Wisconsin Alumni Research Foundation

Ian A Nelson

Thad Gilbert Walker

Bien Chann

A radiation therapy system produces a treatment beam that is detected by an electronic portal imaging device (EPID) after it passes through the subject being treated. A chopper wheel modulates low energy components of the beam while leaving the higher energy components substantially unmodulated. Modulated components in the image signals produced by the EPID are detected and used to produce portal images.

Portal imaging using modulated treatment beam

A high power diode laser system utilizes an external cavity to narrow the spectral width of a high power multimode diode laser to change the output power normally produced by the diode from a broad spectrum to a very narrow spectrum. The power output of the laser system is concentrated over a narrow spectral range which falls within the useable range for particular applications, such as optical pumping of noble gas samples for magnetic resonance imaging. The output of the diode is received by a collimating element which directs the light on a beam path to a diffraction grating which is oriented at an angle to the incident beam. A portion of the beam may be directed from the diffraction grating to provide useable output light, and a portion of the light incident on the grating is directed back to be focused on the diode to provide feedback to cause the diode to preferentially lase at the wavelength of the light that is fed back. A polarization rotation element may be used to orient the polarization of the light passing through it to control the amount of feedback light.

Frequency-narrowed high power diode laser system with external cavity

A high power diode laser array system utilizes an external cavity to narrow the spectral width of a high power diode laser array to change the output power normally produced by the diode array from a broad spectrum to a very narrow spectrum. The power output of the laser array system is concentrated over a narrow spectral range which falls within the useable range for particular applications such as optical pumping of noble gas samples for magnetic resonance imaging. The output of the array is received by a collimating element, which collimates the light in a direction perpendicular to the direction of the length of the array of emitters and directs the light on a beam path to a diffraction grating which is oriented at an angle to the incident beam. A portion of the beam is directed from the diffraction grating to provide useable output light, and a portion of the light incident on the grating is directed back to be focused on the diode array to provide feedback to cause the diode array to preferentially lase at the wavelength of the light that is fed back. A polarization rotation element may be used to orient the polarization of the light passing through it to control the amount of feedback light.

Growing community of inventors

Madison, WI, United States of America

Ian A Nelson