Nonlinear Optical Imaging and Spectroscopy With Ultrafast Laser Pulses

Open Access
Author:
Yang, Chuan
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
April 11, 2013
Committee Members:
  • Zhiwen Liu, Dissertation Advisor
  • Qiming Zhang, Committee Member
  • Siyang Zheng, Committee Member
  • Iam Choon Khoo, Committee Member
  • Victor P Pasko, Committee Member
Keywords:
  • ultrafast laser
  • femtosecond laser
  • nonlinear optics
  • microscopy
  • spectroscopy
  • imaging spectrometer
  • FROG
  • pulse characterization
Abstract:
In the past several years, my Ph.D. research is mainly focusing on developing techniques for nonlinear optical imaging and spectroscopy. After decades of development, nonlinear optical microscopy modalities are playing a vital role in modern medical and biological research and applications. Conventional nonlinear microscopy is usually too slow for dynamic applications due to its imaging approach of three-dimension (3D) point-by-point scanning. By integrating technologies of nanofabrication, spectroscopy and diffractive optics, we successfully eliminated the mechanical scanning along depth dimension, and therefore the three-dimension nonlinear imaging including second harmonic generation (SHG), two-photon absorption (TPA) and confocal can be significantly expedited. In the chapter 2 of this thesis, I will describe two of my Ph.D. research projects on non-axial-scanning 3D nonlinear imaging. In order to further optimize the performance of nonlinear optical microscopy, fundamental research on light-matter interactions has been intensively carried out. Some other related domains like photon coherent control and laser source optimization can also benefit from this research. Critical information of light-matter interactions is contained in the amplitude and phase information of coherent light. Our group proposed a solution of collinear frequency-resolved optical gating (cFROG) based on a second harmonic nanoprobe (SHARP) for in situ characterization of ultrafast laser pulses in the nano-femto spatiotemporal scale. As a further step forward, here we combine holography technique with cFROG method to completely characterize the field and this newly-developed technique has enabled us to obtain detailed information of the pulse propagation. This new technique for spatiotemporal characterization of laser pulse will be detailed in Chapter 3. As the most used instrument for my experimental research on nonlinear optics, the optical spectrometer is one of the most important and most widely used instruments in various research areas. However, most spectrometers are too expensive or too bulky. Therefore, we developed the prototype of a miniature spectrometer with a single diffractive element that integrates the functions of multiple components installed in a traditional spectrometer. Our palm-size prototype has comparative performance to some existing much-more-expensive commercial spectrometers. In addition, the material for fabricating the device was carefully selected so that the cost can be lowered down significantly. Chapter 4 of my thesis will be focusing on this new prototype instrument we named G-Fresnel spectrometer.