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Spontaneous Raman spectroscopy is a well‐established diagnostic tool, allowing for the identification of all Raman active species with a single measurement. Yet, it may suffer from low‐signal intensity and fluorescent background. In contrast, coherent anti‐Stokes Raman scattering (CARS) offers laser‐like signals, but the traditional approach lacks the multiplex capability of spontaneous Raman spectroscopy. We present an ultrabroadband CARS setup which aims at exciting the full spectrum (300–3700 cm−1) of biological molecules. A dual‐output optical parametric amplifier provides a ~7 fs pump/Stokes and a ~700 fs probe pulse. CARS spectra of DMSO, ethanol, and methanol show great agreement with spontaneous Raman spectroscopy and superiority in fluorescent environments. The spectral resolution proves sufficient to differentiate between the complex spectra of L‐proline and hydroxyproline. Moreover, decay constants in the sub picosecond range are determined for individual Raman transitions, providing an additional approach for sample characterization. [ABSTRACT FROM AUTHOR]

Abstract Optical microscopy with optimal axial resolution is critical for precise visualization of two-dimensional flat-top structures. Here, we present sub-diffraction-limited ultrafast imaging of hexagonal boron nitride (hBN) nanosheets using a confocal focus-engineered coherent anti-Stokes Raman scattering (cFE-CARS) microscopic system. By incorporating a pinhole with a diameter of approximately 30 μm, we effectively minimized the intensity of side lobes induced by circular partial pi-phase shift in the wavefront (diameter, d0) of the probe beam, as well as nonresonant background CARS intensities. Using axial-resolution-improved cFE-CARS (acFE-CARS), the achieved axial resolution is 350 nm, exhibiting a 4.3-folded increase in the signal-to-noise ratio compared to the previous case with 0.58 d0 phase mask. This improvement can be accomplished by using a phase mask of 0.24 d0. Additionally, we employed nondegenerate phase matching with three temporally separable incident beams, which facilitated cross-sectional visualization of highly-sample-specific and vibration-sensitive signals in a pump-probe fashion with subpicosecond time resolution. Our observations reveal time-dependent CARS dephasing in hBN nanosheets, induced by Raman-free induction decay (0.66 ps) in the 1373 cm−1 mode.

An innovative scheme of a fiber optical parametric oscillator with two-arm synchronous pumping is presented. Numerical simulation is performed in a wide range of parameters. The domains of existence of stable regimes of generation of parametric pulses are found versus the peak power of pump pulses and their time overlap with parametric pulses (relative delay) for detuning of the carrier wavelengths of the pump pulses in the arms of up to 1 nm and lengths of photonic crystal fibers of 33 and 43 cm. It is shown that such two-arm synchronous pumping makes it possible to increase the maximum energy of the output pulses to 57 nJ (by almost a factor of two compared to the linear scheme) and works like offset filters of the Mamyshev oscillator, making it possible to obtain pulses with parameters inaccessible for alternative schemes. [ABSTRACT FROM AUTHOR]

Optical microscopy with optimal axial resolution is critical for precise visualization of two-dimensional flat-top structures. Here, we present sub-diffraction-limited ultrafast imaging of hexagonal boron nitride (hBN) nanosheets using a confocal focus-engineered coherent anti-Stokes Raman scattering (cFE-CARS) microscopic system. By incorporating a pinhole with a diameter of approximately 30 μm, we effectively minimized the intensity of side lobes induced by circular partial pi-phase shift in the wavefront (diameter, d0) of the probe beam, as well as nonresonant background CARS intensities. Using axial-resolution-improved cFE-CARS (acFE-CARS), the achieved axial resolution is 350 nm, exhibiting a 4.3-folded increase in the signal-to-noise ratio compared to the previous case with 0.58 d0 phase mask. This improvement can be accomplished by using a phase mask of 0.24 d0. Additionally, we employed nondegenerate phase matching with three temporally separable incident beams, which facilitated cross-sectional visualization of highly-sample-specific and vibration-sensitive signals in a pump-probe fashion with subpicosecond time resolution. Our observations reveal time-dependent CARS dephasing in hBN nanosheets, induced by Raman-free induction decay (0.66 ps) in the 1373 cm−1 mode. [ABSTRACT FROM AUTHOR]

