Stimulated anti-Stokes Raman Scattering Research Articles

Low-Threshold Anti-Stokes Raman Microlaser on Thin-Film Lithium Niobate Chip.

Raman microlasers form on-chip versatile light sources by optical pumping, enabling numerical applications ranging from telecommunications to biological detection. Stimulated Raman scattering (SRS) lasing has been demonstrated in optical microresonators, leveraging high Q factors and small mode volume to generate downconverted photons based on the interaction of light with the Stokes vibrational mode. Unlike redshifted SRS, stimulated anti-Stokes Raman scattering (SARS) further involves the interplay between the pump photon and the SRS photon to generate an upconverted photon, depending on a highly efficient SRS signal as an essential prerequisite. Therefore, achieving SARS in microresonators is challenging due to the low lasing efficiencies of integrated Raman lasers caused by intrinsically low Raman gain. In this work, high-Q whispering gallery microresonators were fabricated by femtosecond laser photolithography assisted chemo-mechanical etching on thin-film lithium niobate (TFLN), which is a strong Raman-gain photonic platform. The high Q factor reached 4.42 × 106, which dramatically increased the circulating light intensity within a small volume. And a strong Stokes vibrational frequency of 264 cm-1 of lithium niobate was selectively excited, leading to a highly efficient SRS lasing signal with a conversion efficiency of 40.6%. And the threshold for SRS was only 0.33 mW, which is about half the best record previously reported on a TFLN platform. The combination of high Q factors, a small cavity size of 120 μm, and the excitation of a strong Raman mode allowed the formation of SARS lasing with only a 0.46 mW pump threshold.

Cascaded Stokes and anti-Stokes laser based on an optical resonator with a self-assembled organic monolayer.

Due to their high circulating intensities, ultra-high quality factor dielectric whispering gallery mode resonators have enabled the development of low threshold Raman microlasers. Subsequently, other Raman-related phenomena, such as cascaded stimulated Raman scattering (CSRS) and stimulated anti-Stokes Raman scattering (SARS), were observed. While low threshold frequency conversion and generation have clear applications, CSRS and SARS have been limited by the low Raman gain. In this work, the surface of a silica resonator is modified with an organic monolayer, increasing the Raman gain. Up to four orders of CSRS are observed with sub-milliwatt (mW) input power, and the SARS efficiency is improved by three orders of magnitude compared to previous studies with hybrid resonators.

Low threshold anti-Stokes Raman laser on-chip

Raman lasers based on integrated silica whispering gallery mode resonant cavities have enabled numerous applications from telecommunications to biodetection. To overcome the intrinsically low Raman gain value of silica, these devices leverage their ultra-high quality factors (Q), allowing sub-mW stimulated Raman scattering (SRS) lasing thresholds to be achieved. A closely related nonlinear behavior to SRS is stimulated anti-Stokes Raman scattering (SARS). This nonlinear optical process combines the pump photon with the SRS photon to generate an upconverted photon. Therefore, in order to achieve SARS, the efficiency of the SRS process must be high. As a result, achieving SARS in on-chip resonant cavities has been challenging due to the low lasing efficiencies of these devices. In the present work, metal-doped ultra-high Q (Q>107) silica microcavity arrays are fabricated on-chip. The metal-dopant plays multiple roles in improving the device performance. It increases the Raman gain of the cavity material, and it decreases the optical mode area, thus increasing the circulating intensity. As a result, these devices have SRS lasing efficiencies that are over 10x larger than conventional silica microcavities while maintaining low lasing thresholds. This combination enables SARS to be generated with sub-mW input powers and significantly improved anti-Stokes Raman lasing efficiency.

Stimulated Anti-Stokes Raman Emission Generated by Gold Nanorod Coated Optical Resonators

Plasmonic nanomaterials and nanostructured substrates have made a significant impact in sensing and imaging due to their ability to improve optical field confinement at interfaces. This improved confinement increases the optical field intensity, enabling numerous nonlinear effects to be revealed. However, one challenge is effectively coupling light into and out of the plasmonic nanomaterial. One approach is to directly integrate the plasmonic nanomaterials onto the surface of light emitting optical devices. In this work, the highly nonlinear complex of organic small molecule functionalized gold nanorods is coated on the surface of optical resonators. The evanescent tail of the optical field circulating inside the resonator directly interacts with the nanoparticle complex, creating a hybridized plasmon-whispering gallery mode. Due to the strong field localization by the nanorods and the large circulating power within the resonator, Stimulated Anti-Stokes Raman Scattering is generated with only 14 mW of inp...

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators.

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility Χ((3)) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility Χ(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Mitigating Heat Dissipation in Near- and Mid-Infrared Silicon-Based Raman Lasers Using CARS—Part II: Numerical Demonstration

The mitigation of quantum-defect heating in Raman lasers by the use of coherent anti-Stokes Raman scattering (CARS) is numerically demonstrated for two silicon-based waveguide Raman lasers pumped at a near-infrared (near-IR) wavelength around 1.5 m and at a mid-infrared (mid-IR) wavelength around 2.7 m, respectively. We show that, for the mid-IR laser, the CARS-based heat-mitigation technique attains an efficiency of 35%, whereas the corresponding efficiency for the near-IR laser without taking into account the two-photon-absorption-induced heat equals 15%. The discrepancy between these two values finds its origin in the fact that for the mid-IR laser (quasi-) perfect phase matching for the CARS process can be obtained more easily, and the loss of anti-Stokes photons due to stimulated anti-Stokes Raman scattering (SARS) can be reduced more efficiently. Furthermore, we discuss two important practical aspects of Raman lasers with CARS-based heat mitigation, and we find that this category of Raman lasers could be used as dual-wavelength sources emitting codirectional Stokes and anti-Stokes beams of comparable power.

Minority species detection in aerosols by stimulated anti-Stokes–Raman scattering and external seeding

A novel technique applicable to remote sensing has been developed for determination of the chemical composition of microdroplets. Enhancement of stimulated anti-Stokes-Raman scattering (SARS) by external seeding of stimulated Raman scattering (SRS) at the Stokes shift lowers the detection limit of the minority species in multicomponent microdroplets. The technique is most useful in the investigation of microdroplets that contain fluorophores that can obscure the SRS signal. The SARS signal is to the blue of the pump laser and out of the fluorescence region of the fluorophore. Information about majority and minority species in multicomponent microdroplets can be determined from the enhanced SARS signals.

In situ microparticle diagnostics by stimulated Raman scattering

A novel technique for the identification of the chemical composition of microdroplets has been developed. External seeding of stimulated Stokes Raman scattering (SSRS) has been applied to reduce the minimum detectable concentration of the minority species in multicomponent microdroplets. To avoid complications with polarizer and analyzer in remote sensing applications, we utilize the fact that the probed (seeded) SSRS band of the minority species (at νmin) can efficiently pump SSRS of the majority species (at νmaj). The Raman signal of the minority species appears at a shift of νmin+maj, which can easily be distinguished from the elastically scattered light of the seed laser at the shift of νmin. Furthermore, we investigated fluorescing microdroplets with stimulated anti-stokes Raman scattering (SARS).

Stimulated anti-Stokes Raman scattering in microdroplets

Stimulated anti-Stokes Raman scattering (SARS) generated by one input beam is observed from CCI(4), ethanol, and water droplets. The first-order SARS intensity is approximately 10(4) times lower than the first-order stimulated-Raman-scattering (SRS) intensity for ethanol droplets. Simultaneous detection of SARS and SRS for water droplets shows an occasional lack of correlation between the SARS and SRS spectra.

Diagnostics of sputtering processes of carbon and carbides by laser-induced fluorescence spectroscopy in the VUV at 166 nm

Measurements of velocity distributions of C, B, and Si atoms released in sputtering processes from graphite and carbide targets bombarded with noble gas ions in the 1 keV range are described. Laser-induced fluorescence spectroscopy in the VUV is applied. The VUV radiation necessary to excite the sputtered atoms is provided by stimulated anti-Stokes Raman scattering (SARS) in H2. Surface binding energies are derived from measured velocity distributions; concentrations of sputtered particles, fluxes and sputtering yields are determined.

Up-conversion Using Stimulated Anti-stokes Raman Scattering and Stimulated Collisional Induced Fluorescence in Tl

We have observed stimulated collisional induced fluorescence at 377·6 nm in a Tl anti-Stokes Raman up-converter. The up-converter was operated with an excess pressure of argon, and the influence of the ‘collisional’ pumping of the Tl (72S½) level on both the anti-Stokes Raman and collision-induced fluorescence was investigated.

Up-conversion Using Stimulated Anti-stokes Raman Scattering and Stimulated Collisional Induced Fluorescence in Tl

We have observed stimulated collisional induced fluorescence at 377·6 nm in a Tl anti-Stokes Raman up-converter. The up-converter was operated with an excess pressure of argon, and the influence of the ‘collisional’ pumping of the Tl (72S½) level on both the anti-Stokes Raman and collision-induced fluorescence was investigated.

Picosecond UV Light Source by Stimulated Anti-Stokes Raman Scattering

Picosecond UV Light Source by Stimulated Anti-Stokes Raman Scattering

Observation of Stimulated Anti-Stokes Raman Scattering in Inverted Atomic Iodine

Observation of Stimulated Anti-Stokes Raman Scattering in Inverted Atomic Iodine