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Photonics Research

Ying-Chih Chen
Professor of Physics
Hunter College of CUNY

My research has been focused in laser physics, laser devices and biomedical-related optical physics and technology, such as photoacoustic imaging, imaging and focusing of light through optically diffusive media ( tissues, multimode fibers, etc.) . Recent research highlights are shown below.


Focusing through optically diffusive media 

We have demonstrated that laser beam can be focused through diffusive media such as a ground glass or biological tissue onto a light absorber by shaping the wavefront.

Figure 1

Fanting Kong, Ronald Silverman, Liping Liu, P. V. Chitnis, Kotik K. Lee, and Y.C. Chen, "Photoacoustic-guided convergence of light through optically diffusive media", Opt. Lett. 36, 203 (2011).   PDF


Delivery of a focused laser beam through a multimode fiber

Multimode fibers are a closed system of diffuse reflectors. The interference among the fiber modes creates a random granular pattern, known as speckle, at the output and causes a total loss of spatial coherence.   We have demonstrated that the coherence of the beam transmitted through  multimode fibers can be restored by wavefront shaping.  This can be done at the input or output ends.   Potential applications include delivery of a focused laser beam through an endoscope for laser surgery.

Figure 2

High-resolution photoacoustic imaging of  ocular tissues

Using focused laser beam to generate ultrasound with pinpoint precision, we have achieved 20-fold improvement in the  resolution of photoacoustic images compared to conventional ultrasound images. 

Potential applications of this technique include clinical examination of superficial and thin tissues containing optically absorbing pigments such as melanin or hemoglobin, including skin, mucosa, and ocular tissues (iris, retina and choroid).   

Figure 3

Fanting Kong, Y.C. Chen, Harriet O. Lloyd, Ronald H. Silverman, Hyung Kim, Jonathan M. Cannata , and K. Kirk Shung,  “High-resolution photoacoustic imaging with focused laser and ultrasonic beams”. Applied Physics Letters, 94 , 033902 (2009).  


Phase locked fiber laser arrays

By using a spatial filtering technique we have recently achieved simultaneous and phase-locked generation of short pulses in a two-element fiber laser system. The nanosecond Brillouin-scattering pulses are intense enough to self-destruct the fiber core.   We are currently working to apply this technique to phase locking in two-dimensional fiber laser arrays containing many more elements.

Figure 4

Fanting Kong, Liping Liu, Charlotte Sanders, and Y. C. Chen, and Kotik K. Lee,  “Phase locking of nanosecond pulses in a passively Q-switched two-element fiber laser array”, Applied Physics Letters, 90, 151110 (2007).

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Last Updated on June 2, 2011.

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