Flexible pulse shaping for sum frequency microspectroscopies

Abstract

The complexity of experimental schemes still challenges the broad application of multimodal microscopy beyond fundamental research. Pulse shaping has been a promising candidate to assist in the implementation of flexible and compact schemes. In this work, its application is demonstrated for vibrational resonant sum frequency (SF) spectroscopy in a nonlinear Raman microscope. The mixing of an ultrabroadband NIR laser pulse with a difference-frequency-generated MIR spectrum provides spectral access from 1750 c m − 1 to beyond 3000 c m − 1 via two shaping methods: (i) homodyne MIR scanning and (ii) heterodyne multiplex. The versatility of shaper-based SF is demonstrated in the spectroscopy and microscopy of crystalline cholesterol and cysteine.

Phase-Sensitive Vibrationally Resonant Sum-Frequency Generation Microscopy in Multiplex Configuration at 80 MHz Repetition Rate

“…Moreover, nonlinear techniques have features that overcome some drawbacks of conventional Raman and Fourier transform infrared (FT IR) microscopy. For example, the signal strength in coherent anti-Stokes Raman and stimulated Raman microscopy is larger than that of Raman microscopy. , The poor spatial resolution of mid-IR imaging is highly improved in vibrationally resonant sum-frequency generation (VR SFG) microscopy, − which utilizes a nonlinear process involving an infrared-active vibrational transition and Raman-active signal generation by a tightly focused visible light. IR microscopic techniques with submicron spatial resolution were also possible based on other principles. − Applications of these nonlinear vibrational microscopies have been reported in a variety of research fields, such as life sciences, biomedical analysis, and biophotonics.…”

“…Realization of hyperspectral VR SFG microscopy with a repetition rate of MHz is highly desirable because it can be employed as a valuable research tool to study biological samples. Currently, it can be carried out only by manually scanning the wavelength of narrowband mid-IR pulses , or by a more intricate system based on a sub-10 fs laser and a pulse shaper . It remains as an important goal to technically demonstrate the feasibility and usefulness of multiplex VR SFG microscopy at a high repetition rate.…”

“…Currently, it can be carried out only by manually scanning the wavelength of narrowband mid-IR pulses 15,18 or by a more intricate system based on a sub-10 fs laser and a pulse shaper. 21 It remains as an important goal to technically demonstrate the feasibility and usefulness of multiplex VR SFG microscopy at a high repetition rate.…”