R., Grahn, H.T., Hübers, H.-W.
We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum-cascade laser (QCL) operating at 3.1 THz with a compact, low-input-power Stirling cooler. The QCL, which is based on a two-miniband design, has been developed for high output and low electrical pump power. The amount of generated heat complies with the nominal cooling capacity of the Stirling cooler of 7 W at 65 K with 240 W of electrical input power. Special care has been taken to achieve a good thermal coupling between the QCL and the cold finger of the cooler. The whole system weighs less than 15 kg including the cooler and power supplies. The maximum output power is 8 mW at 3.1 THz. With an appropriate optical beam shaping, the emission profile of the laser is fundamental Gaussian. The applicability of the system is demonstrated by imaging and molecular-spectroscopy experiments.
Terahertz transient stimulated emission from doped silicon
2020, Pavlov, S.G., Deßmann, N., Pohl, A., Zhukavin, R.K., Klaassen, T.O., Abrosimov, N.V., Riemann, H., Redlich, B., Van Der Meer, A.F.G., Ortega, J.-M., Prazeres, R., Orlova, E.E., Muraviev, A.V., Shastin, V.N., Hübers, H.-W.
Transient-type stimulated emission in the terahertz (THz) frequency range has been achieved from phosphorus doped silicon crystals under optical excitation by a few-picosecond-long pulses generated by the infrared free electron lasers FELIX and CLIO. The analysis of the lasing threshold and emission spectra indicates that the stimulated emission occurs due to combined population inversion based lasing and stimulated Raman scattering. Giant gain has been obtained in the optically pumped silicon due to large THz cross sections of intracenter impurity transitions and resonant intracenter electronic scattering. The transient-type emission is formed under conditions when the pump pulse intervals exceed significantly the photon lifetime in the laser resonator. © 2020 Author(s).
Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars
2013, Murdin, B.N., Li, J., Pang, M.L.Y., Bowyer, E.T., Litvinenko, K.L., Clowes, S.K., Engelkamp, H., Pidgeon, C.R., Galbraith, I., Abrosimov, N.V., Riemann, H., Pavlov, S.G., Hübers, H.-W., Murdin, P.G.
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10 5 T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H 2 analogues, and for investigation of He 2, a bound molecule predicted under extreme field conditions.