Optical: systems and elements – Polarization without modulation – By relatively adjustable superimposed or in series polarizers
Reexamination Certificate
2000-01-13
2001-07-31
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Polarization without modulation
By relatively adjustable superimposed or in series polarizers
C359S494010
Reexamination Certificate
active
06268962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical devices. More specifically, the present invention relates to optical rotators.
2. Description of the Related Art
For optical systems, there is often a need to rotate the polarization state of an optical beam. For this purpose, optical rotators are made of quartz are often used. A half waveplate made of birefringent material can also be employed to transform a given linear polarization state into a different linear polarization state. A specific orientation of the half waveplate is necessary to achieve this result, while the optical rotator can have any orientation. These devices are generally passive and reciprocal. Electro-optical crystals are active waveplates, where phase is proportional to applied voltage. Non-reciprocal applications require Faraday rotators.
An optically active rotator rotates the plane of polarization of light passing through it. A typical optically active rotator is generally a fairly long device, requiring a large block of optical grade material such as quartz. One of the advantages of an optically active medium used in fabricating a rotator is that the rotator can be fabricated that rotates the transmitted beam by any desired angle, not just 90°. One of the disadvantages to employing an optically active medium is that high quality material is not available at all wavelengths.
Other inventions by this Applicant also assigned to Raytheon Company include:
“Reeder Rod” Ser. No. 09/482,230, filed Jan. 13, 2000; “Reeder Compensator” Ser. No. 09/482,376, filed Jan. 13, 2000; and “Waveplate Polarization Rotator” Ser. No. 09/482,378, filed Jan. 13, 2000; These applications are incorporated herein by reference.
Thus, there is a need in the art for a rotator which is much thinner than an equivalent 90° quartz rotator using much less optical grade material. There is a Other need for a rotator would be made of any uniformly birefringent medium. This would extend the possible wavelength range of operation as optically active rotators are not currently available at all wavelengths.
SUMMARY OF THE INVENTION
The need in the art is addressed by the optical rotator of the present invention. The inventive optical rotator includes a pair of waveplates which receive a polarized beam having a first state and outputs a polarized beam having a second state rotated 90° with respect to the first state. In the illustrative embodiment, the rotator includes first and second waveplates formed as a monolithic element. In another illustrative embodiment, the waveplates are coupled to one another by an optical spacer.
A rotator constructed in accordance with the present teachings should be much thinner than the equivalent 90° quartz rotator and, thus, use much less optical grade material. Moreover, the inventive rotator is compact and can be made of any uniformly birefringent medium. The uniformly birefringent material extends the possible wavelength range of operation. In addition, in accordance with the present teachings, rotators of larger size are possible because of the reduced amount of material required for a given diameter rotator.
A rotator constructed in accordance with the present teachings may be used for laser applications that require a strongly pumped laser rod that exhibits more than a quarter-wave of thermal birefringence.
REFERENCES:
patent: 4678287 (1987-07-01), Buhrer
patent: 4772104 (1988-09-01), Buhrer
Hect, “Optics”, pp. 305-306, 1987.
Alkov Leonard A.
Lenzen, Jr. Glenn H.
Raufer Colin M.
Raytheon Company
Schuberg Darren
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