International Business Machines Corporation

Daniel R Grischkowsky

Mark B Ketchen

Rodney T Hodgson

Jean-Marc Halbout

Peter P Sorokin

Irl N Duling, Iii

Robert James Bennett

Anne C Balant

A communication system for transmitting and receiving terahertz signals has a emitter employing a resonant radiating structure connected to an ultrafast switch. The switch is a subpicosecond photoconducting switch coupled to a coplanar transmission line having a pair of approximately 1 micron wide A1 lines deposited on an SOS substrate. The transmission line is separated from the tip of the radiating structure by a photoconducting gap forming the switch and is driven by a laser pulse. Utilizing the gap excitation principle, the transmitting antenna radiates a freely propagating signal that may be received by an identical structure either on the same or on different substrates.

Integrated terahertz electromagnetic wave system

A method of generating subpicosecond electrical pulses on a micron sized coplanar transmission line fabricated on an insulating, nonlinear optical substrate, by driving the line with focused ultrashort optical pulses. The pulses are generated directly on the transmission line by the optical rectification effect acting on the focal volume between the two lines of the transmission line of the focused ultrashort laser pulses. In the second embodiment, the transmission line is charged and the electrical pulse is generated by changing the capacitance in the focal volume between the two lines of the transmission line by the optical Kerr effect acting on the focused ultrashort optical pulses.

Direct generation of ultrafast electrical pulses

A method of generating subpicosecond electrical pulses on a micron sized coplaner transmission line fabricated on an insulating, nonlinear optical substrate, by driving the line with focused ultrashort optical pulses. The pulses are generated directly on the transmission line by the optical rectification effect acting on the focal volume between the two lines of the transmission line of the focused ultrashort laser pulses. In the second embodiment, the transmission line is charged and the electrical pulse is generated by changing the capacitance in the focal volume between the two lines of the transmission line by the optical Kerr effect acting on the focused ultrashort optical pulses.

An optical pulse is passed through a nonlinear dispersive delay line, which chirps the pulse by the nonlinear process of self-phase modulation and simultaneously and interactively broadens the pulse by the process of group velocity dispersion. The broadened and chirped pulse is then passed through a linear dispersive delay line, which compresses the pulse to a width less than the original pulse. By making the optical pulse suitably intense, a single-mode optical fiber may act as the nonlinear dispersive delay line. A near-resonant atomic vapor cell or a grating pair may act as the linear dispersive delay line.

Optical pulse compression apparatus and method

Apparatus for producing tunable intense coherent radiation at approximately 628 cm..sup.-1 with a line width less than 0.1 cm..sup.-1. The apparatus includes an optical cavity containing a vapor cell and pumping means including at least one optical pumping source for directing energy at the cavity. In one embodiment the cavity encloses a material capable of stimulated emission in response to said pumping. The material has at least three atomic energy levels with at least a first and second atomic energy level separated by a particular energy quantum approximately equal to 628 cm.sup.-1 ; a transition from said first to said second atomic energy level favored over all other possible transitions from said first atomic energy level; said third atomic energy level, from which atoms can be pumped to said first atomic energy level in response to said pumping means. While this is consistent with classical laser operation the apparatus disclosed herein can also be used for stimulated Raman scattering. Tunability is achieved by tuning the pumping sources in the case of stimulated Raman scattering, or with the aid of the Zeeman or Stark effects for classical laser operation. Typical materials are potassium or strontium vapors. Several pumping arrangements are also disclosed.

Apparatus for producing tunable intense coherent radiation in the

A dark pulse is manifested when the intensity of a laser beam, for example, a continuous wave laser beam drops to zero and returns to its original intensity in a very short time period. A modulator for producing dark pulse outputs is disclosed which includes a two-photon absorption cell provided with two input laser beams: a continuous wave beam having a frequency .omega..sub.1 and a mode-locked laser beam having a frequency .omega..sub.2 selected such that .omega..sub.1 + .omega..sub.2 = .OMEGA..sub.12 where .OMEGA..sub.12 is also the two-photon absorption frequency of the vapor contained in the cell. The mode locked beam modulates the continuous wave beam to produce the desired dark pulses.

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Peekskill, NY, United States of America

Daniel R Grischkowsky