Heterodyne coherent anti-Stokes Raman scattering is presented with a single and compact fiber-based light source only, providing the pump and Stokes as well as local oscillator pulses with a fixed phase relation. The interferometrically superimposed pulses of the CARS signal and the local oscillator generated heterodyne gain, scaling with the LO power, and amplifying the weak CARS signal at the detection site. The functionality of this heterodyne CARS setup was verified by measurements of the heterodyne amplification, the sample concentration, and the phase dependence of the signal. Additionally, 10-fold suppression of non-resonant signal was achieved for background correction.
Systemic drug delivery for dermatological conditions yields little drug to the intended site of action resulting in adverse effects. Topical drug delivery is a viable alternative yet the local cutaneous pharmacokinetics (cPK) is relatively under-explored. Product dosing is dependent upon the knowledge of the dose-cPK relationship, which coincides with the pharmacodynamic (PD) activity. Coherent Raman imaging (CRI) can quantify tissue-specific drug localization and elucidate micro-scale cPK estimates, affording a clinically relevant cPK-PD relationship. This demonstration of a dose-cPK relationship utilizing CRI offers a stepping stone for additional formulation evaluation ex vivo.
Silicon nitride waveguides offer a high nonlinear refractive index and tight mode confinement, ideal for efficient four-wave mixing (FWM) processes. We present a light source for broadband as well as narrowband coherent anti-Stokes Raman scattering (CARS), with the potential to be set up as an all-integrated device, based on FWM in silicon nitride waveguides. Signal and idler pulses are generated via FWM with only 4 nJ input pulse energy and stimulated using a tunable continuous-wave seed source, such that the idler and residual pump pulses can be used for CARS measurements, enabling chemically-selective label-free imaging across the entire fingerprint region.
We present high-speed multicolor stimulated Raman scattering imaging (SRS) enabled by an all-fiber light source. With a relative intensity noise level of -157 dBc above 10 MHz the light source is shot-noise limited up to a detector current of 0.75 mA. Compared to other fiber-based light sources optimized for SRS, the presented system is tunable in under 5 ms per arbitrary step between 700 and 3530 wavenumbers. The compact and environmentally stable system is predestined for fast multicolor assessments of medical or rapidly evolving samples with high chemical specificity.
We present multicolor coherent Raman imaging (CRI) with two orders of magnitude enhanced sensitivity accomplished by a frequency modulation (FM) at 20 MHz of a portable fiber optical parametric oscillator (FOPO). The FM is combined with a rapid and wide tunability for accessing Raman bands between 700 and 3500 1/cm within only 5 ms. This development constitutes an important step for advancing CRI microscopy in terms of portability and sensitivity for applications in medical diagnostics or environmental sensing.
Silicon nitride waveguides offer a high nonlinear refractive index and tight mode confinement, ideal for efficient four-wave mixing (FWM) processes. We present a light source for coherent anti-Stokes Raman scattering (CARS), with the potential to be set up as an all-integrated device, based on spontaneous FWM in silicon nitride waveguides with only a single ultrafast fiber-based pump source at 1030 nm wavelength. Broadband signal and idler pulses are generated with only 5 nJ input pulse energy, such that the idler and residual pump pulses can be used for CARS measurements, enabling chemically-selective and label-free imaging over the entire fingerprint region.
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