High field p-Ge laser operation in permanent magnet assembly

Fredricksen, Christopher J.; Nelson, E. W.; Muravjov, A. V.; Peale, Robert E.

doi:10.1016/s1350-4495(02)00179-2

Cited by 9 publications

(16 citation statements)

References 13 publications

(17 reference statements)

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“…The air gap is 5.1 mm high by 12.7 mm wide. The maximum allowable assembly dimension is 6.8 cm, compared with 3.0 cm for the SmCo magnet tested and reported in [2]. The maximum field in the air gap is 0.97 T, compared with the 0.70 T field reaUzed in [2].…”

Section: Security Classification Of Reportmentioning

confidence: 80%

“…During the period of this grant, our paper on laser experiments with high-field permanent magnet assemblies was completed, submitted, and accepted [2]. Advantages of permanent magnets over superconducting solenoids include compactness and freedom from current leads (which thermally load the cooler) and a current supply.…”

Section: Security Classification Of Reportmentioning

confidence: 99%

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Widely Tunable and High-Duty Terahertz p-Ge Laser in a Closed-Cycle Refrigerator

Peale¹

2002

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Public reporting burden for tNs collection of Infonnation is estimated to average 1 hour per response, Includrng the time for rfviO'jAfgTnstnjctions, searcNng y the coHactlon of information. The R&D objectives of this project are to increase the duty cycle and operation temperature of the far-JR p-Ge laser, to design and test a tunable frequency-stabilized laser for THz sensing and spectroscopy, and to obtain cryogen-free operation. All grant funds were allocated for the purchase of a state-of-the-an closed-cycle refrigerator system to be used in attaining the objectives. Support for other research expenses and salaries comes from the National Science Foundation and subcontracts on Zaubertek SBIR/STTR projects. The R&D objectives of this project are to increase the duty cycle and operation temperature of the far-IR p-Ge laser, to design and test a tunable frequency-stabilized laser for THz sensing and spectroscopy, and to obtain cryogen-free operation. All grant funds were allocated for the purchase of a state-of-the-art closed-cycle refrigerator system to be used in attaining the objectives. Support for other research expenses and salaries comes from the National Science Foundation and subcontracts on Zaubertek SBIR/STTR projects.

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Section: Security Classification Of Reportmentioning

confidence: 80%

Section: Security Classification Of Reportmentioning

confidence: 99%

Widely Tunable and High-Duty Terahertz p-Ge Laser in a Closed-Cycle Refrigerator

Peale¹

2002

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“…Figure 6 compares the calculated field strength and uniformity for the permanent magnet currently in use and the newly designed magnet. The magnet currently in use has a room temperature field in the air gap of ~0.68 T, while the new design should give a field of ~1.02 T. The fields of these magnets drop about 18% on cooling to 4 K [4]. The new design also has a much wider region of uniform field because of the use of iron pole pieces.…”

Section: Methodsmentioning

confidence: 99%

“…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. Immersion in liquid helium has been the most convenient means of cooling the active crystal because it also provides cooling for a superconducting solenoid that gives homogeneous, tunable magnetic fields of at least 0.5 T. However, p-Ge lasers have also been demonstrated using permanent magnet assemblies [3,4] in closed cycle refrigerators [5]. The purpose of this paper is to present new developments of a turn-key p-Ge laser that operates in a closed cycle refrigerator.…”

Section: Introductionmentioning

confidence: 99%

“…The laser control electronics include the HV supply and thyratron pulser. The magnetic field was provided in Voigt configuration by a SmCo permanent magnet assembly [4] mounted on the cold surface. The far-IR radiation was measured by a Si bolometer mounted above the teflon or polyethylene window at the top of the vacuum shroud of the cryostat.…”

Section: Introductionmentioning

confidence: 99%

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

Fredricksen¹,

Muravjov

Peale

2004

SPIE Proceedings

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We report on development of a turn-key, cryogen-free bulk p-Ge laser which is broadly tunable over the range 1.5 to 4.2 THz. A 4 K closed cycle refrigerator was used to eliminate the need for liquid cryogen. A SmCo permanent magnet assembly provides the necessary magnetic field for the laser. A customized high voltage (HV) power supply and thyratron pulser were developed to replace the stack of general electronics previously used to operate the laser.

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Nonlinear THz Spectroscopy of n-Type GaAs

Gaal

Reimann

Woerner

et al. 2007

Ultrafast Phenomena XV

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In this thesis, the ultrafast dynamics of conduction band electrons in semiconductors are investigated by nonlinear terahertz (THz) spectroscopy. In particular, n-doped gallium arsenide samples with doping concentrations in the range of 10 16 cm −3 to 10 17 cm −3 are studied. A novel source for the generation of intense THz radiation is developed which yields single-cycle THz transients with field amplitudes of more then 400 kV/cm. The THz source uses ultrashort optical laser pulses provided by a Ti:sapphire oscillator. In addition, a two-color THz-pump mid-infrared-probe setup is implemented, which allows for two-dimensional time-resolved experiments in the far-infrared wavelength range. Field ionization of neutral shallow donors in gallium arsenide with intense, ultrashort THz pulses and subsequent coherent radiative recombination of electrons to impurity ground states is observed at room temperature. The superradiant decay of the nonlinear polarization results in the emission of a coherent signal with picosecond lifetimes. Such nonlinear signals, which exhibit a lifetime ten times longer than in the linear regime are observed for the first time. At low temperatures and THz field strengths below 5 kV/cm, Rabi flopping on shallow donor transitions is demonstrated. For the first time, the polar electron-LO phonon interaction is directly measured in the quantum kinetic transport regime. Quasi-instantaneous acceleration of conduction band electrons in the polar gallium arsenide lattice by the electric field of intense THz pulses and subsequent probing of the mid-infrared transmission reveals a modulation of the transmission along the THz-mid-infrared delay coordinate with the frequency of the LO phonon. These modulations directly display the relative phase between the electron motion and its surrounding virtual phonon cloud. Quantum kinetic model calculations fully account for the observed phenomena.

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High field p-Ge laser operation in permanent magnet assembly

Cited by 9 publications

References 13 publications

Widely Tunable and High-Duty Terahertz p-Ge Laser in a Closed-Cycle Refrigerator

Widely Tunable and High-Duty Terahertz p-Ge Laser in a Closed-Cycle Refrigerator

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

Nonlinear THz Spectroscopy of n-Type GaAs

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