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Infrared Modulator Using Dichroic Circular Polarizer

IP.com Disclosure Number: IPCOM000095623D
Original Publication Date: 1964-Mar-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Erlbach, E: AUTHOR

Abstract

Solenoid 10 establishes a DC magnetic field in indium-antimonide (In Sb) semiconductor crystal 12. Unpolarized infrared light 14 is incident in the direction of the magnetic field and has the cyclotron resonance frequency of the electron semiconductor. Infrared light 16 from semiconductor crystal 12 is circularly polarized.

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Infrared Modulator Using Dichroic Circular Polarizer

Solenoid 10 establishes a DC magnetic field in indium-antimonide (In Sb) semiconductor crystal 12. Unpolarized infrared light 14 is incident in the direction of the magnetic field and has the cyclotron resonance frequency of the electron semiconductor. Infrared light 16 from semiconductor crystal 12 is circularly polarized.

In the presence of a magnetic field, the energy of the free electrons in semiconductor 12 becomes semi-quantized. For low temperatures, all electrons are normally in the state L = 0 (orbital angular momentum quantum number) and only the transitions to L = 1 can occur. With such a selection rule for electron energy transitions, infrared light is absorbed whose circularly rotating electric field vector 14a rotates in the same direction as the electrons. The other circularly rotating electric field vector 14b is transmitted.

The output circularly polarized infrared light from semiconductor 12 is incident on indium-antimonide crystal 18 established in microwave resonant cavity 20. The crystal is located at a point one-half wavelength from the shorted end of the cavity 20.

At this point, the magnetic field vector of the modulated microwave input 22 is in the direction Hmw. A DC magnetic field H is applied in cavity 20 by coils 24 in the same direction Hmw. Therefore, the magnetic fields H and H(mw) add in the In Sb crystal 18. The output infrared light is modulated at the microwave frequency.

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