Cervical cancer is the fourth most common cancer worldwide. Histopathology, which is currently considered the gold standard for cervical cancer diagnosis, can be time-consuming and subjective. Therefore, there is an urgent need for a rapid, objective, and non-destructive cervical cancer detection technique. In this study, high-wavenumber spontaneous Raman spectroscopy was used to detect cervical squamous cell carcinoma and normal tissues. The levels of lipids, fatty acids, and proteins in cervical cancerous tissues were found to be higher than those in normal tissues. Raman difference spectroscopy revealed the most significant difference at 2928 cm -1 . Additionally, a Coherent anti-Stokes Raman spectroscopy (CARS) instrument was employed to enhance the wavenumber signal intensity and sensitivity. The intrinsic relationship between CARS imaging and cervical lesions was established. The CARS images indicated that the intensity of normal cervical squamous cells was zero, whereas the intensities of keratinized and non-keratinized cervical squamous cell carcinoma tissues were significantly higher. Consequently, diagnostic outcomes could be obtained by observing CARS images with the naked eye. Furthermore, the characteristic structure of keratin pearls in keratinized cervical cancer could serve as a marker for subdividing cervical cancer types. Finally, a ConvNeXt network, a machine-learning model built from CARS images, was utilized to classify different types of tissue images. The results indicated a verification accuracy of 100 %, with a loss function of 0.0927. These findings suggest that the diagnostic model established using CARS images could efficiently diagnose cervical cancer, providing novel insights into the pathological diagnosis of this disease., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Study Question: Can oocyte functionality be assessed by observing changes in their intracytoplasmic lipid droplets (LDs) profiles?, Summary Answer: Lipid profile changes can reliably be detected in human oocytes; lipid changes are linked with maternal age and impaired developmental competence in a mouse model., What Is Known Already: In all cellular components, lipid damage is the earliest manifestation of oxidative stress (OS), which leads to a cascade of negative consequences for organelles and DNA. Lipid damage is marked by the accumulation of LDs. We hypothesized that impaired oocyte functionality resulting from aging and associated OS could be assessed by changes in LDs profile, hereafter called lipid fingerprint (LF)., Study Design, Size, Duration: To investigate if it is possible to detect differences in oocyte LF, we subjected human GV-stage oocytes to spectroscopic examinations. For this, a total of 48 oocytes derived from 26 young healthy women (under 33 years of age) with no history of infertility, enrolled in an oocyte donation program, were analyzed. Furthermore, 30 GV human oocytes from 12 women were analyzed by transmission electron microscopy (TEM). To evaluate the effect of oocytes' lipid profile changes on embryo development, a total of 52 C57BL/6 wild-type mice and 125 Gnpat+/- mice were also used., Participants/materials, Setting, Methods: Human oocytes were assessed by label-free cell imaging via coherent anti-Stokes Raman spectroscopy (CARS). Further confirmation of LF changes was conducted using spontaneous Raman followed by Fourier transform infrared (FTIR) spectroscopies and TEM. Additionally, to evaluate whether LF changes are associated with developmental competence, mouse oocytes and blastocysts were evaluated using TEM and the lipid dyes BODIPY and Nile Red. Mouse embryonic exosomes were evaluated using flow cytometry, FTIR and FT-Raman spectroscopies., Main Results and the Role of Chance: Here we demonstrated progressive changes in the LF of oocytes associated with the woman's age consisting of increased LDs size, area, and number. LF variations in oocytes were detectable also within individual donors. This finding makes LF assessment a promising tool to grade oocytes of the same patient, based on their quality. We next demonstrated age-associated changes in oocytes reflected by lipid peroxidation and composition changes; the accumulation of carotenoids; and alterations of structural properties of lipid bilayers. Finally, using a mouse model, we showed that LF changes in oocytes are negatively associated with the secretion of embryonic exosomes prior to implantation. Deficient exosome secretion disrupts communication between the embryo and the uterus and thus may explain recurrent implantation failures in advanced-age patients., Limitations, Reasons for Caution: Due to differences in lipid content between different species' oocytes, the developmental impact of lipid oxidation and consequent LF changes may differ across mammalian oocytes., Wider Implications of the Findings: Our findings open the possibility to develop an innovative tool for oocyte assessment and highlight likely functional connections between oocyte LDs and embryonic exosome secretion. By recognizing the role of oocyte LF in shaping the embryo's ability to implant, our original work points to future directions of research relevant to developmental biology and reproductive medicine., Study Funding/competing Interest(s): This research was funded by National Science Centre of Poland, Grants: 2021/41/B/NZ3/03507 and 2019/35/B/NZ4/03547 (to G.E.P.); 2022/44/C/NZ4/00076 (to M.F.H.) and 2019/35/N/NZ3/03213 (to Ł.G.). M.F.H. is a National Agency for Academic Exchange (NAWA) fellow (GA ULM/2019/1/00097/U/00001). K.F. is a Diamond Grant fellow (Ministry of Education and Science GA 0175/DIA/2019/28). The open-access publication of this article was funded by the Priority Research Area BioS under the program "Excellence Initiative - Research University" at the Jagiellonian University in Krakow. The authors declare no competing interest., Trial Registration Number: N/A., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

