Cavity-Enhanced Field-Free Molecular Alignment at a High Repetition Rate

Benko, Craig; Lee, Hua; Allison, Thomas K.; Labaye, François; Ye, Jun

doi:10.1103/physrevlett.114.153001

Cited by 17 publications

(16 citation statements)

References 32 publications

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“…However, this previous spectroscopy work has largely neglected the pulsed nature of the intracavity comb, and that these pulses can be used for the sensitive detection of ultrafast time-resolved signals [24,25]. Indeed, as 2 we show here, the gains for nonlinear spectroscopy can actually be larger, since both pump and probe pulses can be resonantly enhanced.…”

mentioning

confidence: 61%

Cavity-Enhanced Ultrafast Transient Absorption Spectroscopy

Chen¹,

Reber²,

Keleher³

et al. 2014

Proceedings of the 69th International Symposium on Molecular Spectroscopy

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We present a new technique using a frequency comb laser and optical cavities for performing ultrafast transient absorption spectroscopy with improved sensitivity. Resonantly enhancing the probe pulses, we demonstrate a sensitivity of ∆OD = 1 × 10 −9 / √ Hz for averaging times as long as 30 s per delay point (∆OD min = 2 × 10 −10 ). Resonantly enhancing the pump pulses allows us to produce a high excitation fraction at high repetition-rate, so that signals can be recorded from samples with optical densities as low as OD ≈ 10 −8 , or column densities < 10 10 molecules/cm 2 . This high sensitivity enables new directions for ultrafast spectroscopy.The advent of the mode-locked Ti:Sapphire laser in the early 1990's [1] made ultrafast pumpprobe measurements routine and widely accessible to a broad range of scientists. This was largely due to the Ti:Sapphire laser's robustness compared to the dye-lasers it replaced.However, another aspect of the Ti:Sapphire laser that made many experiments possible was its capability of low-noise performance. This allowed for measurements of very small changes in the optical properties of a sample induced by a pump pulse, which is necessary when the sample is either dilute [2,3,4] or must be excited weakly to probe the desired these authors contributed equally to this work 1 arXiv:1511.02973v1 [physics.optics] 10 Nov 2015physics [5,6]. Even with relatively noisy chirped pulse amplified systems, one can measure changes in absorbance or reflection to a few parts in 10 6 , and ultrafast transient absorption spectroscopy is the simplest and most widely applied form of ultrafast spectroscopy [7].Despite this enormous progress, there remain many samples for which ultrafast optical spectroscopy is still prohibitively difficult. Most directly related to the current work are the "designer" gas-phase molecules and molecular clusters that can be produced in a supersonic expansion. With optical spectroscopy seemingly hopeless, ultrafast experimenters perform measurements on these systems by ionizing the molecules with UV pulses or strong fields [8,9], detecting the resulting ions and electrons. This is indeed extremely sensitive due to the capabilities of single particle detection and background free signals. However, ionization projects the molecular state of interest onto a very different manifold of final states than optical measurements, and this can make the comparison of experimental data from gas phase and condensed phase highly non-trivial [10,11]. Furthermore, while dynamics of electronically excited states can be probed by ionization, there exists no ionization-based methods for probing purely vibrational dynamics analogous to the powerful tools of ultrafast infrared spectroscopy [12].It was realized in the early days of lasers that an optical resonator is useful for absorption enhancement due to the fact that light passes through a sample many times [13]. Today, cavities are widely used in many different contexts for the enhancement of optical signals [14].Recently, several groups have...

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mentioning

confidence: 61%

Cavity-Enhanced Ultrafast Transient Absorption Spectroscopy

Chen¹,

Reber²,

Keleher³

et al. 2014

Proceedings of the 69th International Symposium on Molecular Spectroscopy

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“…In the past two decades, femtosecond enhancement cavity (fsEC) coupled with high repetition rate lasers (typically ≥10 MHz) not only helps to realize the frequency comb in the extreme ultraviolet (XUV) region [27][28][29][30][31][32], but also provides a new platform to study strong field atomic and molecular dynamics with an unprecedented high repetition rate, and accordingly, with a high signal-to-noise ratio and statistics [32][33][34][35][36][37]. Inside the fsEC which is coupled with high repetition rate laser, the plasma generated in the focal volume by the first pulse does not have time to be cleared before the successive laser pulses arrive and generate even more plasma [38,39].…”

Section: Introductionmentioning

confidence: 99%

Laser Driven Fluorescence Emission in a Nitrogen Gas Jet at 100 MHz Repetition Rate

Zhang,

Hua,

et al. 2021

Preprint

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We report the fluorescence emission which is driven by femtosecond laser pulses with a repetition rate of 100 MHz and a center wavelength of 1040 nm in a nitrogen gas jet. The experiment is performed in a femtosecond enhancement cavity coupled with high repetition rate laser for the first time to the best of our knowledge. In contrast to previous observation at low repetition rate with a nitrogen gas jet, where the 391 nm radiation was observed but the 337 nm emission was missing, the 337 nm emission is 3 times stronger than the 391 nm emission in our experiment. By examining the dependence of the radiation intensity on the flow rate of the nitrogen gas and the polarization of the pump pulse, the formation mechanism of the N2(C 3 Πu) triplet excited state, i.e., the upper state of the 337 nm emission, is investigated. We attribute the main excitation process to the inelastic collision excitation process, and exclude the possibility of the dissociative recombination as the dominate pathway. The role of the steady state plasma that is generated under our experimental conditions is also discussed.

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“…By opening up the vast spectral range of XUV for high-resolution spectroscopy, the feasibility of an optical clock based on a nuclear transition in 229 Th [3,4] driven with an XUV frequency comb is growing rapidly. In the time domain, the high repetition rate and ultrafast characteristics of XUV frequency combs allow time-resolved studies of dynamics in molecular and solidstate systems on femtosecond and even attosecond time scales with superior data acquisition speed and high signal-to-noise ratio [5][6][7].…”

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confidence: 99%

Noncollinear Enhancement Cavity for Record-High Out-coupling Efficiency of an Extreme-UV Frequency Comb

et al. 2020

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We demonstrate a femtosecond enhancement cavity with a crossed-beam geometry for efficient generation and extraction of extreme-ultraviolet (XUV) frequency combs at 154 MHz repetition rate. We achieve a record-high out-coupled power of 600 μW, directly usable for spectroscopy, at a wavelength of 97 nm. This corresponds to a >60% out-coupling efficiency. The XUV power scaling and generation efficiency are similar to that achieved with a single Gaussian-mode fundamental beam inside a collinear enhancement cavity. The noncollinear geometry also opens the door for generation of isolated attosecond pulses at >100 MHz repetition rate.

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Cavity-Enhanced Field-Free Molecular Alignment at a High Repetition Rate

Cited by 17 publications

References 32 publications

Cavity-Enhanced Ultrafast Transient Absorption Spectroscopy

Cavity-Enhanced Ultrafast Transient Absorption Spectroscopy

Laser Driven Fluorescence Emission in a Nitrogen Gas Jet at 100 MHz Repetition Rate

Noncollinear Enhancement Cavity for Record-High Out-coupling Efficiency of an Extreme-UV Frequency Comb

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