Kerr cell light beam modulator
Date1954
Inventory Number1997-1-1770
ClassificationKerr Cell
Subject
Supplier
Tube Light Engineering Company
1928-present
User
Bowdoin College, Department of Physics
founded after 1794
Cultural Region
Place of Origin
Place of Use
Dimensions17.5 x 18.4 x 6 cm (6 7/8 x 7 1/4 x 2 3/8 in.)
Material
DescriptionA cylindrical tube, almost totally filled with a slightly yellow liquid (high purity redistilled nitrobenzene). Inside the tube one sees two electrodes rising from the bottom vertically, parallel to each other. Each of them then holds a metal plate (zinc) through small metal extensions. The two plates are parallel and very close to each other, a 1 or 2 mm separation. Another set of wires at the top of the plates connects to an insulating glass tube that helps keep the plates parallel.
Large portions of the tube have been covered with black tape leaving narrow windows uncovered so that one can see through the space between the two plates. (Aperture of about 1 or 2 mm width x about 1cm height.) The tube, which has a black base (probably bakelite) rests on a larger, grey painted metal base with two electrical sockets, one of which is labeled "GND". This grey base is attached at the bottom to a long metal rod which can rotate around the axis of the tube and has a small screw to fix its orientation.
Large portions of the tube have been covered with black tape leaving narrow windows uncovered so that one can see through the space between the two plates. (Aperture of about 1 or 2 mm width x about 1cm height.) The tube, which has a black base (probably bakelite) rests on a larger, grey painted metal base with two electrical sockets, one of which is labeled "GND". This grey base is attached at the bottom to a long metal rod which can rotate around the axis of the tube and has a small screw to fix its orientation.
Signedlabel on tube, partially covered by black tape: ...SICAL LABORATORY / ... TH AVENUE, N.Y.C. / ... ERR CELL / (In pencil) Jan 1954 / ... m aperture / ... 200 Volts
Inscribedlabel on one side of bulb near base: NEG / NEG / NEG
Curatorial RemarksCurrently stored in a plastic case with instrument 1997-1-1771. Documents related to the purchase of Kerr cells by Bowdoin College stored in the file of 1997-1-1770, but they also related to instrument 1997-1-1771.
FunctionKerr cells are a device used for the conversion of electrical signals to optical signals (for instance for communication). They take advantage of the fact that some liquids change their refractive index in the presence of a strong electric field.
In this particular instrument, a voltage source would be connected to the sockets on the base, and one would pass a light signal between the two parallel plates. For this end, the tube has been masked with black tape except on two narrow windows on opposite sides of the gap between the parallel plates.
The main application of Kerr cells would be for the transmission of signals using light. If a signal is added to the voltage source, polarized light that has passed between the plates will acquire the signal, modulated as changes in its polarization.
The fact that it was acquired by Bowdoin College and the masking tape suggests that this one was used for teaching.
In this particular instrument, a voltage source would be connected to the sockets on the base, and one would pass a light signal between the two parallel plates. For this end, the tube has been masked with black tape except on two narrow windows on opposite sides of the gap between the parallel plates.
The main application of Kerr cells would be for the transmission of signals using light. If a signal is added to the voltage source, polarized light that has passed between the plates will acquire the signal, modulated as changes in its polarization.
The fact that it was acquired by Bowdoin College and the masking tape suggests that this one was used for teaching.
ProvenanceFrom the Department of Physics, Bowdoin College.
American
Date: 1915-1930
Object number: 2008-1-0127
Wilhelm Apel
Date: 1890-1900
Accessories: induction coil (0392c)
Object number: 0392a
Wilhelm Apel
Date: 1890-1900
Accessories: induction coil (0392c)
Object number: 0392b
W. & L. E. Gurley
Date: ca. 1884
Accessories: solar attachment; case; level; green filter; sun shade; tripod (5163b)
Object number: 5163a
Richard W. Thomas
Date: circa 1861
Accessories: bottle and beaker (1998-1-1634a); hydrometer and manual (1998-1-1634b)
Object number: 1998-1-1634
Digital Equipment Corporation
Date: 1960-1970
Accessories: circuit board, "flip chip" cards (10)
Object number: 1998-1-0230
Société Générale des Téléphones
Date: circa 1884
Accessories: switchboard call drop (8035b)
Object number: 8035a
Zeiss-Aerotopograph
Date: circa 1950
Accessories: in wooden storage case with metal handles; documentation booklet is now kept in the instrument's file; all other accessories are kept in the box and are included in the description.
Object number: 2009-1-0002b
Department of Physics, Harvard University
Date: mid 20th-late 20th Century
Accessories: variety of spare parts cataloged as 2004-1-0408c-g
Object number: 2004-1-0408a
See also/See also
