Abstract
We present tunable waveguide-based optical parametric amplification by four-wave mixing (FWM) in silicon nitride waveguides, with the potential to be set up as an all-integrated device, for narrowband coherent anti-Stokes Raman scattering (CARS) imaging. Signal and idler pulses are generated via FWM with only 3 nJ pump pulse energy and stimulated by using only 4 mW of a continuous-wave seed source, resulting in a 35 dB enhancement of the idler spectral power density in comparison to spontaneous FWM. By using waveguides with different widths and tuning the wavelength of the signal wave seed, idler wavelengths covering the spectral region from 1.1 µm up to 1.6 µm can be generated. The versatility of the chip-based FWM light source is demonstrated by acquiring CARS images.
Highlights
Laser-based spectroscopy and imaging have become essential techniques for biochemical and medical applications, especially coherent anti-Stokes Raman scattering (CARS) microscopy [1]
We present tunable waveguide-based optical parametric amplification by four-wave mixing (FWM) in silicon nitride waveguides, with the potential to be set up as an all-integrated device, for narrowband coherent anti-Stokes Raman scattering (CARS) imaging
By acquiring CARS images we showed the versatility of the waveguide-based optical parametric amplifier (WOPA) light source for laser-scanning microscopy
Summary
Laser-based spectroscopy and imaging have become essential techniques for biochemical and medical applications, especially coherent anti-Stokes Raman scattering (CARS) microscopy [1]. In order to overcome the downsides of OPOs, cheaper and more robust fiber-based systems with a dual-color output for CARS applications have been developed These systems, e.g. fiber-based optical parametric oscillators [4,5,6,7] and amplifiers [8,9] as well as spontaneous FWM-based light sources [10,11] or supercontinuum sources [12,13], exploit nonlinear frequency conversion in photonic crystal fibers (PCFs). Silicon nitride (Si3N4) waveguides offer a versatile, CMOS-compatible, onchip platform with a high nonlinear refractive index and a tight mode confinement [16] Nonlinear processes such as FWM can be driven more efficiently [17,18,19,20,21], enabling operation with lower pump energies and shorter interaction lengths. By acquiring CARS images we showed the versatility of the WOPA light source for laser-scanning microscopy
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