## 1 Introduction  
The advent of femtosecond lasers has ushered in an exciting era of modern quantum chemistry and molecular spectroscopy [1; 2] which has provided previously unavailable or hidden insights about structural dynamics, chemical reactivity, and biological functionality [2; 3; 4; 5; 6; 7]. The ultrafast time duration of the incident laser pulses is key to dissect the electronic potential energy surface of the molecular system under investigation, and a time-delayed pump-probe setup is typically implemented to measure the system response on the intrinsic molecular timescale. In comparison to the widely used transient absorption technique that records the electronic responses as a function of time, vibrational spectroscopy is intimately related to molecular structure and the associated normal modes, making the observed vibrational frequencies highly sensitive to the local environment of the chemical bond. By incorporating a preceding actinic pump pulse that induces photochemistry or other chemical reactions, vibrational transitions of the molecular system can be tracked in real time via IR absorption or Raman processes with ultrafast IR or visible laser pulses, typically on the femtosecond (fs) to picosecond (ps) timescale which can report on the incipient stage of photoinduced processes. To exploit the full potential of ultrafast vibrational spectroscopy to characterize functional materials and biomolecules, we have developed femtosecond stimulated Raman spectroscopy (FSRS) as an emerging structural dynamics technique that has simultaneously high spectral and temporal resolutions [7; 8; 9; 10; 11; 12; 13]. The approach measures the ensemble average of system response so the observed structural evolution is insensitive to stochastic fluctuations but useful to report on functional atomic motions that are previously challenging to measure experimentally [2; 7]. The conventional FSRS technique consists of an \(\sim\)800 nm, ps Raman pump pulse from a grating-based spectral filter and a \(ca\). 840-920 nm, fs Raman probe pulse from supercontinuum white light (SCWL) generation [9; 10; 11]. A preceding \(\sim\)400 nm or 520-660 nm actinic pump pulse from second harmonic generation or noncollinear optical parametric amplification needs to be incorporated when the excited state molecular transformation is studied. One limiting factor for wider applications of FSRS is the wavelength tunability of incident pulses, particularly concerning the ps pump-fs probe pair that performs the stimulated Raman scattering process either in the electronic ground state (So) or excited state (e.g., S\({}_{1}\)). Notably, different molecules have different potential energy landscapes so the vibrational energy levels and resonance Raman conditions vary greatly [14]. To turn FSRS into a more powerful and versatile spectroscopic toolset readily accessible to tackle a wide range of problems in energy and biology related fields, more technical innovations and optical advances are warranted. In our earlier work, we reported the implementation of cascaded four-wave mixing (CFWM) in a thin transparent medium such as BK7 glass to generate broadband up-converted multicolor array (BUMA) signals [15]. One of these tunable, ultrabroad laser sidebands was used as the Raman probe in conjunction with an 800 nm Raman pump to collect the anti-Stokes Raman spectrum of a 1:1 \(v\)/\(v\) carbon tetrachloride:ethanol mixed standard solution [16] with high signal-to-noise ratio. We have alsoreported the BUMA sidebands in a 0.1-mm-thick BBO crystal at phase-matching condition for maximal second harmonic generation (SHG) [17]. The resultant SHG/sum-frequency-generation(SFG) assisted cascaded four-wave mixing processes lead to fs sideband signals from _ca_. 350-490 nm that are simultaneously enhanced due to \(\chi^{(2)}\) and \(\chi^{(3)}\)-based four-wave optical parametric amplification [18]. Can this expanded versatility and tunability help expand the available optical methods for fs Raman probe generation?