Improved and Versatile Magnetic Field Sensor: A Magneto-Optoelectronic Device (Case 1424)

Principal Investigator:

Arto Nurmikko, PhD, Professor

School of Engineering

Brown University

Providence, RI


Brief Description:


The ability to remotely sense magnetic fields without direct physical presence or contact with the field location is important in many industrial/commercial and military applications from environmental monitoring/testing to microelectronics manufacturing.  Measurements of magnetic field changes are often needed in a difficult, hostile or otherwise inaccessible environment, as in earthquake warnings, battlefield sensing, in the sensing of information in a magnetic storage medium, such as a computer hard disk drive, or in the contactless sensing of current pulses on a microchip.  In these scenarios, typically, either a magnetometer or a flying head – of a disk drive - performs the measurement in close physical proximity. 


Present sensing and/or measuring methods for magnetic fields, whether macro- or microscale, make telemetry cumbersome, as a wired resistor is needed for detection thereby limiting flexibility and use.  Wireless approaches have obvious advantages of the conventional wired sensing.  However, wireless is more difficult to implement by conventional techniques, such as in the case of the incorporation of a microwave transmitter as part of the sensor package adding cost, complexity and increased power constraints to the package.  Another current approach for examining magnetic properties of substances is through the use of magneto-optic effects (also known as the Kerr and Faraday effects), but this technique requires a disposed light source and detector for illuminating the material of interest and detecting the reflected or transmitted light, respectively, and for a number of important applications, these requirements can be difficult to satisfy in a cost effective and simple manner.  For the above reasons, state-of-the-art magnetic field sensing devices remain inadequate.  The technology offered here not only addresses remaining issues of existing systems, but also realizes further advantages in terms of cost, simplicity, and versatility.


The novel invention is a method and device in the form of a Magneto-Optoelectronic Device (MOD) comprised of a magnetic sensing device, such as a magnetoresistive or magnetic tunnel junction (MTJ) device, and combined with a semiconductor (or light-emitting polymer material) light emitter, such as an LED or a laser diode (e.g., vertical cavity surface emitting laser or VCSEL).  The MOD is a compact integrated device where changes in an ambient magnetic field – in the vicinity of the MOD – are expressed as changes in an optical beam intensity emanating from the MOD.  The MOD enables magnetic field-related information to be transmitted by a light wave over very large distances through a medium, i.e., free space and/or an optical fiber. 


This versatile and robust innovation can be in different, optimal embodiments with varying components depending upon application and environment.  For example, the magnetoresistive sensor can comprise uniform thin films of suitable magnetic materials, as well as their heterostructure multilayers.  Because of the compact device components, the MOD can be wired on a small scale integrated circuit chip with a footprint on the scale of few hundred square micrometers or less; indeed a monolithic, ultracompact integrated MOD on a submicrometer scale can be created.  The technology can be employed to implement high-speed wireless communication between the integrated circuit-scale electronic and optical circuits.  Furthermore, an aspect of this novel MOD provides a method for transmitting information and includes: information expressed as a time varying magnetic field, light generation with an intensity that varies as a function of a strength of the time varying magnetic field, transmitting light, receiving the transmitted light, detecting the intensity of the received light, and obtaining the information from the detected intensity.


Applications include, but are not limited to: any in which measurement of magnetic field changes is desired, and/or in difficult or hostile environments, e.g., earthquake warning or battlefield sensing, or in the sensing of information in a magnetic storage medium, e.g., computer hard disk drive; contactless sensing of current pulses on a microelectronic chip during chip manufacturing.  Markets include: magnetic field sensors - for use in various and numerous market segments; advanced manufacturing instruments for microelectronic chips production.




US patent 7,440,479 is issued (10/21/2008)

US patent 7,551,657 is issued (06/23/2009)

Patent Information:
For Information, Contact:
Brown Technology Innovations
350 Eddy Street - Box 1949
Providence, RI 02903
Arto Nurmikko
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