Widely tuneable fiber optical parametric amplifier for coherent anti-Stokes Raman scattering microscopy

Abstract

We present a narrow-bandwidth, widely tunable fiber laser source for coherent anti-Stokes Raman scattering (CARS) spectro-microscopy. The required, synchronized, two-color pulse trains are generated by optical-parametric amplification in a photonic-crystal fiber (PCF). The four-wave-mixing process in the PCF is pumped by a 140ps, alignment-free fiber laser system, and it is seeded by a tunable continuous-wave laser; hence, a high spectral resolution of up to 1cm(-1) is obtained in the CARS process. Since the PCF is pumped close to its zero-dispersion wavelength, a broad parametric gain can be accessed, resulting in a large tuning range for the generated signal and idler wavelengths. CARS spectroscopy and microscopy is demonstrated, probing different molecular vibrational modes within the accessible region between 1200cm(-1) and 3800cm(-1).

Fiber optical parametric oscillator for coherent anti-Stokes Raman scattering microscopy

“…The peak signal power is twice that, and the average power three times that, of the fiber OPA reported in [10]. The peak power is 15 times that of the fiber source presented in [5], while the average power is 8 times higher.…”

“…Additionally, FWM tends to create noisy signal pulses [8]. This problem is alleviated in the fiber OPAs presented in [9, 10] through the use of continuous-wave (CW) seeding. The source demonstrated in [9] is the only fiber source to provide comparable pulse parameters and energies to the solid state source [2].…”

“…For another, the OPO reaches 13–20% conversion efficiency to the signal wavelength, as compared to only 10% in the OPA. As a practical advantage, the OPO eliminates the CW seed laser used in [9, 10]. The capabilities of this system are illustrated by its use in CARS imaging of mouse tissues.…”

Accumulating advantages, reducing limitations: Multimodal nonlinear imaging in biomedical sciences – The synergy of multiple contrast mechanisms

“…Such lasers allows for the first time complete fiber integration [62]. Seeding the FWM process by a low power cw laser allows for fast wavelength tuning and significantly improves the spectral resolution to 1 cm À1 [63].…”

Coherent anti‐Stokes Raman scattering microscopy: overcoming technical barriers for clinical translation

“…To maximize the excitation controllability, one clinical imaging system selected all-free-space optical components, including a free-space arm for beam delivery [59]. At the opposite end of the spectrum, fiber optic components were predominantly used to avoid frequent optical alignment without compromising the wavelength tunability [46, 60]. Between these two extremes, several approaches adopted a hybrid format of free-space and fiber components to implement optical coherence tomography-like CARS microscopy [61], CARS endoscopy [62], and handheld CARS microscopy [63].…”