Simultaneous pure-rotational coherent anti-Stokes Raman spectroscopy (PRCARS) and vibrational O2 CARS spectroscopy (VCARS) were performed at elevated pressure and lowered temperature conditions in non-reacting compressible flow. We applied dual-pump CARS in a three-laser, three-color configuration to simultaneously acquire the PRCARS and VCARS spectra of O2. PRCARS spectra provide excellent sensitivity to temperature at relatively low temperatures. Pressure was extracted using the differential response of collisional effects in the PRCARS and the VCARS spectra. We used an under-expanded jet outside a choked converging nozzle as the compressible flow-field. We numerically analyze the pressure sensitivity of the combined CARS technique. Finally, we compare the collisional narrowing lineshape models of rotational diffusion narrowing and modified-exponential-gap model, for fitting the experimental spectrum. Graphical Abstract [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the interactions of DNA chains with nanodiamonds (ND) with NV centers by CARS spectroscopy. As a result of a comparative analysis of the obtained CARS spectra of DNA in water and in aqueous suspension of ND, a sign of the destruction of DNA chains as a result of interaction with the surface of ND was found. It was confirmed that DNA molecules interact with the surface groups of nanodiamonds by means of electrostatic interactions: no new CARS spectral bands were detected in the CARS spectra of DNA in the ND suspensions. [ABSTRACT FROM AUTHOR]

Laser diagnostics has been one of the most powerful tools in advancing state-of-the-art combustion research over the last five decades. Prof. Marcus Aldén, one of the most well-known pioneers in this field, has contributed many influential original publications over more than 40 years of his research career. In this paper, we will review some selected contributions, with emphasis on optical techniques developed and applied by Marcus and the group in Lund under his leadership, which are expected to play important roles in facing the challenge of the transition to a carbon-neutral energy system. A brief biography of Marcus is presented in the introduction section, including a summary of his academic services and achievements. The following sections are organized into chapters on different well-recognized techniques, i.e. , laser-induced fluorescence, Raman and Rayleigh scattering, thermographic phosphors, coherent anti-Stokes Raman spectroscopy, resonant four-wave mixing, and additional novel technical developments and approaches. The description often follows different categories, including technique development, activities using relatively mature techniques for studies of combustion phenomena, and applications of the most mature techniques in practical devices. The last part of the paper includes a short interview with Marcus for his comments, suggestions, and thoughts on the future challenges and opportunities in this field. This article, on the one hand, is an acknowledgment of the outstanding contribution of Marcus to the field of combustion research and, on the other hand, intends to provide a valuable review of laser diagnostics in combustion research. [ABSTRACT FROM AUTHOR]

This article reports on the quantification of the heating induced by nanosecond repetitively pulsed (NRP) glow discharges on a lean premixed methane-air flame. The flame, obtained at room temperature and atmospheric pressure, has an M-shape morphology. The equivalence ratio is 0.95 and the thermal power released by the flame is 113 W. The NRP glow discharges are produced by high voltage pulses of 10 ns duration, 7 kV amplitude, applied at a repetition frequency of 10 kHz. The average power of the plasma, determined from current and voltage measurements, is 1 W, i.e., about 0.9% of the thermal power of the flame. Broadband vibrational coherent anti-Stokes Raman spectroscopy of nitrogen is used to determine the temperature of the flame with and without plasma enhancement. The temperature evolution in the flame area shows that the thermal impact of NRP glow discharges is in the uncertainty range of the technique, i.e., ±40 K. [ABSTRACT FROM AUTHOR]

