We demonstrate the operation of a novel portable, fibre delivery miniaturized multimodal microscope (exoscope) for
coherent anti-Stokes Raman scattering and two-photon excitation fluorescence imaging using a single Ti:sapphire
femtosecond pulsed laser. This microscope features a large mode area photonic crystal fibre for light delivery, as well as
biaxial scanning microelectromechanical system mirrors and custom miniaturized optics corrected for chromatic
aberration. We demonstrate imaging of polystyrene beads, two photon excitation fluorescence beads in both forward and
backward (epi) directions. This miniaturized exoscope will enable in-vivo imaging of rat spinal cord.
We discuss the design and implementation of a novel multimodal coherent anti-Stokes Raman scattering (CARS)
miniaturized microscope for imaging of injured and recovering spinal cords in a single living animal. We demonstrate
for the first time, the use of a biaxial microelectromechanical system (MEMS) mirror for scanning and diffraction
limited multiple lens miniaturized objective for exciting a CARS signal. The miniaturized microscope design includes
light delivery using a large mode area photonic crystal fiber (PCF), and multimode fiber for collection of the nonlinear
optical signal. The basic design concept, major engineering challenges, solutions, and preliminary results are presented.
We demonstrate CARS and two photon excitation fluorescence microscopy in a benchtop setup with the miniaturized
optics and MEMS scanning. The light source is based on a single femtosecond laser (pump beam) and a supercontinuum
generated in a nonlinear PCF (Stokes beam). This is coupled using free space optics onto the surface of a resonantly
driven two dimensional scanning MEMS mirror that scans the excitation light in a Lissajous pattern. The novel design of
the miniaturized microscope is expected to provide significant new information on the pathogenesis of demyelinating
diseases such as Multiple Sclerosis and Spinal Cord Injury.
The performance of two different photonic crystal fibers (PCF) of identical lengths for implementation of the Stokes
source in a multimodal CARS microscopy and spectroscopy setup is compared. RIN measurements are performed to
experimentally determine the noise in the supercontinuum from the two fibers as well as in the CARS signal under
similar excitation conditions of the input pulse into the PCF. The RIN of the CARS signal is found to be higher than
the RIN of the corresponding Stokes signal, in both fibers. The implications for CARS microscopy of the SC spectrum
and its noise dependence on input pulse conditions in both fibers, are discussed.
A new method for using a non-selectively filled hollow-core photonic crystal fiber (HC-PCF) as a sensitive
Raman spectroscopy platform suitable for biosensing applications is presented. A 1550 HC-PCF was
completely filled with ethanol (core and cladding holes). Using a 785nm excitation laser, the Raman spectrum
of ethanol in the fiber core was obtained and compared with the equivalent Raman spectrum of an ethanolfilled
cuvette. Using a relatively short 9.5cm length of HC-PCF, a Raman signal enhancement factor of 40 over
a bulk solution of ethanol was observed under the same excitation conditions. The small sample volume
utilized and longer interaction length provides the potential for compact, sensitive, and low-power Raman
sensing of biological materials