Investigation of New Geometries for High Duty Cycle Far-Infrared p-Type Germanium Lasers

1999 ◽  
Vol 607 ◽  
Author(s):  
Danielle R. Chamberlin ◽  
Erik Bruendermannw ◽  
Eugene E. Haller
Keyword(s):  
Electric Field ◽  
Duty Cycle ◽  
Pulse Length ◽  
Far Infrared ◽  
Contact Geometry ◽  
Input Power ◽  
High Resistivity ◽  
Field Uniformity ◽  
P Type ◽  
Planar Contact

AbstractWe report on increasing the pulse length and repetition rate of p-type germanium lasers through miniaturization, increased electric field uniformity, and improved cooling. We have recently demonstrated that it is possible to improve the electric field uniformity necessary for an efficient laser and at the same time decrease the electrical input power by using a geometry with d/L>>1, where d is the distance between electrical contacts and L is the length in the direction of the Hall field. In order to achieve good heat sinking along with a large d/L ratio, we have developed a new, planar contact geometry. Attaching an undoped, high-resistivity, single-crystal Si heat sink to the base of the Ge planar contact laser increases the duty cycle by a factor of 5.5. In order to further decrease the input power by decreasing the volume of laser crystals in the planar contact geometry, we show as a proof-of-concept the use of polished strontium titanate single crystals as electrically insulating far-infrared mirrors based on restrahl band reflection. The physical phenomena underlying these improvements in this novel geometry will be discussed.

Planar contact geometry for far-infrared germanium lasers

1999 ◽  
Vol 74 (25) ◽  
pp. 3761-3763 ◽  
Author(s):  
D. R. Chamberlin ◽  
E. Bründermann ◽  
E. E. Haller
Keyword(s):  
Far Infrared ◽  
Contact Geometry ◽  
Planar Contact

Two-photon excitation microscopy in cellular biophysics

1995 ◽  
Vol 53 ◽  
pp. 62-63
Author(s):  
David W. Piston ◽  
Brian D. Bennett ◽  
Robert G. Summers
Keyword(s):  
Confocal Microscopy ◽  
Laser Beam ◽  
Duty Cycle ◽  
Excited Electronic State ◽  
Input Power ◽  
Two Photon ◽  
Simultaneous Absorption ◽  
Photon Excitation ◽  
Very High ◽  
Two Photon Excitation

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10-5 maintains the average input power on the order of 10 mW, only slightly greater than the power normally used in confocal microscopy.

scholarly journals Charging of Piezoelectric Cellular Polypropylene Film by Means of a Series Dielectric Layer

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 333
Author(s):  
Pedro Llovera-Segovia ◽  
Gustavo Ortega-Braña ◽  
Vicente Fuster-Roig ◽  
Alfredo Quijano-López
Keyword(s):  
Electric Field ◽  
Corona Discharge ◽  
Dielectric Layer ◽  
Dielectric Breakdown ◽  
Piezoelectric Materials ◽  
High Resistivity ◽  
Internal Electric Field ◽  
Dielectric Polarization ◽  
Surface Flashover ◽  
In Series

Piezoelectric polymer cellular films have been developed and improved in the past decades. These piezoelectric materials are based on the polarization of the internal cells by means of induced discharges in the gas inside the cells. Internal discharges are driven by an external applied electric field. With this polarization method, cellular polypropylene (PP) polymers exhibit a high piezoelectric coefficient d33 and have been investigated because of their low dielectric polarization, high resistivity, and flexibility. Charging polymers foams is normally obtained by applying a corona discharge to the surface with a single tip electrode-plane arrangement or a triode electrode, which consists of a tip electrode-plane structure with a controlled potential intermediate mesh. Corona charging allows the surface potential of the sample to rise without breakdown or surface flashover. A charging method has been developed without corona discharge, and this has provided good results. In our work, a method has been developed to polarize polypropylene foams by applying an insulated high-voltage electrode on the surface of the sample. The dielectric layer in series with the sample allows for a high internal electric field to be reached in the sample but avoids dielectric breakdown of the sample. The distribution of the electric field between the sample and the dielectric barrier has been calculated. Experimental results with three different electrodes present good outcome in agreement with the calculations. High d33 constants of about 880 pC/N have been obtained. Mapping of the d33 constant on the surface has also been carried out showing good homogeneity on the area under the electrode.

Dislocation scatterings in p-type Si1−xGexunder weak electric field

2015 ◽  
Vol 26 (49) ◽  
pp. 495201 ◽  
Author(s):  
Ji-Hyun Hur ◽  
Sanghun Jeon
Keyword(s):  
Electric Field ◽  
Weak Electric Field ◽  
P Type
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