To study devolatilization, ignition, and volatile combustion processes of single coal particles at a fundamental level, a flat flame burner was designed to provide oxygen-enriched exhaust gas environments at elevated temperatures and varying gas compositions. In one set of experiments coal particles were carried by a central jet using a gas mixture of the same composition as the flat flame. By this means a homogenous and connected flame was generated. At the instant when single coal particles transited this stationary flame, start of particle heat-up was well defined. This allows studying start of ignition more accurately compared to the other set of experiments where an inert carrier gas jet was used for transportation of coal particles. Heat-up and ignition were retarded temporally due to precedent mixing between inert gas and ambient flue gases. Coal particles with a high percentage of volatiles (36 wt%) and a particle distribution ranging from 90 to 125 µm were used. Coherent anti-Stokes Raman spectroscopy (CARS) measurements were performed to characterize ambient gas phase temperatures. By high-speed laser-induced fluorescence, imaging of OH-radicals ignition and volatile combustion was visualized for individual coal particles. Reaction zones surrounding each coal particle and the corresponding distances to coal particles were identified. This distance depended strongly on oxygen concentration of the ambient flue gas atmosphere. In addition to an improved phenomenological understanding the data may serve for model validation. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate compact and efficient single-pulse coherent anti-Stokes Raman spectroscopy (CARS) via spectral notch shaping implemented with a fiber Bragg grating. We show that a fiber Bragg grating can serve as a narrowband notch filtering component on a 90 nm broadband femtosecond pulsed laser without spectral distortion. Finally, we obtain CARS spectra of various samples in the fingerprint region of molecular vibrations. This scheme has potential for compact implementations of all-fiber single-pulse multiplex CARS due to its compatibility with fiber optics. [ABSTRACT FROM AUTHOR]

• Focus-engineering using concentric 0-pi-phase modulated beam of the wavefront of the incident beam has already demonstrated by our previous works experimentally with respect to 2 beam, degenerately pumped CARS systems to improve optical resolution. Here, we utilize the same technique in the context of the 3-beam non-degenerately pumped CARS. • This results in an inherent-improvement of optical resolution which is utilized to image ZnO nanoparticles at sub 100 nm optical resolution. A critical dimensional comparison between SEM (in a charging-effect-free condition) and CARS was achieved by wrapping the dispersed nanoparticles with single layer graphenes. • We correct the chromatic aberration of the objective lens at the low powered probe beam (at 405 and 455 nm wavelength) using a precise z-directional focal movement induced using a liquid lens. This technique enabled us to overlap the focal volumes of the pump, Stokes and probe beams to ensure efficient generation of the non-degenerate CARS signal. • Further, unwanted focal sidelobes of the focus-engineered nonlinear focal volume is successfully removed using a pinhole in a de-scanning condition which results in additional ∼10% improvement in optical resolution besides the side lobe removal. For the development of microscopic tools that can resolve non-fluorescent samples beyond the diffraction limit, we propose focus-engineered non-degenerate pumped coherent anti-Stokes Raman scattering (CARS) using spatial light modulator (SLM)-based phase shaping, liquid lens focus control, and confocal detection. Non-degenerate pumped CARS (ND-CARS) with frequency-doubled probe pulses resulted in approximately 75% improvement in resolution compared to that of degenerate CARS. Focal adjustment using the liquid lens facilitated the accurate overlapping of three beams. The circular π-phase modulation at the center of the probe-beam wavefront demarcated the net CARS focal volume into a sub 100 nm-scale core and surrounding side lobes. The confocal geometry detection setup successfully removed the side lobes, allowing optical imaging of 81 nm-sized zinc oxide particles at 87 nm, and edge-to-edge resolution was determined to be 103 nm. [ABSTRACT FROM AUTHOR]

Temperature measurements were obtained along the nozzle centerline of CH 4 /H 2 /air partially premixed flames, in a counter-flow burner, using N 2 vibrational coherent anti-Stokes Raman scattering (VCARS). Measurements were performed for flames with no H 2 and varying percentages of CH 4 in the fuel stream and for flames with nearly constant CH 4 content and varying H 2 content in the fuel stream. VCARS measurements were compared against 1-D numerical simulations using different chemical mechanisms within the frame work of COSILAB software. All the mechanisms compared well against experimental data except for flames at low equivalence ratio where the San Diego mechanism performed the best. Interestingly, the peak flame temperature remained nearly constant with increasing percentage of H 2 in the fuel stream. The presence or absence of thermal diffusion made little difference in the comparison between numerical simulations and experiments. The influence of radiation on nozzle centerline temperature profiles was also investigated. [ABSTRACT FROM AUTHOR]

We have studied the coherent molecular vibrational dynamics of CH2 stretching modes in polyethylene by time-resolved femtosecond coherent anti-Stokes Raman spectroscopy. We observed that the coherent vibrational relaxation of symmetric CH2 stretching modes in polyethylene at room temperature is much faster than that previously measured in polyvinyl alcohol. In addition, it was detected that, at low temperature, the coherent vibrational relaxation of the symmetric stretching modes evidently becomes slower compared with that at room temperature. These temperature-dependent measurements enable us to discriminate the contribution of pure dephasing mechanism, due to phonons and two-level systems in polymer, from the contribution of lifetime of the vibrational excited state to the coherent vibrational relaxation of CH2 stretching modes. We conclude that the coherent vibrational relaxation of symmetric CH2 stretching modes at room temperature consists of the contribution of lifetime and approximately 1.5 times larger contribution of pure dephasing. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sensors are perhaps the most important and integral components of our modern society. With global warming and environmental pollution garnering ever-increasing attention, as well as solutions for sustainabile and smart cities, the optimized performance of current and future energy systems and process industries is paramount. The accurate sensing and quantification of key parameters of such systems are essential for monitoring, controlling, and optimization efforts. In situ laser-based optical sensors are most suitable for achieving the desired characteristics of accuracy, sensitivity, selectivity, portability, speed, safety, and intelligence. In recent decades, significant progress has been made in the development and deployment of laser-based sensing solutions, although new challenges and opportunities continue to emerge rapidly. In this review paper, we focus on laser absorption spectroscopy (LAS)-based sensors owing to their simple architecture, easy implementation, and market penetration. We detail recent advancements made in LAS variants using new laser sources and techniques. A brief discussion on other laser-based sensing techniques, namely, photoacoustic spectroscopy, laser-induced fluorescence, coherent anti-Stokes Raman spectroscopy, and laser-induced breakdown spectroscopy, is provided to compare these strategies with LAS. The applications of laser-based sensors in various energy systemsincluding engines, turbines, power plants, furnaces, and boilers—as well as process industriessuch as petrochemical, semiconductor, natural gas leak detection, and corrosion detectionare presented, illustrating their many benefits and possible uses. A distinguishing aspect of this review paper is that we present the comparison of previous studies in tabular formats, making it easy to appreciate the recent progress in laser-based sensing solutions. Finally, suggestions on future directions and emerging technologies to pursue for the further enhancement, development, and deployment of laser-based sensors are proposed. [ABSTRACT FROM AUTHOR]

A new coherent anti-Stokes Raman spectroscopy (CARS) technique is reported for real-time detection and classification of several chemical constituents, utilizing a single detector and a single beam of shaped femtosecond pulses. The technique is based on rapidly switching between differently shaped pulses that either maximize or minimize the targeted vibrational lines excitation, thus creating temporally modulated ‘bright’ and ‘dark’ profiles in the total CARS signal that are measured by a single photomultiplier tube and demodulated by a multi-channel lock-in amplifier. Using a two-dimensional spatial light modulator displaying 24 different pulse shapes, we demonstrate pulse shaping at 80 kHz and chemically specific microscopy with pixel dwell times of less than 0.5 ms. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) of deuteroxide was investigated using a pulsed Nd:YAG laser with a wavelength of 532 nm. After the pump laser passed through the first sample cell (C 1), the output light included the transmitted pump beam and the Stokes SRS lights, and the frequency difference between the two self-matched the O-D symmetric and antisymmetric stretching vibration modes. The 1 st and the 2 nd -order cascaded Stokes and the anti-Stokes SRS (Coherent Anti-Stokes Raman Spectroscopy-CARS) of both two modes were observed. The 2 nd -order Stokes SRS and its CARS were firstly observed at a pump energy of 14.79 mJ. The pure Stokes SRS were always collinear with the pump beam along the axial direction. Some ring-like Stokes SRS and CARS, which originated from the four-wave mixing (FWM) processes, were also observed only in the forward direction along with different angles apart from the pump beam direction, respectively. This method not only reduced the SRS threshold but also increased the SRS intensity of the weak vibration mode, resulting in an energy conversion efficiency reaching up to 54%. The technique can be used in a tunable Raman laser. • The threshold of SRS was decreased because of the resonance enhancement effect. • The weak symmetric and the strong antisymmetrical vibration modes can be excited together in deuteroxide. • The ring-like SRS beams and CARS were originated from FWM processes. [ABSTRACT FROM AUTHOR]

The one-dimensional character of sooting premixed porous-plug (McKenna) burner flames has been examined, motivated by recent investigations where the one-dimensionality has been questioned. The examination employs laser diagnostic techniques to measure different characteristics: temperature using rotational coherent anti-Stokes Raman spectroscopy (CARS) and soot properties using laser-induced incandescence and elastic light scattering. Special attention has been paid to the influence of an outer shroud gas flow of either nitrogen or air. The nitrogen shroud gas leads to flame cooling at the outer edge, whereas the air shroud results in heating through the oxidation of CO/H2/soot. This generally results in a more inhomogeneous spatial particle size profile for the nitrogen shroud flame, with smaller particle sizes at the flame edge. The present results emphasize the need to characterize burner and operating conditions accurately, and also, regarding parameters that at first glance seem less relevant, such as the shroud gas, to provide useful data for comparison between laboratories. [ABSTRACT FROM AUTHOR]

Quantum measurement is a fundamental problem in quantum control theory and experiments. It can obtain unknown information of quantum systems, and can also change state of the systems inevitably. Both the outcome and back action could be used to control quantum systems. This paper presents recent research progress about optimal control of state transformation in finite-dimensional quantum systems by back action of non-selective quantum measurement, and optimal control of signal and background of CARS (coherent anti-Stokes Raman spectroscopy) by phase shaping technique. In measurement sequence control of finite-dimensional quantum systems, the necessary condition for critical points of the underlying state transformation objective is found to be a highly symmetric form as a chain of equalities, and analytical and numerical solutions in several cases are explored. In the CARS control, it is found that the maximal resonant signal and minimal background at a specific frequency can be achieved by shaping the probe pulse only while keeping pump and Stokes pulses in transform limited forms (TLFs). An arctan-type phase function is obtained for the probe pulse to simultaneously enhance the resonant signal and suppress the background. For broadband background elimination, we find that the optimal phase shaping scheme of probe pulse is quasi-time-delay while keeping the pump and Stokes pulses in TLFs. These conclusions could help design control strategies of quantum devices. [ABSTRACT FROM AUTHOR]

This article reviews current scientific literature focusing on Raman spectroscopy modalities that have been successfully applied to the detection of biological samples in aqueous suspensions and in aerosols. Normal Raman, surface enhanced Raman scattering, coherent anti-stokes Raman scattering, resonance Raman and UV-Raman spectropies, allow the detection of biological samples in situ in the near field and as well as in the far field at standoff distances. Applications span from fundamental studies to applied research in areas of defense and security and in monitoring of environmental pollution. A primary focus has been placed on biological samples including bacteria, pollen, virus, and biological contents in these specimens, in suspensions, and in aerosols. Several Raman spectroscopy studies have been reviewed to show how various modalities can achieve detection in these biosystems. Current data generated by our group is also included. Necessary parameters used to accomplish the detection and data analysis, which could also be used to interpret the results and to render the methodologies robust and reliable, are discussed. [ABSTRACT FROM AUTHOR]

Abstract: An efficient vibrationally selective technique to build-up the v″=1 vibrational levels in gaseous hydrogen is demonstrated using stimulated Raman pumping (SRP). Both photo-acoustic Raman spectroscopy (PARS) and coherent anti-Stokes Raman spectroscopy (CARS) are used to study non-radiative and radiative (v″=0 and v″=1) transitions in gaseous H2 molecules. The population fraction in the v″=1 vibrational level has been estimated using combined photo-acoustic and coherent anti-Stokes Raman spectroscopy with stimulated Raman pumping. [Copyright &y& Elsevier]