University of Michigan
Electrical & Computer Engineering
Ann Arbor, MI 48109
Tel: (734) 647-9700
Fax: (734) 647-2718
We are developing super-continuum lasers (SCLs) and their applications to identify materials based on their chemical composition. SCLs are broadband light sources that share desirable traits from lamps and lasers. The bandwidth of the SC laser is broad like a lamp, while the spatial coherence and high intensity or brightness of the output is like a laser. Hence, some have even dubbed SCL as “the ultimate white light.” However, up to now SCL have been used primarily in laboratory settings, because large, table-top, mode-locked lasers have been often used to pump nonlinear media, such as optical fibers. We now replace those large pump lasers with laser diodes and fiber amplifiers used in the mature telecommunications and fiber optics industry, thereby enabling practical applications in defense, intelligence, homeland security, metrology, spectroscopy and healthcare.
By exploiting the nature physics in a fiber, our group has made three major breakthroughs in SCLs. First, we have extended the wavelength range for SC sources into the mid-infrared, covering most of the near and mid-infrared wavelengths simultaneously. For example, our lasers provide continuous spectrum ranging from ~0.8 microns near the edge of the visible, through the near-infrared from ~1-2 microns, and reaching through most of the mid-infrared from ~2-4.5 microns. We are also working on extending the SCL wavelength range from 0.5 to 12 microns. Second, by initiating the SC generation through naturally occurring phenomena in fibers (an effect called modulational instability), we eliminate the need for the mode-locked laser, replacing what in many cases is a large, table-top laser with commercial off-the-shelf (COTS) parts from the mature telecommunications and fiber optics industry. Finally, we can scale the power to 64W or higher by simply increasing the repetition rate and using a high power fiber amplifier. Of course, along with the power increase, engineering challenges arise from packaging and thermal management.
We are an applications oriented group that uses SCLs or laser diodes for various optics and photonics applications. For defense, intelligence and homeland security applications, we use the SCL as a broadband illuminator for active remote sensing and hyper-spectral imaging. This can be important for identifying targets based on their chemical make-up at stand-off and long distances (e.g., we have done field trials identifying targets a mile away). For medical and healthcare applications, we use SCLs to identify tissue differences and blood analyte measurements. For example, we are looking to distinguish normal tissue from cancerous tissue based on the chemical composition of the tissue, such as lipid and collagen content. In another example, we are performing spectroscopy on blood for non-invasive glucose monitoring.
Below are some on-going projects in our group: